EPA evaluated the mercury fractions (species) representative of several locations in OU1 for the purpose of the Human Health Risk Assessment investigation. In particular, the mercuric chloride fraction was of interest to EPA toxicologists, because this is most bioavailable form of the compound in the terrestrial food pathway. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the mercury fractions (species) representative of several locations in OU1 for the purpose of the Human Health Risk Assessment investigation. In particular, the mercuric chloride fraction was of interest to toxicologists, because this is most bioavailable form of the compound in the terrestrial food pathway. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the mercury fractions (species) representative of several locations in OU1 for the purpose of the Human Health Risk Assessment investigation. In particular, the mercuric chloride fraction was of interest to toxicologists, because this is most bioavailable form of the compound in the terrestrial food pathway. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the total mercury representative of several surface and subsurface locations in OU1 for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the total mercury representative of several surface and subsurface locations in OU1 for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the total mercury representative of several surface and subsurface locations in OU1 for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the total mercury representative of several subsurface locations in OU1 for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

EPA evaluated the total mercury representative of several subsurface locations in OU1 for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.

The Region 9 CRMS risk assessor specifically identified the need to obtain data for Tribal lands near Fallon, Nevada. Based on a 1994 study performed on OU1 samples, an estimated 12% of total mercury measurements is mercuric chloride (HgCl2). The Quality Assurance Project Plan (QAPP) summarized the OU1 historical analytical approaches for “speciation” with currently available methods summarized. Based on team scoping meeting with EPA Region 10 and the Region 9 Toxicologist, use of the Brooks Applied Lab (BRL) sequential extraction was selected primarily for reasons of comparability of approaches to simplify data assessment. (EPA Method 3200 was presented for comparative purposes.) There are significant sources of uncertainty in “speciation” using any approach, as each is technically a procedurally defined fractionation that may include other mercury species not specifically identified. As an example of this uncertainty, under the OU1 study of the EPA Las Vegas Lab data, it was unclear which fraction would have captured mercury oxide or whether the residual chlorides caused minor amounts of sulfide to combine with the nitric acid fraction. While the Oak Ridge approach may have reported mercuric chloride in the elemental mercury fraction. The primary factors driving the need for this speciation data were uncertainty about the quality of the historical OU1 data; applicability of the OU1 data at the locations below Lahontan Reservoir, and concerns expressed by the Region 9 CRMS risk assessor to better obtain direct measurement data near the Fallon Paiute-Shoshone Tribe. The data generated by this sampling were reviewed for laboratory quality control but decisions with the data were made by the EPA Region 9 CRMS risk assessor.

EPA evaluated the total mercury representative of vegetables and/or fruit and colocated soil from several gardens located in Dayton and Silver City (OU1) for the purpose of the Human Health Risk Assessment investigation. EPA published this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU1 Remedial Investigation Report (EPA, 1994), which describes the nature and extent of contamination from the Site. The reports contain the Human Health Risk Assessment and Ecological Risk Assessment Reports. Literature and other source Hg data are summarized in the RI report for upland source areas.