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DETERMINATION OF METHYLMERCURY FLUX FROM ONONDAGA LAKE SEDIMENTS USING FLOW-THROUGH REACTORS. GREGORY ALBERT E. GALICINAO DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING MICHIGAN TECHNOLOGICAL UNIVERSITY. STUDY SITE: ONONDAGA LAKE. -surface area: 11.7 km 2 mean depth : 12.0 m - PowerPoint PPT Presentation
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DETERMINATION OF METHYLMERCURY FLUX FROM ONONDAGA LAKE
SEDIMENTS USING FLOW-THROUGH REACTORS
GREGORY ALBERT E. GALICINAODEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING
MICHIGAN TECHNOLOGICAL UNIVERSITY
STUDY SITE: ONONDAGA LAKE
-surface area: 11.7 km2
-mean depth : 12.0 m
-maximum depth: 20.5 m
-short retention time: flushes 2.5 to 4.0 times each year
-distinguished by two depositional basins, with a saddle region between them
-littoral zone occupies only a small area of the lake relative to the profundal sediments
-eutrophic and dimictic
-during summer and winter, the thermally- layered Onondaga Lake also has a sulfidic (>10 mg S·L-1) and anoxic hypolimnion
OTHER WATER QUALITY PROBLEMS
•ammonia, nitrate and phosphorus
•presence of pathogenic microorganisms
•high levels of PCBs, calcium chloride, mercury and other trace metals
•minimum dissolved oxygen concentration standard (4 mg·L–1) is frequently violated
•Mercury.......
Onondaga Lake (sign not to scale)
Testimony to the U.S. Senate has described Onondaga Lake as one of the most polluted in the country – perhaps the most polluted.
Hennigan, R.D., 1990. America's Dirtiest Lake. Clearwaters 19: 8-13.
METHYLATION AND METHYLMERCURY
*picture courtesy of Dr. Betsy Henry, Exponents
-conversion of Hg to methylmercury (MeHg) when a methyl group transfers from an organic compound to a mercury ion
-net methylation is optimal in the absence of oxygen
• elemental mercury
• Ionic mercury
• Organic mercury
-Mercury: a toxic substancefound naturally or as a contaminant introduced to the environment
MERCURY & METHYLMERCURY
*picture courtesy of Betsy Henry, Exponents
-MeHg Bioconcentration Factor: 104 to 107
-methylmercury: microbially-mediated reactions convert Hg to MeHg, a highly toxic form
HISTORY OF MERCURY POLLUTION
-Industrial waste generated and discharged to the lake by two chlor-alkali facilities
-75,000 kg from 1946-1970 -Allied Signal was ordered to reduce external loadings from 10 kg·day-1 to 0.5 kg·day-1 in 1970
-Chlor-alkali production operations halted in 1988
-Largest sources of Hg to the lake are: Ninemile Creek (7.1 kg.year-1), the METRO wastewater treatment plant (3.8 kg.year-1) and Onondaga Creek (1.8 kg.year-1) and unquantified amount from upland sources & resuspended sediments
+ anode
Hg cathode
carbonelectrode
Cl2
26% NaCl
24% NaCl
sodium amalgam, NaHg
H2
HgH2O
50% NaOH
THE CHLOR-ALKALI PROCESS
*picture courtesy of Dr. Martin T. Auer
MERCURY IN ONONDAGA LAKE TODAY
-mercury concentrations in the lake remain high
• water :• sediment :• fish :
-It still contains very high levels of HgT at 2-25 ng·L-1 Hg and 0.3-0.7 ng·L-1 of methyl mercury (MeHg)
-Hg concentration measured in lake fish also exceeded federal food limits set by the US Food and Drug Administration of 1 μg.g-1
-catch & release policy
*pictures courtesy from Dr. Betsy Henry
MERCURY IN ONONDAGA LAKE TODAY
....All roads lead to SEDIMENT as the possible culprit
*pictures courtesy from Dr. Betsy Henry
0
5
10
15
20
0 4 8 12 16 20
Dept
h (m
)
MeHg (ng·L-1)
LAKE RESTORATION EFFORTS:
-Closure of the Allied Signal chlor-alkali plants
-Bottom sediments and adjacent sites were assigned to the Federal Superfund National Priorities List
-Clean-up of upland sites has been completed wherein 8,500 tons of soil were treated
-Wetland Restoration was completed in 2007
-Groundwater Collection System/Barrier Wall—barrier wall construction has begun and groundwater treatment is in progress
Innovative Soil Washing Technology
*pictures courtesy from Dr. Betsy Henry and http://www.cnylink.com/news_images/lrg/onondagaoutletweb.jpg
THE NEXT STEPS•Dredging and Capping of Contaminated Lake Sediments-dredge 2.65 million cubic yards (SMU 1-7)-20% of the bottom area will be covered with clean sediment-isolation cap over 425 acres
•Monitored Natural Recovery-sequestration and burial will ultimately isolate contaminant from the lake water and reduce Hg concentrations, exposure, and mobility -Probable Effects Level (PEL) is set in Onondaga Lake to be attained
*picture courtesy of Betsy Henry, Exponent
Sediment Management Units (SMU) in Onondaga Lake
Long Term Recovery
What do we do while the lake approachesits new equilibrium?
