Heavy Metals in the Bottom Sediments of the Northern Caspian Sea Region during the Period from 2012 to 2021

Heavy metal pollution of the bottom sediments in the Northern Caspian Sea region was assessed for the period from 2012 to 2021. The concentrations and pollution levels of heavy metals were determined using the standard indices as part of the industrial environmental monitoring at the license site in the northern part of the Caspian Sea. Based on the concentrations of all identified metals (zinc, copper, lead, cadmium, nickel, iron, and manganese), significant spatial and temporal variations were observed. The values obtained did not exceed those of international sediment quality standards, thus suggesting that the studied bottom sediments were only slightly polluted by heavy metals. However, certain areas showed high levels of pollution, such as the northwestern area with the elevated iron levels and the central area with the maximum lead and cadmium concentrations. The statistical analysis of geochemical parameters of the bottom sediments revealed distinct patterns in the distribution of heavy metals.