Distribution Charcteristics Of Metals And Rare Earth Elements In Atmospheric Particles In Wuhai

As a typical resource-dependent city in Inner Mongolia.the atmospheric particulate matter pollution of Wuhai is serious and complex,and it is currently changing from soot to composite pollution.The research on the source of atmospheric particulate matter,pollution characteristics,influencing factors,formation mechanisms,and its health risks is of great significance for the prevention and control of ambient air pollution.Based on atmospheric particulate matter and meteorological monitoring data in 2019 in Wuhai,this study analyzes the temporal change characteristics of particulate matter pollution and its correlation with meteorological factors.PM₁₀、PM_2.5 and dust samples was systematically collected at different points in different seasons.Researches were conducted on the spatial and temporal distribution characteristics,sources apportionment and formation mechanism of metals and rare earth elements in particulate matter and dust,and the Tessier five-step extraction method was applied into the research about the environmental geochemical behavior of metal elements in particulate matter and dust,in addition the health risk was assessed combined with biological effectiveness.The main findings are as follows:1.Both PM₁₀0 and PM_2.5 in Wuhai exceeded the standard in 2019,and the seasonal changes among them are obvious.These two index in heating period are higher than that in the non-heating period.Increasing coal combustion and meteorological conditions including low temperature,high humidity,and quiet wind etc.which are against for the diffusion of particulate matter are the main causes of particulate pollution in the heating period.The sand and dust weather are the main causes of particulate pollution in the non-heating period.2.Compared with PM₁₀&PM_2.5 and dust,the elements such as Al,Fe and Ti are higher in coarse particles,while the Zn,Mn,Pb,Cu,Cr,Cd,Ni,V,As,Co,Hg,etc are higher in fine particles.All the elements in PM₁₀ and PM_2.5 in heating period are higher than those in non-heating period,and coal combustion is an important reason for the significant seasonal differences in the content of these heavy metals.3.The sequence of rare earth content in dust,PM₁₀ and PM_2.5.5 is:GWS>HBW>QG>WD>HN.The element concentration law conforms to the even number rule of element distribution and each element possess the geochemical characteristics of light rare earth enrichment and Eu negative anomaly.4.The speciation analysis results show that the dust,PM₁₀ and PM_2.5 have the highest Cd exchangeable state content,the highest bioavailability and the greatest environmental risk.The total amount of Zn and the enrichment factor are high,but its biological effectiveness is low,and it can be considered as being less harmful.The results of health risk assessment showed that Cr in PM₁₀ and PM_2.5 had the highest carcinogenic risk and the risk of it in heating is higher than that in non-heating period.