Ecologo-Geochemical Conditions of the Water Bodies Within the Damodar River Basin (India) During a Low-Water Period

Abstract: Ecologo-geochemical conditions of surface water and groundwater are considered in the case of one of the industrially most developed states of India, West Bengal, within the Damodar river basin near Damodar City. The observations were made in the pre-monsoon period of March 2019, a period with the worst conditions of wastewater dilution. To analyze total chemical composition of water samples, a standard set of analytical methods was used; trace elements were analyzed by inductively coupled plasma mass spectrometry. Data obtained indicate both the unsatisfactory water quality and the intense self-purification processes. The waters under study are, in general, characterized as freshwaters (except for the stream receiving wastewater from the chemical plant where the water is “brackish”), HCO₃–Ca or HCO₃–Na (except for the water in the stream near the chemical plant, which is Cl–Na, and groundwater, which is Cl–Ca). In most cases, the waters are oversaturated with carbonates, compounds with humic acids, quartz and undersaturated with primary aluminosilicates. The main ollutants are organic compounds according to the values of permanganate demand and chemical oxygen demand, Al, F^–, NH₄⁺, Fe, and Mn. Phosphates, As, Pb, and some other chemical elements are also present in significant concentrations It is shown that most pollutants settle in bottom sediments of the streams receiving wastewater from industrial enterprises within a few kilometers from the wastewater discharge points. The mechanism of water selfpurification is, possibly, associated with co-precipitation and sorption of a great number of substances on particles of poorly soluble carbonates and hydroxides of Ca, Fe and some other metals at relatively high pH values associated with the consumption of carbon dioxide by microorganisms.