Patterns and Variability of Phosphate and Heavy Metals in Sediments of Two Shallow Lakes

摘要

It can be stated that the quality of surface water has deteriorated in time. Many impurities can be included in the sediments. Sediments form a chemical reservoir and reduce the concentrations of many chemicals, compounds and materials in the water standing above. Surface water quality can be improved by treating sewage and industrial wastes before discharge onto open water. After this has taken place, the lake sediments can act as a new source of pollution, partly negating the effects of treatment. As a contribution to the study of these effects in the aquatic system, the sediments of two unstratified shallow lakes, Lake Westeinder and Lake Elfhoeven, both located in the Netherlands, were investigated. Lake Westeinder is part of a balancing system of a water-board, Lake Elfhoeven is part of a polder system. The surface water that feeds the lakes contains only small amounts of suspended solids. 30 totally undisturbed core-samples with a length of 50 cm and a diameter of 11 cm were taken. These cores were sliced. The horizontal and vertical distribution of the following elements were determined Al, As, Ca, Cr, Co, Cu, Fe, K, Mg, Mn, Ni, Pb, Si, Sr, Ti and Zn. Furthermore, the water content, the ortho-phosphate and total-phosphate concentrations of the interstitial water and the total phosphate content of the sediment were determined. The fractionation of iron compounds and, by implication, of phosphates in the sediments were studied through Mossbauer Spectroscopy.