A Methodological Approach to Assessing Sources and Pathways for Persistent Organic Pollutants in Freshwater Bodies

Abstract

Introduction: An urgent problem of aquatic ecotoxicology is the global pollution of the aquatic environment with hazardous persistent organic pollutants (POPs). They persist in the environment despite the ban on their production and use in most industrialized countries. The danger of POPs for humans and animals depends on duration of their stay in the environment (short- or long-term) and pathways into the water body (from local point or diffuse atmospheric sources). Objective: To determine the quantitative and qualitative composition of different groups of POPs (PCBs, DDT, HCCH) in bottom sediments of some freshwater bodies of the Russian Federation and propose a methodological approach to determining pollutant sources and pathways. Materials and methods: The study was conducted in 2006–2018 at 13 water bodies of four morphological and hydrological types: large circulating water reservoirs, large lakes, small marsh lakes, and river estuaries. 86 samples of bottom sediments were taken from the surface horizon of 0 to 5 cm. POP concentrations were measured in the air-dried samples by high resolution gas chromatography/mass spectrometry. Results: The analysis showed that, in most cases, POPs entered the studied freshwater bodies with precipitation. That was evidenced by the spectra of their qualitative composition transformed towards dechlorination compared to the initial commercial products, even spatial distribution, and a low content. We found, however, that POPs still get into some water bodies from industrial sources, as shown by the unchanged spectrum of their qualitative composition relative to the initial commercial products, gradient spatial distribution, and high concentrations. Conclusions: To establish the main pathways for POPs to get into water bodies, it is necessary to analyze the upper layer of silty bottom sediments, evaluate the total content of each pollutant and its individual components (homologous groups, metabolites, isomers), and determine spatial distribution of compounds in the water area.