4. Sources of Atmospheric Mercury and Trace Metal Deposition

The global budget of atmospheric mercury and other trace metals reflects cycling of contributions from various emission sources such as volcanoes and fossil fuel use, and historic background levels derived from both natural and anthropogenic sources. Mercury is of particular interest because of the widespread occurrence of fish consumption advisories due to unsafe levels in game fish. As a result, mercury remains one of the most pressing environmental issues before Congress. To date, USGS has concentrated on the important goals of mercury uptake in fish populations and the process by which mercury is transformed to methylmercury in aquatic ecosystems. Assessment of atmospheric mercury is a relatively new area of investigation for the USGS. Delineating the source(s) of atmospheric mercury (and other metals) is becoming increasingly important as progress is made understanding global mercury dispersion, as a ground-truth to atmospheric deposition models, and in light of pending legislative limits on U.S. atmospheric mercury emissions.

A combination of new research initiatives within and outside the USGS, new technical capacity, and availability of nationwide quality-assured measurements of mercury wet deposition over a period of almost 10 years, makes this the appropriate time to address the link between sources and atmospheric deposition of mercury and trace elements. Tools such as a new USGS mobile mercury lab, have the capacity to make real-time determinations of dry mercury species (gaseous Hg0, particulate Hg(II), and reactive gaseous Hg(II)), wet mercury deposition, fine particulate matter (PM2.5), NOx, SOx, ozone, and meteorological data, in order compare results for these diagnostic parameters in the vicinity of known sources such as power stations, vs. remote areas that lack local sources. This work also benefits from ongoing work at DOE and National Laboratories assessing the relative contribution of mercury from sources abroad, such as China, vs. U.S. mercury emissions.

A postdoctoral research associate is sought to conduct field sampling of mercury and trace metals in wet and dry atmospheric deposition, and to integrate these results with existing measurements to determine the provenance of Hg/trace metals in a study area to be defined by his/her research proposal, in mutual agreement with the project research advisors. The incumbent would work closely with USGS staff engaged in trace-element research, USGS researchers working in the area of water quality, and collaborators outside the USGS engaged in quantifying the international budget of mercury sources, and developing atmospheric transport models for global mercury deposition. The proposed study would also make use of data from the National Atmospheric Deposition Program- Mercury Deposition Network (MDN), a continent-wide network of fixed measuring stations for weekly samples of mercury wet deposition, some of which co-determine trace element concentrations. The incumbent will have an opportunity to assist in deployment of the mobile mercury lab, and would be responsible in part for the operation of an MDN station in the vicinity of the duty area. Sampling using these facilities is automated to a large degree, but experience in clean methods of environmental sampling for Hg and/or trace-metals is highly desirable. Experience in microbeam analysis methods (SEM, electron microprobe, etc.) is also desirable for characterization of fine particulate matter.

Facilities available include:

Major supporting laboratory facilities are available in Middleton, WI, Denver, Co, and Reston, VA. With the exception of MDN samples, the USGS low-level mercury speciation laboratory in Middleton, WI, and its mobile atmospheric mercury facility, are primary sources of mercury analyses. MDN samples are determined by a centralized commercial laboratory. Facilities available in Denver include: a cold vapor atomic absorption analyzer (for solid phase mercury analysis), a laser ablation ICP-MS laboratory, and a trace element laboratory equipped with ICP-MS and ICP-AES analyzers. Microbeam facilities in Reston, VA include a JEOL 840 scanning electron microscope and a JEOL 8900R electron microprobe. The USGS also maintains extensive domestic and international databases of coal analyses that include mercury and trace element data.

Proposed Duty Station: Reston, VA

Areas of Ph.D.: Geochemistry; environmental sciences, atmospheric chemistry, coal chemistry

Qualifications: Applicants must meet one of the following qualifications: Geologist, Physical Scientist, Environmental Scientist, Research Chemist (This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Personnel specialist.)

Research Advisor(s): Allan Kolker, (703) 648-6418, akolker@usgs.gov; David Krabbenhoft, (608) 821-3843, dpkrabbe@usgs.gov

Personnel Office contact: Rosetta Alexander, (703) 648-7468, ralexand@usgs.gov

Summary of Opportunities