Local impacts of coal mines and power plants across Canada. II. Metals, organics and toxicity in sediments

A Canada-wide survey was undertaken to study local impacts of coal mines an d coal-fired electrical generating stations. The first part dealt with thal lium in waters and sediments. This, Part II, deals with metals and organics in sediments as well as sediment toxicity to four different organisms. Sev eral elevated metal and PAH concentrations as well as high toxicity (based on biological sediment guidelines) were observed compared to uncontaminated sites. Based on Ontario's sediment guidelines, most of the studied sedimen ts fell in the "marginally to significantly polluted" category of sediment quality, although two belonged to the "grossly polluted" class due to the e xtremely high concentrations of some metals. The observed diversity of PAHs and near-unity carbon preference indices indicate non-biological origins o f the studied sediments. In this initial study, four different organisms, C hironomus riparius, Hyalella azteca, Hexagenia spp. (Hexagenia limbata) and Tubifex tubifex were used to determine sediment toxicity,which showed 50% of the tested sites were highly stressed.