Content of heavy metal compounds in bottom sediments of the Suchedniow water reservoir

Abstract

Water reservoirs become silted at various intensity levels. Within the reservoir bowls, both allochtonic (built up outside the sedimentation area) and autochtonic (built up in the sedimentation area) matter is accumulated. As a result, reservoirs need desilting after a while. Then a problem arises how to manage the sludge removed from the reservoir bottom. The chemical properties of the bottom sludge, and particularly the content of heavy metals, decide whether it will be possible to use the sludge, and in what way. The chemical properties of the bottom sludge depend, to a far extent, on the character of the reservoir basin, the level of its urbanisation, and also on the climatic conditions. The paper presents the results of investigations into the content of heavy metals in the bottom sediments in the Suchedniow water reservoir. This water body is characterised by small mean depth of 1.05 m and mean annual flow across the dam profile of 0.63 m 3 · s -1 . Forests dominate in the reservoir basin covering 45 % of its area, arable land constitutes 18 %, and the percentage of built-up area does not exceed 5 %. In recent years (2009-2011), the water reservoir has become much silted because of storing large soil masses near the local watercourses during the construction of S7 expressway. The amount of stored soil is estimated at 7.8 thousand m 3 . For investigations, nine bottom sediments samples were collected, in which the content of the following heavy metals: Pb, Cr, Cd, Cu, Ni, Zn, Fe, and Mn was determined. Quasi-undisturbed sludge was taken into transparent cylinders with Eijkelkamp sampler, which made it possible to conduct analysis in sediment layers 20 cm in height. In order to evaluate the sediment pollution with heavy metals, the geoaccumulation index, the pollution coefficient and level were calculated. On the basis of admissible soil chemical pollution tables, the possibility of the sludge use in agriculture after extracting it from the reservoir bowl was assessed.