Influence of Atmospheric Precipitation on Geochemistry of City Lake Systems

Abstract

Lakes in urban areas are subject to both anthropogenic and climatic influences that control their chemical composition, as well as water and salt balances. This study presents data on the influence of atmospheric precipitation on the geochemistry of urban lake systems. The chemical composition of lake water is dominated by chlorides, bicarbonates and sodium ions. Dissolved-solids concentrations in the larger lakes range from 0,34 to 0,91 g/l, reaching 2,3 g/l in some lakes. Although the ratios of major components in the lake water chemistry are relatively stable, concentrations of some components in the lakes depend on the chemical composition and amount of precipitation. The study indicates a recent increase in acidity and a decrease in dissolved-solids concentration in the lake waters related to climatic factors, such as the changes in qualitative and quantitative characteristics of precipitation and the increased atmospheric deposition of Н⁺-cation. It is predicted that the lake waters will continue freshening with their quality improved. The decline in major and minor element concentrations is most significant for sulfates and decreases in order: SO ²> Ca²⁺ > Cl^- > Na⁺ > Mg²⁺, pH. The adverse ecologo-sanitary situation in the city lakes will remain for sodium ions, and ammonium and nitrite compounds of nitrogen.