G. Holdsworth

Bio: G. Holdsworth is an academic researcher from Oak Ridge National Laboratory. The author has contributed to research in topics: Mercury (element) & Apolipoprotein C. The author has an hindex of 2, co-authored 3 publications receiving 141 citations.

Distribution of mercury species in soil from a mercury-contaminated site

Abstract: The distribution of mercury species was determined in soil from a site with Hg contamination. Mercury contamination was primarily confined to the top 40 cm of soil, and the concentration of total Hg ranged from 0.5 to 3000 µg Hg g−1. Of total Hg present, we determined that 91% was inorganic, 0.01% organic (as methyl Hg), and 6% elemental Hg. Furthermore, of total inorganic Hg present, 85% was in the insoluble mercuric sulfide form. Thus, of total Hg present in soil at this contaminated site, 91% was in the relatively insoluble HgS and Hg0 forms.

Mercury in soil: A method for assessing acceptable limits

Abstract: Acceptable limits for mercury in soil were determined at a site with mercury contamination after measuring the soil concentration of total mercury, the species of mercury, and the intestinal absorption of mercuric sulfide by mice. The total concentration of mercury at this site ranged from 0.5 to 3,000 ppm. Of the total mercury present, 88% was identified as mercuric sulfide, 0.01% as methyl mercury, and 7% as elemental mercury. Intestinal absorption studies in mice following the intubation of203mercuric sulfide showed that 0.4% of the intubated dose was absorbed. We estimated an acceptable limit for mercury in soil at this site based on results of this study, on reports in the literature on the intestinal and pulmonary absorption of mercury species from air, water and food; and on the normal intake of total mercury in humans reported by the World Health Organization. Based on reports in the literature and results from the present studies, we suggest an acceptable limit for mercury in soil (at this site) to be 722 ppm. With a safety factor of 10 this limit would be reduced to 72 ppm.

Water Quality Criterion for the Protection of Human Health: Methylmercury

Abstract: This document is the basis for a human health Ambient Water Quality Criterion (AWQC) for methylmercury This AWQC replaces the AWQC for total mercury in published in 1980 and partially updated in 1997 Under Section 304(a) of the Clean Water Act, EPA must periodically revise criteria for water quality to accurately reflect the latest scientific knowledge on the kind and extent of all identifiable effects of pollutants on human health This document uses new methods and information described in the Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000) (2000 Human Health Methodology) (USE PA,2 000a,b) These new methods include updated approaches to determine toxicity dose-response relationships for both carcinogenic and noncarcinogenic effects, updated information for determining exposure factors, and new procedures to determine bioaccumulation factors

Determination of Mercury Binding Forms in Contaminated Soils: Mercury Pyrolysis versus Sequential Extractions

Abstract: Binding forms of mercury (Hg) in contaminated soils were studied by means of a pyrolysis method and a sequential leaching procedure (SEP). Changes of the Hg-binding forms occurring during the sequential extraction procedure were characterized by determination of the thermal mercury release characteristics after each extraction step. Soil samples were selected from the site of a former chloralkali plant, a wood preservation site, and two mining areas contaminated by metallic mercury (Hg0), mercury(II) chloride (HgCl2), or mercury sulfide (HgS), respectively. The results show that Hg0, matrix-bound Hg, and HgS occurring in the studied soils could be identified by their thermal release behavior. In contrast, results obtained from sequential leach ing did not allow the identification of any specific Hg compounds as in all samples most of the Hg is extracted in the nonspecific residual Hg fraction. Results of pyrolitic measurements after each extraction step demonstrated the insufficient selectivity of the use...

Review : evaporation of mercury from soils. An integration and synthesis of current knowledge

Abstract: Understanding the mechanisms of mercury evaporation from soil to the atmosphere is necessary for tracing the fate of mercury in the biological environment and for assessing potential health effects and the impact of anthropogenic mercury emissions on the environment. In this article an integrating overview of the current knowledge of the mechanisms of mercury evaporation is presented. Abiological and biological formation of Hg(0) and/or (CH3)2Hg in the uppermost soil layers are the rate limiting processes of mercury evaporation from soils in background areas; the evaporation rate in background areas is probably strongly influenced by deposited airborne mercury. The evaporation rate limiting factors in mercury enriched mineralized areas with large fractions of total mercury being volatile mercury species (relative to background soil in the non-mineralized vicinity) meteorological variations and the transport characteristics of soils for volatile mercury species. Mercury evaporation rates from background soils are usually <0.2 μg·m–2·h–1 and significantly smaller than from mercury-enriched mineralized areas.