The spatial and temporal variability of dissolved organic carbon (DOC) in surface and pore waters is being studied in the Everglades in an effort to define the effect of DOC on the transport and reactivity of mercury (Hg). It is hypothesized that the organic sulfur content, molecular weight, functional group chemistry, and lability of the organic matter have a controlling influence on Hg cycling processes such as methylation and volatilization. Specific ultraviolet absorbance (SUVA) measurements, in combination with DOC and DOC fractionation analyses, were used to determine both the amount and nature of DOC along a north-south transect (approximately 40 mi.). Samples collected in the northern part of the transect had higher DOC concentrations, were more aromatic, and had a greater amount of hydrophobic acids and hydrophobic neutrals than samples collected further south. In addition, pore waters were found to contain greater DOC concentrations than overlying surface waters. The pore waters in the eutrophic areas to the north were found to contain the highest DOC concentrations. DOC concentrations and SUVA were found to be lower in those areas with higher concentrations of methyl mercury. Nonvolatile hydrophobic and hydrophilic organic acids were found to be the major fractions of the DOC at all locations along the transect. Isolated samples were found to be highly aromatic and to contain greater amounts of organic sulfur compared to similar samples from other environments. Preliminary results of laboratory studies indicate strong interactions between the isolated samples and Hg+2.

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