Influence of Seasonal and Anthropogenic Factors on Changes in Concentrations of Heavy Metals in Urban Water Systems

The concentrations of zinc (Zn), cadmium (Cd), lead (Pb) and copper (Cu) compounds in bottom sediments and surface waters of the Chernaya River in St. Petersburg in the spring-summer and autumn periods were determined. Analysis of water quality at the river source (sampling point S1) revealed a persistent anthropogenic impact on the water system associated with heavy metal pollution throughout the entire observation period. The ecological situation in bottom sediments was assessed. The most polluted areas were found near the source of the river, at point S1. According to the geo-accumulation index (I_geo), contamination with cadmium and copper is assessed as moderate, while for mercury (Hg) this indicator ranges from moderate (spring) to severe (summer). In areas with high anthropogenic impact, the proportion of mobile forms of metals in bottom sediments increases.