1. LE HUY BAChu bien(Tai ban lan th ba, co chnh ly va bo sung)NHA XUAT BAN AI HOC QUOC GIATP HO CH MINH - 2008

2. LI NHA XUAT BANGiao s Tien s khoa hoc Le Huy Ba la mot trong nhng nha moi trnghoc au tien cua Viet Nam c ao tao bai ban, tot nghiep Tien sy Khoa hocve oc chat moi trng nc ngoai va la nha khoa hoc co nhieu kinhnghiem. Trong nhng nam qua, va tham gia cong tac giang day nganh Moitrng cac trng ai hoc, cho he ai hoc, he cao hoc va hng dan luan antien s trong nc va day ngoai nc, va trc tiep nghien cu ong thi lamcong tac thc tien ket hp vi viec hoc tap nhng kinh nghiem cua ncngoai, Giao s Tien s khoa hoc Le Huy Ba a nghien cu, bien soan nhieucong trnh ve moi trng va sinh thai hoc nh: Moi trng hoc c ban, Sinhthai moi trng hoc c ban, Sinh thai moi trng at, Quan tr moi trngc ban, Moi trng kh hau thay oi - moi hiem hoa cua toan cau, Tainguyen moi trng va s phat trien ben vng, Kinh te moi trng hoc, Sinhthai moi trng ng dung, Nhng van e at phen Nam Bo, Ly thuyet vakinh nghiem thc tien ISO/4001, Quan tr moi trng trong nong lam ngnghiep, Du lch sinh thai Cac cong trnh nay hau het a c xuat ban, kpthi phuc vu nhu cau hoc tap, nghien cu cho nganh Moi trng, ong thigop phan nang cao nhan thc ve van e moi trng nc ta. Cuon sach oc hoc moi trng c ban la cong trnh tiep theo cua Giaos Le Huy Ba cung cac cong s. ay la mot cuon sach c bien soan congphu, e cap en nhieu van e ve oc chat, oc to. Moi loai oc chat, oc toeu c phan tch ro ve nguon goc, tnh chat va bien phap phong chong.Sach cung a ra nhieu dan chng minh hoa cu the.oc hoc moi trng c ban la cuon sach ve oc chat hoc moi trng autien c bien soan va xuat ban Viet Nam. Nhieu khai niem mi ve occhat, oc to c gii thieu trong cong trnh nay.Nha xuat ban ai hoc Quoc gia Thanh pho Ho Ch Minh tran trong giithieu cuon oc hoc moi trng c ban vi ban oc.NHA XUAT BAN AI HOC QUOC GIA TP HO CH MINH3 3. CHNG 1 TONG QUAN VE OC HOC MOI TRNG(ECOTOXICOLOGY, AN OVERVIEW)1.1. GII THIEUTrong nhng thap nien gan ay, con ngi a quan tam en tacong o nhiem moi trng oi vi sc khoe cong ong, bi v ngoai slay lan cac benh truyen nhiem (dch ta, thng han) do vi sinh vat gay ra,nhng benh nguy hiem nh ung th, AIDS, quai thai, cac d tat bam sinh tre do cac chat oc hai trong moi trng a xuat hien va ngay cang giatang nhieu ni tren the gii.Xa hoi cang phat trien, cong nghiep hoa cang nhanh th ty le chatthai oc hai t san xuat cong nghiep va nhng anh hng bat li t cachoat ong cua con ngi tac ong vao moi trng cang tang nhanh. Cacchat oc hai con sinh ra do ro r t qua trnh san xuat, van chuyen va lutr cac chat oc. Ngay ca nc r, tham thau t bai rac cung gay nguy hiemcho khu dan c xung quanh. Cac loai o nhiem hoa hoc sinh ra t qua trnhsan xuat cong nghiep va khai thac qua mc tai nguyen thien nhien angngay cang lam nguy hai cho sinh quyen. Cac tac ong ay khong nhng anhhng en loai ngi ma ca cac sinh vat song tren trai at. S phat xa, cac kh thai, chat thai dang vo c, hu c, bui gia tangang e doa moi trng va sc khoe con ngi. Them vao o, s thai rangay cang nhieu cac kim loai oc, cac chat hu c co tnh oc va o bencao, sau o ton lu, tch luy trong chuoi thc an va gay hai nghiem trongen con ngi va cac ong vat hoang da. anh gia bien co (riskassessment) va quan ly bien co (risk management) t cac nguy c tiemtang la rat can thiet e bao ve cac the he tng lai. Chu trnh tng tac gia chat o nhiem va c the sinh vat la quatrnh tiep xuc, gay nen tac ong sinh hoc, the hien qua s hap thu, phanbo trong c the, chuyen hoa, tng tac vi cac thanh phan sinh hoa nhaycam, t o co the gay nhng bien oi ve sinh hoa trong c the, dan enbenh tat.5 4. Chuyen hoa Chat o nhiem,C the sinh vat chat ocTac ong e nghien cu tat ca cac tac ong neu tren oi vi con ngi, cathe sinh vat va cac quan xa sinh vat trong he sinh thai, chung ta se tiepcan mot mon khoa hoc mi, o la mon oc hoc moi trng (environmentaltoxicology) hay con goi la oc hoc sinh thai (ecotoxicology). No la motbo mon cua nganh oc chat hoc (toxicology) nhng lai nam trong nganhMoi trng hoc (environmental sciences). Can phan biet hai khai niem: oc chat hoc va oc hoc moi trng. a) oc chat hoc J.F. Borzelleca nh ngha: "oc chat hoc la nganh hoc nghien cu velng va chat cac tac ong bat li cua cac tac chat hoa hoc, vat ly, sinh hoclen he thong sinh hoc cua sinh vat song". oc chat hoc la nganh khoa hoc vechat oc. No la mot nganh khoa hoc c ban va khoa hoc ng dung. b) oc hoc moi trng Hai khai niem oc hoc moi trng (environmental toxicology) va ochoc sinh thai (ecotoxicology) trong moi trng hoc c xem la ong nhat.o la nganh khoa hoc chuyen nghien cu cac tac ong gay hai cua oc chat,oc to trong moi trng oi vi cac sinh vat song va con ngi, ac biet latac ong len cac quan the va cong ong trong he sinh thai. Cac tac ong baogom: nguon goc phat sinh, con ng xam nhap cua cac tac nhan hoa, ly vacac phan ng gia chung vi moi trng (Butler, 1978). oc hoc moi trng nghien cu s bien oi, ton lu va tac ong cuatac nhan gay o nhiem von co trong thien nhien va cac tac nhan nhan taoa anh hng en cac hoat ong song cua sinh vat trong he sinh thai, cactac ong co hai en cho con ngi. Nh vay, khac vi oc chat y hoc hayHoa oc hoc, oc hoc moi trng co oi tng nghien cu khong ch lacon ngi ma ca cac loai sinh vat, quan the va quan xa. Phng phapnghien cu oc hoc moi trng th nghiem s tac ong va tch luy oc6 5. chat, oc to tren nhng sinh vat song ch khong nghien cu rieng rethanh phan cua oc chat trong phong th nghiem. Cac nghien cu ve oc hoc moi trng rat phc tap v co lien quanen nhieu loai oc to, lieu lng, nong o anh hng khac nhau, tacong en nhieu loai khac nhau. Thi gian tien hanh anh gia mc o anhhng cua chat oc tren mot quan xa sinh vat kha dai. oi tng thnghiem thng tien hanh tren cac loai co c a, sinh ly gan giong nhcon ngi. Sau o, dung phng phap ngoai suy nhng ket qua tm ce ap dung cho con ngi. Tuy nhien, cac nha sinh thai moi trng hoccung th nghiem mot vai trng hp tren con ngi nh vi trung sot ret,mot vai loai ky sinh trung... e tm ra thuoc cha tr.Muc tieu cua oc hoc moi trng la phat hien cac tac chat (hoa hoc,vat ly, sinh hoc) co nguy c gay oc e co the d oan, anh gia cac s cova co bien phap ngan nga nhng tac hai oi vi cac quan the t nhien (baogom ca con ngi) trong he sinh thai. Cac th nghiem vat ly, hoa hoc, sinhhoc cung vi th nghiem oc chat moi trng a c phoi hp thc hien ed toan cac anh hng xau cua oc chat co the xay ra trong moi trng. e hieu ro hn ve nganh khoa hoc mi me nay, chung ta can namvng cac khai niem, moi quan he gia cac thanh phan trong he sinh thaiva nhng ieu kien e ac tnh hoa hoc cua mot chat tr thanh oc tnhoi vi sinh vat va con ngi.1.2. MOT SO KHAI NIEM C BAN (xem them phan Glossary cuoi sach tr 546-570) oc hoc moi trng (environmental toxicology) va oc hoc sinhthai (ecotoxicology) la hai khai niem gan giong nhau. o la mon hocnghien cu cac oc tnh cua cac tac nhan gay oc nh mot oc to, oc chatt chat gay o nhiem trong qua trnh o nhiem moi trng. oi tng gayoc lai chnh la tren con ngi va sinh vat va he sinh thai.Tac nhan gay oc (toxic factor) la bat ky mot chat nao gay nennhng hieu ng xau cho sc khoe hoac gay chet. Hau het cac chat euco oc tnh tiem tang, ch co o ln cua lieu lng (hay nong o) hiendien cua chat o trong moi trng mi quyet nh no co gay oc haykhong (Paracelsus, 1538).7 6. Lieu lng oc (dose) la mot n v bieu hien o ln s xuat hiencac tac nhan hoa hoc, vat ly hay sinh hoc. Lieu lng co the c dien taqua n v khoi lng hay the tch tren mot trong lng c the (mg, g,ml/kg trong lng c the) hay n v khoi lng hay the tch tren mot nv dien tch be mat c the (mg, g, ml/m2 be mat c the). Nong o trongkhong kh co the c the hien qua n v khoi lng hay the tch trenphan trieu the tch khong kh (ppm) hay miligam, gam tren m3 khong kh.Nong o trong nc co the dien ta qua n v ppm hay ppb. o oc cap tnh la o oc tnh thng c xac nh bang nong ocua mot hoa chat, mot tac nhan gay oc tac ong len mot nhom sinh vatth nghiem trong thi gian ngo oc ngan, trong ieu kien co kiem soat.e anh gia oc tnh cap va ngng oc, ngi ta dung cac ai lng saue anh gia:LD50 (median lethal dose): lieu lng gay chet 50% ong vat thnghiem, n v mg/kg ong vat song tren can. LC50 (median lethal concentration): nong o gay chet 50% ongvat th nghiem, n v mg/l dung dch hoa chat; thng dung e anh giaoc tnh cua chat oc dang long hoa tan trong nc song, suoi hay nongo hi hoac bui trong moi trng khong kh o nhiem co the gay chet 50%so ong vat th nghiem. To chc Y te the gii (WHO) a da vao gia tr LD50 e phan loaioc tnh cua oc chat. Gia tr LD50 cua mot chat cang nho, oc tnh cuachat o cang cao. Co nhieu qui c phan loai cac chat oc da vao LD50 cua chungnh sau:Nhom I :rat oc, LD50 < 100 mg/kg.Nhom II : oc cao, LD50 = 100 - 300 mg/kg.Nhom III :oc va, LD50 = 300 - 1000 mg/kg.Nhom IV : oc t, LD50 > 1000 mg/kg.Trong moi trng nc, oc tnh cua hoa chat oi vi thuy sinhc anh gia bi LC50. Gia tr nay cang thap, oc tnh cang cao.Neu giai oan cuoi th nghiem khong gay chet ong vat thnghiem ma cac nong o (lieu lng) th nghiem dan en cac tac ong8 7. khac nhau oi vi 50% vat th nghiem th goi la lieu anh hng 50% ED50(median effective dose) hay nong o anh hng 50% EC50 (Rand vaPetrocelli, 1985). Gia tr EC50 hay LD50 thng c thc hien trong vong 24 en 96gi va c th nghiem tren mot loai chat nhat nh. V du nh thnghiem tren nguon nc ao ho, thuoc bao ve thc vat, mot loai chat ienhnh trong nc thai cong nghiep... e xac nh nong o va ngng antoan. Thi gian cung thng c ghi cung vi lieu lng gay chet: LD5048 h hay EC50 24 h. Mot phng phap nghien cu khac la o thi gian can thiet e xacnh 50% sinh vat th nghiem co phan ng ac biet (v du nh chet).Phng phap nay oi hoi phai gi mc o cua cac tac ong chon loc luonkhong oi va theo doi trong thi gian th nghiem e xac nh thi iem50% vat th nghiem chet, hay 50% vat th nghiem song sot. Thi gian ogoi la median lethal time LT50 thi gian chet 50%.Do t vong la mot yeu to de xac nh trong cac phan hoi nen thnghiem o oc cap tnh thong thng nhat la th nghiem nong o gaychet cap tnh; trong o, 50% phan hoi la thong so ch ve ham lng octo c s dung va 96 h (hay t hn) la thi gian ngo oc tieu chuan (dono la thi gian can cho s ngo oc gay chet cap tnh). Thong so dung choo oc cap tnh thng c s dung nhat cho ca va cac ong vat khongxng ln la 96 h LC50. Tuy nhien, do t vong khong de xac nh cho cacsinh vat khong xng, mot thong so khac, EC50 (nong o anh hng trungbnh), thng c s dung hn la LC50. Anh hng c s dung e ctnh EC50 cho mot so ong vat khong xng song (chang han daphnia, autrung ruoi nhue) la s bat ong, c xac nh la khong di chuyen. Cactac ong thng c s dung e c tnh EC50 cho cua, tom bien, tomong la s bat ong va mat can bang, c xac nh la mat kha nang duytr t the bnh thng.oc to cap tnhe xac nh o oc cap tnh, mot phng phap th nghiem thongdung la xay dng mot th nghiem ma mot ket qua xac nh (ngha la, motphan hoi toan phan hay khong: chet hay khong) c suy luan ra. Moiquan he gia nong o chat th va phan tram ca the b ngo oc c xacnh va mot ng cong nong o gay chet se c xac lap. Ket qua cua 9 8. cac th nghiem ngan han cho thay (1) phan tram ca the sinh vat b giethay bat ong trong moi nong o th, va (2) LC50 hay EC50 c ghi nhant quan sat, tnh toan hay noi suy.Bang 1.1: LC50 cua mot so hoa chat oi vi ca tue Hoa chat LC50Triethylene glycol (TEG) 92,500mg/lDimethyl formanide (DMF) 10,410mg/lAcetone9,100mg/lDimethyl sulfoxide 33,500mg/l(Nguon: US EPA, 1979) o oc cap tnh tnh theo Micro (TM test) e xac nh o oc cap tnh, ngi ta con dung phng phap thgoi la TM test (Microtox Test) model 500 Analyser, Protocol for BasicText (Microbix, 1992). Nguyen ly phng phap th la kiem soat qua trnh trao oi chat cuavi sinh vat phat quang thi gian ngan 5 15 phut qua o, anh gia o occap tnh cua moi trng nc hay at, bun kh. Nhiet o c duy tr 15 27oC. Thiet b o la may Microtox model 500, o cng o phat quangcua vi sinh vat Vibrio fischeri NRRL B-11177, thuoc th MicrotoxReagent. May th c noi vi mot may tnh cai at san phan memMicrotox data collection and reduction software version 6.0 hoac phanmem Microtox OmiTM. Trong ieu kien moi trng cha co hoac t occhat, vi sinh vat phat quang manh do qua trnh ho hap te bao cua chung.Neu moi trng b nhiem oc, chat oc cang tang th lng phat quangcang giam. Ngi ta a ra mot ch so EC50 cng o phat sang cua visinh vat trong khoang thi gian 5 phut (hoac 15 phut) vi nhiet ot = 15 0,5oC. Tr so EC50 c oc qua may tnh. o oc cap tnh tnh theo loai giap xac CeriodaphniaTrong moi trng nc ngot co loai phieu sinh vat giap xacCeriodaphria, thng la thc an cho ca nho. Ngi ta s dung tnh nhaycam cua no vi nong o oc chat vi so lng ca the chet e xac nhmc o nhiem oc cua moi trng sau 24 gi, 48 gi.10 9. So lng ca the chet cua no cung c bieu dien qua EC50 24hEC50 48h hoac LC50 24h va n v tnh o oc ay la mg/l. n v oc chat (TU Toxicity Units): la ai lng thehien lng oc chat cua mau th vi sinh vat th nghiem. Mot nv tnh tng ng vi mau pha loang giet chet 50% so lng sinh vatth nghiem. 