ISSN:
1573-515X
Keywords:
diel variability
;
Everglades
;
mercury cycling
;
methyl mercury
;
photochemical processes
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
Notes:
Abstract 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1005938607225
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