纳米羟基磷灰石钝化修复重金属污染土壤的稳定性研究

Long-term stability of immobilizing remediation of a heavy metal contaminated soil with nano-hydroxyapatite

为评估纳米羟基磷灰石（Nano-hydroxyapatite,NAP）钝化修复重金属污染土壤的稳定性,采用一次性添加不同用量（0.5%、1%、2%,W/W）的NAP进行水稻盆栽试验,研究了一年和三年后土壤性质、有效态重金属（Cd、Cu、Zn、Pb）含量和水稻体内重金属含量的变化。结果表明：不同NAP施用量下土壤p H值在第一年和第三年分别显著提高了0.71～1.24和0.60～1.16,年际间p H提高幅度的差异较小,表现出较好的稳定性;第三年土壤中有效态Cd、Cu和Zn含量与对照相比降幅（62.7%～96.5%）要显著低于第一年（66.6%～98.4%）,而有效态Pb含量的降幅（百分比）则略有提高,表明随着时间的延长,NAP固定土壤Cd、Cu和Zn含量的能力有所减弱,而对Pb的固定能力有所增强。添加NAP显著降低了水稻根中的重金属含量和糙米中Cd含量,糙米中的Pb、Cu和Zn含量也有所降低。糙米中重金属含量与土壤中有效态重金属含量呈正相关关系,表明NAP通过降低土壤有效态重金属来降低重金属在水稻籽粒中的累积。

Nano-particles have been widely used to remediate heavy metal polluted water and soil. Here, a batch of pot experiments were conducted to evaluate the long-term stability of nano-hydroxyapatite（NAP）in remediating heavy metal contaminated soils by applying NAP at rates of 0.5%, 1% and 2%（W/W）. Changes of soil properties and content of heavy metals（Cd, Cu, Zn and Pb）in soil and in rice were investigated one year and three years after remediation. Results showed that soil p H rose 0.71～1.24 units in the first year and 0.60～1.16 units in the third year, having little variation over years. After three-year remediation, soil available Cd, Cu and Zn concentrations decreased by 66.6%～98.4% and 62.7%～96.5% for one-year and three-year of remediation, respectively. Available Pb decreased by 61.3%～74.2% in one-year and69.2%～74.4% in three-year of remediation. These results indicated that the immobilization ability of NAP for Cd, Cu and Zn was significantly weakened over time, while was slightly improved for Pb. Addition of NAP significantly reduced heavy metal content in roots and Cd content in brown rice. There was a positive correlation between heavy metal content in brown rice and available heavy metal concentrations in soil, indicating that NAP could reduce heavy metal accumulation in brown rice by reducing their concentrations in soil available heavy metals.