西安市大气降尘中Cu、Pb、Zn、Ni的化学形态及生物有效性——以燃煤电厂、生活垃圾电厂、产业开发区和建材商业区为例

Study of the chemical species and their biological availabilities of heavy-metal contents in the dustfall in Xi'an

为了解垃圾焚烧、燃煤发电和相关产业排放对重金属污染水平和生物有效性的影响,利用Tessier提取法和原子吸收光谱仪分析法研究了西安市垃圾发电厂、西郊热电厂、灞生态园、未央工业园、大明宫建材市场和高新区降尘中Cu、Pb、Ni、Zn的化学形态。结果表明:垃圾发电厂Cu(358.3 mg/kg)、Pb(851.3 mg/kg)、Ni(163.5 mg/kg)、Zn(1 226.1 mg/kg)的总量,超过热电厂、生态园、工业园、建材市场和高新区;生活垃圾焚烧、燃煤、石化和机械加工等对降尘中这些元素的贡献超过电子和先进制造业;降尘中Cu、Pb、Zn质量比约是土和道路灰尘平均值的若干倍,表明垃圾焚烧、燃煤和相关产业排放的贡献显著高于表土扬尘、道路扬尘。高新区Cu、Pb的生物有效性系数超过其他区域,表明电子和先进制造业排放的重金属元素具有更大的潜在生态风险。Cu、Pb、Ni(除垃圾焚烧厂外)的生物有效性系数均大于0.2,而Zn的生物有效性系数均小于0.2,说明降尘中Cu、Pb、Ni存在潜在风险,而Zn是安全的。

The present paper aims to make a study of the chemical species and their biological availabilities of heavy-metal contents in the dustfall in Xi＇an. For our study purpose, we have collected dustfall samples from the areas of Xijiao Coal-combustion Power Plant （XCP）, Domestic Waste-burning Power Plant （DP）, Xi＇an High Technology Zone （TZ）, Weiyang Industrial Area （WA）, Daminggong Building Materials Shopping Mall （BS） and Chanba Ecological-Industrial Park （CP）, in addition to some other spots. And then we have analyzed the chemical contents of the heavy metals, such as Cu, Pb, Zn and Ni extracted by the Tessier＇s method by Atomic Absorption Spectrophotometry （AAS） so as to make clear the effects of combustion of coal and domestic waste, industrial and commercial activities on the chemical species and biological availabilities of such heavy metals on the environment. Our investigation results show that the total contents of Cu （358.3 mg/kg）, Pb （851.3 mg/kg）, Zn （1 226.1 mg/kg） and Ni （163.5 mg/kg） in the dustfall samples collected in the DP are the highest among all other of all the samples. This result implies that the power plants of domestic waste and coal, petrochemical and mechanical industries could contribute significantly to the emission of the heavy metals in comparison of electrical and advanced manufacturing industries. The total contents of Cu, Pb, Zn in the dustfall samples prove to exceed a few times on average in comparison with their respective counterparts both in urban road dusts and Lou Soil in Shaanxi province, which indicates that the emissions of the above industrial and commercial activities tend to contribute more significantly to the heavy metal emission inventory of dustfall than those of aeolian and road dust. In contrast to the total contents of Cu, and Pb in the dustfall samples in the above areas, the biological availabilities of the above contents in the samples collected in the TA are the highest among all the above said areas. It could be thus interpreted that the heavy metals emitted from the electrical and advanced manufacturing industries are likely to induce greater eco-environmental hazards than those from the power plants. Moreover, the biological availabilities of Cu, Pb, Ni in the dustfall samples except in DP are over 0.2 whilst those of Zn in the samples are less than that level. It indicates that Cu, Pb, Ni in the dustfall samples are of potential ecological hazards respectively.