Inorganic mercury speciation for Everglades surface water is calculated to be similar using either WHAM or PHREEQC computer programs. WHAM predicts that for Everglades surface water in Water Conservation Area 2A, site U3, the predominant mercury containing (dissolved) species is a mercury hydroxide-fulvic acid complex. This prediction may hold true for much of the Everglades surface water. The mercury ion plus hydroxide ion apparent (valid at the U3 temperature, ionic strength, and pH) binding constant to DOC is about 1023. Mercury-DOC complexes must be considered in models of Everglades surface and pore waters to get an accurate description of mercury chemical reactivity and bioavailability.
Incorporation of sulfur containing functional groups into the WHAM model is an ongoing project activity. Requirements for incorporation of the discrete site/electrostatic model from WHAM into PHREEQC are being examined.