Characteristics Of Heavy Metals In Atmospheric Particulate Matter

Temporal distribution of PM₁₀/PM_2.5mass concentration and its relation withmeteorological factors in different seasons were studied in this research, based on the dailyaverage data obtained from air-supersites monitor network from February2012to December2012. Nine heavy metals, namely Cu、Cd、Mn、Cr、Ni、Zn、Pb、Sn、As in PM₁₀/PM_2.5were analyzed with their sources investigated as well,then countermeasures for pollutionprevention were proposed.The variations of daily average concentration of PM_2.5and PM₁₀were similar to eachother, with the highest mass concentration of PM_2.5/PM₁₀emerging in spring and winter andthe lowest in autumn and summer.The average values of PM₁₀/PM_2.5in spring are167.57μg/m³and88.90μg/m³respectively, compared to121.3μg/m³and93.2μg/m³in summer,86.2μg/m³and66.2μg/m³in autumn and130μg/m³and96.1μg/m³in winter.PM₁₀/PM_2.5mass concentrations are related to meteorological factors.Under thecircumstance of fast speed and low humidity, the mass concentration of PM_2.5/PM₁₀becamelow, and at the same time visibility rose. However, when the PM concentration fell downevidently, visibility did not rise, because of the humidity increase. Therefore, high temporary、low humidity and the fast speed could help reduce PM concentration. Compare with the fourmeteorological factors, visibility correlation with the PM_2.5mass concentration of everyseasons was found in this study.It is found that of Zn、Pb are the highest concentration among all heavy mental studiedand Cd and Ni had the lowest. Besides, seasonal mass concentration of As exceeded thelimitations indicated in “Ambient air quality standards”, which means serious contamination.Nevertheless, the year average concentrations of Pb and Cd were below limitations. Moreover,seasonal concentrations of Zn、Mn、Cd showed no obvious change while those of Pb、Cu、Sn、Ni were clearly lower in summer compared to other seasons, the highest concentration ofCr showed in winter. It also found that Pb、Sn、As were more easily to enrich on particlematters with diameters of below2.5μm, In contrary to the Cu、Cd、Mn、Cr、Ni、Zn.When it comes to the sources of heavy metals in PM, it is found that Cr in spring PM_2.5came from the earth, however, in other season and in PM₁₀, it mainly derived from humanactivities. Meantime, Mn in spring PM₁₀and in summer PM_2.5mainly resulted from thehuman activities while in other season it came from the earth. The remaining seven heavymetals all stem from human activities.