Evaluation of chemical composition and source apportionment of fractional rain samples collected in urban and semi-urban sites of Bolu

In this study, the volume-based wet deposition samples were collected fractionally in May and June of 2020. The 167 samples were obtained from two different districts of Bolu. One hundred twenty-one samples were obtained from the city center of Bolu, the urban site, and forty-six samples were obtained from the Bolu Abant Izzet Baysal University campus, the semi-urban site. Major ions (F-, Cl-, NO2-, Br-, NO3-, PO43-, SO42-, Na+, NH4+, K+, Mg2+, Ca2+) and elements (Ag, Al, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mg, Mn, Mo, Ni, Pb, Sb, Sn, Sr, V, Zn) were determined by using IC and ICP-MS, respectively. The results showed that Bolu had not suffered acid rain during the sampling period. The mean pH value for the urban site was 6.29, while the mean pH value for the semi-urban site was 6.79. The VWM (volume-weighted mean) concentrations of anions and cations were 176 µeq/L and 202 µeq/L for the urban area and 524 µeq/L and 798 µeq/L for the semi-urban area, respectively. Furthermore, The VWM concentrations of elements were 68.5 mg/L and 103 mg/L for the urban and semi-urban areas, respectively. The neutralization potential is dominant in both areas. Calcium and NH4+ greatly impacted the neutralization of both areas. The Na+% and SAR (sodium adsorption ratio) values demonstrated that the precipitation in Bolu had good quality and had no risk of using irrigation in agricultural activities. Using positive matrix factorization (PMF 5.0), six sources for urban sites and five for semi-urban areas were identified. The major sources affecting the urban area were the iron-steel factories (37%), Bolu cement factory (6%), the biomass burning (10%), the transportation from Anatolia (14%), the coal burning (17%), and the urban atmosphere (16%). Likewise, the major sources affecting the semi-urban area were the long-range transportation (16%), the nitrate factor (5%), the iron-steel factory (39%), the biomass burning (12%), and the mixture of vehicular emission and coal burning (28%).