METHYLMERCURY DISTRIBUTION AND UV-254 SPECIFIC ABSORBANCE AS A REAL-TIME INDICATOR OF MERCURY METHYLATION, LAKE FORT SMITH, ARKANSAS, USA

Mercury contamination associated with human activities poses global human health and environmental risks. A fish-consumption advisory has been in effect at Lake Fort Smith in central west Arkansas for more than a decade. Lake Fort Smith is an important water supply and recreational resource. Water samples from tributary streams were collected periodically, , under differing hydrologic conditions, to quantify the allochthonous mercury load delivered to the lake. Temperature, specific conductance, dissolved oxygen, and specific (254nm) ultraviolet absorbance data were collected and used to estimate total organic carbon delivery to the lake. Total organic carbon concentration has been previously shown to have a strong correlation with methylmercury in surface waters. As such, measurement of total organic carbon by ultraviolet absorbance can serve as an inexpensive, real-time proxy for qualitative determination of methylmercury. This methodology provided better understanding of variations in mercury load seasonally and under differing hydrologic regimes and provided a comparison of allochthonous mercury vs. mercury delivered by direct fallout to the lake.