Organochlorine compounds in subarctic small lakes

Abstract

The article presents the results of studies of the environmental properties of organochlorines which differ in properties and origin, in the lake ecosystems of the Bolshezemelskaya tundra (Nenets Autonomous Okrug, Russia). The purpose of this study was to evaluate and assess the levels, distribution characteristics and composition of organochlorines in the bottom sediments of small lakes located in the Adzva river basin in Pymvashor natural boundary (the northernmost location of the exit of thermal-mineral springs of the continental Europe) and in the adjacent area, outside this unique subarctic hydrothermal zone.In order to meet this goal, multi-method (hydrochemical, geochemical, etc.) research was carried out using standard generally approved laboratory practices with their adaptation to the study goals. The quantitative content and composition of the target individual organochlorines were determined by gas chromatographic method with electron-capture detection.The presence of chlorophenol compounds and polychlorinated benzenes (including persistent organic pollutants) was shown in the lakes sediments. The influence of specific microclimatic conditions of subarctic hydrothermal system on the composition and distribution of chlorophenol compounds in lake sediments was considered. In the small lake sediment core in Pymvashor natural boundary a reducing trend in the levels of organochlorines with depth has been recorded (conditioned among other things by the lithological features of bottom sediments). The chlorophenol compounds were found at highest concentrations (619.3–765.5 ng/g) in the sediment upper layers, rich in organic matter; chlorophenol composition was represented mainly by chlorinated phenols, most likely of biotic origin. A lower concentration (185.0 ng/g) of chlorophenol compounds of predominantly abiogenic origin was determined in the lake sediments outside hydrothermal system. The presence and levels of persistent organochlorine pollutants (pentachlorophenol 0.1–2.4 ng/g; hexa- and pentachlorobenzenes 0.4–3.6 ng/g) in the lake sediments were associated with long-range atmospheric transport from various origin sources in nearby regions and low-latitude territories.