How humic substances dominate mercury geochemistry in contaminated floodplain soils and sediments

Journal Article · Tue Sep 01 04:00:00 EDT 1998 · Journal of Environmental Quality

DOI:https://doi.org/10.2134/jeq1998.00472425002700050009x· OSTI ID:290139

Wallschlaeger, D; Desai, M V.M.; Spengler, M; Windmoeller, C C; Wilken, R D ^[1]

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1. GKSS Forschungszentrum GmbH, Geesthacht (Germany). Inst. fuer Physikalische und Chemische Analytik

The interaction of mercury (Hg) and humic substances (hs) was studied in floodplain topsoils and surface sediments of the contaminated German river Elbe. An intimate coupling exists between the geochemical cycles of Hg and organic carbon (OC) in this ecosystem. Humic substances exert a dominant influence on several important parallel geochemical pathways of Hg, including binding, transformation, and transport processes. Significant differences exist between the Hg-hs associations in floodplains and sediments. Both humic acids (ha) and fulvic acids (fa) contribute to Hg binding in the sediments. In contrast, ultrafiltration experiments proved that Hg in the floodplain soils is almost exclusively bound to very large humic acids (ha) with a nominal molecular weight (MW) > 300,000. Successive cation and anion exchange experiments demonstrated that those Hg-ha complexes are inert toward competition by other cations, and also apparently predominantly electroneutral. Speciation transformation reactions in the solid phase were investigated by sequential extraction and thermal release experiments. Upon addition of Hg model compounds to a sediment matrix, all species were transformed to the same new speciation pattern, regardless of their original speciation. The accompanying alterations in availability and solubility were partially due to interconversion between the different Hg redox states, including Hg(I). Simultaneously, partial transformation of added Hg{sup 2+} into volatile Hg compounds (35% in 10 d) was observed. Finally, Hg association with water-soluble ha continuously increased downstream, indicating that hs play a key role in both lateral and longitudinal Hg transport in the Elbe ecosystem.

• Sponsoring Organization: USDOE
• OSTI ID: 290139
• Journal Information: Journal of Environmental Quality, Journal Name: Journal of Environmental Quality Journal Issue: 5 Vol. 27; ISSN JEVQAA; ISSN 0047-2425
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ENVIRONMENTAL TRANSPORT
FEDERAL REPUBLIC OF GERMANY
GEOCHEMISTRY
HUMUS
MERCURY
SEDIMENTS
SOIL CHEMISTRY
SOILS
WATER CHEMISTRY
WATER POLLUTION