100(%) TU = EC 50 (50%) TU cang cao, EC50 cang thap th moi trng cang oc hai. Toc o phat thai oc chat (Toxicity Emission Rate) la lng occhat, oc to thai ra moi trng xung quanh trong thi gian mot ngay TER = TU/ngay = TU x Q (m3/ngay) He so phat thai oc chat (Toxicity Emission Factor TEF): lalng oc chat phat thai tnh tren mot tan chat thai ran cac bai rac thai. TEF = TU/tan rac ang phan huy =TERH (tan rac / ngay) o oc man tnh Mot cong cu quan trong e hieu ro va anh gia kha nang gay occua hoa chat oi vi sinh vat la o oc man tnh hay o oc toan vongi. o oc man tnh co the cho thay cac nong o cua hoa chat co theanh hng en qua trnh phat trien bnh thng va kha nang sinh san cuamot ca the sinh vat. Noi chung, nong o gay ra ngo oc man tnh thngthap hn nong o ngo oc cap tnh. Do o, o oc man tnh cung capnhieu so lieu nhay cam hn o oc cap tnh.Trong cac th nghiem e tm ra o oc man tnh, nong o ngnggay ra cac tac ong co hai ang ke thng c goi la nong o gay occc ai co the chap nhan c (MATC). MATC la mot nong o ly thuyetnam tren nong o cao nhat khong gay ra anh hng (NOEC) va nam dinong o gay oc thap nhat (LOEC), do o NOEC < MATC < LOEC.Trong viec thiet lap moi quan he gia o oc cap tnh va o ocman tnh, mot thong so a c a ra s dung, o la yeu to ap dung(AF), la mot thong so khong th nguyen, thuan tuy hoa hoc, c tnhbang nong o ngng cua o oc man tnh chia cho nong o gay oc captnh. Yeu to ap dung AF c xem nh la dai nong o. Chang han, neu11 10. 0,5 < MATC < 1,0mg/l va LC50 la 10 mg/l, va AF = MATC / LC50 0,5 5mg/kg co the ngan can hoat ongcua vi khuan mitrifying trong at (Thompson va Corke, 1969). Short cungong nghiep (1991), thc hien phan tch, nghien cu trong at vi chatchung la acid 2,4 diclorophenolxyaxetic (2,4 D) a rut ra ket luan quatrnh nay lam giam pseudomnas putida PP0301. Trong o, vi khuan lamgiam nong o cua 2,4 D t 500 mg/l en 100 mg/l. S dao ong nong o2,4 D t 10 en 25 mg/l co the lam ngan can s phat trien cua cac loainam noi chung.Nh vay, phuc hoi bang bien phap sinh hoc cho cac trng hp ato nhiem la can thiet va mang lai tnh hieu qua cho viec giam bt haychuyen hoa cac chat o nhiem hu c, tc la lam giam oc to cho moitrng at.2.3. CAC CHAT OC TRONG AT NGAP NC, YEM KH - TAC HAI CUA CHUNG, BIEN PHAP PHONG CHONG2.3.1. Cac oc chat trong at ngap nc2.3.1.1. Mot so chat ien hnhat ngap nc la mot moi trng yem kh, viec phan huy yem khcac chat t rac thai hu c, tan tch sinh vat, thong qua hoat ong vi sinhvat se lam sinh san mot so chat ma khi nong o vt qua mc o chophep se tr nen oc oi vi cac thuy sinh vat. Cac oc chat chnh cuaqua trnh phan huy yem kh chu yeu la cac chat: H2S, NH4+, P, S, kimloai nang. Cac oc chat nay t nhieu cung co cac tac ong tieu cc en isong cua sinh vat trong moi trng at ngap nc. Tuy nhien, vi kha nangthch ng cua mnh, cac sinh vat a co c che hoat ong thch hp e tontai va phat trien c trong moi trng nay. Trong ieu kien at ngap nchoan toan, th tnh trang yem kh luon tao nen cac qua trnh kh trong at48 48. va hnh thanh cac san pham: Fe2+, Mn2+ (kh Fe3+ thanh Fe2+, Mn4+ thanhMn2+), SO32-, (kh sulfate thanh sulfide) va NH4+ t NO3-. ong thi sinhra nhieu oc chat trong at nh CH4, H2S, FeS2 cung vi hang loat vi sinhvat, gay tac ong xau en moi trng.Theo Van Ranst (1991), phan ng kh manh co the xay ra trongnhng tram tch cha mot lng ln cac chat hu c va b tram langthng xuyen ma ta thng thay cac vung ngap nc ven bien. Neusan pham cua Fe3+ co mat trong vat lieu c chuyen en do song vamuoi SO42- co mat trong moi trng nh trong chat hu c hoac hoa tantrong nc ngam, chung se c s dung nh nhng chat oxy hoa bi heong vat at song trong cac tan d thc vat.Cac phan ng tao ra kh H2S dien ra trong at ngap nc:Na2SO4 + CH4 2Na+ + S2- + CO2 + 2H2OS2- + H2OHS + OH-HS + OH- H2S + OH- Phan ln cac phan ng trong ieu kien yem kh la nhng phan ngsinh hoa, co s tham gia cua cac vi sinh vat trong at. ong thi, cacphan ng nay cung la nhng phan ng oxy hoa - kh vi cac chat nhanva cho ien t. Phan ng tao ra Fe2+ va sulfide trong at c the hiendi dang phng trnh ien t rut gon nh sau:S2- + Fe2+FeS 2-2+2S+FeFeS2 + 2e-SO42- + 8H+ + 8e- S2- + 4H2OFe3++ e-Fe2+ Ngoai ra, trong ieu kien yem kh, san pham cua qua trnh co stap trung cua mot lng kha ln kh CO2, H2, CH4 va N2. Mot trong nhng qua trnh kha quan trong trong at ngap nc, mathong qua no nhieu oc chat c sinh ra trong at la qua trnh gley hoavi cac bc sau:1) S mat oxy do b ngap nc va lay i oxy do s ho hap cua vi sinh vat hieu kh.2) S kh nitrate do vi sinh vat s dung no nh nhng chat nhan ien t thay the cho oxy. Ket qua cua qua trnh nay sinh ra NO, N2O, va N2 trong at. 49 49. 3) S chuyen hoa goc methyl cua cac acid acetic va mot phan tgoc CO32- trong at. Nh a e cap ve s kh Fe3+ thanh Fe2+ cung vi s tham gia cuacac vi sinh vat ma ac trng la s ho hap cua vi sinh vat yem kh, cacchat hu c cao phan t bien oi va phan giai thanh cac acid hu c vasau o nh vi khuan bacteria methane e tr thanh CH4.Trong moi trng yem kh, cac chat co qua trnh bien oi khacnhau, tuy thuoc vao san pham cua qua trnh bien oi ma chung co thec coi la chat oc hoac khong oc. Dien bien oc chat cua mot chatchnh trong moi trng at ngap nc c trnh bay nh sau: + Nitrogen: trong at, nitrate thng b thay the bi cac amonium,du s hap thu cua thc vat lai dang nitrate. Tuy nhien, s thay oi naytrong cac can ay cho thay chung co kha nang duy tr ty le nitrogen mc bnh thng. Kha nang nay lien quan en ba qua trnh chnh: - Kha nang oxy hoa amonium thanh nitrate trong bo re thong quaviec lay oxy t cac long hut.- Mot so loai ac biet co kha nang hap thu amonium mot cach trc tiep. - Kha nang hap thu cua cac loai thc vat e duy tr hoat ong traooi chat hap thu, chat dinh dng.Nh vay, hoat ong yem kh a lam thay oi qua trnh bien oiam cua moi trng at. Tuy nhien, anh hng oc en hoat ong cuasinh vat la khong cao. + Sat va mangan: Nhu cau ve Fe va Mn cua cay trong ch mc ratthap. V vay, chung co the se at en mc o oc hai rat nhieu moitrng khac nhau. Hai nguyen to nay eu b bien oi va tr nen giau hntrong at ngap nc. Ham lng cua sat va mangan tham gia vao cachoat ong trao oi cation va tch tu lai trong cac mo cua thc vat. Thcvat ngap nc chu ng c hai nguyen to nay ch la nh vao mot sothch nghi rieng: Th nhat la kha nang oxy hoa cua bo re co the co nhva bien oi chung xuong en mot nong o thch hp. Th hai, nhieu chatkhoang tham vao ben trong cac mo co the c tch tu lai trong cackhoang bao cua te bao, trong cac khoang bao cua cac mam choi. o,chung khong tac ong en s trao oi chat cua te bao chat. Th ba, nhieuloai thc vat ngap nc xuat hien mot c che co the s dung mot ham50 50. lng hai nguyen to nay (Fe, Mn) cao hn mc thch ng trao oi chattrung bnh. + Lu huynh: lu huynh xuat hien di dang sulfide th rat oc oivi cac mo thc vat. Lu huynh b bien oi thanh dang sulfide trong quatrnh phan huy yem kh trong at va tch luy en nong o gay oc trongam lay ngap man. S thch ng vi nong o sulfur cao cua thc vat ngapnc co bien o thay oi rong. Cac loai thc vat khac nhau th co kha nangchu oc khac nhau. o la nhng c che thch nghi vi viec oxy hoa sulfidethanh sulfate, tch tu sulfate trong cac khoang bao. ac iem nay chung tathay moi trng at ngap nc cua rng ngap man ven bien.2.3.1.2. Tac hai cua cac oc chat Cac chat c sinh ra trong ieu kien yem kh c xem nh nhngoc chat co kha nang gay hai cho sinh vat. V du: lng Fe2+ va H2S trongat cao se lam bam vao re lua, lam rung long hut, re en, cha nhieu FeS,roi thoi dan co khi ca cay lua b chet. Mat khac, H2S cung gay tac hai lammot so nhom thc vat b ngo oc, cay phat trien kem va chet.Qua trnh gley hoa a lam cho moi trng at b chua hoa do quatrnh kh sinh ra mot so acid hu c, hoac mat am do N2 bay hi, H2Slam ngo oc re thc vat, gay chet cho ong vat va mot so vi sinh vat hieukh trong moi trng at. Cac kh CH4, NO2, NO va CO2 con gop phangay ra 15% hieu ng nha knh.2.3.1.3. Bien phap phong chong e han che hien tng ngo oc cho cac sinh vat tren vung at ngapnc, yem kh, bien phap hu hieu nhat la lam cho at c luan phien thoangkh. S oxy hoa trong at xay ra lam cho nong o cac chat oc c giamxuong di ngng gay oc cho sinh vat (ngoai tr at phen tiem tang).2.4. CAC CHAT OC TRONG AT PHEN - DIEN BIEN CUACHUNG TRONG IEU KIEN SINH THAI MOI TRNG - CACBIEN PHAP KHAC PHUC2.4.1. Cac oc chat trong at phen (bao gom ca at phen hoat ong va at b o nhiem phen)Cac oc chat trong at phen bao gom cac ion chu yeu sau: Al3+,Fe2+, Fe3+, SO42- , Cl-, H+. ac biet, at phen hoat ong, moi trng at51 51. co pH thap (nhieu ni pH nho hn 3,5, o pH nay cac ion noi tren trnen di ong vi nong o kha cao). - oc chat nhom (Al3+): Al3+ la nguyen to kim loai pho bien nhattrong vo trai at, ac biet la trong at phen, la cation trao oi chnh cuaat phen. oc chat nhom ton tai trong moi trng khi dang hoa tr +3(Al3+), gia tr pH < 4,5 th Al3+ co kha nang hoa tan rat cao. Al3+ cotng quan chat vi pH, ham lng Al3+ co the tang len 10 lan tng ngvi o pH giam xuong 1 n v. Cac th nghiem cua Le Huy Ba (1982)chng to quan he gia Al3+ va pH co dang hypebon vi ng tiem candi co pH = 2,35.Qua trnh hydrolysic cua ion nay tao ra moi trng acid kha manh.V vay, nhieu thanh phan trong at phen thng b kiem soat bi ac tnhhoa hoc cua Al (Frink,1971):Al3+ + H2OAlOH2+ +H+Trong moi trng at co pH < 5, phan ln Al eu hien dien danghoa tan co the gay ngo oc cho thc vat va mot so loai thuy sinh. Trongphan ng di ay cho thay Al c hnh thanh t dang ion sang dangcation hydrate:Al3+.6H2O Al(OH)3 +3H+ + 3H2ONguon cung cap nhom chu yeu t cac khoang set alumin- silicate.Trong moi trng at phen, co cha nong o H+ kha cao; chnh ion nayse tan cong vao cac khoang set e giai phong Al3+.Vao mua kho trong at phen hoat ong xuat hien nhieu muoialuminium sulfate tren cac mat ruong. Nhng khi pH trong at gia tangth Al xuat hien dang Al(OH)3. - oc chat sat (Fe2+, Fe3+) Trong at thoang kh, sat ton tai chu yeu dang Fe3+. S bien