9.humanities-speciation of some heavy metals in ngong river-david k. kariuki

8/10/2019 9.Humanities-Speciation of Some Heavy Metals in Ngong River-David K. Kariuki

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Speciation of Some Heavy Metals in Ngong River using the Joint Expert Speciation System (JESS) 59

S E!"#$"%N %& S%ME HE#' ME$# S "N N*%N* R"'ER +S"N* $HE J%"N$ E, ER$

S E!"#$"%N S S$EM (JESS)

-#M#R"S M.+" / 0 -+1E %2 %R#$# 30 *R#H#M E0 J#!1S%N 4 -#'"- 12 1#R"+1" 6

1,2,4Department of Chemistry, University of Nairobi, Kenya3Department of Chemistry, University of Cape Town, South Afri a

#.S$R#!$

N!on! "iver, a tributary of Nairobi "iver in the Capita# City of Nairobi in Kenya, was assesse$ for heavy meta#

an$ their spe ies usin! atomi absorption spe tros opy %AAS& an$ the 'oint ()pert Spe iation System %'(SS& a omputer

pro!ram for e*ui#ibrium a# u#ations+ Si) samp#in! points in the mi$$#e stream of N!on! "iver+

hysi o- hemi a# parameters were ana#yse$ insitu whi#e !rab samp#es were ana#yse$ for seven meta#s an$ their

spe ies were pre$i te$ usin! '(SS+The samp#es ha$ p. va#ues of about /+0, e) ept for samp#e no+3 whi h re or$e$ a p.

va#ue of +3+ f the seven ana#y e$ ions, the most abun$ant meta# was iron with an on entration of +0 m!56 whi#e some

of the meta#s were be#ow the $ete tion #imits in some samp#in! points+

The on entrations of the heavy meta#s were use$ to onstru t a spe iation pre$i tin! mo$e# of the N!on! river

usin! the '(SS+ Usin! this mo$e#, the ma7or spe ies in most of the samp#es were pre$i te$ to be 8Cr% .& 291: , 8;e% .& 291: ,

8t is a#so #ear that some ions were foun$ in #abi#e state for e)amp#e


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&igure /8 Section of Ngong River at Sampling oint No2 5

A or$in! to the B#oba# (nvironment Assessment "eport 819 in $eve#opin! ountries, untreate$ water is the most

ommon#y-en ountere$ hea#th threat an$ auses about 20,@@@ $eaths per $ay $ue to water-borne $iseases+ Nairobi resi$ents

have fe#t the impa t of the $e!eneration of the Nairobi "iver throu!h water borne $iseases su h a ho#era, an$

!enera# $e rease in the ity s so ia# an$ e onomi $e #ine+ Stu$ies by Kera?a an$ ami ha in 2@@3 in$i ate$ that in two

wee?s 12+EF of hi#$ren #ivin! in s#ums a$7a ent to the Nairobi "iver are prone to $iarrhoea, an$ 3+4F $eve#op $iarrhoea

with b#oo$ 829+ A morta#ity rate of +1F hi#$ren un$er five years has been reporte$ 839+ There, however, are other #ess

obvious effe ts of water po##ution su h as those ause$ by short or #on! term e)posure to to)i substan es+ These may

ause more harm as they are subt#e, the effe ts more #on! term an$ the ure more $iffi u#t to a$minister+ .eavy

meta#s are one su h possibi#ity+

=eta# ions are e)pe te$ to be in eff#uents from in$ustries $ue to their various uses in su h a tivities as stain#ess

stee# formu#ations 849, use in batteries 809, anti- orrosion a!ents 8 9, as o#orin! e#ements 8/9, ata#ysis 8 9, pipin!

an$ e#e tri a# app#i ations amon! others+

.eavy meta#s in e) ess are ?nown to be harmfu# in #ivin! systems, for e)amp#e hi!h #eve#s of heavy meta#s are

?nown to be to)i 8E9 an$ affe t systems in the bo$y 81@9+ They a#so ause ?i$ney prob#ems 811, 129, sei ures,

oma an$ $eath 8139, affe t repro$u tive an$ foeta# hea#th 8149, ause #earnin! $isabi#ities, wei!ht #oss, an$ !rowth an$

hearin! prob#ems 8109+

>t is a#so ?nown that some spe ifi ompoun$s of a parti u#ar substan e may be more to)i than others+

