An integrated approach to assessing the quality of sediments in the Great Backa and Bega canals, Serbia

To improve the process of achieving good ecological and chemical status of waters, it is proposed that issues regarding the sediment in water bodies be incorporated in national and international river basin management programs. For a more realistic sediment quality assessment, multidimensional approaches that include various methods are preferred. The northern part of Serbia has an intertwined network of canals that receive untreated industrial and municipal wastewaters and pollution from the surrounding agricultural land. This leads to the accumulation of large amounts of sediments with varying quality in the canals. To assess the quality of the Great Backa and Bega canal sediments, an analysis based on chemical, ecological and ecotoxicological methods was conducted and the sediment quality triad approach was applied. Ecotoxicological data was obtained in a battery of tests on standard organisms belonging to different trophic levels in various exposure scenarios. Sediment contact tests on Myriophyllum aquaticum, immobilization tests on Daphnia magna (in water–sediment and elutriates) and Allivibrio fischeri bioluminescence tests (in elutriates) were performed. In addition, a small-scale accumulation test of potentially toxic elements on exposed plants was conducted. Responses of test organisms in the Great Backa samples were in line with the results of chemical analysis or stronger, while the analysis of aquatic macroinvertebrates reflected bad ecological potential of the canal. The Bega samples were highly contaminated and the ecological potential of the canal was graded as bad, but the ecotoxicological tests did not reveal high toxicity of samples. Plants exposed to samples from both canals took in metals, but inhibition of growth was detected only in the Great Backa samples, while the growth in the Bega samples was stimulated. The principal component analysis revealed no significant correlation between organism responses and results of chemical analysis. Based on the SQT applied, there is a likelihood of adverse effects posed by sediments from both canals. Ecotoxicological tests complemented the commonly applied methods for sediment quality evaluation. The triad approach applied with the addition of the accumulation test contributed to a more ecologically relevant sediment quality assessment. Results indicated that remediation, dredging or mitigation measures are required.