Application of ultra-clean sample handling and analysis to routine monitoring of Hg at ambient (ng-L{sup {minus}1}) levels
- Frontier Geosciences, Seattle, WA (United States)
- Brown and Caldwell, Sacramento, CA (United States)
- CVRWQCB, Sacramento, CA (United States)
Recent advances in ultra-clean sample handling and analytical methods have shown that environmental levels of aquatic Hg are far lower than previously estimated by regulatory bodies. Methylmercury generation sufficient to adversely impact fish tissue concentrations may occur in waters containing 1--5 ng-L{sup {minus}1} Hg, depending upon ancillary parameters such as pH and DOC. Even grossly polluted water bodies may contain concentrations of only 10--50 ng-L{sup {minus}1} Hg, far below currently regulated levels. With these findings in mind, agencies in several states have sought to monitor surface waters for Hg at ambient concentrations. Through careful attention to clean technique in field sampling, especially in the use of pre-cleaned and tested Teflon bottles, good reproducibility at the ng-L{sup {minus}1} level was attained with little additional cost over standard protocols. Storage experiments indicate that for total or methyl Hg monitoring, the best approach is overnight shipping of unpreserved samples in Teflon bottles. The samples may then be analyzed immediately, filtered, or acid preserved under clean controlled conditions for longer storage. A blind intercomparison of several contract analytical laboratories provides some concern for the general capability to perform such measurements, however.
- OSTI ID:
- 49612
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
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