THE IMPACT OF HUMAN ACTIVITIES ON FRESH-WATER AQUATIC SYSTEMS

The roles of oxygen and its activated species (superoxide radicals, hy drogen peroxide, hydroxyl radicals), as well as that of sulfur compoun ds, are considered in relation to biological quality and the self-clea ning capacity of freshwater aquatic systems. The effects on the aquati c redox-processes are discussed in terms of atmospheric fallout of sul fur compounds, bottom sediment composition, and input of wastewaters c ontaining reducing substances. It is shown that the totality of anthro pogenic influences, and/or unfavourable natural geochemical conditions , as well as climatic effects in a region can increase the signifcance of one-electron transfer processes in bio-geochemical cycles of oxyge n, sulfur and manganese, compared with the significance of two-electro n transfer processes. The resulting, reactive intermediate products of one-electron transfer processes are very important with respect to th e composition and properties of aquatic systems. Examples are given of practical applications of wastewater treatment, using hydrogen peroxi de and UV-irradiation, and of regulation of consumers' activities whic h affect natural waters.