Wintertime chemical compositions of coarse and fine fractions of particulate matter in Bolu, Turkey.

Coarse (particulate matter (PM)2.5-10) and fine (PM2.5) fraction of PM samples were collected between December 2014 and February 2015 at an urban sampling site located at the Bolu plain, of the western Black Sea region of Turkey. The collected samples were analyzed in terms of metals (Al, As, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Pb, S, Si, Ti, V, and Zn); elemental carbon (EC); and organic carbon (OC). Elevated concentrations measured in this wintertime study were ∼7.8 μg/m(3) in sum of PM2.5-10 and PM2.5 for SO4 (2-) and ∼59.9 μg/m(3) in PM2.5 for OC. The contributions of primary and secondary OC (POC and SOC, respectively) to total OC mass were 60 and 40 %, respectively, while contribution of SOC to OC increased by up to 74 % in stable atmospheric conditions. The significantly high OC/EC ratio (∼10.1) found in this study relative to other wintertime studies was attributed to increased emissions from residential heating and lower mixing height observed during the study. Two and three factors were resolved by factor analysis for PM2.5-10 and PM2.5, respectively. Two Saharan dust episodes were observed on 31 January and 1 February, during which crustal PM components such as Mg, Si, and Al increased as much as three times their background concentrations.