Chemical characterization of surface snow in Istanbul (NW Turkey) and their association with atmospheric circulations

The understanding of the impurities in natural snow is important in realizing its atmospheric quality, soil characteristics, and the pollution caused to the environment. Knowledge of the occurrence of major ions and trace metals in the snow in the megacity of Istanbul is very limited. This manuscript attempts to understand the origin of major soluble ions (fluoride, acetate, formate, chlorite, chloride, nitrite, chlorate, bromide, nitrate, sulfate, phosphate, and perchlorate) and some trace metals (Fe, Mn, Cd, Co, Ni, Pb, Zn, Cu) in winter surface snow, collected in Istanbul, Turkey. The sampling of the surface snow was conducted after each precipitation during the winter of 2015–2016 at three sites in the city. Besides the statistical evaluation of the major ions, and some trace metal concentrations, the chemical variations along with atmospheric circulations, which are important modification mechanisms that influence the concentrations, were investigated in the study. At examined locations and times, 12 major anions were investigated and in these anions fluoride, chlorite, chlorate, bromide, and perchlorate in the snow samples were below the detection limit; only SO₄ ²⁻, NO₃ ⁻, and CI⁻ were found to be in the range of 1.11–17.90, 0.75–4.52, and 0.19–3.01 mg/L. Also, according to the trace element determination, the concentration was found to be 29.2–53.7, 2.0–16.1, 1.0–2.2, 50.1–71.1, 24.2–35.2, ND–7.9, 43.2–106.6, and 3.0–17.7 μg/L for Fe, Mn, Cd, Co, Ni, Pb, Zn, and Cu, respectively. The major anions and investigated trace elements here originated mainly from anthropogenic and atmospheric circulation and mainly influenced by northerly and southerly circulation patterns. While the main limitations in the present study may be the low number of samples that may not be entirely representative, accurately reflect identification, or support other previously observed local measurements, we believe that the type of data presented in this study has the potential to be used in the field of environmental risk assessment and, as result, for human health.