不同洗涤蜂窝煤灰渣对污染土壤中铅的稳定作用研究

Immobilization of Lead in Soil with Washed Honeycomb Briquette Combustion Residue

蜂窝煤灰渣具有稳定污染土壤中铅的作用,但可增大土壤pH和电导率(EC)。将蜂窝煤灰渣经过水洗和稀盐酸酸洗后加入铅污染土壤(1000mg·kg-1Pb),研究了不同处理灰渣对铅有效性和土壤性质的影响。结果表明,灰渣经水洗和酸洗后,其pH(分别下降1.94、3.70)和电导率(0.785、0.890mS·cm-1)明显下降,重金属有效性和全量也有一定程度的下降。水洗和酸洗灰渣加入土壤后,土壤磷有效性有一定的上升。污染土壤在未加磷条件下加入原灰渣、水洗灰渣和酸洗灰渣后,DTPA-Pb含量分别下降67.2、195、117mg·kg-1,加磷情况下加入这3种灰渣土壤DTPA-Pb含量分别降低102、91.8、86.8mg·kg-1,各处理与对照的差异均达到0.05的显著水平。连续提取的结果表明,不同处理对土壤铅形态的影响不明显。

Phosphate has been widely used as the most effective amendment for lead （Pb） in soil~ Due to the limited phosphate rock resource, people are trying wastes or by-products as alternatives for phosphate. Honeycomb briquette combustion residue （HBCR） is a common solid waste in rural China. Our earlier work observed that HBCR could be used to immobilize Pb in soil, however, application of HBCR in soil resulted in elevated pH and electric conductivity（EC ）. In order to decrease its negative effect on the pH and EC of soil, I-IBCR was washed with water or dilute hydrochloric acid（HC1） before being applied to a soil spiked with 1 000 mg. kg^-1 Pb. The wateror dilute HCl-washing decreased pH （1.94 and 3.70 pH unit, respectively, compared with the un-washed HBCR） and EC （0.785 and 0.890 mS-cm^-1） of the HBCR greatly, and the availability and the total content of heavy metals slightly. Application of the wateror dilute HCl-washed HBCR resulted in higher availability of phosphorus in the soil. The concentrations of DTPA-extractable Pb in the soils amended with un-washed, water-washed and dilute HCl-washed HBCR decreased 67.2 mg·kg-1, 195 mg·kg-1 and 117 mg·kg-1, while these values were 102 mg·kg-1, 91.8mg·kg-1 and 86.8 mg·kg-1, when amended with additional amendment of phosphate. The differences between the amended soils and the control were statistically significant at 0.05 level. Sequential extraction of the soil Pb indicated that the effect of different amendments on the Pb speciation was not robust. These results suggested that both water-and dilute HCl-washings were effective in reducing the pH and EC of the HBCR, while water-washing was more effective in improving or maintaining the immobilization effect of Pb of HBCR.