natural attenuation of amd by acidophilic and acidotolerant fe(iii

Natural Attenuation of AMD byAcidophilic and Acidotolerant Fe(III)

and Sulfate-Reducing Bacteria

Sarina J. Ergas, Mercedita Monserrate,Kristin Forloney, David P. Ahlfeld,

Klaus R.L. Nüsslein, Richard F. Yuretich

University of Massachusetts,Amherst

Create PDF with PDF4U. If you wish to remove this line, please click here to purchase the full version

http://www.pdfpdf.com

Acid Mine Drainage (AMD)AKA: Acid Rock Drainage

p Occurs when pyrite (FeS2) is exposed tooxygen and moisture.

p Process is accelerated by coal and metal (iron,copper, lead, zinc) mining and other large scaleearth moving activities.

p AMD characterized by low pH, high Fe(III),sulfate and heavy metals concentrations.



Effects of AMDp AMD has polluted >180,000 acres of reservoirs

and lakes and > 12,000 miles of streams andrivers in U.S.

p Toxic to most life forms except hardy plants andspecialist microorganisms.

p Can cause health hazards to humans when AMDenters a drinking water source.

p Can corrode structures such as bridges.

p EPA (2001) estimates clean up costs >$35 billion.



AMD Generationp Pyrite oxidation catalyzed by acidophilic and acid

tolerant chemolithotrophic iron and sulfuroxidizing bacteria.

p Use reduced sulfur and iron compounds as e-

donors, O2 as e- acceptor and CO2 as carbonsource.

Summary Reaction

4FeS2 +15O2 +14H2O 4Fe(OH)3 + 8H2SO4



Pyrite oxidation ecology : new insightsusing molecular tools

Baker and Banfield, 2003:novel archaea morenumerous and active thanThiobacillus ferroxidans



AMD Attenuation Mechanismsp Dilution with surface and groundwater from

unaffected areas.

p Reaction with carbonates and silicates insurrounding bedrock.

p Formation of Fe, Al and Mn oxyhydroxides thatprecipitate out.

p Adsorption of trace elements (Cu, Zn, Pb, As)onto oxyhydroxides and clay minerals.

p Biological Fe(III) and sulfate reduction.



Sulfate reducing bacteria (SRB)p Diverse group of anaerobes capable of

dissimilatory sulfate reduction

CH3COO- + SO42- + H+ ⇒ H2S + 2HCO3

-

p Increase pH and alkalinity of the water.

p Biologically generated sulfide reacts with metalsin AMD to form insoluble metal sulfides.



Fe(III) reducing bacteriap Diverse group of organisms with wide range of

electron donors, acceptors and conditions:

CH2O + 2Fe2O3 + 3H2O ⇒ 4Fe2+ + HCO3- + 7OH-

p Fe(III) reduction generates alkalinity.

p Lowers Fe3+ concentrations.



Davis Mine Rowe, MA•Once the largest operatingpyrite mine in Massachusetts.

•Operated 1882-1910.

•Collapsed due to poor miningtechniques.



Davis Mine Todayp Ground water

infiltrating frommine shaft has pH~ 2

p High in SO42- and

metals (Fe, Al,Zn).

p Small area ~3 ha.

p No remediationundertaken.



Davis Mine

Acidic Mine Effluent

100 m

Shaft #1

Davis Mine Brook

No Name Brook



Goal: Greater understanding of naturalattenuation of AMD.

p Hypotheses:n A complex community of acidophilic and acid tolerant

anaerobes play a key role in AMD attenuation atDavis mine.

n Attenuation processes at Davis mine are similar tothose at other AMD impacted watersheds.

p Methods: Field, laboratory and modeling.

p Interdisciplinary –Environmental Engineering,Geosciences, Microbiology, Education



Field Monitoringp Multilevel monitoring

wells.

p Sample sites alongmine drainageeffluent and DavisMine Brook.

p Soil cores: columnsand microcosms,community structure,mineralogy.



Field Measurementsp Monthly analysis of

cations (ICP), anions(IC), TOC/DOC, pH,conductivity, ORP.

p DNA extraction andpurification from soilcores.

p Surface waterdischarge, raingauges, pump tests.



