engleski

Levels and seasonal variations of polychlorinated biphenyls in ambient air, Zagreb, Croatia

The air is significant compartment for the environmental distribution and fate of persistent organic pollutants such as polychlorinated biphenyls (PCB). Levels of PCBs in air are influenced by many factors such as proximity of pollution sources and meteorological conditions. The atmospheric levels of six PCB congeners (PCB-28, PCB-52, PCB-101, PCB-138, PCB-153, PCB-180) were measured continuosly during 9 months in Zagreb between June 1999 and February 2000. Air samples (about 1000 m^3) were collected on the polyurethane foam and quartz fiber filter paper. The extraction was done with 5 % diethyl-ether in n-hexane for 12 hours in Soxhlet apparatus. Qualitative and quantitative analysis were performed using high resolution gas chromatography with electron capture detector. The method recovery and reproducibility were checked over a longer period; recoveries and relative standard deviations ranged between 56-76 % and 15-40%, respectively. All analysed PCB congeners were found in all 47 collected air samples except PCB-180 whose presence was determined in 30 positive samples. The concentrations of PCB congeners ranged as follows: 3.0-312.2 pg/m^3 (PCB-28), 1.6-65.2 pg/m^3 (PCB-52), 1.6-222.8 pg/m^3 (PCB-101), 1.5-128.3 pg/m^3 (PCB-138), 0.4-91.7 pg/m^3 (PCB-153) and 0,0-6,8 pg/m^3 (PCB-180). Their medians are 35.7 pg/m^3 (PCB-28), 12.5 pg/m^3 (PCB-52), 14.2 pg/m^3 (PCB-101), 5.5 pg/m^3 (PCB-138), 4.4 pg/m^3 (PCB-153) and 1.8 pg/m^3 (PCB-180). The comparison between PCB median concentration in air samples collected at same place in 1997 and this study shows that the levels of all six congeners slightly decreased. In 1997 air samples were collected in October and November, and PCB medians ranged between 4.6 (PCB-180) and 29.6 pg/m^3 (PCB-28). PCB medians collected in October and November in 1999 ranged between 1.9 (PCB-180) and 19.0 pg/m^3 (PCB-28). Pronounced seasonal variations of all six PCB congeners was observed, with higher levels in warmer than in colder seasons. These data are in agremeent with the thesis that air concentrations of PCBs depend on volatilization of PCB residues from soils and other sorbents. The increase of sum PCB concentrations in the air can be described by an exponential curve. When the temperatures were above 10 ^oC the sum of six PCBs were between 30.6 and 577.8 pg/m^3 and when they were below 10 ^oC sum of six PCBs were between 10.7-71.0 pg/m^3. At the temperatures above 10 ^oC prominent increase in PCB levels was observed, which is in accordance with the literature data.

Polychlorinated biphenyls; ambient air; seasonal variations

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