oitrang thai t Fe2+ sang Fe3+ phu thuoc vao ieu kien oxy hoa kh cuaat. Tuy nhien, Fe2+ de hoa tan trong nc co tnh chua. Trong ieu kienco oxy, Fe2+ de dang b oxy hoa thanh Fe3+ co mau vang nau o, Fe3+ coo hoa tan thap nen t gay oc hoa hoc nhng Fe3+ co the bam vao re caylam cho kha nang trao oi chat cua cay b han che (Le Huy Ba, 1982). Cahai dang Fe3+, Fe2+ eu c xem nh nhng oc chat trong at phen.52 52. Trong ieu kien thoang kh hoac khi tiep xuc vi oxy th Fe2+ rat deb oxy hoa tao thanh Fe3+, ngay ca ben trong at ang b ngap (VanBreemen, 1976):Fe2++ 3H2O Fe(OH)3 + 3H+ + e-Phan ln Fe ton tai dang co nh ferric hydroxide, ngoai tr khi pH< 3 (Van Ranst, 1971).Theo Le Huy Ba (1982), quan he gia nong o Fe2+ trong dungdch vi pH moi trng cung co dang hypebon vi ng tiem can dico pH = 2,95.Fe3+ .6H2O Fe(OH)3 + 3H++3H2O Nong o Fe3+ hoa tan trong at cao se gay han che cho s trao oichat cua thc vat do chung bam quanh re va than thc vat.Mot ieu can noi them la, qua trnh bien oi oc chat Fe2+ Fe3+ luon luon co s tham gia cua he vi sinh vat sat, v du ThiobacilusFeroxidance. Tuy nhien vi sinh vat nay co gay oc cho moi trng athay khong th en gi ngi ta van cha biet.oc chat SO42- ton tai trong at phen vi mot lng ln t 0,1 -5,0% (nhng ch chiem 0 - 5% tro thc vat). Lu huynh la chat dinhdng cho cay nong o thap nhng neu nong o cua no vt qua giihan se gay ngo oc cho cay bi s ngng tu cao cua muoi co hai cho isong thc vat. Mat khac, SO4 2- con co ac iem la ra troi rat cham,ngha la kha nang tch luy trong at rat lau.oc chat Cl co trong at phen hien tai di 1%, nhng oi vi atphen man va phen tiem tang th co the ham lng rat cao. Tuy nhien,no la nhng ion hoa tr mot nen o di ong cua no rat ln va de ra troi. oc chat H+ khong ch trong moi trng at phen ma bat c moitrng at nao cung vay, H+ c xem la tac nhan chnh lam pH trong at haxuong thap khi nong o H+ tang cao. at phen co bieu hien nay ro nhat: Motmoi trng co pH thap se dan en lam gia tang cac chat oc nh Al3+ vaFe2+ . ay la nguyen nhan c ban lam o oc moi trng tang.2.4.2. Dien bien cua cac oc chatTrong at phen ngap nc, cac qua trnh kh thng xay ra lamgia tang nong o CO2, HCO3-, Fe2+. Phan ng ien hnh dien ta s kh53 53. hoa cua Fe cung vi s tham gia cua chat hu c trong at phen ngapnc la: Fe(OH)3 + 2H+ + 1/4CH2O Fe2+ + 11/4H2O + 1/4CO2S gia tang nong o Fe va CO2 lam giam i mot t o chua cua at. Mot qua trnh quan trong khac la s oxy hoa khoang pyrite (FeS2)tao thanh khoang jarosite (KFe3(SO4)2(OH)6); sau o khoang nay thuyphan tao ra geothite (FeO.OH) va hematic (Fe2O3): FeS2 + 15/4O2 + 5/2H2O+1/3 K+ 1/3KFe3(SO4)2(OH)6 +4/3SO42-+3H+KFe3(SO4)2(OH)6 3FeO.OH + K+ + 3H+ + 2SO42-2FeO.OH Fe2O3 + H2O Nh vay, nh qua trnh nay ma ham lng H+ tang len rat cao lamcho moi trng at tr nen chua, mot so oc chat khac tr nen hoa tanhoac tan nhieu hn trong dung dch at, gay hai cho sinh vat. Rieng Alc giai phong ra t cac khoang cha cac lp aluminium silicate. Trongieu kien moi trng at chua, mc o khoang hoa cac khoang set naytang them. Theo Dent (1980), trong ieu kien at phen hoat ong ngoaiong co o pH = 3,2 3,8, qua trnh hydrolysis de dang thc hien viecgiai phong Al3+ tham gia trong cac phan ng tao phen hoa khac.2.4.3. Anh hng cua cac oc chat Al3+, Fe2+ va Fe3+ trong at phen oi vi sinh vata) Anh hng cua Al3+, Fe2+ oi vi tom Anh hng cua oc chat Al3+, Fe2+ oi vi tom c nghien cuqua ieu tra hien tng tom chet da tren c s phan tch cac yeu to sinhthai moi trng. Trong o, tac nhan gay chet tom c xac nh ro rangnhat la ham lng cua cac oc chat Fe2+, Al3+ thay oi theo mua va theos phan bo cua cac ao tom.+ Bien oi cua Fe2+ trong nc Fe2+ la yeu to thng xuyen gay oc hai cho tom khi nong o cao(gii han cho phep la di 500 ppm). Qua trnh oxy hoa Fe2+ thanh Fe3+lam tieu hao nhieu oxy hoa tan trong nc va tao thanh cac r sat bamvao mang tom can tr qua trnh ho hap, lam cho tom chet.54 54. Ham lng sat Fe2+ giam trong mua ma so vi mua kho do co spha loang cua nc ma. S ra troi sat t b bao co the xay ra ngay khima, nhng chung se trung hoa vi cac thanh phan trong nc ao tom,tao ket tua trong ao tom. Trong giai oan nay, qua trnh oxy hoa Fe2+thanh Fe3+ chiem u the. Khi nc trieu ang len, lng Fe2+ cao hn luctrieu xuong; chng to rang lng sat Fe2+ trong nc ao tom chu yeu lanc trieu mang en. + Bien oi cua Al3+ trong nc ao tom: Al3+ hoa tan khong xuathien trong mot moi trng co o pH trung tnh ma ch ton tai khi pH cuamoi trng ieu kien acid.+ Bien oi cua Fe2+ trong bun, at: oi vi Fe2+ th nong o t790 ppm tr len co anh hng en s ra troi phen vao ao tom, gay ngooc cho tom do cac r sat bam vao mang tom.Bang 2.1: Nong o cua Al3+, Fe2+ gay chet tom trong bun, at TayNgoc HienAo tom Bunat ao tom 2+ 3+ Fe (ppm)Al(ppm)Fe2+ (ppm)D2 2743 696,9790D3 388272 1390,5D5 287637,8-D6 232218,9 2119,5 D18 206175,5-(D3: la ao tom nuoi co hieu qua; D2: ao tom nuoi kem hieu qua). (Nguon: Le Huy Ba, 2000).Tom co kha nang chu nong o Fe2+ co trong bun 3882 ppm. Quao cho thay, mac du lng Fe2+ trong bun va trong at cao nhng cha cokha nang gay oc cho tom.+ Bien oi cua Al3+ trong bun, at ao tomNong o cua Al3+ trong cac ao tom nghien cu ch thay oi t 18,9 -75,5 ppm. Ket qua tren cho thay nong o nay, Al3+ cha gay oc chotom. Nhng khi ham lng Al3+ tang len en 669,6 ppm trong bun ao thgay chet tom hang loat. 55 55. Nh vay, lng sat Fe2+ trong nc thng thap hn trong at,bun ao tom va thng khong gay anh hng oi vi tom. Rieng Al3+trong bun nong o t 20 100 ppm khong gay anh hng cho tomnhng nong o 669,6 ppm trong bun th gay chet cho tom. Trong qua trnh nghien cu Tra Vinh, Ca Mau, Le Huy Ba vacong s a rut ra nhan xet: oc chat Al3+ , Fe2+ tren cac b bao quanhruong vung phen la rat nguy hiem. Khi co cac tran ma, nhat la maau mua, Al3+ va Fe2+ cung SO2 se chay vao ao tom, lam tang ot ngot4PH, nong o oc cua chung gay cho tom chet v soc. Cai kho phat hienla sau khi trieu len no a lam PH tang, xoa het tat ca dau tch cua vungo oc nay.b) Anh hng cua oc chat nhom (Al3+) va sat (Fe2+) trong atlen s sinh trng cua cay lua Al3+ co the gay oc ngay ca nong o thap 1 - 2 ppm (D. Dent-1986; Le Huy Ba, 982) quan sat va phan tch tren at phen a chobiet: tren ruong khi at kho co mot lp muoi Al2(SO4)3 noi len thanhtng am co mau trang, nhe va xop; khi t th lay nhay, trong o cocha 4,26% Al3+ va 38,4% SO42-; muoi nay tan ra en au th ca, tom,cay co chet en o. Ngo oc Al3+ co cac trieu chng khong phai lucnao cung de dang nhan ra c. oi vi cay lua th trieu chng thehien ngay re (re b d dang, chun lai va de gay, mac du mau sac rekhong en nh ngo oc sat). Neu ngo oc nhom cao th re lua ngan,rung het long hut va chet.Nghien cu cua Le Huy Ba chng to, nong o 135 ppm trongdung dch dinh dng IRRI va 500 ppm thc a, Al3+ a gay occho cay lua. Ngoai ra, khi ton tai ong thi ca Al3+, Fe2+ th oc tnhcua at cung tang len nhieu so vi bnh thng. Trong at phen, Fe2+, Fe3+ ket hp vi S2- tao thanh hp chatFeS gan chat vao cac re lua lam can tr qua trnh hut dngchat trong at cung nh lam anh hng en qua trnh ho hap, lam relua b chet.+ Anh hng cua Al3+ len cay lua non Al3+ la mot oc chat nguy hiem trong giai oan ba la that. TheoLe Huy Ba (1982), nong o Al3+ = 135 ppm trong dung dch dinh56 56. dng konsac a bat au co anh hng, nhat la vi giong chu ockem, va 150 ppm th co dau hieu chet va en 600 ppm th chetnhieu. 1.000 ppm trong 20 ngay th cay lua chet mem nh b luocnc soi. Mot ieu ang lu y la re b ngo oc mac du long hut brung i nhieu, re b teo top nhng mau sac van trang.+ Anh hng cua Fe2+ len cay lua non nong o Fe2+ = 150 ppm a bat au anh hng va 600 ppmth gay chet cho giong lua non kem chu oc; tuy nhien, bieu hien reen va ty le chet cao. Giong chu oc gioi th mc o chu ng caohn nhng neu Fe2+ 1.000 ppm th bieu hien chet ca hai giong luarat nhanh. Khi cay lua b ngo oc, Fe se anh hng en re (so longhut b giam). Khac vi ngo oc Al la, khi b ngo oc sat, re khongtrang ma tr thanh en, do ket qua cua H2S a tac dung vi Fe taothanh FeS, bam vao lp ngoai cua re lua. Ti ay, mac du nong oFe2+ a giam nhng van gay tr ngai cho cac qua trnh trao oi chatcua long hut va re lua. Hn the na, tren chop re thng b vet i motmanh, con la th co nhieu om giong nh benh tiem la (Le HuyBa,1982).+ So sanh anh hng cua oc chat Al3+ va Fe2+ nong o Fe2+ = 600 ppm, Al3+ = 135 ppm cay lua b ton hai.Mat khac, khi nong o tong hp Fe2+ = 600 ppm + Al3+ = 135 ppm thtac hai cua chung lai tr nen ln gap nhieu lan so vi tng oc chatrieng re. ieu o c the hien ro tat ca cac ch tieu va lan lt it giong kem chu oc en giong chu oc trung bnh roi en giongchu oc kha (Le Huy Ba,1982).2.4.4. Anh hng cua oc chat len he enzym trong cay lua va vai tro khang oc cua enzym va cua phot phoXin lc trch gii thieu cong trnh nghien cu cua Le Huy Bacung cong tac vien (nam 1982, 1984, 1985, 1986, 1990) sau ay:a) Anh hng cua nong o oc trong moi trng at phen en hoat tnh cua enzym catalase trong cay ch th va cay lua Ket qua hnh 2.1 ghi nhan rang, hoat tnh cua enzym nay phuthuoc trc het vao thi ky sinh trng. Chung co xu hng giam dan ca at khong phen lan at phen, sau o mi en anh hng cua57 57. oc chat moi trng at. Mat khac ta thay, trong moi trng at phen,hoat tnh enzym catalase luon luon thap hn tren at phu sa khongphen (so lieu trung bnh cua 8 giong); nhan xet nay mc o tin cayvi t = 4,936 so vi t0,99 = 2,977. Anh hng nay co y ngha ro hn khita so sanh gia giong chu phen gioi nh giong Ca ung (giong aphng) va giong kem chu phen nh IR38 (Hnh 2.1), cung vi o tincay 95%. Trong khi tren moi trng at phu sa, hoat tnh enzym catalasetrong cay giong IR38 luon cao hn giong Ca ung, th tren at phenlai ngc lai: khi nong o oc len cao (ngay th 35 va 102 ) hoat tnhgiam (oc chat trong at tang cao Al3+ = 800 900 ppm, SO4-2 = 0,3 -0,35%, pHH2O = 3,5 - 3,6) (hnh 2.2). catalase trong cay (E/p) Hoat tnh Cac giong lua trenmoi trng at khongoc chat 3 2,5Cac giong lua tren 2moi trng at oc 1,5phen 1 0,5 0 Ngay sau khi gieo2035 77102115 Hnh 2.1: Anh hng cua oc chat trong at len hoat tnh enzym catalase,so sanh gia at khong co oc chat va at co oc chat.58 58. Hoat tnh catalase trong cay(E/p)32,521,510,50Ngay sau khi gieo 20 35 77 102115IR38, tren moi trng at khong oc chat IR38, tren moi trng at co oc chat phenCa ung, moi trng at khong oc chatCa ung, moi trng at co oc chatHnh 2.2: Anh hng cua oc chat trong moi trng at len hoat tnh cua enzym catalase trong cay lua va cay co nang. b) Anh hng cua oc chat trong moi trng at phen len hoat tnhenzym peroxydase trong la cay ch th va cay lua - Anh hng len hoat tnh enzym peroxydase trong la cay ch th vacay lua. Vai tro cua peroxydase trong la cay Khong giong nh catalase, khi oc chat trong moi trng at phen tangcao ( cac thi ky 21, ngay th 60 sau khi gieo), hoat tnh cua enzymperoxydase trong la lua lai tang cao (hnh 2. 3). Qui luat nay c khang nhvi o tin cay cao t = 3,400 > t0,99 = 2,977. Ket qua nghien cu a chng to rang hoat tnh cua enzymperoxydase trong la phu thuoc vao thi ky sinh trng cua lua: cao giaioan gia (60 70 ngay). Mat khac, no con phu thuoc vao ac tnh cayva giong: cay ch th co nang (Eleocharis Dulcis) va giong chu phen caung luon co hoat tnh cao hn va the hien ro hn tnh chong lai oc to sovi giong kem chu phen IR38.So vi hoat tnh trong at phu sa khong phen, khi oc chat tang caogiong ca ung co hoat tnh nay tang + 280% (so vi oi chng), congiong IR38 ch tang +247% (so vi oi chng). 