Determination of moderately polar arsenolipids and mercury speciation in freshwater fish of the River Elbe (Saxony, Germany)

Abstract

Arsenic and mercury are frequent contaminants in the environment and care must be taken to limit their entrance into the food chain. The toxicity of both elements strongly depends upon their speciation. Total amounts of As and Hg as well as their species were analyzed in muscle and liver of 26 fishes of seven freshwater fish species caught in the River Elbe. The median concentrations of As were 162 μg kg−1 w.w. in liver and 92 μg kg−1 w.w. in muscle. The median concentrations of total Hg were 241 μg kg−1 w.w. in liver and 256 μg kg−1 w.w. in muscle. While this level of Hg contamination of the freshwater fish in the River Elbe is significantly lower than 20 years ago, it exceeds the recommended environmental quality standard of 20 μg Hg kg−1 w.w. by a factor of 5–50. However, the European maximum level of 500 μg Hg kg−1 for fish for human consumption is rarely exceeded. Arsenic-containing fatty acids and hydrocarbons were determined and partially identified in methanolic extracts of the fish by HPLC coupled in parallel to ICP-MS (element specific detection) and ESI-Q-TOF-MS (molecular structure detection). While arsenobetaine was the dominant As species in the fish, six arsenolipids were detected and identified in the extracts of liver tissue in common bream (Abramis brama), ide (Leuciscus idus), asp (Aspius aspius) and northern pike (Esox lucius). Four arsenic-containing fatty acids (AsFA) and two arsenic-containing hydrocarbons (AsHC) are reported in freshwater fish for the first time. With respect to mercury the more toxic MeHg+ was the major species in muscle tissue (>90% of total Hg) while in liver Hg2+ and MeHg+ were of equal importance. The results show the high relevance of element speciation in addition to the determination of total element concentrations to correctly assess the burden of these two elements in fish.