PM₁₀ concentration in urban atmosphere around the eastern Tien Shan, Central Asia during 2007-2013.

Based on the daily records from 16 cities around the eastern Tien Shan (Tianshan Mountains), central Asia from 2007 to 2013, the spatial pattern and seasonal/interannual variation of urban particulate matter up to 10 μm in size (PM10) concentrations and influencing factors were analyzed. Annual mean PM10 concentrations (±standard deviation) in most cities on the northern slope mainly range from 55 ± 28 μg/m(3) to 92 ± 75 μg/m(3), and those on the southern slope range between 96 ± 65 and 195 ± 144 μg/m(3). PM10 concentrations are maxima in winter on the northern slope, while they maximize in springtime on the southern slope. There is an increasing trend in annual mean concentrations during the period 2007-2013, which is not statistically significant at the 0.05 level. Urban PM10 concentration in the study region is jointly influenced by anthropogenic emission and regional natural processes, especially dust events and precipitation. The northern slope usually has heavy anthropogenic air pollution (mostly in winter) and relatively rich precipitation especially in summer, and the southern slope always suffers more frequent dust events (mostly in spring) and less precipitation. Modeled back-trajectory indicated that the Taklimakan desert source can greatly increase the PM10 concentration on the southern slope, and the mountain ranges may hinder the transport of dust to the northern slope.