;or e)amp#e perman!anate e)hibits a hi!her to)i ity than the man!anese %>>& ompoun$s 81 9+ The free in ion in so#ution

is hi!h#y to)i to p#ants, invertebrates, an$ even vertebrate fish 81/, 1 9+ Triva#ent hromium %Cr 3: &, in tra e amounts,

is essentia# in humans, an$ its $efi ien y is suspe te$ to ause a $isease a##e$ hromium $efi ien y 81E9, whi#e,

he)ava#ent hromium %Cr%G>& or Cr : & is very to)i an$ muta!eni when inha#e$,82@9 an$ is to)i an$ may be ar ino!eni

$ue to its o)i$i in! potentia# an$ easy permeation of bio#o!i a# membranes+ 8219

Know#e$!e of the tota# on entration an$ spe iation of heavy meta# ions wou#$ be a$vanta!eous in estab#ishin!

the ris? fa tor pose$ by their presen e+ >t may a#so assist in i$entifi ation of point sour es an$ thus ontribute !reat#y to its

subse*uent minimi ation or e#imination of po##utants+ Thus, in a$$ition to monitorin! spe ifi heavy meta#s, their

spe iation stu$ies may be ne essary+ This is ma$e possib#e by omputationa# pro!rammes su h as the 'oint ()pertSpe iation System %'(SS&


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Speciation of Some Heavy Metals in Ngong River using the Joint Expert Speciation System (JESS) ?/

Computationa# metho$s have been uti#i e$ for e*ui#ibrium a# u#ations an$ the $etermination of e*ui#ibrium

onstants sin e the ear#y 1E @s 821, 229+ hereas other pro!rams #i?e SHC.(= 8239, D(ND"A6 8249, B( C.(=

820, 2 9, =>N(I6 82/9, ."((I( 82 9, (I35 82E9, (CC6(S 83@9 e)ist, users have en ountere$ $iffi u#ties su h as

te hni a# obsta #es in preparin! input $ata, as we## as $iffi u#ty in obtainin! re#iab#e thermo$ynami $ata+ or? on '(SS be!an in 1E 0 8319 an$ attempte$ to so#ve some of these $iffi u#ties primari#y by a umu#atin! riti a##y se#e te$ $ata into

a unifie$ primary sour e, fin$in! ways of estimatin! unmeasure$ e*ui#ibrium onstants an$ en oura!in! informe$

fee$ba ? %ma?in! the pro!ram amenab#e to han!e&, usin! a o##e tion of a number of omputer pro!rams rather than a

sin!#e one+ >n '(SS, a mo$e# is set up by fee$in! the ana#yti a# $ata into the $atabase to!ether with the re*uire$ on$itions

of on entration, temperature, pressure, ioni stren!th an$ p.+ Garious e*ui#ibrium a# u#ations ta?e p#a e before the fina#

output+

C#eanin! up the Nairobi "iver has be ome an ur!ent tas? an$ has been !iven $ue priority by the Bovernment of

Kenya+ UN( , Unite$ Nations .abitat %UN.abitat&, Unite$ Nations Deve#opment ro!arm %UND & in on7u tion with the

!overnment have a#rea$y !one throu!h three phases in Nairobi "iver #ean up, throu!h the Nairobi "iver Jasin ro!ram

%N"J &+ The Nationa# (nvironmeta# =ana!ement Authority %N(=A& have a#so attempte$ to ta ?#e the matter+ hereas

#eanin! up the river wou#$ $o the ity a #ot of !oo$, monitorin! of po##utants, thus ?now#e$!e a umu#ation of the nature

an$ on entrations of the po##utants as we## as settin! up systems to ontain the po##utants before they are $eposite$ into

the water system wou#$ so#ve this prob#em in the #on! term+

.eavy meta# ions have been ?nown to e)ist in N!on! "iver, but spe iation of the same has not been arrie$ out+

>n this stu$y, ana#ysis of some heavy meta#s at points a#on! the N!on! "iver have been performe$ usin! the Atomi

