A Study on Characteristics of Heavy Metal Elements in Atmospheric PM2.5 During Winter in Chengdu

Abstract

This paper conducted an in-depth analysis on the characteristics of components of heavy metals in PM2.5 by studying the atmospheric heavy metal elements during winter in Chengdu. On the basis of the limiting value of heavy metal element concentration in PM2.5 in major cities at home and abroad and the national standard limiting value on heavy metal element concentration, this paper compared and evaluated the pollution level of heavy metal elements in PM2.5 during winter in Chengdu and analyzed the typical characteristics of heavy metal elements in haze days and non-haze days as well as the potential sources. The following conclusions were drawn: 1) in PM2.5 during winter in Chengdu, the major component was K, minor components were Fe, Ca, Zn, Cu, Pb, Ba, Mn, As, Cr and Cd, trace components were Se, Ag, Hg, Ni, V, Au and Ga and ultra-trace components were Co, Sb, Ti and Sn, and the proportion of the aforementioned components was 2.10706%, 2.14783%, 0.01933% and 0.00009% respectively; 2) the major component, minor component, trace component and ultra-trace component of heavy metal elements respectively accounted for 1.621%, 1.641%, 0.016% and 0.00004% of PM2.5; 3) the proportion of all the heavy metal components in PM2.5 in haze days was lower than that in non-haze days, which indicates that the relatively high concentration of PM2.5 might be caused by non-metallic salts; 4) in PM2.5, the proportion of Pb, Cd, Mn and Cu was lower than both the domestic average level and the international average level; the proportion of Zn and Ni was at the domestic average level but slightly higher than the international average level; and the proportion of As was at both the domestic average level and the international average level; 5) the mean value of Pb concentration during winter was 0.08717µg/m3, which was lower than the limiting value of the national standard GB 3095-2012; and 6) there was a rather high level of consistency between such elements as were K, Ca, Fe, Zn and Ag as well as PM2.5 on the typical haze day, which shows that obvious colinearity existed in the emission source of the aforesaid elements and such elements might come from road dust sources; on the typical non-haze day, random-peak daily variation occurred in heavy metal components, which might result from unorganized emission from peripheral pollution sources; however, the proportion of ultra-trace components of heavy metals on the typical non-haze day was slightly higher than that on the typical haze day, which might be closely related to the local background transmission.