Investigation of atmospheric concentrations of persistent organic pollutants in urban areas

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) constitute the largest group of persistent, semi-volatile and toxicologically significant trace organic contaminants. These pollutants can be formed as unwanted by products of anthropogenic and natural processes like incineration of wastes, vehicle use having internal combustion engines, ferrous/non-ferrous metal production, volcanic emissions and forest fires. PCDD/Fs can be transported from source to long distances by atmospheric transportation mechanisms. Therefore, atmospheric transport and deposition is accepted the primary distribution pathway moving PCDDs/DFs from numerous emission sources to the environmental compartments such as soil, sediment and water sources. They are accumulate in the fatty tissue of living organisms because of the low chemical reactivity and lipophilic properties. In addition, 2,3,7,8-substituted PCDD/Fs congeners has been reported to be significant toxic compounds. In this study, the concentrations, seasonal variations, gas/particle distributions of polychlorinated dibenzo-p-dioxins and furans (PCDD/F)s were investigated in air samples collected at three sampling sites located in İstanbul: i) industrial/residential (Davutpasa), ii) residential (Yildiz), iii) semi-rural (Fenertepe). Samples were collected from May 2011 to May 2013 by using high-volume samplers. Glass fiber filter and polyurethan foam were used for the sampling of particle and gas phases respectively. Before sampling, filters were conditioned at 450°C for 5h and PUFs were precleaned with asetone in soxhlet extractor for 16 h for the removal of organic pollutants. Extraction, clean up and fractionation were applied after sampling to all filter and PUF samples. As a final step, PCDD/F compounds were determined as a qualitative and quantitative by using high resolution gas chromatography and high resolution mass spectrometer. The average concentrations of ?17PCDD/Fs were determined to be 3325 fg/m3, 1257 fg/m3 and 902 fg/m3 for industrial/residential, residential and semi-rural sampling stations, respectively. I-TEQ concentrations were determined to be 172 fg I-TEQ/m3, 67 fg I-TEQ/m3 and 48 fg I-TEQ/m3 for Davutpasa, Yildiz and Fenertepe sampling stations, respectively. The highest concentrations were determined at industrial/residential sampling area while the lowest concentrations were determined at semi-rural sampling area. OCDD (21%), 1,2,3,4,6,7,8-HpCDF (15%), OCDF (14%) were determined as the most abundant congeners at all sampling locations. In general, homologue profiles were quite similar for all locations, the concentration of PCDD and PCDF homologues increased with increasing degree of chlorination. The concentration level of PCDD/F compounds showed seasonal variations in this study. The highest mean concentration was determined to be 6056±4256 fg/m3 in 2012-Winter while the lowest mean concentration was determined to be 189±114 fg/m3 in 2012-Summer. To evaluate their gas/particle partitioning, samples were collected in both gas and particle phases. The mean concentrations were determined to be 133 fg/m3 and 1605 fg/m3 for gas and particle phases, respectively. Gas phase contributions of PCDD/Fs were calculated as 11% for winter and 33% for summer sampling periods. Different homolog patterns were observed in the gas and particle phases. For example, high chlorinated dioxin/furans dominated in the particle phase while low chlorinated ones dominated in the gas phase. According to statistical analysis between the PCDD/F concentration and meteorological parameters, temperature, ultraviolet, solar radiation, solar energy, atmospheric pressure and mixing height were determined to be main parameters affecting the variation of the atmospheric PCDD/F concentrations. Consequently, combustion sources such as, uncontrolled incineration of household wastes in domestic stoves and furnaces, combustion of fossil fuels of low quality, including hard, brown coal and woods in small local boiler/stoves and traffic emissions from motor vehicles are considered as the main emission sources of PCDD/F compounds in Istanbul atmosphere.