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MERCURY MEASUREMENTS FOR SOLIDS MADE RAPIDLY, SIMPLY, AND INEXPENSIVELY
Citation:
HINNERS, T. A. MERCURY MEASUREMENTS FOR SOLIDS MADE RAPIDLY, SIMPLY, AND INEXPENSIVELY. Presented at Internet Seminar Presentation at the EPA Region 9 ORD Product Expo, San Francisco, CA, February 08, 2005.
Impact/Purpose:
The overall goals of the task are to apply NERL's core capability in advanced chemical science and technology for maximum benefit in estimating exposures of ecosystems and humans to chemical stressors and to identify emerging pollution concerns, in particular long-range airborne transport of contaminants. This task comprises several subtasks, each with individual objectives:
Subtask 1: screen exposures of National Park PRIMENet ecosystems to chemical stressors, identifying indications of exposure requiring further evaluation, and use these samples evaluate new analytical methods as replacements for standard methods in future assessments of ecosystem contaminant exposures.
Subtask 2: evaluate a new mercury analytical approach with superior performance on complex solid matrices such as biological tissues, and apply the approach to estimating exposure of ecosystems and humans to mercury.
Subtask 3: determine distribution patterns of chemical contaminants in the southern Sierra Nevada Range of California, investigate topographic and weather factors that may influence the distributions, and determine if a correlation exists between contaminant distributions and extirpation patterns of the mountain yellow-legged frog.
Subtask 4: provide analytical methods to measure a number of inorganic and organic arsenic species in a variety of environmental matrices, elucidate the environmental transformations undergone by organoarsenic animal-feed additives, and determine if the potential exists for substantially increased exposure of humans and aquatic organisms to arsenic.
Description:
While traditional methods for determining mercury in solid samples involve the use of aggressive chemicals to dissolve the matrix and the use of other chemicals to properly reduce the mercury to the volatile elemental form, pyrolysis-based analyzers can be used by directly weighing the solid in a sampling boat and initiating the instrumental analysis for total mercury. Although not well suited for trace-level analyses of liquids because of the limited capacity (0.5 mL) of the sampling boat, such pyrolysis-based mercury analyzers (EPA Method 7473) have the following advantages:
1) Throughput: a measurement every 10-15 minutes (including the weighing and logging time)
2) Learning Curve: operation simple enough for those with no prior analytical skill
3) Low Cost: capital cost about $35K
4) Green: generation of waste virtually eliminated
5) Sample Size: 1.00 mg to 500 mg, or 0.5 mL, (but use less if absorbance starts before 5 s)
6) Detection Limit: 0.01 nanogram Hg
7) Applications:
non-lethal monitoring of fish (e.g., tissue biopsy)
longitudinal analysis of hair (to locate peak-exposure periods)
exposure assessments for other tissues (e.g., feathers, fur, toenails, botanicals)
near real-time monitoring of contaminated-soil and sediment during remediations
coal-fired power plant emissions (from difference between coal Hg and solid waste Hg)
speciation for mercury in tissues (via suitable extracts of the methyl mercury)