59 59. (E/p)a) Cay ch th nang ngot (eleocharis) (Dulcis)4+1,3253,125 +1,1803 2,6482,648 2,548 1,862 1,1 1,10,810 Ngay sau Ghi chu:66 87 gieoMoitrngb) Cay lua chu phen ca ungatkhong1.51,8 1,498 1,232oc2 0,4841,141,2 0,788chat10,7690,5210 Ngay sau 36 6687gieoc) Cay lua kem chu phen IR38 Moi trng1,301 1,2341,5 at co0,853 0,53 oc 1 0,328 0,8240,7070,706 chat0.50Ngay sau gieo oc chat trong MT at CaoThap Cao Thap Al3+ (ppm) 805465 850 475 Fe2+ (ppm) 898609 908 621 SO42- (%)0.32 0.130.350.15 Hnh 2.3: Anh hng cua oc chat trong moi trng at len hoat tnh enzym peroxydase trong la cay ch th va giong lua.60 60. 10a) Cay ch th nang 8,197,745 87,1426,238 6 2,93 4 211,148 1,749 21,14 0 Ngay sau gieoMT at 66 87khongb) Cay lua chu phenco occhat (at9phu sa) 8 7 6 6,063 5 4,459 44 3,705 32,449 2Ngay sau gieo 111,168 0MT atco oc 21 366687chat(atphen) c) Cay lua chu phen kem 1413,071 12 106,35987,3425,8826 4,1125,244 3,283 2,7762Ngay sau gieo021366687oc chat trong MT at CaoThapCaoThapAl3+ (ppm) 805465850475Fe2+ (ppm) 898609908621SO42- (%)0,32 0,13 0,35 0,15Hnh 2.4: Anh hng cua oc chat trong moi trng at len hoat tnh peroxydase trong re lua va cay ch th. 61 61. ieu nay a c so lieu cua Eleocharisdulcis - thc vat ch th cho atphen, bo sung va khang nh vi o tin cay tuyet oi (99%). ieu o lam taphai anh gia cao, ung vai tro cua peroxydase vi tnh khang oc phen. Anh hng cua oc chat trong moi trng at phen len enzymperoxydase trong re thc vat Ngc lai vi trng hp cua la, enzym peroxydase trong re luasong tren at phen b c che rat manh cua oc chat trong moi trng at(Hnh 2.4). Ngha la, khi oc chat trong at len cao th hoat tnh enzymnay trong re cua cay lua kem chu phen va chu phen, ke ca trong re conang eu giam so vi oi chng (at phu sa khong phen). Mat khac, hoattnh enzym trong re lua cung ong mot vai tro nho: giai phong nanglng, cung cap cho cay lua, thi ky phuc hoi, sau khi b ngo oc. Vdu: ngay th 87 khi oc chat giam, hoat tnh enzym nay tang 63% vigiong ca ung va 40,1% vi giong IR38. Gii han vai tro peroxydase trong la en anh hng cua oc chatmoi trngNh vay, theo ket qua tren th enzym peroxydase trong la ong motvai tro xuc tien cay co nang va cay lua chong lai oc chat xam nhap vao.Tuy vay, vai tro nay ch xuat hien trong mot gii han nhat nh cua mco oc chat trong moi trng at va ac tnh cua giong cay lua khacnhau (bang 2.2).Bang 2.2: Gii han tac dung khang oc cua enzym peroxydase trong la lua va conang oi vi oc chat trong moi trng, ngay th 25 sau khi trong.(n v hoat tnh enzym: E/p) Nong o tong hp cua oc chat trong moi trng Loai thc vat (ppm)Cac variant Al3+ Fe2+SO42- Cay ch th-coCay lua chuCay lua chu nang chu phenphen kha-phen kem-GionggioiGiong ca ungIR38 1 100 5135 4 1000 181,65 0,071,26 0,07 1,10 0,08 2450 12 467 18 1500 472,47 0,081,38 0,04 1,15 0,06 3750 16 676 24 2108 863,28 0,101,62 0,05 1,25 0,05 4890 24 842 32 2606 583,30 0,041,92 0,10 0,62 0,0462 62. 5950 31907 44 3209 48 3,85 0,141,64 0,060,13 0,00 61085 525 1050 583693 92 1,67 0,12 0,10 0,00,00 0,00 7Moi trng at khong oc chat (oi chng)1,51 0,041,45 0,031,00 0,05(t0,95 = 2,447) So lieu bang 2.2 chng to, hoat tnh cua enzym nay co y ngha tronggii han cac oc chat trong moi trng at: - oi vi cay ch th co nang co the chu c lng oc chat trongmoi trng at mc cao nhat vi: Al3+ 950 31 ppm + Fe2+ 907 44 ppm + SO42- 3209 48 ppm - oi vi giong ca ung, chu phen gioi th mc: Al3+ 890 ppm + Fe2+ 842ppm + SO2- 0,26% - oi vi giong chu phen kem nh IR38 th ch mc: Al3+ 750 ppm + Fe2+ 676ppm + SO2- 0,28% c) Tng quan gia oc chat cung P2O5 trong moi trng at vihoat tnh enzym peroxydase trong cay.Anh hng cua oc chat len hoat tnh enzym nay va s tac ong qualai gia chung mot phan c phan anh thong qua he so tng quan (R).Bang 2.3: He so tng quan (R) gia nong o cac oc chat P2O5 trongmoi trng at va hoat tnh enzym peroxydase (M) trong cay.Tng quan M - SO42-M - Fe2+M - Al3+M - P2O5 gia Trong cayLa ReLaReLaReLaRe Ch th +0,7204 -0,2015 +0,6344-0,2104 +0,8432 -0,3215 -0,3467+0,5241(nang ngot)Lua, Ca ung +0,6843 -0,2254 +0,6278-0,2447 +0,8023 -0,3254 -0,3670+0,4632 Lua, IR38+0,3452 -0,4568 +0,4312-0,5649 +0,6174 -0,8592 -0,2891+0,3434 - Ghi chu: M la hoat tnh cua enzym peroxydase R0,95 = 0,754 Trong hang loat he so tng quan ke tren, ang chu y la: s tngquan thuan gia hoat tnh enzym nay trong la cay ch th (co nang) viR = +0,8432. ong thi, ta cung tm thay tng quan thuan gia hoat tnh 63 63. men nay trong la cua giong chu phen ca ung vi nong o oc chat Al3+trong moi trng at, vi R = +0,802. Mat khac, can lu y rang, tngquan nghch gia hoat tnh enzym nay trong cay lua kem chu phen(IR38) vi ham lng Al3+ trong moi trng at vi R = -0,859.o la ac tnh cua cay chu phen khac vi cay kem chu phen. d) Anh hng oc chat trong moi trng at phen len hoat tnhenzym phosphatase trong cay ch th va cay lua- Anh hng en hoat tnh phosphatase trong la cay ch th va cay luaoc chat trong moi trng at phen khong nhng han che hoat tnhcua enzym catalaza, peroxydase trong re ma con han che len hoat tnhcua enzym phophatase trong la cay ch th va cay lua. ieu nay c thehien khi oc chat hai lan tang cao, hoat tnh enzym nay giam xuong mc -21,2% va -53,6% vi giong ca ung; -40,7% va -69,6% vi giongIR38, con vi cay ch th (co nang) th co giam nhng ch giam mc -45% va -18%.Mot ieu cung ly thu khong kem g s phat hien vai tro cuaperoxydase trong la, ay, hoat tnh enzym phosphatase nay ong motvai tro quan trong giup cay lua phuc hoi sau thi gian b ngo oc. ieu khang nh la quy luat nay phu thuoc vao ac tnh loai vagiong. Chung tr nen co y ngha trong trng hp cua cay ch th vagiong chu phen ca ung. V du, ngay th 87 khi oc chat trong at tcao giam xuong thap, hoat tnh nay trong cay ch th co nang tang 59,9%va ac biet trong cay chu phen Ca ung tang 643%, con giong chu phenkem cung tang nhng thap hn, ch mc +314% so vi oi chng. Motac iem khac can lu y la, hoat tnh nay cung phu thuoc vao thi giansinh trng cua lua: giai oan sau cao hn giai oan trc. Anh hng en phosphatase trong re cayKhac vi trong la, enzym phosphatase trong re cay co hoat tnh ratyeu (bang 2.4). So sanh gia hai giong lua thay rang, hoat tnh men naytrong re cay ch th (co nang) la cay hoang dai thch nghi, chu oc a cohoat tnh ln hn re cay lua chu phen (Ca ung). Re cay lua chu phenlai co hoat tnh ln hn cay lua kem chu phen (IR38). ieu nay c bieu hien bat ang thc:64 64. M>M > MChu phen gioiChu phen khaChu phen kem(co nang) (ca ung) (IR38) (M: hoat tnh cua phosphatase trong re cay).Bang 2.4: Anh hng cua oc chat trong moi trng at phen len hoattnh enzym phosphatase trong re cay ch th, cay lua chu phen va kemchu phen. Ngay oc chatat phen, co oc chatat khong co oc chatsau trong moi Cay ch th Giong lua Cay ch th Giong lua gieo trng atco nang (co nang) Ca ung IR38Ca ungIR38 21Cao1.29 1.29 0.96 0.14 3.502.21 36Thap0.42 0.34 small0.42 0.300.41 66Caot t tVet Vet Vet 87Thapt t tVet Vet Vet e) Tng quan gia oc chat va P2O5 vi phosphatase So lieu bang 2.5 cho thay rang, co s tng quan nghch va chatgia ham lng oc chat Al3+ trong at vi hoat tnh phosphatase trong lacay lua, ac biet oi vi giong chu phen kem IR38 (R = -0,7972). ieunay chng to, thc vat a huy ong phosphatase vao c the nang scsong cua cay. Mat khac, phosphatase cung co tng quan nghch va chatvi lng Al trong cay (R = -0,7149). ieu o chng to, co s tng tacnghch, phan lai nhau, c che nhau gia oc chat vi peroxydase vaphosphatase. ac biet ang chu y la tng quan thuan, chat gia hoattnh men nay vi s tch luy cua phot pho t do cua giong chu phen caung (R = +0,6441), vi o tin cay 99%.Bang 2.5: Tng quan (R) gia nong o oc chat trong moi trng at vahoat tnh (A) cua enzym phosphatase trong giong cay chu phen vakem chu phen. CayA va SO42-A va Fe2+A va Al3+ A va P2O5 Ca dung -0,3648-0,5601 -0,6462 ***+0,6441*** IR38 -0,5001-0,6239 -0,8972+0,4427Ghi chu: A: hoat tnh enzym phosphatase trong cay (R0,95 = 0,6320).***: o tin cay 94,9%.65 65. ieu o cho phep ta suy luan rang, phot pho va phosphatase co vaitro ln trong c che khang oc cua thc vat oi vi oc chat trong moitrng at. Nh vay, tren c s nhng ket qua cac th nghiem nghien cu t1997 en nay co the i en ket luan: 1/ Nong o cao cua oc chat trong moi trng at a c chemanh hoat tnh cua enzym catalase va phosphatase trong re, trong la caych th va nhat la oi vi cay lua, ac biet la cay lua kem chu phen.2/ Enzym phosphatase trong la co tac dung cung cap nang lngcho cay phuc hoi sau khi b ngo oc. Hoat tnh cua enzym nay tng quanty le nghch vi ham lng Al3+ trong at va Al3+ trong cay. ieu ochng to s oi khang gia cac enzym va oc chat bieu hien ro, nhat lavi oc chat Al3+.3/ oc chat cao trong moi trng at phen c che hoat tnhenzym peroxydase trong re lua. Trong ieu kien o, peroxydase trong reong mot vai tro nho giup cay lua phuc hoi. 4/ Chung toi a co u c s e khang nh rang, enzymperoxydase trong la ong mot vai tro quan trong, chong lai tac hai cuaoc chat. Khi oc chat trong at, trong cay tang cao th hoat tnh cuaenzym nay cung tang cao so vi oi chng.Cay chu phen co hoat tnh>M va A> M va Aenzym peroxydase (M), peroxydase (A) cao hn giongkem chu phen. M va ACay chu phen gioi Cay chu phen Cay chukhaphen kem M: hoat tnh enzym trong re cay A: hoat tnh enzym trong cay. Khi oc chat tang cao th peroxydase trong la cay chu phen tangcung cao (+ 280% so vi oi chng); con cay kem chu phen th khongtang (so vi oi chng).66 66. Khi oc chat giam, peroxydase trong cay chu phen cung cao hnkem chu phen (+ 643% vi cay lua chu phen so vi oi chng); congiong chu phen kem ch tang 314% (so vi oi chng). 2.4.5. Bien phap phong chong oi vi at phen, cac oc chat tch luy nhieu nen khong nhng noco the gay hai cho sinh vat song trong at ma con co the gay hai cho sinhvat song trong lp nc tiep xuc vi at, lp nc mat ay de tr thanhnc phen.e han che phat sinh phen, cung nh tac hai cac oc chat trong atphen, co the ap dung mot so bien phap nh sau:+ Gi nc mat ruong e ngan nga s oxy hoa cac vat lieu chakhoang pyrit trong at phen tiem tang.+ oi vi at phen hoat ong, can phai tieu ra oc chat ra ben ngoaibang cac nguon nc khac. Viec tieu ra oc chat ra ben ngoai cung can chuy bao ve, khong lam nhiem oc nhng vung ha lu.+ Trong canh tac cay trong cung nh viec nuoi trong thuy san,viec s dung voi e trung hoa cac acid trong at va lam co nh cacoc chat khac trong at to ra co hieu qua vi nhng vung at phennhe va phen trung bnh. Viec ket hp dung voi va tieu ra bang ncngot se ay nhanh qua trnh thieu ra oc chat trong at.