Absorption Spe trometry, an$ spe iation of the same assesse$ usin! the 'oint ()pert Spe iation System %'(SS&+

E, ER"MEN$# SE!$"%N

Si) samp#in! points, a#on! 1+ ?m of the N!on! "iver were i$entifie$ an$ mappe$+ This is se tion that runs

throu!h the ity s in$ustria# area+ Samp#in! oints one an$ two are #o ate$ 7ust before the river !ets to the in$ustria# area+

These may be sai$ to be the ontro# points before the river !ets po##ute$ by the in$ustria# waste+ Samp#e points number

three, four an$ five were in the mi$$#e se tion of the in$ustria# area, whi#e samp#in! point number si) is #o ate$ 7ust after

the in$ustria# area+ An overview of the points is as shown in the map %fi!ure 2& be#ow

&igure 38 Map of Nairo@i River .asin an Neigh@ouring rovinces


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Samp#in! was arrie$ out in the $ry months of the year si!nifyin! the $ry season+ ater samp#es were obtaine$ in

1- 6itre p#asti ontainers, previous#y rinse$ with $i#ute hy$ro h#ori a i$ %JD. hemi a#s&, thorou!h#y washe$ with

$eter!ent an$ eventua##y rinse$ with $isti##e$ water to minimise ontamination an$ ensure re#iabi#ity of $ata+ .eavy meta#s

were ana#yse$ usin! an atomi absorption spe trophotometer of the type Shima$ u AA- 3@@ at appropriate wave#en!ths+The samp#es were $i!este$ usin! the metho$ $es ribe$ e#sewhere 8329+

The '(SS mo$e# was reate$ usin! $ata obtaine$ from AAS to!ether with other measure$ parameters,

at a temperature of 20 oC an$ at the p. va#ues obtaine$ for the various water samp#es %tab#e 2&+ This were fe$ into the '(SS

%v /+3& pro!ram, simu#ations $one an$ the spe iation resu#ts obtaine$

RES+ $S #N- -"S!+SS"%NS

Tab#e 1 be#ow shows the $ata obtaine$ from AASL

$a@le /8 !oncentrations of Heavy Metals in Ngong River

Metal 7ho(MgB )!oncentration (MgB ) "n Sample oints

/ 3 4 6 5 ?Cr @+@0 ND ND @+@41 @+@20 ND @+0//;e M 1+012 @+E E @+/ @ 1+ 1E 4+@03 +00Et is worth notin! that the on entration of #ea$, iron an$ man!anese were foun$ to be hi!h in most of the

samp#in! points+ This is matter of !reat on ern for the peop#e #ivin! at the river ban?s, for e)amp#e the s#um, an$ may betempte$ to use the water for $omesti purposes+ The hi!h on entration of iron, hi!h#y o#ours the water an$ may stain

#aun$ry, orro$e pipes %$ue to rust& an$ ause turbi$ity in the waterL for in! the users to use a #ot of $eter!ent,

whi h is e)pensive to an a#rea$y e onomi a##y straine$ popu#a e+

RES+ $S &R%M JESS

The '(SS pro!ramme was ran on the heavy meta# on entrations usin! p. as orroborate$ by Korfa#i an$ 'ur$i

8319+ The heavy meta#s that were not $ete te$ %ND& were estimate$ to be 1+@ ) 1@ -/ m!5#+ The rationa#e bein! that, $ifferent

spe ies were observe$ a#on! the water ourse, hen e the heavy meta#s were present in very #ow on entrations+


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Speciation of Some Heavy Metals in Ngong River using the Joint Expert Speciation System (JESS) ?4

ea

&igure 38 Speciation of the ea in NgongC River

6ea$ on entrations in a## samp#in! points was foun$ to be onsi$erab#y hi!her than the . s re ommen$e$

@+@1 m!56 va#ue+ This imp##ie$ that the peop#e who use the water are pre$ispose$ to #ea$ poisonin!+ "esear h shows that

e)posure of hi#$ren to hi!h #eve#s of #ea$ may ause #earnin! $isabi#ity+

>n terms of spe iation, #ea$ was pre$i te$ to be preva#ent#y in o)i$ation state two an$ of the hy$ro)i$e spe ies+

