Content and potential sources of PAHS and PCBS in soils and bottom sediments of the Siberian Arctic

Abstract

Assessment of environmental pollution in the Arctic is becoming increasingly important in the context of active industrial development and global climate change. In this study, soils and bottom sediments from the northern regions of Western and Central Siberia were analyzed for persistent organic pollutants including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Total contaminant concentrations were quantified and spatial trends in the relative distribution of individual PAH and PCB groups were identified across Arctic subregions defined by the CAFF working group. Potential pollution sources were evaluated using non-metric multidimensional scaling (nMDS) and ANOSIM. Furthermore, the specific characteristics of lake bottom sediment pollution under the influence of active oil and gas production were examined. Total PAH concentrations in background soils and sediments ranged from 0.3 to 112.6 µg/kg dry weight, exhibiting a significant northward increasing gradient, heavily dominated by low-molecular-weight (2–3 ring) compounds. In contrast, total PCB concentrations remained uniformly low, ranging from 0.2 to 9.0 µg/kg dry weight regardless of the subregion. The nMDS ordination demonstrated a pronounced decrease in the diversity of PAH compositions with increasing latitude and proximity to nearest industrial center, reflecting the combined effects of temperature-dependent atmospheric fractionation and regional emissions. Compositional fingerprinting confirmed that the background PCB pollution was predominantly driven by the historical regional footprint of Soviet “Sovol” technical mixtures. Compared to pristine background baselines, lake sediments within active oil and gas fields exhibited an increase in both the total content and the relative abundance of heavy PAHs. In contrast, local hydrocarbon extraction activities did not influence either the total loads or the homologous profiles of PCBs, leaving the stabilized regional historical background unaltered.