模拟酸雨对磷酸二氢钾钝化污染土壤Cu、Cd、Pb和P释放的影响

以磷酸二氢钾(PDP)钝化后的重金属污染土壤为研究对象,通过室内土柱淋溶实验,考察在pH为3.5、4.5和5.6的模拟酸雨作用下土壤Cu、Cd、Pb和P的释放特征。结果表明:PDP处理较对照处理显著增加了淋出液中pH、电导率(EC)和总有机碳(TOC)含量,但不同pH模拟酸雨对对照和PDP处理淋出液pH、EC和TOC含量影响较小。对照处理中,正磷酸盐含量维持在较低水平(0.02~0.13 mg·L-1)；PDP处理下,正磷酸盐含量在1~3 L和4~12 L分别是《地表水环境质量标准》(GB 3838-2002)五类水标准(总磷含量0.4 mg·L-1)的55.1~819倍和9.46~46.6倍,对地表水表现出较大的富营养化风险。PDP处理较对照处理显著降低了淋溶初期淋出液中的Cu、Cd和Pb含量,但是随模拟酸雨pH降低,对照和PDP处理的土壤淋出液中Cu、Pb含量均未表现出显著差异。因此,PDP处理能够显著钝化污染土壤中的Cu、Cd和Pb,但需关注酸雨淋溶下过量磷释放对地表水富营养化的潜在风险。

Effects of simulated acid rain on release of Cu,Cd, Pb and phosphorus in contaminated soil immobilized by potassium dihydrogen phosphate

The potential release of copper (Cu), cadmium (Cd), lead (Pb) and phosphorus (P) from a potassium dihydrogen phosphate (PDP) treated soil were investigated by a laboratory column leaching experiment under simulated acid rain (SAR) with pH of 3.5, 4.5 and 5.6. The results showed that the leachate pH, electrical conductivity (EC) and total organic carbon (TOC) were significantly increased compared with the control, but they were not markedly differed with increasing SAR pH. The concentrations of orthophosphate in the control was kept a low level (0.02 to 0.13 mg·L-1). But they in PDP treated columns were 55.1 to 819 times and 9.46 to 46.6 times higher than the class Ⅴ limit (total phosphorus content 0.4 mg·L-1) of the Chinese National Quality Standards for Surface Waters (GB 3838-2002) in 1 to 3 L and 4 to 12 L, respectively, which posed a great eutrophication risk to surface water. Compared with the control treatment, the contents of Cu, Cd and Pb were noticeably decreased in PDP treated columns, but there was no significant difference among different pH values of SAR. Therefore, PDP treatment can effectively immobilize Cu, Cd, Pb in soil, but more concern should be pose on the potential risk of eutrophication induced by high leaching of P.