Sources Apportionment And Controls Of Particulate Matter In Xianyang City,Northwest China

As an important participating city of the national“Belt and Road”strategy,Xianyang city will further develop its economy and society.However,its atmospheric particulate pollution is currently facing severe problems.In order to understand the characteristics and sources of atmospheric particulate pollution in Xianyang,airborne particles were collected and analyzed from October 2016 to August 2017.The seasonal and spatial variations of mass concentration,carbon components,water-soluble ions,and elemental components in the particulates were discussed.Besides,the sources apportionment of PM_2.5 in Xianyang were analyzed using PMF and CMB receptor models.For particulate pollution,there were no significant in spatial variation,and seasonal variation presented the characteristic of winter>autumn>spring>summer in Xianyang.During sampling periods,the average mass concentration of PM_2.5 and PM₁₀in winter,autumn,spring and summer were 115.2±77.2?g·m^-3,102.9±64.5?g·m^-3,91.9±56.9?g·m^-3,45.2±17.5?g·m^-3 and 232.1±91.3?g·m^-3,192.3±123.0?g·m^-3,189.8±125.7?g·m^-3,81.4±24.0?g·m^-3,respectively.Those all exceed the second level of daily average concentration of national air quality standard in winter,autumn and spring.The annual average concentration of OC and EC in PM_2.5 and PM₁₀ were18.0±14.7?g·m^-3,5.1±3.4?g·m^-3 and 21.9±13.8?g·m^-3,5.6±3.2?g·m^-3.The correlations of OC and EC in autumn,winter and summer were better than those in spring.In addition,the composition of SOC in autumn was higher than other seasons.The results of water-soluble ion analysis showed that NO₃^-,SO₄^2-and NH₄⁺accounted for the major proportion of ionic components and existed mainly in the form of NH₄NO₃and NH₄HSO₄ in particulate matter.The concentration of SO₄^2-was higher than NO₃^-in summer,but the NO₃^-concentration was higher than SO₄^2-in winter,autumn and spring.The particles were overall acidic in autumn,winter and summer and generally alkaline in spring.Elemental analysis results showed that the concentrations of Mg,Al,Si,Ca,Fe and Ti were relatively high,especially in spring.Al,Si,Ti,and Mg are mainly derived from natural sources.Ca,Na,Mn,K,Ni,and Cr are influenced by both natural and anthropogenic sources.Co,Cu,As,Zn,Pb,Cl,and S are mainly derived from anthropogenic sources.The mass balance results indicated that the main components of PM_2.5 were SNA and dust components in fall,organic matter and SNA components in winter,dust and organic components in spring,and organic matter,SNA,and dust in summer.The results of source apportionment showed that PM2.5 in Xianyang mainly come from secondary inorganic ions,fugitive dust,motor vehicle emission,coal combustion,biomass burning,and industrial activities,of which the annual source contribution analyzed by CMB receptor model were 26.1%,20.3%,18.8%,15.8%,11.5%and 7.4%,respectively.Through the evaluation of the control effects of different sources of pollution,the results show that the control of airborne particulates needs to give priority to controlling the sources of dust and motor vehicles.