Collaborative Research: Investigation of the Effects of Organic Matter and Sulfur in the Environmental Fate of Mercury

GSTDTAP

项目编号	1629698
	Collaborative Research: Investigation of the Effects of Organic Matter and Sulfur in the Environmental Fate of Mercury
	Joseph Ryan
主持机构	University of Colorado at Boulder
项目开始年	2017
	2017
项目结束日期	2019-12-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	72603(USD)
国家	美国
语种	英语
英文摘要	Mercury is responsible for more than 80% of the fish consumption advisories in fresh waters of the United States. Most of this mercury is released by the combustion of coal and is deposited from the atmosphere near and far from the sources. Once deposited, the threat of mercury to food webs depends on the extent to which ionic mercury is converted to (1) methylmercury, the form of mercury that is accumulated from plankton to fish and ultimately to humans, and (2) elemental mercury, the form of mercury that is removed from aquatic systems by volatilization. Mercury is converted to methylmercury mainly by sulfate-reducing bacteria that thrive in aquatic environments deprived of oxygen. The ability of these bacteria to methylate mercury depends on the form of the ionic mercury -- whether or not its availability to sulfate-reducing bacteria is limited by its association with organic matter or its precipitation as mercuric sulfide minerals. Mercury is converted to elemental mercury by reduction by a variety of processes for which the influence of organic matter association and precipitation as mercuric sulfide is not well known. The goal of this research is to assess the role of organic matter and sulfur in influencing the conversion of ionic mercury to methylmercury, the first step in making mercury available to aquatic organisms. The focus of this proposal is to improve understanding of the interactions between mercury, sulfur, and organic matter. The research is driven by two main hypotheses that investigate the role of sulfur cycling and redox conditions on the reactivity of organic matter to mercury. The first hypothesis examines the abiotic incorporation of sulfide into organic matter as a function of organic matter composition, and the role of metals on the stability of the newly-incorporated organic sulfur to oxidation. The second hypothesis addresses the effects of the composition and redox state of organic matter on the reduction of mercury from Hg(II) to Hg(0), and inhibition of the reduction of Hg(II) by complexation to reduced sulfur groups in organic matter and inorganic sulfide. The hypotheses will be tested by (1) examining sulfide incorporation into organic matter and reduction of Hg(II) to Hg(0) by organic matter using laboratory experiments and field studies at sites in the Florida Everglades and interior Alaska that represent a range of sulfur and organic matter conditions and (2) characterizing sulfur and mercury in these materials by X-ray absorption near-edge structure (XANES) spectroscopy. These efforts will be enhanced by the use of electrochemistry to study coupled metal-organic matter redox reactions and high energy-resolution XANES spectroscopy to resolve sulfur functionality. The research goals will be complemented by a high-school teacher training program focusing on the laboratory research and participation in ongoing and new science, technology, engineering, and mathematics (STEM) education efforts.
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/70667
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Joseph Ryan.Collaborative Research: Investigation of the Effects of Organic Matter and Sulfur in the Environmental Fate of Mercury.2017.