广州市秋季PM2.5中重金属的污染水平与化学形态分析

采用消解法和连续提取法分析了广州市秋季PM_2.5样品中10种重金属元素的总量和化学形态,对广州市PM_2.5中重金属的污染水平和生物有效性进行了评价.结果表明,广州市PM_2.5和重金属污染非常严重,其中PM_2.5日浓度高达0.083 3～0.190 0 mg·m^-3,为1997年美国EPA相应标准的1.3～2.9倍.PM_2.5中Cd、Pb、Zn、Cu和Mo的富集因子K>10,是典型的污染元素;而Ni、Mn、Co和Fe的K值为1～10,除部分来自人为活动外,主要还是自然作用来源.化学形态分析结果显示,超过80％的Al和Fe分布在有机质、氧化物与硫化物结合态和残渣态,而大部分Zn、Pb、Cd 和Cu分布在可溶态、可交换态、碳酸盐态、可氧化态和可还原态.生物有效性系数(K)分析结果说明,PM_2.5中重金属的生物有效性相对强弱顺序为：Cd>Zn>Pb>Cu>Mn>Mo>Co>Ni>Fe>Al.其中Cd、Zn和Pb的K>0.8,为生物可利用性元素;Cu、Mn、Mo、Co和Ni的K值在0.5左右,为潜在生物可利用性元素;Fe和Al的K<0.2,为生物不可利用性元素.

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.