Characteristics of size distributions and sources of water-soluble ions in Lhasa during monsoon and non-monsoon seasons

摘要: Abstract To understand the physical and chemical characteristics, particle size distribution sources of size-separated aerosols in Lhasa, which is located on Tibetan Plateau (TP), six sizes aerosol samples were collected Lhasa 2014. Ca2+, NH4+, NO3−, SO42− Cl− dominant ions. The ratio cation equivalents (CE) to anion (AE) for each segment indicated that atmospheric alkaline. NO3− could be neutralized by but not according [NH4+]/[NO3− + SO42−] [Ca2+]/[NO3− + SO42−] ratios. Mobile PM0.95–1.5, PM1.5–3 PM3–7.2, while stationary other three fractions [NO3−]/[SO42−] all water-soluble ions during monsoon non-monsoon periods was characterized a bimodal due different formation mechanisms, it revealed had seasons segments combining with correlation analysis. Source analysis performed using Principal component (PCA) first time, combustion sources, motor vehicle exhaust, photochemical reaction various types dust main aerosols. Furthermore, Lhasa's air quality also affected long-distance transmission, expressed as pollutants from South Asia West Asia, transmitted backward trajectory