粉煤灰重金属铬的二次污染:某电厂灰场周围地下水Cr^(6+)污染事例

SECONDARY POLLUTION OF CHROMIUM IN POWDERY COAL ASH: AN EXAMPLE OF CR^(6+ ) IN UNDERGROUND WATER AROUND AN ASH SITE IN A POWER-STATION

重金属铬含量低于岩石圈的平均值 ,而与沉积岩平均含量大体相当的某电厂灰场的粉煤灰 ,竟是该区地下水 Cr6 +的污染源 ,的确是令人难以理解 ,并因而导致当地发生了一件难断的民事纠纷。本项工作通过一系列的浸泡和淋溶模拟试验 ,弄清了铬的转移过程及迁移机理 ,结果表明 :降水相对集中的半干旱地区 ,在表生作用氧化条件下 ,主要由于大气降水的淋溶和浸泡 ,粉煤灰中的三价铬可以氧化为六价铬转入水体 ,并进入地下水造成污染。这与通过该电厂灰场周围地下水 Cr6 +浓度的监测 ,其浓度值与灰场下水方向的距离成反向相关的结果得到了进一步的证实。

The content of Chromium in powdery coal ash around an ash site of a power station is lower than the average content of that in the lithosphere,but is roughly equal to that in sedimentary rock. However, Cr 6+ in underground water around the area is a pollution source, which leads to civil disputes that is hard to be settled.The transfer process and migratory mechanism of Chromium has been clarified through a series of soaking and leaching simulation experiments. The results indicate that, in semi arid region where precipitation is relatively concentrated, and under oxidizing conditions of epigenesis, due to the soaking and leaching of atmospheric precipitation the three valence Chromium ions in powdery coal ash are oxidized into six valence ions and move into groundwater, then polluting it. It is clear that the concentration of Cr 6+ is in reverse proportion to the distance vertically from the ash ground by monitoring Cr 6+ concentration in the underground water around the ash site of the power station.