title: Principal biogeochemical factors affecting the speciation and transport of mercury through the terrestrial environment.
abstract: It is increasingly becoming known that mercury transport and speciation in the terrestrial environment play major roles in methyl-mercury bioaccumulation potential in surface water. This review discusses the principal biogeochemical reactions affecting the transport and speciation of mercury in the terrestrial watershed. The issues presented are mercury-ligand formation, mercury adsorption/desorption, and elemental mercury reduction and volatilization. In terrestrial environments, OH-, Cl- and S- ions have the largest influence on ligand formation. Under oxidized surface soil conditions Hg(OH)2, HgCl2, HgOH+, HgS, and Hg0 are the predominant inorganic mercury forms. In reduced environments, common mercury forms are HgSH+, HgOHSH, and HgClSH. Many of these mercury forms are further bound to organic and inorganic ligands. Mercury adsorption to mineral and organic surfaces is mainly dictated by two factors: pH and dissolved ions. An increase in Cl- concentration and a decrease in pH can, together or separately, decrease mercury adsorption. Clay and organic soils have the highest capability of adsorbing mercury. Important parameters that increase abiotic inorganic mercury reduction are availability of electron donors, low redox potential, and sunlight intensity. Primary factors that increase volatilization are soil permeability and temperature. A decrease in mercury adsorption and an increase in soil moisture will also increase volatilization. The effect of climate on biogeochemical reactions in the terrestrial watershed indicates mercury speciation and transport to receiving water will vary on a regional basis.
authors.affiliation: Department of Civil and Environmental Engineering, The University of Alabama, 260 MIB 7th Avenue and Campus Drive, Tuscaloosa, AL 35487-0205, USA.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Gabriel
authors.forename: Derek G
authors.initials: DG
authors.lastname: Williamson
mesh_terms: D000327:Adsorption; D001682:Biological Availability; D055593:Geological Phenomena; D005844:Geology; D006801:Humans; D008628:Mercury / Q000737:chemistry* / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000737:chemistry* / Q000378:metabolism*; D009930:Organic Chemicals; D012989:Soil Pollutants / Q000378:metabolism*; D012995:Solubility; D014835:Volatilization; D014873:Water Pollutants / Q000378:metabolism*
chemical_list: D008767:Methylmercury Compounds; D009930:Organic Chemicals; D012989:Soil Pollutants; D014873:Water Pollutants; D008628:Mercury
references.citation: Appl Microbiol. 1975 Apr;29(4):491-4
references.pmid: 804851
references.citation: Science. 1972 Mar 10;175(4026):1142-3
references.pmid: 17797394
references.citation: Arch Environ Contam Toxicol. 1981;10(2):193-201
references.pmid: 7224671
references.citation: Environ Pollut. 2001;111(1):67-74
references.pmid: 11202716
references.citation: Ecotoxicol Environ Saf. 1979 Mar;3(1):36-8
references.pmid: 44244
references.citation: Appl Environ Microbiol. 1985 Aug;50(2):498-502
references.pmid: 16346866
references.citation: Environ Sci Technol. 2002 Feb 15;36(4):690-5
references.pmid: 11878384
references.citation: Sci Total Environ. 2000 Oct 9;260(1-3):191-200
references.pmid: 11032127
references.citation: Bull Environ Contam Toxicol. 1994 May;52(5):691-8
references.pmid: 8186639
references.citation: Appl Environ Microbiol. 1993 Jan;59(1):290-5
references.pmid: 8439155
references.citation: Environ Health Perspect. 1993 Apr;100:31-8
references.pmid: 8354179
references.citation: Environ Pollut. 1991;71(2-4):131-69
references.pmid: 15092118
references.citation: Appl Environ Microbiol. 1997 Nov;63(11):4267-71
references.pmid: 9361413
references.citation: Environ Sci Technol. 1995 Jul 1;29(7):1867-75
references.pmid: 22176462
references.citation: Biotechnol Bioeng. 1984 Nov;26(11):1330-3
references.pmid: 18551657
references.citation: Environ Sci Technol. 1994 Dec 1;28(13):2366-71
references.pmid: 22176056
references.citation: Pestic Monit J. 1976 Dec;10(3):111-3
references.pmid: 1005063
references.citation: Environ Sci Technol. 2001 Dec 15;35(24):4773-82
references.pmid: 11775152
references.citation: Environ Sci Technol. 1973 Nov 1;7(11):1028-34
references.pmid: 22263944
references.citation: Science. 1974 May 24;184(4139):895-7
references.pmid: 17782380