*pictures courtesy of Dr. Martin T. Auer
Protect the ecosystemFrom MeHg flux
•Electron Acceptor Amendment-chemical-augmentation by adding oxygen and nitrate
INTERIM MANAGEMENTOF CONTAMINATED LAKE SEDIMENTS: ELECTRON ACCEPTOR AMENDMENT
-2
8
18
28
38
48
58
0 2 4 6 8 10
Fate of mercury in the sediments:Advection in Sediments > Diffusion
Engineered solution: Chemical Augmentation
SULFATE REDUCTION & METHYLATION
•Electron-donor (carbon)
•Electron acceptor (sulfate)
•Bioavailable species of inorganic Hg (HgS0)
C
O
S
N
HgmgS
2-L-1
ngMeHgL
-1
0
5
10
15
20
0
2
4
6
8
22 4 2 2 2( )C H O SO H S CO H O
THE ROLE OF in METHYLATION
-Sulfate-Reducing Bacteria-principal methylators of mercury
SRB utilize sulfate as an electron acceptor in metabolizing organic carbon
-Hg2+ forms a neutrally-charged complex, HgS0
-Uncharged Hg-S complexes have fair lipid solubility and are relatively nonpolar.
-Sulfate-concentration:100-200 µM
-High levels of sulfate yield high concentrations of sulfide which has an inhibitory effect on methylation
C(H2O) SO4
NO3
O2
INTERIM MANAGEMENTOF CONTAMINATED LAKE SEDIMENTS: ELECTRON ACCEPTOR AMENDMENT
SINK PROCESSES:
SORPTIONDEMETHYLATION
It is the sink processes that exert a major control on the flux of methylmercurytransported to the overlying water
-2
8
18
28
38
48
58
0 2 4 6 8 10
THE ROLE OF ELECTRON ACCEPTORS in METHYLATION
2006
15
12
9
6
3
0
2.0
1.5
1.0
0.5
0
Apr May Jun Jul Aug Sep
O2Bump
NO3Bump6
5
4
3
2
1
0
Oxy
gen
(mg
L∙-1)
Nitr
ate
(mgN
L∙-1)
MeH
g (n
gNL∙-1)
18 m
18 m
12-19 m
C(H2O)
O2
SO4
NO3
As the sequestered mercury is buried, it passes through a sediment layer (sulfate reduction) favorable for methylmercury production with subsequent diffusion to the overlying water
-2
8
18
28
38
48
58
0 2 4 6 8 10
sulfideMeHg
Dep
th (
mm
)
mg S·L-1 and ng MeHg·L-1
*pictures courtesy of Dr. Martin T. Auer
Delete this page
GAUGING ELECTRON ACCEPTOR AMENDMENT EFFICIENCY:USE OF FLOW-THROUGH INCUBATION CHAMBERS
OBJECTIVE: to demonstrate that addition of electron acceptors can inhibit MeHg flux from the sediments
FeedStock
Q C∙ in Q C∙
EXPERIMENTAL SET-UP
J
THEORY AND OPERATION: MASS BALANCE
FeedStock
Q C∙ in Q C∙
EXPERIMENTAL SET-UP
J
indCV Q C Q C J Adt
0.0
0.2
0.4
0.6
0.8
1.0
0 2 4 6
Flow
(m
Lm
in∙
-1)
Days
0
1
2
3
1 2 3 4 5 6
Nitr
ate
(mgN
L∙-1)
Days
0
2
4
6
8
10
12
1 2 3 4 5 6
Oxy
gen
(mg
O2.L
-1)
Days
Q
0.0
0.1
0.2
0.3
0.4
0 2 4 6
MeH
g (n
g.L
-1)
Days
ssQJ CA
Css
A BASELINE FOR EVALUATING THE RESPONSE TO ELECTRON ACCEPTOR AMENDMENTS
ssQJ CA
Q
0
50
100
150
200
1a 2a 2c 4a 4b 4c 5c 5d 6c 6d
10a O2
