我国污灌污水中重金属含量特征及年代变化规律

通过查阅文献数据库,统计发表的我国各地污灌污水中的重金属含量,并对数据进行统计分析,总结近30a来我国污灌污水中重金属的含量特征及年代变化规律。文献数据统计结果表明,近30a来我国污灌污水中重金属Pb、Cr、Zn、Ni的含量均值或中位值随年代逐步降低,Hg、As平均含量呈先上升后下降的趋势,Cu、Cd平均含量则是呈现先下降后上升的趋势;近30a来污灌污水中8种重金属浓度的平均值或中位值均低于农田灌溉水质标准（GB5084—2005）,但污灌污水中重金属浓度的90%分位值均超过该农田灌溉水质标准,污灌污水中重金属浓度75%分位值20世纪80年代Hg、Pb、Cd超标,90年代Hg、Cr、As超标,近10aCd、As超标。对污灌污水中Hg、Cd、As在污染源头控制中需要优先控制。

Concentration Characteristics and Historical Changes of Heavy Metals in Irrigation Sewage in China

Sewage irrigation is one of the main factors which could cause contamination of heavy metals in the farmland. In this study, we collected the published data concerning the concentrations of heavy metals in irrigation sewage all over the country from literature databases, then analyzed all the data and summarized the concentration characteristic of heavy metals and their historical changes in the past 30 years. The results showed that the mean or median values of Pb, Cr, Zn, Ni concentrations in the irrigation sewage decreased gradually with the age in the last three decades. The mean concentrations of Hg and As increased firstly and decreased then, however, the mean concentrations of Cu and Cd decreased at the beginning and increased afterwards. The mean concentrations of the eight heavy metals were all lower than the standards prescribed in ＂Standards for irrigation water quality＂（GB 5084—2005）in nearly three decades, but about 10% of heavy metals concentrations were higher than this standard. About 25% of Hg, Pb, Cd concentrations in 1980—1989 were higher than the standard, 25% of Hg, Cr, As concentrations in 1990—1999 also higher than the standard and the same as 25% of Cd and As concentrations in 2000—2009. In summary, Hg, Cd and As should be considered as a priority in pollution source control of heavy metals in irrigation sewage.