Accumulation and coarse mode aerosol concentrations and carbonaceous contents in the urban background atmosphere in Amman, Jordan

In this study, we analyzed the concentrations of accumulation and coarse modes measured during November 2013-July 2017 at an urban background site in Amman, Jordan. The concentrations showed distinct seasonal variations with high concentrations with a monthly average higher than 100 cm(-3) and 1.5 cm(-3), respectively, for accumulation and coarse modes during the winter and low concentrations with a monthly average less than 40 cm(-3) and 1-1.5 cm(3) , respectively, for accumulation and coarse modes during the summer. Sand and dust storms (SDS) affected the coarse mode during the early spring whereas local dust resuspension affected them during the autumn. The gravimetric analysis confirmed the seasonal variation of the calculated particulate mass concentration but suggested that the assumption of spherical particles and unit density is not always proper. The ATR-FTIR analysis of selected filters revealed that aerosols in the background atmosphere of Amman are a mixture of locally emitted (fossil fuel combustion) and local/regional dust. Based on the 24-h average of the calculated PM10, the pollution standard index (PSI) revealed that about 81% of the days were either good or moderate air quality conditions. About 71% of the days were below the 24-h PM10 limit value according to the Jordanian air quality standards (120 mu g m(-3) ).