Keywords: fish, gold mining, human exposure, mercury contamination, water pollution, environmental pollution, surface water, Venezuela, rivers, streams, mining ponds, springs, human health risks
Mercury contamination of surface water and fish in a gold mining region (Cuyuni river basin, Venezuela)
In the Cuyuni river basin (Venezuela), artisanal gold mining has caused significant mercury pollution due to extensive use of Hg in Au amalgamation processes. High Hg concentrations up to 4.60 ?g/l were recorded in surface water samples (rivers, streams, mining ponds, springs), which are three orders of magnitude higher than normal worldwide background values (0.003?0.005 ?g/l). Furthermore, Hg contents in river water are two orders higher than the EPA guideline for aquatic life and the concentration in drinking water exceeds the WHO recommended value. The seasonal Hg variation in the Cuyuni river samples shows high loading rates during the raining period, which can be associated with high particulate and TOC contents caused by high run-off rate. Mercury concentration in edible fish tissue depends on the feeding habit, e.g. carnivorous species show higher Hg concentration (range 0.32?1.92 mg/kg) than herbivorous species (range 0.12?0.46 mg/kg). Carnivorous species present a high potential health risk to local populations since they exceed the established limit of 0.5 mg/kg for food (EU Regulations). Human health risk calculations based on WHO and EPA reference doses are presented.