Concentration Trends for Lead and Calcium-Normalized Lead in Fish Fillets from the Big River, a Mining-Contaminated Stream in Southeastern Missouri USA

Lead (Pb) and calcium (Ca) concentrations were measured in fillet samples of longear sunfish (Lepomis megalotis) and suckers (Catostomidae) collected in 2005‒12 from the Big River, which drains a historical mining area in southeastern Missouri, where a consumption advisory is in effect due to elevated Pb concentrations in fish. Regression analysis indicated that fillet Ca explained 75‒>99% of fillet Pb variation in mining-affected stream reaches. We used analysis-of-covariance to standardize Pb concentration to a common Ca concentration (415 ug/g wet weight), which reduced differences between taxa. Variation among sites and years also was reduced after Ca-normalization, as was the number of samples that exceeded the 300 ng/g wet weight advisory threshold used in Missouri. Concentrations of Pb in 2005-12 were lower than they were in the past, especially after Ca-normalization, but the consumption advisory is still warranted. A simple linear regression model is proposed for estimating Ca-normalized Pb concentrations in fillets.