| PM2.5 samples from Yuelu(YL), Kaifu(KF), and Yuhua(YH) districts of Changsha in March 18th~April 15 th of 2013 were collected by TH-150 intelligent medium-flow total suspended particle sampler. Also the size-segregated airborne particulate matter(APM) in Changsha April 16th~May 6th of 2014 were sampled by by an 8 Stage Non-Viable Cascade Impactor.As for the PM2.5 samples,gravimetric analysis showed that the concentrations of YL, KF and YH were 94.88, 101.49 ? 103.69 ?g/m3, respectively.After digestion and sequential extraction, Cu?Zn ?Cd and Pb in PM2. 5 samples were measured by Atomic Absorption Spectroscopy. The concentrations of the four heavy metals(HMs) in three sampling sites were ranged from 2.27 ~ 2498.87 ng/m3, the highest concentration appeared to be Cu and the lowest was Cd. According to the chemical speciation of the HMs in PM2.5 results, almost 50%of Cu, Cd and Pb in PM2.5 of all sites were accumulated in soluble and reducible fractions.The correlation coefficients and principal component analysis showed that HMs in PM2.5 of Changsha in spring were mainly from vehicular emissions, fuel combustion, resuspension of dust and other pollution sources. The average potential ecological risk index of HMs in PM2.5of Changsha was 6193.80 which suggesting that HMs in PM2.5 was extremely serious.Gravimetric analysis of the size-segregated airborne particulate matter(APM) showed that the total APM concentration of Changsha ranged from 120.24 ~ 271.15 ?g/m3. And the fine particles, particularly the average PM1.1-2.1 concentration was 57.36±10.62 ?g/m3. And it was the highest APM concentration appeared in all size fractions, approximately 30% of the total APM mass. Zn, Pb, Cd, Ni, Fe, Mn, Cr and Cu in size-segregated APM were measured using an inductively coupled plasma optical emission spectrometer after digestion. The concentration of HMs in total APM was in the range of 25.97~23998.82 ng/m3 and the order of total concentrations of HMs in APM was Fe > Zn > Mn > Pb > Cr > Cd > Cu > Ni. The health risk of HMs in APM was evaluated by average daily exposure dose(ADD) and hazard index(HI) and the results showed that ADD of each HMs in APM through all exposure pathways for both children and adults followed the similar variation pattern of Fe > Zn > Mn> Pb > Cd > Cu > Cr > Ni. And the average daily exposure doses of HMs in APM through three exposure pathways were in the following order: ingestion > dermal contact > inhalation.In terms of the HI value for both the children and adults, it decreased in the order of Cd > Mn> Pb > Cr > Cu >Zn > Ni. The HI values of Cd, Mn, Pb and Cr for children and Cd, Mn and Pb for adults exhibited higher than 1 which indicated that there may be concern for potential non-carcinogenic effects. The HI values of Cu, Zn and Ni for children and Cr, Cu, Zn and Ni for adults were less than 1 showed that no chronic risks are likely to occur. The cancer risk for Cd, Ni and Cr followed the order of Cr > Cd > Ni, and they were all below the acceptable level(10-6-10-4), indicating that carcinogenic risks of Cd, Ni and Cr in size-segregated APM can be negligible in Changsha. |
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