+ Mot so ky thuat nh lam at, len liep e trong cac giong caychu phen cung c ap dung vung at phen ong Thap Mi, tgiac Long Xuyen.2.5. CAC CHAT OC TRONG AT MAN DIEN BIEN CAC BIEN PHAP BAO VE 2.5.1. Cac oc chat trong at man Trong at rng ngap man, ham lng muoi NaCl, Na2SO4,MgSO4, BaCl2 kha cao co the gay ngo oc cho cay trong va mot soloai ong vat khong chu c man. Hau het cac cay trong ch co thechu ng c nong o NaCl < 4%. Nguyen nhan chnh trong viecgay ngo oc la do nong o muoi trong dung dch at cao, gay ra trieuchng han sinh ly cho cay trong. Nong o muoi cao trong dung dch 67 67. at con lam pha v cac te bao re cua mot so loai cay do tnh thamthau manh t moi trng u trng sang moi trng nhc trng. Anh hng xau cua at man oi vi cay trong, trc het la do apsuat tham thau cao cua dung dch at. Ap suat nay tang theo ty lethuan vi nong o muoi tan. Khi ap suat tham thau cua dung dch att 10 12 atm, cay trong khong sinh trng va phat trien c. Khivt qua 40 atm, cay b chet. S co mat cua mot lng ln cac muoi tan trong at lam cho tnhchat vat ly hoa hoc, vi sinh vat cua at tr nen xau. Khi kho, at nt ne,cng nh a. Khi t, at rat dnh, deo, hat at trng manh, bt kn tat cacac khe h, lam cho at tr nen bao hoa nc va hoan toan khong thamnc. Cac thanh phan muoi la oc chat trong at lam cho at co o pHcao t 7,5 en 11-12, cay trong khong phat trien c. Cac ion thngxuat hien trong at man va man kiem la Cl-, SO42-, HCO3-, Na+, Mg2+.Cac anion oc hn rat nhieu so vi cac cation. Trong cac anion th Cl- ochn SO42-. Trong so cac chat oc khong the bo qua Bo. Neu at ch chamot loai muoi tan th se oc hn rat nhieu so vi at co cung tong lngmuoi tan nhng lai co nhieu thanh phan muoi hn. V du at di rngngap man co cung mot o man nhng cha nhieu loai muoi tan khacnhau se t oc hn la at ch mot loai muoi tan. Hien tng nay c giaithch bang s oi khang cua cac ion. Tac hai cua muoi cung con tuythuoc vao o chu man cua cay.2.5.2. Dien bien cua cac chat oc trong ieu kien sinh thai moi trng at man Lay at rng ngap man lam v du, cong trnh nghien cu cua LeHuy Ba va cong s cho thay: at rng ngap man cha nhieu muoi hoatan (1 - 1,5% hoac nhieu hn), ac biet la lp at mat. Nhng loai muoitan thng thay trong at man la NaCl, Na2SO4, CaCl2, CaSO4, MgCl2,NaHCO3 co nguon goc t cac thanh phan khoang b hoa tan, di chuyen,tap trung xuong vung a hnh trung, khong thoat nc. Sau o, trongieu kien kho hanh, muoi t trong mach nc ngam di chuyen va taptrung len mat at thanh mot lp vo muoi day t 0,1 - 1,0cm. S hnhthanh cac muoi trong at man la ket qua tong hp cua nhieu yeu to: atco cha muoi, a hnh trung khong thoat nc, mc nc ngam man nong, kh hau kho han, nang nong. Trong o, mc nc ngam man lai68 68. xuat hien gan mat at thng la nguyen nhan trc tiep lam cho at bman hoa. Gia o sau va o man cua nc ngam va o man cua at cotng quan chat che vi nhau. Polunop (1956), a a ra khai niem osau lam gii cua nc ngam xac nh moi tng quan gia o sau va oman cua at, nc ngam. o sau nay con phu thuoc vao o kho han,thanh phan c gii, o chat va o xop cua at.Ngoai yeu to man la ban chat cua at rng ngap man (RNM), sman hoa cung la nguyen nhan lam cho at b man them.a) Man hoa: la qua trnh xam nhiem va tch tu cua cac muoi va cackim loai kiem trong moi trng at, nc khi cac moi trng nay cha bman nay tr nen man hoac a b man t nay thanh man nhieu hn. Sman hoa la mot qua trnh do cac nguyen nhan: - Man hoa do them vao at mot lng muoi (gom cac muoi NaCl,Na2SO4, MgSO4, MgCl2, NaNO3, Mg(NO3)2, CaCl2, CaSO4). Trong oco muoi kim loai kiem va kiem tho, vi cac goc acid va se la nhnganion: Cl-, SO42-, NO3- , CO32- ma Cl- ong vai tro chu ao. - Man hoa do kiem (la cac kim loai kiem va kiem tho nh Na, K,Mg, Ca) tch luy vi ham lng cao trong at, nhat la Na. Anh hng cua man hoa len moi trng sinh thai atTrong hau het cac trng hp ma at hap thu ion Na eu c giaithch theo phan ng sau:Set-Ca +2Na+Set-Na2 + Ca2+Set-Mg +2Na+ Set-Na2 + Mg2+ Neu Ca2+ va Mg2+ c giai phong va ket tua dang muoi khonghoa tan th phng trnh tren nghieng ve ben phai va trong nhieu trnghp, phan ng nay gan nh dien ra hoan toan. Ket qua nghien cu cuaKelley Lumins (1921) cho thay, neu moi trng at tch luy nhieu muoiNa (bang 2.6), th ong thi mot lng ln Na+ c hap thu se co motlng Ca2+, Mg2+ c hap thu theo. Nhng ieu o t xay ra neu choNa2CO3 hap thu vao at. Khi co Na2CO3 th lng Na+ hap thu vao atlai cao hn so vi khi ch co mot mnh NaCl va mot t NaNO3. Cac muoicua Ca2+ va Mg2+ co goc chloride hay nitrate de hoa tan hn cac gockhac trc khi chung c thay the. Trong khi vi goc cacbonate, Mg2+ 69 69. va Ca2+ dang muoi nay hoa tan nhieu hn mot t. Khi o, mc o hoatan cua Na+ cua cac base trao oi trong at b anh hng lau dai bi cacloai muoi Na tch tu trong at. Noi chung, at man cha mot nong omuoi Na2CO3 (mot chat co oc tnh manh) cao th tng oi de hoa tanhn ch mot mnh muoi NaCl (at en man, theo Hilgard). Ngoai ra, Na+cung de hoa tan hn khi trao oi vi cac nguyen to khac trong at khongco Na2CO3.Bang 2.6: Anh hng cua cac loai muoi Na khac nhau len at Yolo(Kelley va Cummins,1921) Them 10 m.e. vi Cac base trong dung dch (m.e)Na+ c hap thu cac muoi (m.e.) Ca2+Mg2+ Na+ NaCl 2,21,0 7,62,4NaNO3 2,21,0 7,12,9Na2CO30,30,2 5,05,0 Anh hng cua ty le Na+ hoa tan en cac base hoa tan > Khi cac muoi cua Ca2+ hoac Ca2+ va Mg2+ hay Na+ tch tu trong atth s trao oi base cung dien ra khac han.Bang 2.7: Anh hng cua ty le gia Na:Ca.(Kelley, Brown va Liebig,1940) en kha nang hap phu Na+ Dung dch c s dungTy le Dung dch at phan ng (m.e./lit)Hap thu Na+ Na : Ca (m.e./lit) NaClCaCl2Ca++Mg++ Na+ 10,4 0 1:1 2,221,137,74 2,66 10,410,4 9,302,989,40 1,30 20,8 0 2:1 3,631,70 15,40 5,40 20,810,410,703,40 18,30 2,50 41,6 0 4:1 5,752,64 34,60 7,00 41,610,412,453,80 36,54 5,06 Anh hng cua muoi Na len CaCO3Cac phan ng hoa hoc, ngoai tr qua trnh trao oi base, cung dienra do ket qua cua qua trnh tch tu cac muoi hoa tan trong at man. Cac70 70. phan ng gia cac muoi cua Na va CaCO3 lai co tam quan trong hn,CaCO3 hoa tan trong muoi trung tnh nhieu hn la trong nc cat do anhhng cua mot phan ap lc cua CO2. CO2 co mat trong khong kh, rethc vat va vi sinh vat trong at thai CO2 trong qua trnh song va o amat luon cha CO2 hoa tan.Cac nha nghien cu a cho thay kha nang hoa tan cua CaCO3 khico mat cua muoi Na2SO4, NaCl se nhanh chong at bao hoa nhng laikhong cao lam. Cummins (1926) chng minh rang, kha nang hoa tancua CaCO3 trong cac muoi NaCl hay Na2SO4 yeu i neu them vao dungdch o mot muoi Ca hoa tan hay Na2CO3. Con Ca2+ c sinh ra nh strao oi cac base va co xu hng giam lng CaCO3 hoa tan khi maNa2CO3 la mot thanh phan cua cac muoi tch tu, lng CaCO3 hoa tanco the bien mat. Do o ma ieu nay gay ra tranh luan ve tac dung cuacac dang Na2CO3. Anh hng cua Na+ len vi sinh vatSinh vat at co the chu anh hng bi s tch tu muoi. Lipmen(1912) chng minh rang, them mot lng 0,20% NaCl hay Na2SO4 selam giam qua trnh amon hoa cua mao mach trong at cat. Neu hn 10%,th qua trnh amon hoa hau nh b c che hoan toan. Mat khac, khi themNa2CO3 vao se thuc ay qua trnh amon hoa len en nong o 0,1%.Greazes (1916), cung a ra ket qua tng t vi mot loai at Logan,Ultah. Ngc lai, cac nghien cu khac ve anh hng len qua trnh amonhoa (Lipmen, 1912b) cho thay, 0,10% NaCl va 0,20% Na2SO4 lam thucay qua trnh nitrate hoa, nhng Na2CO3 co tnh oc cao hn oi vi atngay ca vi nong o thap (0,05%).Lipmen va Sharp (1912) cho rang, NaCl nong o di 0,5% gayanh hng en qua trnh co nh am cua cac vi khuan not san, conNa2SO4 th the hien tnh oc nong o 1,20%. NaCl nong o 0,5%c ghi nhan la oc. Na2CO3 nong o 0,40% th qua trnh co nham c thuc ay nhanh hn mot t, nong o 0,50% Na2CO3 th s conh am that s c ay manh. Greaves va Lund (1921) cung Greaves(1912) thao luan ve anh hng cua cac cation va anion len hoat ong visinh trong at va trong moi lien quan vi ap lc tham thau cua dung dch.Cac muoi ban au trong at man nong o thap thng la khong oc.Thc te th qua trnh amon hoa va nitrate hoa co the b ong hoa. Nhng71 71. gii han oc co mot s tng quan mat thiet gia oc tnh va ap suattham thau. ap suat tham thau la 15 atm, qua trnh amon hoa giamxuong gan mot na so vi at khong man.b) Cac nguyen nhan cua qua trnh man hoaBay hi: Cac muoi hoa tan tch luy nhng ni ma qua trnh bayhi troi hn qua trnh ket tua. o la ni tap trung nc t ni khac o veva nc boc hi t long at len, hay qua trnh nc ngam man i len bemat at bang mao dan ket hp vi cac muoi tan tren mat at. Nc ti man: khi s dung nc man e ti, cac ion Ca2+, Mg2+ bgi lai trong at dang ket tua CO32-, con Na+ th b gi lai dang dungdch hay dang hap phu.2.5.3. Tng tac gia at man va s phat trien cua cay trong+ Thc vat ch th Thc vat t nhien ch th cho at man cung de nhan biet. Mac du comot vai loai, qua quan sat cho thay, co the song c tren at man lanat khong man, mot so loai co kha nang chu man rat cao; tuy nhien, aso thc vat lai khong thch hp vi at man. S phan bo va phat trien cua cac loai thc vat a man chu tacong cua kh hau va ieu kien at ai. California, loai chu man tot lafrankenia grandi folia (campestris), c thay rat nhieu tren loai at manen cua thung lung Joaquin. Trong khi o, cay go dau th dng nhkhong co mat tai thung lung nay ma lai thay rat nhieu va phat trien manhliet tren at man en pha tay Great Basin cua vung nui Sierra(Desgmond, 1967) co o cao khoang 200-300m va co mua ong quanhnam, nhiet o thap hn nhiet o ong bang rat nhieu. Thc te la cac loaithc vat tren at man tiep tuc gia tang sinh khoi trong khi cac loai thcvat tren at khong man th lai b mat sinh khoi vao luc thi tiet nong bc. Viet Nam, thc vat chong chu man gioi nhat la cac loai cay rng ngapman nh mam, ban, c, vet, su, gia, cha la, oro, coc ken mai dam vacuoi cung la da nc va mot so loai co nc man... Wadleigh (1984)cho rang, s mat sinh khoi trong ieu kien kh hau nong la do s ngng tuqua mc, neu ieu nay ung th khuynh hng se la: muoi hoa tan giams ngng tu trong cac loai thc vat nay.72 72. Nh vay, ro rang la mot hay nhieu yeu to kh hau (nhiet o, anhsang, o am) eu co anh hng len sinh ly thc vat di tac ong cuamuoi. Theo Hilgard, phan ln thc vat chu man t nhien phat trien vachu han mot cach manh liet, nham km ham s van chuyen va giaiphong nc ra khoi c the cua chung.+ Tac ong cua muoi hoa tan - Ap suat tham thau: khi tang them mot lng muoi hoa tan vaodung dch lam tang ap suat tham thau cua no. Sinh trng cua thc vattren at man co the gap kho khan trong viec thoa man nhu cau ve nccua chung. Tnh chu han cua sinh vat chu man oi vi at man, quatrnh hap thu nc cua thc vat b km ham nong o 0,5% muoi hoa tanva khi nong o 3,0% muoi hoa tan th viec hap thu nc cua thc vatket thuc. Anh hng tham thau chu yeu co kha nang phan ng oi vi skm ham toc o tang trng cua thc vat tren vung at man. So sanhnong o tham thau cua muoi oi vi toc o tang trng cho thay, ap suatcua cay co tng quan gan vi ap suat tham thau cua dung dch at. NaCl, Na2SO4 cung cho cung mot ket qua, khi co s pha loangtuyet oi th hoat ong cua Na2SO4 se yeu hn so vi NaCl. Nh vay, nhucau ap suat tham thau cua Na2SO4 ln hn so vi NaCl. Trong dung dch,re thc vat cha nhieu nong o anion khac nhau oi vi Cl- va SO42-. Nhvay, ap suat tham thau cua thc vat rat quan trong trong at man. Bi vno lien quan en tnh chu oc man cua cay.- Tac ong cua chlorideCl- va co li va va co hai cho cay, tuy nhien, hai nhieu hn li.Khi Cl- nong o thap th nhieu loai cay an qua b giam nang suat.Do o, vai tro cua Cl- trong at man va nc ti la quan trong. nhieuvung khac nhau th Cl- tch luy trong nhieu loai thc vat khac nhau.Thng cac loai cam, quyt rat nhay cam vi Cl-. Theo Kelley va Thomas(1920), ch vai tram ppm Cl- trong at la co the gay ua sau o kho la cay cam, quyt. Chu trnh nay co the tiep dien trong nhieu nam ma khonglam cho cay chet. ay la hien tng chay la do chloride, ieu nay cchng minh khi la cay cam, quyt b chay do at tch tu nong o vtqua bnh thng.73 73. oi vi anh hng cua muoi NaCl, thng muoi nay gay ra benh cay ma khong co trieu chng ro rang lam cho toc o phat trien cua caykhong bnh thng.2.5.4. Bien phap cai tao at manAnh hng cua at man ban chat chnh la anh hng cua oc chattrong at e han che oc chat trong vung at b man, viec bao e, ngan mantran vao ong ruong, oi khi, co the la mot sai lam v chung ta lam mati sinh thai ac trng cua rng ngap man ven bien. Ben canh o, ta co the thc hien chng trnh cai tao at man thanhat trong trot tot cho nang suat cao khong kem cac loai at bnh thngkhac. Tuy theo ieu kien thuy van, thuy a chat, tuy theo o man vahoa, ly tnh cua tng loai cu the ma co the phan chia at man theo cacmc o cai tao nh sau: Thanh ong co chan nuoi gia suc bang cach gieo cac loai hatco chu man co gia tr lam thc an gia suc . Bang bien phap ky thuat canh tac: cay sau khong lat, xi atnhieu lan, cat t mao quan, lam cho muoi khong the boc len mat. Bang bien phap trong giong lua chu man hoac cay chu mangioi nh coi, lac, rng ngap man. Bang cach ap dung tong hp nhieu bien phap. ieu nay acbiet thch hp vi loai at man kho cai tao (at kiem man co o thamnc kem, mc nc ngam nong). Cac bien phap cai tao ket hp o la: + Bien phap thuy li: ra man, loai tr muoi tan trong at, ha ncngam va tieu nc ngam man.