Svalbard local air contamination by PAHs and nitro- and oxy- PAHs
Résumé
Polycyclic aromatic hydrocarbons (PAHs) are of great public concern due to their toxicity and potential carcinogenicity. PAHs are listed as chemicals of emerging concern in the Arctic (AMAP, 2016). The coal power plant in Longyearbyen (78°13′N 15°38′E), Svalbard was hypothesized to be a major local source of PAHs. Gaseous and particulate phase air samples were collected in the power plant stack and at 1 km and 6 km transect distance downwind the plant. The sampling campaign was performed in summer when long-range atmospheric transport input is low and thus the coal burning emissions are easier to quantify. The samples were analysed for 16 parent PAHs and 22 nitro- and 8 oxy-PAHs by GC-EI-MS/MS and GCECNI-MS. An emission factor of 2.3 µg/kg coal was estimated for the Σ47 PAHs. The relative distribution of the contaminants was as follows: 66% PAHs, 21% oxy-PAHs, and 13% nitro-PAHs. Approximately 90% of the compounds were found in the gaseous phase, confirming high efficiency of exhaust particles removal by an electrostatic precipitator in the power plant. The PAH levels observed in ambient air of Longyearbyen (Σ15 PAHs ~556 pg/m3) were significantly lower (up to 2 orders of magnitude) compared to rural sites in Europe and China but were about an order of magnitude higher compared to the Canadian Arctic (Alert station) concentrations. Nitro- and oxy-PAH concentrations (Σ22 nitro-PAHs ~32 pg/m3 and Σ7 oxyPAHs ~352 pg/m3) were found at the same order of magnitude as detected at other background Scandinavian (Råö and Pallas) and central European (Košetice) monitoring stations. A multivariate statistical analysis confirmed local coal burning as the source of PAHs, as well as vehicle and marine traffic. Oxy-PAHs and nitro-PAHs also result from reactions of primary PAHs with atmospheric oxidants. Such secondary formation was concluded as an additional source of several nitro-PAHs. However, a preliminary study on the annual distribution of PAHs in Longyearbyen air revealed 2 orders of magnitude higher PAH levels in spring. Maximum concentrations were detected during Easter holiday and different profile of nitro-PAHs (markers of vehicle emissions) during that period was determined. This suggests that petrol driven snowmobiles are the main candidate source for PAH vehicle emissions in spring, although long-range transport may be of influence too. Temperature inversions are frequent in Arctic regions, and limited vertical air movement can trap and accumulate contaminants near the ground with potential consequences for public health and the environment.