Persistent organic pollutants in the recent soils in the south of the Arkhangelsk Region
The paper presents the results of observations over the concentration levels and distribution patterns of pentachlorophenol (PCP) and hexachlorobenzene (HCB) in the recent soils in the south of the Arkhangelsk region after intensive long-term use of pentachlorophenol sodium salt (Na-PCP) as a commercial chemical in the past. In 2012, seventeen years after the termination of Na-PCP use as wood-preservation agent (biocide), the presence of PCP and HCB classified as persistent organic pollutants was determined in soils of the industrial site of the shutdown timber mill. The tendencies towards a decrease in the residual amounts of toxic organochlorine components of Na-PCP were revealed. At the same time, soil pollution with HCB remained at a high levels, several times higher than the health-based exposure limit (approximate permissible concentration, Rospotrebnadzor, Russia), while the concentrations of PCP for the most part already complied to the approved quantitative national regulations (human health soil quality guideline, CCME, Canada; regional screening level, US EPA). It has been shown that residual amounts of biocide impurity component (HCB) in soils repeatedly (by a factor of 4-47) exceed the main component (PCP) concentrations, determining the role of HCB as the high priority soil pollutant at present. The presence of PCP and HCB in the soils of the residential settlement area suggests that recent soils of the industrial site of the timber mill present an active secondary source of persistent organic pollutants to the environment, with the threat of its distribution as a result of local, regional and global transport in the long-term future.