Technogenic pollution of pine forests by polycyclic aromatic hydrocarbons

Anthropogenic pollution of boreal forests by polycyclic aromatic hydrocarbons was assessed by polycyclic aromatic hydrocarbon (PAH) concentrations in needles of Scots pine (Pinus sylvestris L.) trees growing in the vicinity of the Bratsk aluminium smelter – one of the largest aluminium smelters in the world. The fieldwork was performed in 2012–2013 on 34 index plots, set in mixed herb and sedge-mixed herb pine forests (mostly site class III). It is shown that the total accumulation of PAHs reaches its highest level (more than 6000 ng/g) in pine needle samples collected at sites up to 3 km from the aluminium smelter. PAH total quantity decreases with increasing the distance from the pollution source and at a distance of 50 km reaches values close to background ones. The highest concentrations of PAHs were detected in needle samples collected at plots located from the plant in a direction corresponding to the prevailing emissions transfer. There was also detected a significant difference in compositions of individual PAHs: there were 18 compounds identified in samples collected near the aluminium smelter whereas only 6 compounds were identified in samples collected on the background territories. Among the PAHs accumulated in pine trees assimilation organs the substances with 3–4 aromatic rings (phenanthrene, fluoranthene, pyrene, chrysene) were dominant with their total number reaching 90 % of the total. Compound with 5–6 aromatic rings (benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[e]pyrene, perylene, indeno[1,2,3-c,d]pyrene, benzo[g, h, i]perylene, dibenz[a, h]anthracene).comprises a smaller proportion (from 6 to 27 %) in total PAHs content. High concentrations of benzo[a]pyrene and perylene in needle samples collected in the vicinity of the aluminum smelter indicate technogenic character of forest pollution