[Pollution level and chemical speciation of heavy metals in PM2.5 during autumn in Guangzhou city].

PM2.5 samples were collected in Guangzhou city during autumn. Total concentration and chemical speciation of 10 heavy metals in PM2.5 were quantified by acid digestion method and sequential extraction procedure. The pollution level and bioavailability of these metals were also evaluated. Results showed that PM2.5 and heavy metal concentration were significantly high in Guangzhou city. Ranged from 0.0833 to 0.1900 mg m(-3), PM2.5 levels in the region were much higher than outdoor PM2.5 standard recommended by US-EPA. High enrichment factor values (K > 10) were obtained for Cd, Pb, Zn, Cu and Mo, reflecting the importance of anthropogenic inputs. In contrast, K values of Ni, Mn, Co and Fe were among 1 to 10, suggested that they were mainly from natural sources except for human activities. According to the results of chemical speciation analysis, more than 80% of Al and Fe were found bound to organic matter, oxidisable and sulphidic fraction, and residual fraction. Meanwhile, most of Zn, Pb, Cd and Cu were distributed in soluble and exchangeable fraction and carbonate, oxide and reducible fraction. Bioavailable coefficients (k) revealed that the order of comparative mobility and bioavailability of heavy metals is: Cd > Zn > Pb > Cu> Mn> Mo> Co> Ni> Fe> Al. With k > 0.8, Cd, Zn and Pb were classified as bioavailable elements, while Cu, Mn, Mo, Co and Ni (k approximately equal 0.5) were remarked as potential bioavailable elements, and Fe and Al (k <0.2) as non-available elements.

[Distribution of heavy metals in PM10 and its release in the simulated acid rain].

The distribution of heavy metals in inhalable particulate matter (PM10), which were collected in Foshan during December of 2004, was characterized by scanning electron microscope-X-ray energy dispersive analysis technique (SEM-EDS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The releases of Cu, Pb, Zn and Cd were also examined for their potential releases in simulated acid rain, which were quantified with batch reactors. The results showed that the daily average concentration of PM10 was 0.19 mg/m(3), about 79% higher than the secondary standard of China. The relatively contents of Zn and Pb in PM10 were much higher than Cd and Zn, whereas the releasing rates of Cd and Zn in simulated acid rain were greater than that of Cu and Pb. The releasing rates of heavy metals from PM10 were increased as the pH of the acid rain decreased.