RESUMO
Mercury (Hg) is a highly toxic metal posing a hazard to water ecosystems. This investigation was aimed at determining Hg content in the Tanew River, Poland, and subsequent transfer to fish inhabiting this lake. The area studied included approximately a 50-km distance of the river, with 5 sampling locations selected. Samples of water and bottom sediments were collected from 10 sites along the river-bank zone for each location. At the same location, fish were caught and samples of coastal water plants were collected. Fish that were caught included the following species: chub (Leuciscus cephalus), pike (Esox lucius), ide (Leuciscus idus), and roach (Rutilus rutilus). Dominanting species of water plants included reed-mace (Typha angustifolia), rigid hornwort (Ceratophyllum demersum), and water knotweed (Polygonum amphibium). Mercury content in samples of water, bottom sediments, water plants, and fish tissues (muscles and gills) were determined by using a Mercury/MA-2000 system (NIC, Japan). The average Hg content in the waters of Tanew ranged between 1 and 5 microg/L, and in the bottom sediments ranged between 17 and 214 microg/kg dry weight, which are characteristic values for typical unpolluted areas. The highest Hg contamination of waters and bottom sediments was found where the Tanew estuary enters the San River. Mercury levels in fish from the Tanew delta appeared to be higher compared to other sampling sites. Data indicated that even if water environment is contaminated with Hg to a limited extent, fish accumulate this metal at higher levels, probably due to a bioaccumulation or bioconcentration factor.
