Grantee Research Project Results

Photo Induced Reduction of Mercury in Lakes, Wetlands, and Soils

EPA Grant Number: R827632
Title: Photo Induced Reduction of Mercury in Lakes, Wetlands, and Soils
Investigators: Nriagu, Jerome O. , Keeler, Gerald J. , Zhang, Hong , Lehrnan, John , Lindberg, Steve
Current Investigators: Nriagu, Jerome O. , Keeler, Gerald J. , Zhang, Hong , Lehrnan, John , Lindberg, Steve , Qang, Xia-Qin
Institution: University of Michigan , Oak Ridge National Laboratory
EPA Project Officer: Chung, Serena
Project Period: September 1, 1999 through August 31, 2002 (Extended to September 30, 2003)
Project Amount: $865,771
RFA: Mercury: Transport and Fate through a Watershed (1999) RFA Text | Recipients Lists
Research Category: Watersheds , Heavy Metal Contamination of Soil/Water , Water , Safer Chemicals

Description:

Project Summary: Release of mercury by natural processes, including re-emission of previously deposited anthropogenic mercury, remains an important source that has been ignored in most published national emission inventories such as the recent US EPA Report to Congress. Emission of mercury from soils and vegetation has been estimated to be 150-600 t/y in the United States, compared to industrial emission of 242 t/y. The long-term role of soils and water bodies as diffuse sources of Hg to the atmosphere may, in fact, determine the success of any program aimed at reducing the loading of anthropogenic mercury into the Great Lakes (or any watershed). It should equally be emphasized that processes within watersheds which serve to convert mercury to the volatile elemental (Hg(0)) form also have the effect of reducing the availability of Hg for methylation and incorporation into biota.

Objective: This proposal will undertake a comprehensive evaluation of photo induced formation of Hg(0) in a watershed: experimental studies will involve field measurements, in situ incubation and ship-board experiments, and lab studies under controlled conditions; study site will include a lake, wetlands and soils; photo-dependent processes to be investigated may be biotic, abiotic, physical or chemical; and reaction mechanisms to be studied may be homogeneous or heterogeneous. An over-aching aim will be to compare the similarities and differences in pathways and rates of Hg(0) formation in different segments of a watershed.

Approach:

Saginaw Bay to Lake Huron system has well defined gradients In chemical parameters (including chlorophyll-a, DOC, phosphorus, nitrogen, chloride and suspended particulates), trophic conditions, taxonomic composition and biomass and provides a unique study site. Diurnal and seasonal variations in cross-gradient generation of Hg(0) will be monitored, and total release of Hg(0) from surface waters of Lake Huron will be estimated. Laboratory experiments will be conducted to test a number of working hypotheses including: (a) oxidation of Hg(0) is an important factor in its accumulation and release from aquatic environments, (b) solid phases can activate the reduction of Hg(II) and Hg(I) compounds in soils and wetlands, (c) polymeric Hg(I) species are formed in significant quantities in aquatic environments and should be considered in methylation processes, (d) free Hg+ (mainly) and Hg2+ (possibly) are formed as photo products during solar irradiation of dissolved organic matter (DOM) in water, and subsequent methylation of these ions through a number of intra-cellular or extra-cellular pathways provides the link between DOC and accumulation of Hg by aquatic biota, (e) degradation of organic matter under light leads to the formation of Hg(0) (and possibly Hg+) whereas organomercury complexes and Hg(Il) are formed primarily in the dark.

Publications and Presentations:

Publications have been submitted on this project: View all 4 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

Water, atmosphere, bio-availability, re-emission, ecosystem, wetland, soil, exposure, heavy metal, photochemistry, photo-lysis, toxic, volatilization, RFA, Scientific Discipline, Air, Water, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Hydrology, Ecology, particulate matter, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemistry, Fate & Transport, Ecological Effects - Environmental Exposure & Risk, Ecological Indicators, Great Lakes, Mercury, anthropogenic stress, aquatic ecosystem, fate and transport, hydrological stability, nutrient supply, ecological exposure, wetlands, anthropogenic disturbances, aquatic, re-emission, bioavailability, mercury loading, photo induced reduction, mercury cycling, soils, lakes, soil, photo induced reduction of mercury, methylation, suspended particulates, aquatic ecosystems, ecosystem, mercury in lakes, ecosystem stress, Lake Huron, lake ecosystem, wetland, heavy metals

Relevant Websites:

ORNL ESD atmospheric chemistry group Web page Exit
Synthesis Report of Research from EPA’s Science to Achieve Results (STAR) Grant Program: Mercury Transport and Fate Through a Watershed (PDF) (42 pp, 760 K)

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.