METHODS DEVELOPMENT FOR REPRODUCIBLE METAL BIOMONITORING ANALYSES IN FISH

While economically important, metals pose significant environmental and human health risks. Anthropogenic industrial activities release significantly more metals into the atmosphere and water systems than natural sources (e.g., weathering of rocks, volcanism). Quantifying metals in fish has global applications for biomonitoring in aquatic environments. Metal analyses in fish can elucidate contamination in the environment and health risks associated with fish consumption. However, we found in a survey of 115 published studies that sample preparation techniques in this field lack standardization, hindering data comparison between publications. To improve this potentially compromising situation, we carry out a three-part study that investigates the following areas in the analysis of metals in fish: (1) contamination during sample drying and homogenization, (2) analysis of biological reference materials alongside samples, and (3) selection of appropriate tissues and organs for analysis. Previous studies frequently report drying with an oven or freeze-drier and grinding with an agate or a porcelain mortar and pestle. In this study, we report measurable sample contamination in salmon muscle samples during homogenization with porcelain tools compared to the use of agate, but no difference between freeze- and oven-dried samples. The analysis of certified reference material TORT-3 samples yields typical recovery percentages based upon elemental concentrations (83 – 106 %) and reproducible Pb isotope ratios, supporting the use of TORT-3 as an in-house reference for Pb isotopic analyses but not as a reference material for all metal concentrations. Finally, we report metal concentrations in six tissues (digestive system, gills, gonads, kidney, liver, and muscle) from wild Pacific pink salmon. Concentrations are lowest in muscle (3.18 ± 0.89 ppb Cd, 0.24 ± 0.07 ppb Pb) and gonad tissues (4.39 ± 2.06 ppb Cd, 0.34 ± 0.13 ppb Pb) while other organs show considerable variation (34.4 – 2031 ppb Cd, 10.2 – 12.8 ppb Pb), highlighting the importance of tissue selection and dissection techniques to fish biomonitoring studies. The methodological improvements presented here can lead to the standardization of sample preparation techniques that will improve the quality of metal monitoring studies essential to protecting water quality from anthropogenic contamination.