Case History Sediment Redox Processes and Mercury Management in Onondaga Lake, New York

1. O C N Hg S ENVE5504 – Surface Water Quality Modeling Case History Sediment Redox Processes and Mercury Management in Onondaga Lake, New York

2. Onondaga: America's Dirtiest Lake 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.

3. Salt • Syracuse, New York: The Salt City • 1615 – first European visitor, Samuel Champlain • 1654 – salt springs discovered, Father Simon Lemoyne • 1794 – salt industry in place, James Geddes • 1820 – local brine springs failing • 1838 – wells dug around Onondaga Lake fail to locate source • 1862 – salt industry reaches its peak

4. Solvay The Solvay Process In 1865, a Belgian chemist, Ernest Solvay, developed a process to produce soda ash from calcium carbonate (limestone) and sodium chloride (salt). Soda ash is used in softening water and in the manufacture of glass, soap and paper: Ernest Solvay 1943: wastebeds collapse flooding region with soda ash waste http://pubs.acs.org/subscribe/journals/tcaw/11/i02/html/02chemchron.html

5. Allied-Honeywell Solvay Process Allied Chemical  Allied Signal Honeywell

6. Another Industrial Process The Chlor-Alkali Process The mercury cell chlor-alkali process was used to produce chlorine gas and sodium hydroxide through electrolysis of a salt brine solution. Cl2 anode + 26% NaCl 24% NaCl Hg cathode sodium amalgum, NaHg H2 50% NaOH Hg carbon electrode H2O

7. 75 mg∙kgDW-1 0 With Consequences The Chlor-Alkali Process There is loss of mercury through leakage and dumping as the cells are cleaned or replaced.Approximately 75,000 kg of mercury were discharged to Onondaga Lake over the period 1946-1970. Adapted from Atlantic States Legal Foundation http://www.aslf.org/ONONDAGALAKE/gallery1.html

8. Mercury

9. Mercury Forms Hg(0) – mercury can be present as elemental or metallic mercury, a form that is subject to volatilization and release to the atmosphere; Hg(II) – mercury can be present in ionic form, associated with salts and existing in equilibrium with Hg(0); MeHg, (Me)2Hg – mercury may be present in the mono- and dimethyl forms, readily available for biotic uptake and produced from ionic mercury by sulfate-reducing bacteria. Source: Global Mercury Assessment, United Nations Environment Programme http://www.chem.unep.ch/mercury/Report/GMA-report-TOC.htm

10. MethylMercury

11. 75 mg∙kgDW-1 0 Widespread contamination Adapted from Atlantic States Legal Foundation http://www.aslf.org/ONONDAGALAKE/gallery1.html

12. MSNBC, 16 October 2006 Superfund Dredge and Cap: the plan includes dredging of 2.65 million cubic yards of contaminated sediment with capping of 579 acres (20%) of the lake bottom.

13. Superfund • -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

14. Sediment Remediation Plan: dredge and cap, 20%

15. Sediment Remediation Plan: the other 80% Monitored Natural Recovery EPA does not consider monitored natural recovery to be a ‘no-action’ alternative, but rather an alternative means of achieving remediation objectives (U.S. EPA 1999). Selection of this approach implies that contaminant degradation and/or sequestration will eventually lead to remediation of the sediment environment (U.S. EPA 2005) and restoration of lost beneficial uses.

16. me-Hg Hg(0) SRB SRB Hg(II) Hgp complexation - sequestration The Mercury Cycle • Monitored Natural Recovery • fully protective of human health and the environment • objectives achieved in a reasonable time • Enhanced Natural Recovery • where MNR guidelines are not met, consider in situ approaches to reduce risk as sediments proceed toward a new SS following source controls. • Chemical Augmentation • oxygen • nitrate

17. Mercury Sulfur Interactions Methylmercury production is associated with the activities of sulfate reducing bacteria. mgS2-L-1 ngMeHgL-1 J A S O Source: Matilainen, T. 1995. Involvement of bacteria in methylmercury formation in anaerobic lake waters. J WAS, Vol. 80. Data from Dave Matthews, Upstate Freshwater Institute (S) and Svetoslava Todorova, Syracuse University (Hg)

18. O2 C(H2O) NO3 SO4 Sulfur and the Ecological Redox Series

19. O2 C(H2O) NO3 SO4 Sulfur and the Ecological Redox Series

20. O2 C(H2O) SO4 Sulfur and the Ecological Redox Series NO3

21. Oxygen mgO2L-1 mgN-L-1 Nitrate mgS2-L-1 Hydrogen Sulfide A M J J A S Redox Manifestations in Onondaga Lake The depletion of alternate electron acceptors (oxygen and nitrate) and the accumulation of an end-product of sulfate reduction (hydrogen sulfide) in the hypolimnion of Onondaga Lake tracks the ecological redox series. Data from Dave Matthews, Upstate Freshwater Institute

22. Oxygenation and Nitrate Augmentation Oxygen Nitrate augmentation is one means of blocking sulfate reduction and the attendant production of methylmercury. mgO2L-1 mgN-L-1 Nitrate mgS2-L-1 Hydrogen Sulfide A M J J A S Data from Dave Matthews, Upstate Freshwater Institute

23. Mapping Diagenesis electron acceptor electron donor reduced species end product  + CO2 + various various

24. Sediment Profiles

25. Measuring Methylmercury Flux • Determine the MeHg flux from the sediments with the nitrate concentration in the hypolimnion maintained at 2 mg/L. • Describe setup and conditions for the laboratory measurements. • Write the equation that will yield the desired flux and identify the source of the input terms to that equation. J

26. Measuring Methylmercury Flux J EXPERIMENTAL SET-UP

27. Results Q Css J EXPERIMENTAL SET-UP

28. Results ng.m-2.d-1

29. Results ng.m-2.d-1 Hi O2 + Hi NO3 Low O2 + NO3 No/No O2 NO3

30. Application Net demethylation Sulfate Reduction and Methylmercury Production