engleski

PAH levels in the air in rural area

Polycyclic aromatic hydrocarbons (PAHs) have been found in the air, water, soil, and sediment. They are products of incomplete combustion of fossil fuels and other organic materials. They consist of two or more benzene rings. Most PAHs with fewer rings are gases while those with more benzene rings bind to particles according to their affinity for bounding on particles and temperatures. Some of them are mutagen and some carcinogen. Benzo-a-pyren (BaP) has been the most commonly measured PAH since it is always present. This paper presents PAHs measured in suspended particulate matter (SPM) collected 1998 during four seasons in rural area about 50 km away from Zagreb. Levels and profiles of PAH/BaP were studied with the aim to determine dominant sources of PAH in each season. All samples were collected over 24-hour period with high volume sampler (about 300 m3) on glass fibre filters. They were kept in the deep frese at -18 °C, wrapped in aluminium foil until analyse. PAH samples were extracted with cyclohexane in the ultrasonic bath for one hour, separated from undissolved parts by centrifugation and evaporated to dryness. Then they were redissolved in acetonitrile and analysed with a high-performance liquid chromatograph (HPLC) and determined by a fluorescence detector. Samples were analysed for the following PAH: fluoranthene (Flu), benzo-b-fluoranthene (BbF), benzo-k-fluoranthene (BkF), benzo-a-pyrene (BaP), dibenzo-ah-anthracene (DahA), and benzo-ghi-perylene (BghiP). The average mass concentrations of measured PAHs during the whole measuring period were as follows. Flu has the highest average value of 3.42 ng/m3 and DahA the lowest with 0.48 ng/m3. The average value for BaP was 1.55 ng/m3 and were under the limit value (LV) (2 ng/m3) set by the Ordinance on Recommended and Limit Air Quality Values in Croatia. The average BaP mass concentration in winter was 3.83 ng/m3 and the average BaP mass concentration in summer was 0.13 ng/m3. Such a low concentrations of PAH in summer are not only the consequence of the absence of space heating, but also of the increased reactivity of those compounds at higher temperatures resulting in their photochemical, thermal, and chemical degradation. The concentrations of PAHs measured in SPM and collected in rural area on working days and weekends were the highest in winter and the lowest in summer. The spring PAH concentrations were lower than the autumn ones, because there were more sunny and warm days in spring than in autumn.

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