Groundwater pH

p Acidification ofgroundwater locallyintense

p Extreme values inold tailings piles

p Ambientgroundwater fromunimpacted areas(pH ~6) helpsrestrict the AMDzone

100 m



Groundwater Sulfate

p Sulfate concentratednear discharge of mineeffluent

p Ambient groundwatercontains 7.8 mg/lSO4

2-.p Reduction only

possible removalmechanism

100 m



pH Cond Na Fe Zn Cl SO4 Si Al

Upstream(-10m)

5.24 41 2.06 0.27 0.38 3.69 8.56 3.19 0.36

Effluent(0 m)

2.92 624 5.30 10.60 8.48 9.31 238.60 15.27 4.65

Downstream(+10m)

3.65 123 2.50 1.44 1.32 5.00 41.37 5.05 0.80

mg/l

Pristine vs. Impacted Water



Laboratory Columnsp Aquifer material from

AMD generating andattenuation zones.

p Groundwater from siteat constant HLR.

p Tracer (Br-) studies.

p Influent, effluent,profiles: pH, ORP,conductivity, TOC,SO4

2-, S2-, Fe2+, Fe3+

p DNA analysis.

Groundwaterreservoir

pump

N2 spargesample ports

effluent

glass column packedwith aquifer materialsunder anaerobicconditions



Column Studies pH Well 2

pH vs Time

3.5

4

4.5

5

5.5

6

6.5

60 80 100 120Time (day)

pHInfluent Effluent

`



Sulfide Generation Well 2

S-2 Generation Rate

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

60 75 90 105 120

Time (days)

Rat

e(m

g/L-

day)

Cre

ate

PD

F w

ith P

DF4

U. I

f you

wis

h to

rem

ove

this

line

, ple

ase

clic

k he

re to

pur

chas

e th

e fu

ll ve

rsio

n


16S rRNA phylogenetic analysis of fieldand column samplesp Functional analysis –

Fe(III) and SRB inwells and columns –primarily in AMDattenuating zones.

p Decreased diversityobserved in columns.

p Bacteriodetes incolumns but not wells.

Column 2, Port 3

acidobacteriaactinobacteriaalpha proteobacteriabacteriodetesbeta protebacteriadelta proteobacteriaf irmicutesgamma proteobateriagemmatimonadetesplanctomycetesspirochaetesverrucomicrobianitrospira

Well 2

acidobacteriaactinobacteriaalpha proteobacteriabacteriodetesbeta protebacteriadelta proteobacteriaf irmicutesgamma proteobateriagemmatimonadetesplanctomycetesspirochaetesverrucomicrobianitrospira



Laboratory Microcosmsp Inoculum: AMD generating, attenuating andbackground zones.

p Mine water media.

p Postgate’s and Pfennig’s.

p pH 2, 3, 6, 7.

p DNA analysis.

0

10

20

30

40

50

60

70

80

90

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

EastWestNorth



Microcosms: pH well 2Well 2 pH

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

pH

Zero

Killed

Month 1

Month 2

pH 2 pH 3 pH 6 pH 7



Well 2 ORP

-200.00

-100.00

0.00

100.00

200.00

300.00

400.00

500.00

600.00

OR

P(m

V)

Zero

Killed

Month 1

Month 2

pH 2 pH 3 pH 6 pH 7



Microcosms: TOC well 2Well 2 TOC

-500.000

0.000

500.000

1000.000

1500.000

2000.000

TOC

(mg/

L)

Zero

Killed

Month 1

Month 2

pH 2 pH 3 pH 6 pH 7



16S rRNA phylogenetic analysis ofpositive ferrous sulfide microcosms

p Desulfosporosinuspresent in allenrichments.

p Sequences clusteredwith Desulfosporosinusstrains from AMD sitein Germany.

pH 7.0

Davis Mine Groundwater MediaWell 1

Desulfosporosinus Acetobacteria

Sporomusa

pH 4.0 pH 5.0

pH 7.0



Desulfosporosinus Acetobacteria

Sporomusa

pH 4.0 pH 5.0

Desulfosporosinus SRB

Acetobacterium homoacetogen

Sporomusa fermentor



Interdisciplinary Journal Club



Involvement of Teachers as Researchers



Conclusionsp Sulfate reducing

activity and bacteriaevident in field,columns andmicrocosms.

p Activity of SRBappears to limitimpacts of AMD onground and surfacewater.

p Interdisciplinaryresearch –communication is key.



Future workp Continue field and microcosm work - rates

of SO42- and Fe(III) reduction.

p Comparison of Davis mine with UK sites:Mynydd Parys Mine, Wales; Mam Tor,Derbyshire, England

p Integration of field and lab results withhydrologic and geochemical models.



Thank youp TEAM AMD:

n Christine Barreton Liam Bevann Jessica Bloomn Jennifer Clarkn Phil Dixonn Jaime Harrisonn Jason Jeann Melissa Russelln Melinda Solomonn Janice Wing

p NSF Biocomplexity in theEnvironment ProgramCHE-0221791



natural attenuation of amd by acidophilic and acidotolerant fe(iii

Documents