;ree #ea$ ion % b2:

& was pre$i te$ to be present in Samp#e oints 2 an$ 4+ The univa#ent #ea$ hy$ro)i$e omp#e)%8 b3% .&09:1 was pre$i te$ to be on#y present in Samp#e oint 3, be ause this ion is on#y stab#e un$er s#i!ht#y basi

on$itions as in this ase where the water is p. +3+ This orroborates with the UN( fin$in!s 8339 whi h reporte$ that at

hi!her p., #ea$ forms hy$ro)i$e omp#e)es i+e, 8 b% .& 492-+ The pre$ominant #ea$ spe ies in Samp#in! oints 1, 3 an$

were pre$i te$ to be the tetrava#ent #ea$ hy$ro)i$e spe ies 8 b 4% .&494: whi#e that for Samp#in! oints 2, 4 an$ 0 were

pre$i te$ to be the triva#ent 8 b 3% .&393: + This is most probab#y $ue to the fa t that the on entration of #ea$ ion in the

Samp#in! oints 1, 3 an$ were onsi$erab#y hi!her ompare$ to Samp#in! oints 2, 4 an$ 0+

Dinc

The tota# in on entration in N!on! river was reporte$ to be #ower than the . a##owab#e va#ue of 4 m!56+The amounts, however, varie$ from one samp#in! point to another, for e)amp#e the on entration is hi!hest at Samp#in!

oint , most probab#y $ue to a point sour e at the in$ustria# area+ The re#ative#y hi!h #eve# of in in Samp#in! oint1 may

be $ue to $we##in!s ma$e of orru!ate$ iron sheet onstru te$ #ose to the river ban?+ >n rease in p. may tri!!er

pre ipitation of in ompoun$s, sin e in hy$ro)i$es an$ in su#phates $ominate 8349 an$ therefore #ess in to be

$ete te$ in the water+ .owever, when the p. re$u e$, the spe iation of in was a#tere$ an$ the in omp#e)es therein

forme$ be ame more so#ub#e thereby in reasin! in on entration in water after Samp#in! oint 3+ The tota# in

on entration in rease$ from Samp#in! oints 4 to +


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&igure 48 Speciation of Dinc in NgongC River

>, whi h supports the observation by etru i an$

.arwoo$ %1EE3& 8309 with in hy$ro)i$e omp#e)es an$ tra es of the hromate ion in & ions+ The free in ion >+ ;ree Ni 2: ion was pre$i te$ to be pre$ominant, espe ia##y when

ni ?e# #eve#s are re#ative#y #ow %fi!ure 4&+ This is in a!reement with observation by =artino et a#+ 83 9, that $isso#ve$ ni ?e#

fra tion in fresh an$ sea water forms free hy$rate$ Ni %>>& ation an$ so#ub#e ni ?e# inor!ani an$ or!ani omp#e)es of

$ifferent stabi#ity+ >n Samp#in! oints 2 an$ 3 there are tra es of the hromate an$ hy$ro)i$e omp#e)es with ni ?e#+ This


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may be $ue to hi!her ni ?e# on entrations in these two Samp#in! oints as we## as the e#evate$ p. in Samp#in! oint 3

whereby the tetrava#ent ni ?e# hy$ro)i$e ion %8Ni 4% .&494: is pre$ominant+ Corne##is et a#+ 83/9 observe$ that the spe iation

of ni ?e# in sea an$ fresh water $epen$s on p., re$o) on$itions, ioni stren!th, type an$ on entration of inor!ani

#i!an$s, pressure an$ temperature on$itions amon! others+

!hromium

Tota# hromium on entration was a#so foun$ to be within the . a eptab#e #imits in a## the Samp#in! oints

e) ept %See Tab#e 1&+ The spe iation stu$ies of hromium pre$i te$ that the univa#ent hy$ro)i$e spe ies 8Cr% .& 291: was

pre$ominant e) ept in Samp#in! oint 3, with hy$ro)i$e 8Cr 4% .& 9 : + Chromate ion %Cr 42-& omp#e)in! with man!anese,

ni ?e# or in , was a#so pre$i te$+ The uni*ue behavior at Samp#in! oint 3 is attribute$ to the hi!h p. of +3+ At this p.

