Seasonal variation of PCDD/Fs in the metropolis of Istanbul, Turkey.

Atmospheric concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) compounds were investigated at three different regions of Istanbul which reflect urban, urban/industrial, and sub-urban characteristics. Air samples were collected simultaneously for both gaseous and particulate phases using high volume samplers on monthly time intervals from May 2011 to October 2012. The highest concentrations (3,056 fg/m(3) and 156 fg I-TEQ/m(3)) were observed at the sampling site that reflects traffic, residential, and industrial emission source characteristics, while the lowest concentrations (829 fg/m(3) and 38 fg I-TEQ/m(3)) were observed at the sampling point which is far away from centrum and reflects sub-urban characteristics. Concentrations of PCDD congeners were, in general, found to be higher than PCDF congeners, and OCDD, 1,2,3,4,6,7,8-HpCDD/F, and OCDF congeners were recorded to be the most abundant congeners. Winter season concentrations were also found to be higher especially in particulate phase. As a result, combustion processes such as motor vehicles and residential heating equipment were thought to be the principal sources of emissions of PCDD/F compounds when both congener profiles and seasonal variations are considered. Basic statistical evaluation of the data resembled high degree of inverse correlations between PCDD/F concentrations and UV and solar radiation.