Selenium, arsenic, and mercury in fish inhabiting a fly ash exposure gradient: interspecific bioaccumulation patterns and elemental associations.

Releases from coal ash impoundments can be a significant source of trace elements to the aquatic environment. In the present study, whole-body concentrations of As, Hg, and Se in various fish species inhabiting streams receiving a gradient of fly ash exposure are reported. High-exposure sites had elevated water concentrations of As, Mo, Se, and SO(4) . Fish were collected during two seasons in 2007. Mercury concentrations in all fish samples were low (range = 1.2-99 ng/g wet wt); highest As concentrations occurred in fish from high-exposure sites. Whole-body Se concentrations were low at reference sites but increased as the magnitude of fly exposure increased. For all sites combined, a significant (r(2)  = 0.60) correlation was observed between the geometric mean of each species' whole-body Se concentration and log-transformed water Se concentration. A significant inverse relationship was apparent with log-transformed whole-body Hg and Se concentrations (r(2)  = 0.56 for all species and sites combined), suggesting that high tissue Se levels antagonistically regulated Hg bioaccumulation. Sunfish (Lepomis sp.) from high- and medium-exposure sites had significantly higher Se body residues, but significantly lower Hg, relative to fish from low-exposure and reference sites. Ninety percent of fish from high-exposure sites had a surplus of Se, whereas all fish from reference sites had Se/Hg molar ratios <1.0. These ratios increased as water Se increased. Where fish have moderate to high exposure to fly ash-influenced water, Se tissue levels can be expected to be elevated (as well as As, in some cases), but tissue Hg concentrations will likely be low.