Cr %G>& ions are rea$i#y re$u e$ to Cr %>>>& in the presen e of or!ani matter 83 9+ The stu$y shows in a$$ition to

?now#e$!e of the tota# on entration, spe iation of the e#ements is ?ey in estab#ishin! water po##ution+

&igure 58 Speciation of !hromium in NgongC River

"ron

>ron was foun$ to be the most abun$ant heavy meta# in the Nairobi "iver %Tab#e 1&+ The on entration in a## the

Samp#in! oints was *uite hi!h imp#yin! that the N!on! river water have o#our, ba$ taste, may stain #aun$ry an$ #ea$ to

rust overin! pipes an$ tan?s+ Samp#in! oint 1 ha$ the hi!hest iron ontent an$ is surroun$e$ by stru tures ma$e of

orru!ate$ iron sheets an$ thus a $ire t sour e of iron+ The on entration $e reases in Samp#in! oints 2 an$ 3 before

bein! e#evate$ in Samp#in! oints 4 to + The inf#uen e of the man-ma$e a tivities ne)t to river ourses is therefore *uite

si!nifi ant+

The spe iation pre$i tions show that the ferri hy$ro)i$e is pre$ominant in most of the Samp#in! oints

%;i!ure &, an$ that the free ferrous iron is a#so present in substantia# amounts+ The most pre$ominant spe ies of iron in a##

Samp#in! oints e) ept Samp#in! oint 3, is 8;e% .& 29:1 %;i!ure &+ The ferri hy$ro)i$e spe ies is pre$ominant in

Samp#in! oint 1+ The ferri ion is pre$i te$ to be re$u e$ to ferrous ion in Samp#in! oint 2 whi#e the abun$an e of the

univa#ent ferrous hy$ro)i$e ion 8;e% .& 291: remaine$ the same+ >n Samp#in! oints 4, 0 an$ the ;e 2: on entration

in rease$ whi#e that of ;e% .& 3 $e rease$+ This an be attribute$ to re$u in! a!ents from in$ustria# eff#uents inf#ows near

this Samp#in! oints+ The o)y!en $eman$ was observe$ to in rease a ross Samp#in! oints 4, 0 an$ %Tab#e 2&+


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The spe iation in Samp#in! oint 3 was mar?e$#y $ifferent from a## the others, with the spe ies 8;e 3% .&49 : bein! the most

pre$ominant+

&igure ?8 Speciation of "ron in NgongC River

Manganese

The tota# man!anese on entrations in a## the Samp#in! oints e) ee$e$ the . a eptab#e va#ue of @+4 m!5#+

Samp#in! oint 1was foun$ to have =n on entration+ The on entration of =n $e reases in Samp#in! oints 2 to 4,

then in reases in Samp#in! oints 0 an$ +

Spe iation pre$i tions in a## Samp#in! oints e) ept 3 showe$ that the pre$ominant spe ies is the free a*uoomp#e), =n 2: + This a#so has been observe$ by ;au#?ner et al 84@9, who observe$ that on#y upon o)i$ation, are tra es of

the o)i$i e$ form, =n 4: are observe$+ The water was *uite $eprive$ of o)y!en !iven the o)y!en $eman$ va#ues %Tab#e 2&

an$ therefore on#y =n 2: was e)pe te$+ They a#so note$ that man!anese o)i$ation is primari#y bio#o!i a##y me$iate$ but

above p. , man!anese o)i$ation is observe$+ This e)p#ains the $ifferen e in spe iation in Samp#in! oint 3 whi h ha$ a

p. va#ue of +3 %Tab#e 2&+ Tra es of the hy$ro)i$e an$ hromate were a#so envisa!e$ in most of the samp#in! points

%;i!ure /&+

&igure =8 Speciation of Manganese in NgongC River


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!%N! +S"%NS #N- RE!%MMEN-#$"%NS

