Distribution of pollutants in the Odra River system. Part V. Assessment of total and mobile heavy metals content in the suspended mattr and sediments of the Odra River system and recommendations for river chemical monitoring

The extensive investigations of total and mobile heavy metals concentrations in sus­pended matter (SPM) and bottom sediments of the upper and middle Odra river were carried out over the years 1997–2000. Significant levels of contamination were found. Median concentrations for Cd, Pb, Cu, Zn and As in the SPM and sediments were (mg/kg) 7.3 and 8.9, 97.2 and 119, 79.2 and 92.7, 1221 and 1158, and 52.9 and 67.9, respectively. The highest metal pollution of Odra river solids was found with cadmium, zinc, lead and arsenic. The frequency distribution of Cd, Zn, Pb and As in both type of samples, i.e. SPM and sediments, shows high similarity. >From all metals studied, Cd, Zn and As appear to be of particular concern because of the high levels, that appear to be bio­available, and their high mobility. The exchangeable and carbonatic fractions of Cd and Zn reached up to 50% of their total amount. Besides the determination of total metal concentration, the “mobilisation test” of metals in river solids is rec­ommend for monitoring purposes, allowing evaluation of the most mobile, and bioavailable metal fractions. The results of four years of very wide studies of Odra river system suggest that for river monitoring pur­poses, the fre­quency and numbers of samples for chemical analysis of both water and solids - preferably suspended matter - could be reduced to twice a year, with few select sampling sites.