Diel Variability of Mercury Phase and Species Distributions in the Florida Everglades

Preliminary studies of mercury (Hg) cycling in the Everglades revealed that dissolved gaseous mercury (DGM), total mercury (HgT), and reactive mercury (HgR) show reproducible, diel trends. Peak water-column DGM concentrations were observed on or about noon, with a 3 to 7 fold increase over night-tim...

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Bibliographic Details
Published in:Biogeochemistry 1998-03, Vol.40 (2/3), p.311-325
Main Authors: Krabbenhoft, David P., Hurley, James P., Olson, Mark L., Cleckner, Lisa B.
Format: Article
Language:English
Subjects:
Algae
Arithmetic mean
Biogeochemistry
Chromophores
Desorption
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Everglades
Exact sciences and technology
Geochemistry
Mercury
Methylmercury
Mineralogy
Photolysis
Pollution, environment geology
Rain
Rubber
Silicates
Soil water
Sorption
Surface water
Water column
Water geochemistry
Water temperature
Wetlands
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Summary:Preliminary studies of mercury (Hg) cycling in the Everglades revealed that dissolved gaseous mercury (DGM), total mercury (HgT), and reactive mercury (HgR) show reproducible, diel trends. Peak water-column DGM concentrations were observed on or about noon, with a 3 to 7 fold increase over night-time concentrations. Production of DGM appears to cease during dark periods, with nearly constant water column concentrations that were at or near saturation with respect to the overlying air. A simple mass balance shows that the flux of Hg to the atmosphere from diel DGM production and evasion represents about 10% of the annual input from atmospheric deposition. Production of DGM is likely the result of an indirect photolysis reaction that involves the production of reductive species and/or reduction by electron transfer. Diel variability in HgT and HgR appears to be controlled by two factors: inputs from rainfall and photolytic sorption/desorption processes. A possible mechanism involves photolysis of chromophores on the surface of a solid substrate (e.g., the periphyton mat) giving rise to destabilization of sorbed mercury and net desorption during daylight. At night, the sorption reactions predominate and the water-column HgT decreases. Methylmercury (MeHg) also showed diel trends in concentration but were not clearly linked to the solar cycle or rainfall at the study site.
ISSN:0168-2563
1573-515X
DOI:10.1023/A:1005938607225