10b
10c
NO
3 1b
High
O2
+ Hi
NO
3
2b 3a 3b 3c 5a 5b 6a 6b 7a 7b
Low
O2
+ N
O3
7c 8a 8b 9a 9b 9c 9d
10d
0/0
ng.m
-2.d
-1
A BASELINE FOR EVALUATING THE RESPONSE TO ELECTRON ACCEPTOR AMENDMENTS
ssQJ CA
Q
“How much is the flux coming out of the lake sediments? How big is the ‘monster’? ”
0
30
60
90
120
150
Hypolimnetic Accumulation Rates
Porewater Calculations
Flow-through No/No
ng.m
-2.d
-1
ELECTRON ACCEPTOR AMENDMENT
ssQJ CA
Q
0
40
80
120
160
200
Hi O2 + Hi NO3
Low O2 + NO3
No/No O2 NO3
ng.m
-2.d
-1
DECREASING TREND IN MeHg RELEASE
ssQJ CA
Q
Recent 2008 data translates to a ∽85% decrease in MeHg flux over a four-year period
*Data provided by Upstate Freshwater Institute
0
200
400
600
800
1000
2005 2006 2007 2008
ng.m
-2.d
-1
ELECTRON ACCEPTOR AUGMENTATION IN A LARGER CONTEXT
ssQJ CA
Q
Sediments serve as a repository of the “sins of the past”-Dr. Martin T. Auer
0102030405060708090
100
0 3 6 9 12 15
Net demethylation
Sulfate Reduction and Methylmercury Production
ssQJ CA
Q
Less organic matter means less “fuel” topower the sulfate-reduction engine (and consequently methlyation of mercury)
0%
20%
40%
60%
80%
100%
1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
aerobic metabolism
denitrification
sulfate reduction
methanogenesis
ELECTRON ACCEPTOR BUDGET OF ONONDAGA LAKE
•At the onset of 2004, there was a decrease in sulfate-reduction
•Advanced Nitrification program of METRO
* Data provided by Upstate Freshwater Institute
ssQJ CA
Q
CONCLUSION
•Chemical-augmentation as an interim management procedure effectively inhibited the release of MeHg to the water column of Onondaga Lake
•Percent reduction of MeHg release after addition of oxygen and nitrate is between 65-97%
FUTURE WORK•Further experimental work with nitrate additions is needed
•More research to characterize and identify which, between sorption or demethylation, is the controlling MeHg sink process
ssQJ CA
Q
ACKNOWLEDGMENT
I want to thank the following people for making this project possible:
•Dr. Hand, Dr. Urban and Dr. Bagley for agreeing to be part of my committee
•Upstate Freshwater Institute , Syracuse University and Cornell University for collaborating with us in this research project
•Honeywell Inc.
•Jesse Nordeng, Rob Fritz and Dave Perram
•Denise Heiniken and the MTU Writing Center
•To my friends here at MTU
•To our Research Group: Brandon Ellefson and Phil Depetro and the undergraduate students, Justen Stutz, Adam Di Pietro & Ken Windsand
•To my family and friends
•To my great adviser, Dr. Martin T. Auer
•To God
ssQJ CA
Q
QUESTIONS?