+ Bien phap nong ly: cay sau, a CaCO3 va CaSO4 cac lp at saulen tang tren mat, cay pha ay, lam ti xop tang B, san bang mat ruong. + Bien phap nong hoa: s hien dien cua ion Na+ trong dung dch atlam xau i tnh chat hoa hoc, ly hoc, sinh vat hoc cua at man va kiemman. Do o, e cai tao at theo hng co li cho s phat trien cua caytrong, bang cach loai bo Na+ trong dung dch at va trong phc he happhu, thay the Na+ bang Ca2+ la rat can thiet.74 74. + Bien phap sinh hoc: xac nh he thong cay trong co kha nang chuman khac nhau, phu hp vi tng giai oan cai tao at, xac nh he thongky thuat canh tac hp ly, am bao at khong b tai nhiem man. Cai tao at man bang dong ien: cho dong ien mot chieuvao trong at. Do hien tng ien phan, ngi ta thu c cac anion vacation cua muoi tan trong at anod va catod. Tuy nhien bien phap nayt ap dung v qua ton kem S dung at man nuoi tom ket hp trong lua theo ung kythuat. Noi dung bien phap nay la theo quan iem: khong phai at mannao cung xau. Ma vi mot o man thch hp (vung nc l) se co thenuoi tom su, cua ghe, ong vat than mem hai manh vo. Trong trng hpnay oc chat man ch gay hai cho sinh vat nc ngot, ngc lai rat thchhp cho sinh vat nc l.2.6. OC CHAT NGOAI LAI XAM NHIEM2.6.1. Nguon gocNhieu yeu to ngoai lai co the lam gia tang oc chat trong moitrng at. Nguyen nhan la:- Do tan tch thc vat: c the sinh vat, khi chet i nam trong moitrng at, se phan huy tao mun cho at. Neu ieu kien phan giai taomun t th kha nang chuyen hoa thanh mun t, ong thi cac vat lieu naychuyen hoa thanh nhng dang mun kho tieu va gay chua nhieu cho at. - Do chat thai ong vat cua cac loai gia suc, gia cam nh trau bo, ga,ln, la cac nguyen to vi lng rat can cho cay trong (N, P, K, Ca) nhng khinong o qua nhieu cung lai tr nen chat oc va gay oc cho cay trong. - Do cac hoat ong cua con ngi. Hoat ong cua con ngi canga dang th chat thai va o nhiem cang phc tap, cang nhieu. Trong cachoat ong cong nghiep, ngi ta a o vao long at nhieu chat thai congnghiep nh: Hg, Pb, Al, Fe chat thai t cac khu dan c (rac sinh hoat,nc thai phong xa) a gop phan lam tang lng oc chat trong at, suythoai moi trng at.V du: kh CO la san pham cua s ot chay khong hoan toan (80%la t ong c xe, cac lo gach ), khi tiep xuc vi moi trng at co thehoa tan vao khong kh at, lam hai en ong thc vat trong at. 75 75. Trong cac hoat ong nong nghiep cac chat thai nh phan bon, thuoctr sau, chat thai gia suc va tan tch rng, mot mat lam cho moi trngat ph nhieu; mat khac, lam cho moi trng at tr nen oc hai cho thcvat. V du, cac loai phan N, P, K vi ham lng qua nhieu se lam chaiat. ay la hien tng at trong khong con kha nang gi lai cac chatmun cho cay trong. Phan am la mot loai phan mang hieu qua ro ret nhatcho nang suat cay trong nhng cung la mot chat oc khi s dung qua lieu.Phan am ure cha nhieu NH4+, khi bon cho at kho no tr thanh NO3-,cay ch hap thu c 30%, phan con lai b ra troi theo nc; neu tch tulai trong nc ngam hn 10% se gay oc hai, nc b o nhiem, khongdung e uong c. Them vao o, qua trnh nitrate hoa tao ra dang acidHNO3, lam tang tnh chua cua at.Trong chien tranh ong Dng, quan oi My a rai mot lng lnchat oc hoa hoc xuong lanh tho Viet Nam, Lao, Campuchia. Hai loaichat oc chnh s dung trong cuoc chien tranh nay (xem them chngsau) bao gom: + Chat oc s dung trong chien tranh sinh thai la cac chat diet coc rai vi qui mo ln tren toan chien trng ong Dng vao thi kyt nam 1961-1971. Thc te viec s dung chat oc hoa hoc van tiep dienen nam 1975 qui mo nho hn. + Chat CS s dung lam mat kha nang chien au cua oi phngTrong giai oan t 1966-1970, chat oc mau da cam c s dung chnhla e thay the tat ca cac hoa chat khac a dung t trc. Chat nay la hon hpcua 2,4-D; 2, 4, 5-T va tap chat 2, 3, 7, 8 -TCDD goi tat la dioxin. Theo Arthur P. Westing, c tnh 44.300m3 chat da cam chakhoang 170kg dioxin c rai xuong lanh tho Viet Nam va mot phanlanh tho Lao, Campuchia, trong o khoang 43% la rai xuong vung rngnui va 44% xuong nhng vung at canh tac. Vi 170kg dioxin, theo tnh toan cua Westing th lng dioxin tonlu tai Viet Nam la: - 8 kg vao nam 1980 - 3 kg vao nam 1985 - 1 kg vao nam 199076 76. Chnh s ben vng cua cac chat oc hoa hoc (ac biet la dioxin) ae lai hau qua xau, lau dai oi vi con ngi va ong thc vat.2.6.2. S nhiem cac oc chat phong xa trong atNguon goc:- Trong thanh phan at co san chat phong xa- Chat thai t cac nha may cong nghiep- S co t cac nha may ien hat nhan- Th vu kh hat nhan.Plutonium (Pu), uranium (U), americium (Am), neptunium (Ap),curium (Cm) va cesium (Ce) la nhng nguyen to co trong cac chat thaiphong xa. Hat nhan cua cac chat phong xa co trong chat thai co o hoa tanthay oi rat ln. Hp chat uranium th hoan toan hoa tan trong thanhphan cua plutonium va americium. ieu nay lam cho con ng lantruyen cua cac chat phong xa t at vao nc de dang hn va gay hainghiem trong oi vi sc khoe cua sinh vat, nhat la con ngi va caytrong. Vi mot ac tnh bien oi trong viec hap thu cac chat phong xa tat, cay hap thu Pu thap nhat, trung bnh oi vi Am va Cm, nhng oivi Np th kha cao. Trai cay va qua, hat th hap thu cac chat nay t hn la.Ngoai ra, moi trng at co kha nang hap thu oi vi cac nguyen tophong xa. V du: Cs c at hap thu ln hn Sr. Cac thc vat bac thapnh nam, a y song tren moi trng at nhiem xa tch tu Cs trong c thechung; en lt ong vat va ngi an phai no se tch tu trong c the gayngo oc hoac ung th. Kha nang ton lu cua cac chat phong xa co thekeo dai en 50 nam hoac khong the khoi phuc tr lai moi trng attrong sach khi lng phong xa trong at qua cao.Cac chat phong xa C14 sinh ra t phan ng cua hp chat nit vi tacdung cua cac neutron len cac proton, t cac vu no bom H va vi tac dungbc xa cua vu tru. Chat nay xam nhap vao trong moi trng at tham chvao cac thc vat, ong vat trong cac chu trnh carbon. Ngoai ra, Radon cung la mot chat phong xa t nhien, co san trongcac lp at a nen. No co kha nang len loi qua cac khe h xam nhap vagay oc. Tuy nhien, mc o tac hai cua chung cha ln. ang ke hn,77 77. con co chat phong xa t nhien Sr90 xam nhap vao trong moi trng at;do kha nang hap phu ly hoc manh cua no ben ngoai hat at. Vu ngooc Cs noi tieng cua ngi Laponic (Thuy ien) a thay, Cs tch tutrong c the ngi cao gap 10 lan so vi ngi bnh thng, bi v ho aan phai tht tuan loc ma chung a an thc vat co nhiem Cs trong at).ac biet can chu y cac chat phong xa trong vu no hat nhan, ro r cua nhamay hat nhan, t cac trung tam nghien cu a gay hai moi trng at.Hau qua cua vu no nha may ien hat nhan Trecnobil cho en nay nongo phong xa trong at van cao gap 50 lan cho phep. Cac nghien cu ve cac vu no hat nhan Bac ban cau trong nhngnam qua cho biet no a at ti 1030 lan lng chat phong xa t nhien,gay o nhiem moi trng, trc het la o nhiem moi trng at.2.6.3. Nhiem dau trong atTac ong ve moi trng cua viec tham do khai thac va van chuyendau la mot trong nhng hau qua tat yeu cua s phat trien kinh te cua xahoi trong thi ai cong nghiep hoa. Dau tho lam o nhiem s song trentrai at, di nc, lan truyen dau tren mat nc va lam nhiem dau trongat, tat ca eu gay cac tac hai nghiem trong en moi trng.a) Ban chat cua viec o nhiem dau trong at O nhiem dau se lam giam hieu qua trang thai at, hai vi sinh vat,thc vat, ong vat trong at va tren at. Schwingdinger (1968) cho biet,ham lng dau vt qua 3% tr nen cc ky co hai en sinh vat at vaphat trien mua vu. Cac trng hp nhiem oc dau luon lam hai s phattrien cua mua mang.b) Cac tac ong cua oc chat kim loai nang t o nhiem dauJohn M. Stark, Edward, Fredennte (1984) nghien cu ve moi nguyhiem cua moi trng co s tap trung nhng oc chat kim loai nang (Ar,B, Cu, F, Mo, Se) nong o cao oi vi s phat trien cua cay tren lo thnghiem tan tch cua at b nhiem dau (sau khi chng cat, say dau theochu trnh sinh hoc). Moi nguy hai tao ra t qua trnh chuyen hoa dau languyen nhan gay ra s o nhiem trong at (Schmehl va McCashin, 1973;Reente et al, 1980). Nhng oc chat kim loai nang di chuyen ra khoi lpa va lam ban at s dung, ngan can s phat trien va sinh san cua cay.Qua trnh tham dang len theo mao dan, khuech tan dang hi dan en s78 78. phan bo lai cua muoi va nguyen to kim loai nang trong thanh phan phaudien cua at (Klem et al, 1981). Nhng cay phat trien tren nhng v tr codau chuyen hoa co the hap thu nhng nguyen to kim loai nang, hap phutren tan la va tra chung lai tren lp at mat khi chet i. S van chuyen cua cac kim loai nang len lp at mat bi thc vathien dien mot mc o ln theo cach hap thu xay ra cho tiep xuc cuaat va he re trong tang canh tac. Tuy nhien, mc o cao nhat cua s vanchuyen xuat hien vi tng quan thap la nhng thc vat phat trien trenchat nhiem dau, thng cha nong o cao cua Mo la nguyen nhan cuabenh molipden oi vi ong vat nhai lai (Kilkelly Lindsay, 1982,Schward et al, 1983). - Anh hng cua dau len s nay mam Dau tho lam cham va giam ty le nay mam. Mot so nghien cu Ano cho thay, trong trot tren at o nhiem dau ma khong bon them chatdinh dng a lam ty le nay mam thap nhat (37%) so vi cay trong trenat khong b o nhiem (70%) trong thi gian giong nhau. - Anh hng cua dau len s phat trien O nhiem dau co s tng quan chat che vi tat ca nhng thong sophat trien. S khac nhau ve ch tieu chieu cao cua cay gia nhng loaiat khong o nhiem va at o nhiem dau khong bo sung chat dinh dng,khac nhau t 24 - 41%. - Anh hng cua dau en sinh khoi Kiem tra ve tng quan ch ra rang, viec x ly o nhiem la quan trong.Thong ke mc o o nhiem quan he ngc lai vi sinh khoi kho. o la anhhng oc hai len qua trnh sinh trng bi tong hp cac nhan to: cac hoatchat oc hai lan tnh chat ly - hoa cua at va cac hp chat sinh hoc va cungvi cac oc chat kim loai nang khong can thiet cho s song cua cay. - Anh hng cua dau len van chuyen dinh dngX ly o nhiem dau a c trnh bay tng quan vi nong o chatdinh dng trong cay.Quan he gia x ly dau va thanh phan dinh dng la mot ch so canquan tam. Trong mot nghien cu, mac du at a c cai tao lai vi viecbon them dinh dng bo sung, tnh oc cua Mn trong at b nhiem dau79 79. van la nguyen nhan chnh lam giam mua vu. Hn the na, nhng thcvat phat trien tren nhng o at th nghiem co dau chuyen hoa thng conong o Mo u cao e la nguyen nhan cua benh molipden cua ong vatnhai lai ni b tray da.c) Tac ong cua dau trong at S tch ong cua nhng chat o nhiem dau trong at chu yeu kmham qua trnh van chuyen, bay hi va phan huy sinh hoc, qua trnh laiva lu chuyen c biet khi nhien lieu ong c b ro r t nhng thungcha va chay tran vao trong at. Tac ong cua trong lc keo cac chatlong theo chieu i xuong, ngc lai vi lc gi lai do lc hap phu phan tva lc lien ket trong thanh ong mao dan; nen, no hoac la se hap thu trenhat khoang hoac nam trong lo hong cau truc cua at. Dau la chat kho bphan huy bi cac vi sinh vat song trong at. Tuy nhien, at lai la moitrng khong the pha loang cac chat thai ma ngc lai cac chat nay tchluy lau dai trong at. Cho nen, dau co tac hai lau dai oi vi moi trngat. nhng khu at b nhiem dau, cac tinh the dau se che lap cac kheh va mao quan cua at, lam tac cac ng dan nc trong at dan ens can coi cua at trong khu vc. V nguyen nhan nay ma cac vi sinh vattrong at khong co kha nang ton tai va phat trien do dau ngan can khanang ho hap va pha huy nguon cung cap thc an cho cac vi sinh vat trongat. at b nhiem dau gay ra hien tng cay b heo va rung la, phat triencham va nghiem trong hn la dan en chet cay.d) Anh hng cua dau oi vi ong vat hoang da Cac ieu tra cua Hoi ong vat hoang da the gii (WAS) a cho bietrang: o nhiem oc hai t at b nhiem ban dau tac ong len cac loai ongvat hoang da a tr thanh van e bao ong trong nhng nam gan ay.