Role of Oxidation-Reduction Processes in Formation of Toxic Properties of Natural Aqueous Environment

Abstract

Redox processes involving hydrogen peroxide, as oxidizing agent, and compounds of sulfur as carrier of reducing equivalents form the quality of natural waters. The inflow of reductants interacting with H2O2 can lead to a toxic quasi-reductive state. Dynamic change of redox in a natural aqueous medium is pernicious for organisms with intensive water-exchange, such as larvae of fishes, despite the concentration of dissolved oxygen being normal. Favorable conditions for “flowering” of emerging toxins blue-green alga are formed. In reductive state, copper ions become biologically unavailable. Sewage after biological cleaning are the main anthropogenic source of the reductants, mainly hydrosulphide. The natural sources of reductants are blue-green alga and the bottom sediments. The ions of Cu(I) and Fe(II) form high-strength 1:1 complexes with reduced sulfur compounds that are stable to O2 but efficiently react with H2O2. The increased content of manganese can form mixed-valence manganese species Mn(III,IV) giving super-oxidizing state of the aquatic environment, which is also toxic.