Long-range transported pollution from the Middle East and its impact on carbonaceous aerosol sources over Cyprus

Abstract

Abstract. The geographical origin and source apportionment of submicron carbonaceous aerosols (organic aerosols, OA, and black carbon, BC) have been investigated here for the first time by means of high time resolution measurements at an urban background site of Nicosia, the capital city of Cyprus, in the Eastern Mediterranean. This study covers a half-year period, encompassing both the cold and warm periods with continuous observations of the physical and chemical properties of PM1 performed with an Aerosol Chemical Speciation monitor (ACSM), an Aethalometer, accompanied by a suite of various ancillary off and on-line measurements. Carbonaceous aerosols were dominant during both seasons (cold and warm periods), with a respective contribution of 57 % and 48 % to PM1, respectively, and exhibited recurrent intense night-time peaks (>20–30 µg m-3) during the cold period associated with local domestic heating. Findings of this study show that high concentrations of sulfate (close to 3 µg m-3) were continuously recorded, standing among the highest ever reported for Europe and originating from the Middle East region. Source apportionment of the OA and BC fractions was performed using the Positive Matrix Factorization (PMF) approach and the combination of two models (aethalometer model and multilinear regression), respectively. Our study revealed elevated hydrocarbon-like organic aerosol (HOA) concentrations in Nicosia (among the highest reported for a European urban background site), originating from a mixture of local and regional fossil-fuel combustion sources. Although air masses from the Middle East had a low occurrence and were observed mostly during the cold period, they were shown to strongly affect the mean concentrations levels of BC and OA in Nicosia during both seasons. Overall, the present study brings to our attention the need to further characterize primary and secondary carbonaceous aerosols in the Middle East; an undersampled region characterized by continuously increasing fossil fuel (oil and gas) emissions and extreme environmental conditions, which can contribute to photochemical aging.