This study is a follow-up to a fish sampling study conducted in the Flint Creek by the Alabama Department of Public Health that showed mercury levels slightly elevated in fish over regulatory standards which led to the public health advisory for largemouth bass from Flint Creek. Mercury concentrations were measured in tissues of 30 fish samples from 3 trophic species collected at 3 sites along the Flint Creek in 2011-2013. The water and soil/sediment samples were also collected and analyzed for total mercury (tHg), total organic carbon, dissolved organic carbon and other water quality parameters. tHg in sediment in all sites ranged 0.0138-0.0624 ppm dry weight, with the highest levels in Site 3. Mercury levels in sediment there were above the threshold effects level suggested as a preliminary screening level by NOAA (Acute = 0.0014 ppm, Chronic = 0.00077 ppm). The range for fish sample total mercury concentration in this study was 0.0303-0.295 ppm. The FDA’s mercury concentration limit (MCL) for human consumption is 1.0 ppm in fish. This study’s MCL range for Summer and Fall was 0.0112-0.0876 ppm and 0.0125-0.295 ppm for Winter and Spring. USEPA MCL is 0.3 ppm. The differences in tHg concentrations in fish can be attributed to higher flows and mercury associated with increased sediment and organic material in the water during the winter months and, therefore, higher bioaccumulation. Mercury levels measured in water of Flint Creek are low and pose little risk to drinking water contamination, but the mercury levels in soil/bed-sediment are high and pose high risk to aquatic species in the river reaches. However, both the source of mercury in Site 3, and the mechanisms resulting in higher fish mercury level in winter have yet to be clearly identified

Seasonal differences in mercury concentrations in fish from Flint Creek, Alabama: Implications for monitoring

253rd National Meeting (2017)

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