Pollution Characteristics And Health Risk Assessment Of Atmospheric Particulate Matter In Northwest China

Due to the special geographical position,topographic and climatic conditions,the atmospheric environment in northwest China is influenced by both man-made and natural sources.Atmospheric particulate matter,as one of the most complex and harmful pollutants in atmospheric environment,has attracted much attention.To understand the characteristics of atmospheric particulate pollution in northwest China,this paper first discussed the air pollution characteristics of six prefecture-level cities（Jinchang,Jiuquan,Hami,Urumqi,Karamay,Altay）in Northwest China in Xinjiang and Gansu in 2018.Secondly,samples of particles(PM₁₀0 and PM_2.5)with different sizes in spring were collected from 7 typical areas（Jinchang,Yumen,Hami,Urumqi,Karamay,Jeminay,Fuyun）under six prefecture-level cities of Gansu（Xinjiang）,and the pollution levels of heavy metal elements,OC/EC and PAHs,in atmospheric particles were analyzed and determined.Finally,the human health risk assessment model proposed by the US Environmental Protection Agency（US EPA）was adopted to assess the health risk of human exposure to PAHs and heavy metals in PM₁₀0 and PM_2.5.5 combined with the exposure parameters of China.Some results are obtained:（1）The time distribution characteristics of main air pollutants(SO₂,NO₂,CO,O₃,PM_2.5.5 and PM₁₀)in six cities in Northwest China are different.The air pollution in the six cities is mainly particulate matter pollution,among which the pollution levels of PM_2.5.5 and NO₂ in Urumqi are higher,which exceed the national air quality standard,and the air quality in Karamay and Altay is good as a whole.There are seasonal differences in air pollutants.Except for the highest CO in autumn in Altay,CO and atmospheric particulate matter in other cities are"high in spring and winter,low in summer and autumn",and O₃ is"high in spring and summer and low in autumn and winter".According to the annual variation characteristics,the six air pollutants in Urumqi and Karamay reached the highest in November-December and January-February,while the atmospheric particulates in Jinchang,Hami and Jiuquan generally reached the highest in March-May.The diurnal variation characteristics of O₃ showed that the concentration of O₃ in daytime was higher than that at night,and NO₂,CO basically showed bimodal pattern.Except in Jinchang,Jiuquan,Hami and Altay,the diurnal variation characteristics of SO₂ and PM_2.5.5 were not obvious,and the diurnal variation in daytime was higher than that at night.（2）During the study period,atmospheric particulates and their components in typical cities in Northwest China had obvious pollution characteristics.The mass concentrations of PM_2.5.5 and PM₁₀0 range from 14.81μg/m³ to 91.49μg/m³ and 20.11μg/m³ to 262.07μg/m³,and the atmospheric particulate matter concentration in Jinchang is higher than that in other cities.The concentration of OC in PM_2.5.5 and PM₁₀0 from 2.55 to 9.06μg/m³ and 2.81 to 17.26μg/m³ respectively.The concentration of EC in PM_2.5.5 and PM₁₀0 from 0.41 to 1.78μg/m³and 0.46 to 2.99μg/m³ respectively.The concentrations of OC and EC in Jinchang and Urumqi were higher,and the proportion of OC and EC in atmospheric particulate matter in Jeminay was much higher than that in other cities.The concentration of heavy metals in PM_2.5.5 and PM₁₀range from 0.417 to 0.838μg/m³ and 0.687 to1.857μg/m³,respectively.The proportion of heavy metals in PM_2.5.5 was higher than in PM₁₀.The concentrations of Ni,Pb and Cu in Jinchang were higher,the concentrations of Cr,Mn and Sr in Yumen were higher and Cu,Zn in Urumqi were higher.The mass concentration of 16 kinds of optimal control PAHs in PM_2.5.5 and PM₁₀0 range from 17.87 to 54.48 ng/m³ and28.73 to 84.51 ng/m³,respectively.Except for Jeminay,the proportion of PAHs in PM_2.5.5 was higher than that in PM₁₀,the concentrations of PAHs were higher in Yumen,Jinchang,Jeminay and Fuyun.The concentration of PAHs in 7 cities was mainly in the central ring,especially the concentration of Chr,was much higher than that of other components.（3）During the study period,the OC,EC and PAHs of PM_2.5.5 and PM₁₀0 in northwest China were mainly affected by coal combustion,which was reflected as a mixture of combustion sources or coal-burning sources and other sources;the sources of heavy metals in PM_2.5.5 and PM₁₀0 were mainly industrial sources and crustal sources,and different cities showed different heavy metal concentration characteristics.（4）During the study period,the carcinogenic and non-carcinogenic exposure doses of heavy metals and PAHs in PM₁₀0 were higher than those in PM_2.5,and the carcinogenic and non-carcinogenic risks of males were higher than those of females.The non-carcinogenic exposure doses of heavy metals in PM_2.5.5 and PM₁₀from high to low were Jinchang,Urumqi,Yumen,Hami,Fuyun,Jimnai,Karamay and Jinchang,Urumqi,Hami,Yumen,Jimunai,Karamay,Fuyun.The carcinogenic exposure dose from high to low was Yumen,Hami,Jinchang,Jimunai,Fuyun,Urumqi,Karamay and Jinchang,Yumen,Urumqi,Hami,Jimnai,Karamay,Fuyun.Among which Mn and Cr had higher non-carcinogenic risk and higher non-carcinogenic risk to other cities except Altay.The carcinogenic risk of Cr was higher and exceeded the acceptable level.（5）During the study period,The Bap-TEF of PM_2.5.5 and PM₁₀0 in Jinchang,Yumen,Jimunai and Fuyun counties and of PM₁₀0 in Urumqi and Hami all exceeded the Environmental Air quality Standard.The non-carcinogenic exposure doses of PAHs in PM_2.5.5 and PM₁₀0 from high to low were Jinchang,Yumen,Jimunai,Urumqi,Fuyun,Karamay,Hami and Jinchang,Yumen,Urumqi,Fuyun,Jimunai,Karamay,Hami.For different PAHs monomers,the exposure dose of Flua was the highest;the non-carcinogenic risk of PAHs to men and women in 7 study cities was less than 1,there was no potential non-carcinogenic risk,and the carcinogenic risk was less than1×10^-4,which was at an acceptable level.To sum up,the main air pollutants in typical cities in northwest China is particulate matter pollution with a certain time distribution,especially in spring.Different components of atmospheric particulates in 7 typical cities have different pollution characteristics.although the sources of pollution components in atmospheric particulates in different cities are different,they are all affected by coal burning,and the carcinogenic and non-carcinogenic risks of heavy metals,especially Cr,are higher,and the carcinogenic and non-carcinogenic risks of PAHs are lower than the threshold,and the carcinogenic and non-carcinogenic risks are at an acceptable level.