The development of freshwater deltas and their environmental and economic significance

Abstract

The article presents the results of studies concerning the delta forms that arise as a result of the sedimentation of the debris fed to water bodies by watercourses. The study covered several dozen anthropogenic water bodies in the Upper Silesia region, which is well known for its high degree of urbanisation and industrialisation. Basic research work included morphometric measurements of deltas, analyses of the mechanical and chemical composition of delta sediments and analyses of the chemical composition of the common reed growing on the deltas. The research has demonstrated that the deltas exhibit certain characteristics typical of anthropogenic forms that result from the pollutants found in watercourses. In delta sediments, grains of sand usually dominate, but in many cases the share of the < 0.02 mm fraction is as high as ca. 30%. Sediments often contain fine coal and other organic pollutants, which is reflected by high weight loss on ignition. The content of trace elements in delta sediments is usually many times higher than the geochemical background for all types of sedimentary rocks. Deltas are an environment where pollutants accumulate and some of them are assimilated by plants. The content of macro elements in common reed tissues from different deltas does not vary widely while the content of trace elements often results from their content in the sediments. The material that forms deltas can be extracted and in some cases even used as fuel.