- Anh hng oi vi chim Ngay nay, o nhiem dau trong at va tren at a tr nen pho bienkhap ni. ieu o gay hai cho hau het cac loai chim kiem an trong vung:vac, seu, vt tri, a ieu ac biet la nhng loai chim kiem an, sinh songbam vao at va bun.e) Bien phap khac phucKhac phuc o nhiem dau trong at co nhieu cach:80 80. - Cay xi len va x ly tang at o nhiem e no tiep xuc vikhong kh lam cho dau bay hi hay vi sinh vat phan huy.- X ly at bang hoa chat- Trong cay a dau, co kha nang chu c nong o dau (xemthem Sinh thai moi trng ng dung cua Le Huy Ba, NXBKH&KT, 2000)- Th nghiem cac cach khac nhau, chon ra mot phng phapthch hp- Boc lp at b o nhiem dau (neu mong th a i x ly)- Tao cho at kha nang t lam sach, hoac bang tiep xuc khongkh hoac vi sinh vat, hoac bang ra troi, chuyen hoa t nhien.2.7. CAC CHAT OC SINH RA T QUA TRNH TCH LUY PHANBON VA THUOC BAO VE THC VAT Cac chat thai sinh ra t qua trnh s dung hoa chat trong nongnghiep nh phan bon, thuoc tr sau, thuoc diet co lam cho moi trng atb nhiem oc do s ton d cua chung trong at qua cao va tch luy trongcay trong. Tuy mot so loai thuoc diet co, tr sau benh hien ang c s dungco the b phan huy bi cac vi sinh vat nhng no cung co the bien thanhmot so san pham tr cuoi cung nh: DDT, lindane, andkin va diedrin.Nhng can ba hay chat d tha cua cac loai chat diet co, thuoc bao vethc vat thng ben vng hay tch luy vao cac cau t nh cac chatkhoang, chat hu c. Chung co the lam h hai ca rot, khoai tay, khoailang. Thuoc tr sau con gay oc cho con trung co li noi chung va keodai sau 5 nam dung thuoc tr sau e x ly sau hai.Thuoc BVTV, gom nhieu nhom khac nhau, nhng chu yeu la ba nhom: + Nhom hu c: ben vng trong moi trng t nhien va co thi gianban phan huy dai. V du: DDT co thi gian ban phan huy la 20 nam. Khii vao c the thc vat, chung c tch luy va t c ao thai ra ngoai.+ Nhom vo c (parathion, nalathion): co thi gian ban phan huynhanh hn so vi nhom tren, song thng co o oc cao hn oi vingi va ong vat. 81 81. + Nhom cacbamat (metylizoxinat hoac Mie CH3NCO): t ben vnghn trong moi trng t nhien, nhng cung co oc tnh cao oi vi ngiva ong vat.Khi s dung thuoc BVTV th mot phan se troi vao at va nc.Trong at, cac vi sinh vat co ch (phan huy chat thai, chat hu c, chuyenhoa nguyen to dinh dng) eu b hai v thuoc BVTV va lam giam oph nhieu cua at. Thuoc BVTV co thi gian phan huy dai nen dan dan se tch tu laitrong at mot lng ang ke gay hai en sinh vat theo con ng at -cay - ong vat - ngi.2.8. OC CHAT T MA ACIDMa acid la ma ma trong thanh phan cua no cha nhieu acid do shien dien cua cac chat gay o nhiem (SOx, NOx), trong khong kh cac chatnay se chuyen thanh H2SO4 hoac acid HNO3. Khi ma ri va tham vao at, no phan ng vi cac thanh phankhoang trong at, cac chat hu c va sinh thc vat, lam tang mc o acidcua at, lam cho cac ion, hp chat oc de dang c hnh thanh. Tacong trc tiep cua ma acid la cac acid trong ma se tac hai trc tiep caycoi, cong trnh nha ca.2.9. OC CHAT T CHAT THAI CONG NGHIEP Cac chat thai t cong nghiep hoa chat co the sinh ra nhng oc chatkhong phan huy trong moi trng at: Pb, Hg, nhng hp chat cua muoit acid arsenic ket hp vi nhau trong at tao thanh nhng chat can langben vng va tch luy trong moi trng. Chat thai co nguon goc t Al2O3(48 - 49%), Fe2O3 (20 - 21%), SiO2 (2 - 5%) co anh hng xau en moitrng at khu vc xung quanh, gay nen s thoai hoa cua at, giam nongo cac chat hu c, giam o ph nhieu cua at, lam anh hng xau enhe thc vat, giam nang suat cay trong.S nhiem cac oc chat ngoai lai khong nhng bi cac loai chat thaic thai trc tiep vao trong moi trng at ma con b o nhiem thong quadong nc, gio, ma mang cac chat thai i vao moi trng at. Kha nanglan truyen o nhiem theo dong nc thng tang gap nhieu lan so vinhng lan truyen khac.82 82. 2.10. CAC CHAT OC KIM LOAI NANG TRONG AT (xem them Chng 5) Kim loai nang (KLN) c quan tam nhieu cho chung c sdung rong rai trong mot so hoat ong cong nghiep tren hau het cac quocgia. Mat khac, chung co the c coi la nhng yeu to vi lng can thietcho cay trong va suc vat. Tuy nhien, chung cung c coi la chat oc chomoi trng sinh thai neu chung ton tai nong o vt qua mc nhu caus dung cua sinh vat. Hien nay, KLN trong at a c quan tam hn bis phat trien cua khoa hoc va van e o nhiem moi trng at a bat auc coi trong. - Cac nguyen to KLN c goi la vi lng khi nong o thap vava phai th no co tac dung kch thch s sinh trng va phat trien cuathc vat. Tuy nhien, mot khi no ton tai nong o thap hn "nhu cau sinhly" hoac cao hn "ngng chu oc" eu co anh hng len s sinh trngva phat trien cua cay. Le Huy Ba, Nguyen T, Le Tho, Nguyen Van e (2000) a nghiencu nong o cac KLN trong moi trng at va tac ong cua no en motso thc vat (cay lua, cay rau muong), ong vat (giun at, trai, tom cang)va s tch luy cac oc to kim loai Cu, Fe, Al, Mn, Cd, Zn, Hg t trongnc thai t o th ha lu song Sai Gon (Nha Be). Ket qua ghi nhannh sau: 2.10.1. O nhiem KLN trong bunBang 2.8: Nong o tong so KLN va s thay oi kim loai nang trong bunva trong at. Chat chiet rutHumic acid Fulvic acidV tro Cu Zn Fe Al o acidCu Zn FeAl Acid(mg/ (mg/ (mg/ (mg/(%)(mg/ (mg/ (mg/(mg/ (%) 100g) 100g) 100g) 100g) 100g) 100g) 100g) 100g) TramRO 0,026 1,06 2,35 2,35 3,49 0,186 5,29 1,91 3,1422,93tch MC0,015 0,06 0,97 0,97 Trace0,059 3,48 0,53 0,56 vetatRO 0,067 0,32 1,30 1,30 1,79 0,016 0,20 0,14 1,721,21 MC0,184 0,56 0,92 0,92 2,39 0,023 2,52 0,68 0,6011,10 Ghi chu: RO = Rach Ong ; MC = kenh Mng Chuoi 83 83. Bang 2.8 cho thay, mac du nong o cua tong cac KLN khong caonhng nong o cua cac KLN trao oi th lai cao. Ngha la, o nhiem KLNchu yeu gay ra bi s hap phu trao oi gia cation KLN va hp chat huc hay cac hydroxyt trong at.Tuy nhien, neu so sanh gia hai dang hap phu KLN trong acid munhumic va acid fulvic ta thay dung lng hap phu van con thap. ong thi,hap phu bi acid fulvic lai cao hn acid humic, ac biet la hap phu cuaacid fulvic vi Cu va Al. Ngc lai, acid humic lai hap phu Zn2+ trong atcao. ay co le la mot ac tnh cua KLN trong thanh phan moi trng.Nh vay, KLN ton tai trong moi trng at khong nhng dangphc hu c ma con dang hydroxyt va dang chat l lng.Bang 2.9: O nhiem KLN trong hai tang at vung ha lu song Sai Gon(Nha Be) NiMau OM Pb2+ (ppm) Mn2+ (ppm) Cd2+ (ppm) (%) ChietHoat TongChiet Hoat Tong Chiet HoatTongrut tnhcong ruttnhcong rut 2 tnh congacid2 acid2 acidLong Tang A 4,03 0,745,053,5 24,0 182,2 175,30,3 0,5 1,5 Thi Tang B 3,86 0,751,0 48,20,2RachTang A 4,00 1,348,059,0 24,2 88,665,7 0,1 0,5 1,0 a Tang B 3,62 1,032,5 23,40,0Ni Mau OM Cr (ppm) Cu (ppm) (%)Chiet rut Hoat TongChiet rutHoat Tongtnhcong tnhcong2 acid2 acid LongTang A4,03 0,4 12,5n107,0 3,0 33,058,5 Thi Tang B3,86 0,62,5 Rach Tang A4,00 0,515,599,55,5 28,060,5aTang B3,62 0,31,084 84. Ni MauOM (%)Zn (ppm) Ni (ppm)Chiet rut 2 Hoat tnh TongChiet rut 2 HoatTongacid congacidtnh cong LongTang A4,0317,1144,5369,5 3,1 9,5 42,0 Thi Tang B3,8616,6138,03,9RachTang A4,0023,4161,5383,0 4,512,5 34,0 a Tang B3,6210,574,0 1,9 Ghi chu: Long Thi: cach nguon o nhiem 25kmRach a: cach nguon o nhiem 34km Bang 2.9 cho thay, o nhiem KLN trong tang at A (0-5 cm) luonluon cao hn tang B (5 - 25 cm). ieu o co ngha la, o nhiem KLN tangtheo tng ngay qua cac nguon bo sung.Neu so sanh gia hai vung co khoang cach en nguon o nhiemkhac nhau, Rach a va Long Thi, co the ket luan rang, tch luy KLN hai ni co khac nhau phu thuoc ac tnh moi KLN khac nhau: co loai cokha nang i xa nguon o nhiem, co loai b tram lang gan nguon o nhiem. 2.10.2. S tch luy KLN trong atKet qua ve s tch luy cac oc chat KLN trong at khi so sanh trongcung thi gian hai tang at c the hien trong bang 2.10Bang 2.10: O nhiem KLN trong hai tang at va tch luy cua chung trong at.Ni MauPb (ppm)Mn (ppm)Cd (ppm)Hoat tnhChiet rut 2 acidChiet rut 2 acid LongTang A45,0 24,00,3 Thi Tang B51,0 48,20,2 RachTang A 48,0 24,20,1 aTang B 32,5 23,40,0 85 85. Ni Mau Cr (ppm)Cu (ppm) Chiet rut 2 acid Chiet rut 2 acid Long Tang A 0,43,0Thi Tang B 0,62,5 RachTang A 0,55,5a Tang B 0,31,0 Mau Zn (ppm)Ni (ppm) Chiet rut 2 acidChiet rut 2 acid Long Tang A17,1 3,1 ThiTang B16,6 3,9 RachTang A23,4 4,5 aTang B10,5 1,9Bang 2.10 cho thay, o nhiem KLN trong tang at mat luon cao hntang di hay o nhiem KLN tang theo tng ngay qua cac nguon bo sung.Nh vay, KLN ngay cang tch luy cao trong at vung ha lu ngoai thanh.2.10.3. Anh hng cua KLN tong hp trong at len sinh trng cua cay luaKet qua cua cac th nghiem trong nha knh chng minh rang, onhiem KLN trong at co anh hng rat ln len sinh trng cua cay luanon so vi trung bnh cua sau cong thc oi chng trong trong cat sach vangay ca trong tren at nguyen dang. Anh hng cua Pb2+ va Cd2+Trong th nghiem ve anh hng cua cac KLN trong dung dch lenlua non cho thay, vi hai KLN: Pb2+ va Cd2+, nong o khac nhau theu co anh hng khac nhau. Trc het, anh hng cua nong o Pb2+ va Cd2+ bieu hien qua sthay oi pH cua dung dch. Nong o Pb2+ va Cd2+ cang cao th pH cangcao. Mat khac, pH dung dch cung tang theo thi gian sau khi gieo. otang nay c ghi nhan mc o tin cay 99,9%.86 86. Khi nong o Pb > 0,5 ppm, anh hng len cay lua tang len tren50%. oi vi Cd, anh hng nay lai manh hn, ch can nong o Cd >0,25 ppm a anh hng len tren 60% cay lua. Ro rang, anh hng cua Cdlen cay lua manh hn anh hng cua Pb.Ty le chet cua cay lua tang khi nong o KLN tang.So sanh gia anh hng cua Pb2+ va Cd2+, ket qua cho thay cungmot nong o, Cd2+= Pb2+= 0,6 ppm, anh hng cua Cd2+ luon cao hnPb2+ nhieu lan va ngc lai. Cac bo phan khac nhau cua cay lua b nhnganh hng khac nhau cua oc chat KLN.