>ron was foun$ to have the hi!hest with an avera!e on entration of + / ) 1@ -0= whi#e the #east was opper with

an avera!e on entration of 2+E0 ) 1@ -/ =+ Usin! this mo$e#, the ma7or spe ies pre$i te$ in most of the Samp#in! oint

were foun$ to be 8Cr% .& 29:1 , 8;e% .& 29:1 , 8


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13+ ear e, '+ =+ S+ %2@@/&+ JurtonQs #ine in #ea$ poisonin!+ European &eurolo y 5= %2& 11 11E

14+ Je##in!er, D+ %2@@0&+ Terato!en up$ate 6ea$ an$ pre!nan y+ %irth defects research. Part A# Clinical and

molecular teratolo y =4 % & pp 4@E 42@+

10+ Nevin "i ? %2@@@&+ .ow 6ea$ ()posure re#ates to tempora# han!es in >I, vio#ent rime an$ unwe$ pre!nan y+

Environmental Research +:4 %1&

1 + Houn!, "+, Crit h#ey, 'A, Houn!, KK, ;reebairn, "C, "eyno#$s, A , 6o#in, H> %1EE &+ ;ata# a ute hepatorena#

fai#ure fo##owin! potassium perman!anate in!estion+ "uman ' Experimental Toxicolo y /5 %3& 20E

1/+ (is#er, "ona#$ %1EE3&, Pnvertebrates A Synopti "eviewP % D;&,

Contaminant "a(ard Reviews %6aure#, =ary#an$ U+S+ Department of the >nterior, ;ish an$ i#$#ife Servi e& %1@&

1 + =uyssen, Jrita, T+ A+L De S hamphe#aere, Kare# A+ C+L 'anssen, Co#in "+ %2@@ &, =e hanisms of hroni

waterborne , "aison D Rtre+ Talanta , 4: ,

No+ 12 pp 14@E 141

32+ Breenber!, (+ A+, S+ 6+ C#eseri an$ (+ A+ (aton %1EE2&+ Stan$ar$ =etho$s for ()amination of ater an$

astewater, 1 th e$+


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=< -amaris M@ui0 -uAe %2 %rata0 *raham E0 JacAson -avi 12 1ariuAi

33+ Korfa#i, S+> an$ 'ur$i, =+S+ %2@11& Spe iation of =eta#s in Je$ Se$iments an$ ater of Iaraaoun "eservoir,

6ebanon+ Environ monit assess /=: %1&, 0 3-0/E+

34+ Unite$ Nations (nvironmenta# ro!ramme %2@1@& ;ina# "eview of S ientifi >nformation on 6ea$+ "eport to the

Bovernin! Coun i# at its Twenty-si)th Session in Nairobi, Kenya+

30+ J7orns$ottir, >+ %1EE & =eta#s an$ =eta# Spe iation in aste ater from the Nes7ave##ir Beotherma# ower #ant,

Sw-i e#an$ an$ ossib#e (ffe ts on #a?e Thinva##avain+ =s thesis, Cha#mers University of Te hno#o!y+

3 + etru i an$ .arwoo$ %1EE3& Benera# Chemistry rin ip#es an$ =o$ern App#i ations+ th ($ition+ =a mi##an

ub#ishin! Company, New Hor?+

3/+ =artino =+, A+ Turner an$ =+ Nimmo %2@@4&+ Distribution, Spe iation an$ arti #e- ater >ntera tions of Ni ?e#

in the =ersey (stuary, UK+ Marine Chemistry +:: %3-4&+ 1 1 1//

3 + Corne#is, "+, Crews, .+, an$ Caruso, '+ %2@@0& .an$boo? of (#ementa# Spe iation >> Spe ies in the (nvironment,;oo$, =e$i ine an$ upationa# .ea#th+ 'ohn i#ey an$ son s #t$+ Bermany

3E+ Tetsushi S+, (+ = Cur$y an$ S+ i#bur %2@@0&+ >on Chromato!raphy %>C& >C -=S for Chromium Spe iation in

Natura# Samp#es+ A!i#ent Te hno#o!ies, >n + 2@@0, USA+

4@+ .op?ison J+ =+ an$ K+A+ Jarbeau %2@@/&+ r!ani an$ re$o) spe iation of iron in the eastern Tropi a# North

a ifi Subo)i

9.humanities-speciation of some heavy metals in ngong river-david k. kariuki

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