evaluation of some physiochemical parameters and heavy metal contamination in hara biosphere reserve, iran, using a new pollution index approach

background: the pollution of the aquatic environment with heavy metals has become a worldwide problem during recent years, due to their potential toxic effects and ability to bio-accumulate in aquatic ecosystems. heavy metals are sensitive indicators for monitoring changes in the aquatic environment. methods: in this study, total concentrations of cr, pb, cu, zn, and fe were measured in water and sediments from nine sites, based on ecological conditions and human activities and the effects of sediment ph and sediment organic matter on bioavailability of selected metals were determined. modified degree of contamination (mcd) was computed in order to determine anthropogenically derived sediment contamination. results: mean concentration of metals in water found to be in the following order: pb > fe > zn > cu > cr, while in sediment samples it was fe > cr > zn > pb > cu. the average content of examined metals in water was higher than the chronic values in marine surface water guideline values. mean content of cr, pb and fe in sediments were higher than average of the less contaminated sample but cu and zn were lower than this guideline value. in the study area, mcd values were less than 1.5 with values ranging from 0.71 to 1.02. conclusion: the results of this study indicated with a decrease in organic matter and ph in sediments, the concentration of copper and iron increased. base on modified contamination degree, the sediments of hara biosphere reserve are considered to be in the zero to very low contamination status.