- Trc het la canh, than, sau o la la lua va cuoi cung la re lua.Bang 2.11: Ty le % suy giam cua cac bo phan cay lua di anh hng cuaoc chat KLN Pb2+ va Cd2+ trong dung dch. Pb2+ Cd2+ NghiemNong o Than, LaReNghiem Nong o Than, LaRethc(ppm)canh thc (ppm)canh Pb40,6 30,2 27,1 4,10 Cd60,60028,1 31,0 8,60 Pb50,9 38,2 32,3 14,8 Cd20,11031,3 27,1 14,3 Pb61,1 34,1 39,0 22,0 Cd10,00834,4 28,0 22,6 Anh hng cua Hg2+ va As3+ len s sinh trng cua lua nona) Anh hng len sinh trng cua la that 1 va 2 theo thi gian Hg2+ nong o thap nhat (0,10 ppm) co tac dung kch thch s phattrien cua la that th nhat cua cay lua. Cac nong o cao hn cua Hg2+ vaAs3+ th nghiem eu khong co tac dung kch thch ma bieu hien c ches phat trien cua la that 1. Nong o cang cao th kha nang c che cangmanh, la khong phat trien chieu dai va sm b kho ot. Quan sat hientrang la that 1, nghiem thc co As3+ nhan thay, la co mau trang va xanhnhat trong suot qua trnh ton tai, la khong co kha nang tong hp diep lucto, khong co kha nang quang hp va sm b kho ot so vi nghiem thcoi chng. Co the ay la bieu hien anh hng trc tiep As3+ len s phattrien va qua trnh tong hp chlorophyl cua la lua. La that 2 cua cay lua trong trong moi trng co oc chat trong ncthai, xuat hien vao ngay th 10 va bat au kho ot la vao ngay th 20,thi gian ton tai ngan hn 3 ngay so vi nghiem thc oi chng. 87 87. Khong nh trng hp la that 1, Hg2+ tat ca cac nong o euanh hng len s phat trien cua la that 2. La that 2 ngan, xuat hien vaongay th 10 va kho ot vao ngay th 20. Mau sac cua la bien oi motcach ro ret, chuyen t mau xanh sang mau vang, xuat hien cac vet nho ot la. cac nghiem thc co As3+, th As3+ a anh hng manh len la that 2,ca ve thi gian xuat hien ton tai lan chieu dai la. Mac du co xuat hiennhng la that 2 cac nghiem thc nay nhng nhng la o khong co khanang phat trien, sm b kho ot, thi gian ton tai ch trong vong 7 ngay. Vemau sac, la that 2 cung nh la that 1, co mau trang va hi xanh nhat.b) Anh hng cua Hg2+, As3+ len s phat trien cua la that 3 Nh vay, mac du la that th 3 co xuat hien nghiem thc co As3+va Hg2+ nhng nhanh chong b kho ot la sau khi xuat hien 2 - 3 ngay.Hay noi cach khac, Hg2+ va As3+ a anh hng ro ret len la that th 3.c) Anh hng cua Hg2+ va As3+ len re lua+ Chieu dai re lua Kim loai nang trong nc thai co anh hng len chieu dai re lua:Chieu dai re lua ngan hn so vi oi chng. Sang tuan th 3, bo re comau vang en va tuan th 4 th re b thoi hoan toan. cac nghiem thcKLN, re ch dai ra tuan th nhat, sang hai tuan ke o (tuan th 2 va 3)th gan nh chieu dai cua re khong tang va bat au b thoi chop re vaogia tuan th 4.Quan sat thay hnh dang cua re cac nghiem thc co Hg2+ vao cuoituan th 1 nhan thay, re b vang, cng va thang; trong khi o, cacnghiem thc co As3+ th re b vang, cng va co lai.+ Anh hng len phat trien re lua Tuan th 1 va 2, s phat sinh re lua nghiem thc co nc thaidien ra bnh thng, s phat sinh cac lp re tng ng vi s phat sinh la.Qua tuan th 3, so re gan nh khong oi so vi tuan th 2, kha nang phattrien cua cay lua kem, cac la that khong xuat hien na - la that th 3xuat hien ngay th 15 va kho ot la vao ngay th 18. ay cung la lathat cuoi cung trong qua trnh th nghiem.88 88. Hg2+ tuan th 1, tat ca cac nong o co tac dung kch thch s ra recua cay lua, ieu nay tiep tuc the hien tuan th 2. Nhng sang tuan th3 th so re khong xuat hien na ma gan nh gi nguyen so vi tuan th 2.La lua cung khong xuat hien. ieu nay phu hp vi quy luat sinh hoc cuacay lua. As3+ khong nhng tac ong len chieu dai cua re ma con anh hngen s phat sinh re cua cay lua. Ngay tuan th nhat, oi vi cac nongo th nghiem th so re/cay eu thap hn so vi oi chng. Sang tuan leth 2, so re/cay chi bang 1/3 so vi oi chng ( o tin cay 95%) va conso nay hau nh khong oi tuan tiep theo cho en khi cay chet. So re t,chieu dai re ngan (co lai), bo re phat trien khong bnh thng la nguyennhan lam cho kha nang sinh trng cua cay lua trong moi trng dungdch co As3+ kem i. d) Anh hng cua Hg2+, As3+ len trong lng kho cua cay lua theothi gian sinh trng tuan th nhat, s phat trien cua cay lua trong trong moi trng conc thai dien ra tot, trong lng kho tng ng vi nghiem thc oichng. Nhng sang tuan th 2, mac du cay lua phat trien ve chieu caoln hn so vi oi chng nhng trong lng kho lai nho hn so vi caytrong trong moi trng nc thai co cac chat hu c, s hien dien cuaam amon (NH+4) lam cho cay lua phat trien la va chieu cao nhng tronglng khong tang. Tuan th 3, he re vang en va hien tng cay chetdien ra, cay lua khong tang trng va trong lng kho gan nh khong oiso vi tuan th 2. Cay lua song cam c them mot thi gian va chet hoantoan vao tuan th 4. Hg2+ khi nong o thap (0,10 ppm) kch thch s phat trien chieudai la, chieu cao cay va khong anh hng en trong lng kho cua caylua tuan th nhat va tuan th 2. Nhng cac nong o Hg2+ cao hn thanh hng ro ret en trong lng kho cua cay lua ngay tuan th 1. Tuanth 3 va tuan th 4, trong lng cay lua cac nong o nay gan nhkhong oi so vi tuan th 2. ieu nay cho thay cay lua co xu hng songcam c vi oc chat Hg2+ trong moi trng va khong tch luy chat kho.Trng hp cac nghiem thc co As3+, ngay nong o thap nhat (2,50ppm) a anh hng len s sinh trng cua cay lua. The hien cay luakhong tang trng chieu cao va trong lng kho nho hn so vi oi89 89. chng. ay, ta thay co s tng quan nghch gia nong o As3+ vi ssinh trng cua cay lua: khi nong o As3+ cang cao th trong lng khocua cay lua cang nho. Cung nh trng hp Hg2+, cay lua phat trien trongmoi trng co As3+ song cam c tuan th 2 va tuan th 3, sau o chetgan nh hoan toan tuan th 4 va khong tch luy chat kho.2.10.4. Ty le song sot cua cay lua theo thi gianKet qua khao sat ve s phat sinh re va chieu dai cua re cho thay,Hg2+ co tac dung kch thch s phat trien cua re cay lua hai tuan au tat ca cac nong o th nghiem. Nhng cay ch song toi a c 3 tuan tuoiNh vay, Hg2+ nong o thap (0,1 ppm) kch thch s phat trienchieu cao cay lua trong thi gian au (t 1-16 ngay); sau o cay lua bkho la, khong phat trien chieu cao va song cam c trong moi trng. cac nong o Hg2+ cao hn, c che chieu dai, chieu cao cua cay. enngay th 22, chieu cao cua cay dng lai va la kho dan, cay bat au chet.Vi As3+ tat ca cac nong o th nghiem eu gay anh hng enchieu cao cua cay lua: thap hn so vi oi chng va sau o dng lai ngay th 18 . Cay lua khong co kha nang phat trien ve chieu cao, cac laco mau trang va sm b kho ot. Co the ay la phng thc ma cay luachong chu vi oc to As3+ trong moi trng hoac co the As3+ a anhhng en s tong hp diep luc to cua la lam cho cay mat kha nangquang hp, khong phat trien bnh thng.2.10.5. Anh hng cua Pb2+, Cd2+ len s sinh trng cua cay rau muonga) Anh hng len sinh trng rau muong Moi trng nc thai khong anh hng len bo re, chieu cao than vatrong lng kho cua than rau muong. Ket qua nghien cu cua chung toi cho thay, cac nong o thnghiem 0,1 ppm KLN cha anh hng len trong lng kho than raumuong. Nong o Cd2+ = 5 ppm tac hai gay oc manh, cay rau muong brung la va chet nen trong lng kho nho nhat la tuan th 2 sau khi xly. Tac ong cua oc to Pb2+ khong dien ra ot ngot ma tang theo nongo, cay rau muong co tnh thch ng manh vi Pb2+ trong moi trng. Khinong o Pb2+ tang len, cay rau muong khong co bieu hien chet ma chvang la va khong phat trien tuan th 2.90 90. Sc chong chu cua cay rau muong vi oc tnh Cd2+ thap hn sovi Pb2+. Cay rau muong khong the song sot khi ti ngng gay oc cuaCd2+, hien tng chet cay dien ra ot ngot va trong lng kho giam han.b) Anh hng len ty le song sot cua cay rau muongCd2+ gay chet cay rau muong, vao tuan th 1 nong o 5 ppm.Tuan th 2, nong o 2,5 ppm cung a gay chet nhanh.c) Anh hng cua Cd2+, Hg2+ len chieu dai than cay rau muongTrong moi trng nc thai o th, khong kim loai nang cay raumuong phat trien chieu dai than bnh thng, khong co dau hieu nao cche s phat trien chieu dai than cua cay rau muong. Ngng oc Cd2+ the hien ngay tuan au, nong o th nghiemcao nhat (5 ppm), cay rau muong co ra la nhng la vang va rung nhanh,than b thoi va cay chet hoan toan vao ngay th 6. nong o 2,5 ppm,cay rau muong cung co la mau vang va chet vao ngay th 10. Tuy nhien,khi nong o thap (0,1 - 0,5 ppm) th Cd2+ lai kch thch cay rau muongphat trien ve chieu dai. Ngng gay oc cua Pb2+ oi vi cay rau muong cao hn so viCd2+: khi nong o Pb2+ la 7,5 ppm th cay co dau hieu chet. Nh vay, cayrau muong co kha nang thch nghi va chong chu cao trong moi trng onhiem Pb2+. Van e con lai cua viec trong va s dung cay rau muongphat trien tren vung b o nhiem kim loai nang la xac nh tnh chong chucua Pb2+ hay nong o kim loai nang nhng vung tren.d) Anh hng cua Pb2+ va Cd2+ len re rau muong Trong moi trng nc thai thanh pho khong kim loai nang chieudai re rau muong phat trien bnh thng. Kim loai nang Pb2+ va Cd2+ tacong len bo re cay rau muong tuan le th 2. Pb2+ cac nong o 5 ppm,7,5 ppm, 10 ppm lam cho re rau muong co mau en vao au tuan th 2va thoi dan vao nhng ngay ke tiep, bo re b thoi. Hien tng rung la vachet cay tiep tuc dien ra. Tng t Pb2+, Cd2+ cung gay ra hien tng en va thoi re raumuong tuan th 2 .2.10.6. Nhan xet chung - O nhiem KLN t nc thai thanh pho len moi trng at vung halu bao gom: Mn, Cu, Pb, Zn, Fe va Cd. Co s khac biet rat ro ve KLN 91 91. gia nc song Sai Gon va nc he thong kinh rach cung nh trong dungdch at vung ha lu Nha Be. - Con ng xam nhap va gay o nhiem cua KLN trong moi trngat khong ch la hap phu trao oi vi keo at ma chu yeu di dang lienket vi cac acid mun fulvic. - Nc thai Thanh pho Ho Ch Minh gay o nhiem KLN cho moitrng at vung ha lu, chu yeu la Zn, Cr va Cu va t nhat la Cd. Xet vetong lng theo th t: Zn (3575 ppm) > Mn (120 ppm) > Cr (100 ppm) >Cu (60 ppm) > Pb (555 ppm) > Ni (37 ppm) > Cd (1,3 ppm). - Ve o nhiem hu c, vung ha lu, N - NH4 b anh hng manhnhat: trieu len o nhiem cao nhat; ngc lai, N-NO3: chan trieu lai caonhat. Con N - NO2 khong b anh hng cua trieu cao hay thap.- Co s tch luy cua KLN trong c the giun at va tang cao khi onhiem tang. Nh vay, giun at co the s dung nh cong cu anh gia onhiem KLN.- ieu kien th nghiem, anh hng cua Pb2+(0,63 ppm - 0,75 ppm)va Cd2+ (0,32 - 0,43 ppm) tr nen ro rang tren cay lua thi iem 7 ngaysau khi gieo; sau 21 ngay th gay chet 100%.- Anh hng cua Cd len cay lua manh hn Pb. Ngng chu oc cua cay lua vi: Pb = 0,31 ppm, lua chet 50%; Pb = 0,44 ppm lua chet 100%; Cd = 0,121 ppm, lua chet 50%;Cd = 0,32 ppm lua chet 100%. * nong o thap nhat (0,01 ppm), Hg2+ con kch thch s phat trienla va chieu cao cua cay lua. Tuy nhien, qua tuan th 3 tat ca cacnghiem thc Hg2+ gay ngo oc cho cay lua va hien tng cay chet dienra. Hg2+ c che s ra la va phat trien cua la, lam thoi chop re, long hutrung sm. Ngng nong o Hg2+ gay chet lua la 0,1 ppm (khi trong trongdung dch). * Con As3+ khong kch thch s ra re cua lua. Mat khac, As lam chore co lai, khong hap thu c chat dinh dng, kha nang phat trien cuacay lua kem. La lua co mau trang hoac xanh nhat, hien tng nay xuathien trong thi gian ngan th cay lua b kho ot.92 92. - Anh hng cua Pb va Cd len s sinh trng cua cay rau muong:cay rau muong thch nghi cao vi moi trng co o nhiem Pb.* nong o Pb = 5,0 ppm trong moi trng dung dch lam cho rerau muong co mau en va thoi, sau o chet mot so cay sau khi trong cmot tuan. Qua tuan th 2, nhng cay khong chet, trong lng cua cayrau muong giam khi tang nong o Pb. Ket qua khao sat ty le song sot cua cay rau muong sau hai tuannuoi trong co the a ra ngng gay oc cua Pb oi vi cay rau muongtrong dung dch dinh dng co Pb2+ t 5,0 ppm tr len.* Cd2+ gay chet cay rau muong t nong o 2,5 ppm.2.10.7. Cac nguon chnh gay o nhiem kim loai trong at- Cong nghiep luyen kim, cong nghiep khai khoangChat thai (kh thai, bui) va nc thai cua cac cong nghe nay chanhieu KLN. Nc cuon chat o nhiem t cac bai khai thac cung la nguyennhan gay o nhiem at ve pha ha lu.Trong qua trnh khai thac se phat tan kim loai vao at, nc, khongkh. Qua trnh phat thai cac chat kh, bui cha cac kim loai di chuyentrong khong kh va sa lang xuong at, len than thc vat gay anh hngen at va he thc vat.- O nhiem do nc thai san xuat- O nhiem at do bai rac thai ien t- Chat thai ran cong nghiep t cac nha may san xuat pin (chanhieu Ni, Cd, Hg) va bnh acquy xe hi (nhieu Pb), cac lo ot rac congnghiep a lam tang ham lng mot so KLN oc hai trong at.- Chon lap rac thai sinh hoat gay nen tnh trang o nhiem KLN trong at- Bun lang trong cac nha may x ly nc thai thng cha nhieukim loai oc hai, khi chon lap se a ra mot lng KLN vao at.- Phan bon hu cCha nhieu trong phan heo, phan chim... trong o nhieu nhat la Cuva As. Phan bun cong thng c s dung trong nong nghiep co chacac KLN vi ham