磷酸钙对铀矿下游水系沉积物中铀的钝化效果

利用Ca₃（PO₄）₂对模拟铀污染土壤进行钝化处理，分析了Ca₃（PO₄）₂投加量对其中有效态铀的钝化效果，基于此，采集粤北某铀矿下游水系沉积物，利用逐级化学提取法开展了Ca₃（PO₄）₂固定前后铀赋存形态研究。结果表明:沉积物中铀主要赋存于铁锰氧化物结合态中，添加Ca₃（PO₄）₂可降低沉积物中有效态铀的含量。溪流沉积物、池塘底泥、水稻田土壤中可交换态铀含量分别平均下降58.27%、58.04%、52.62%；碳酸盐结合态铀含量分别平均下降33.58%、47.98%、32.58%。Ca₃（PO₄）₂的投加显著增加了活性较低形态以及活性最低的残渣态铀含量；溪流沉积物、池塘底泥、水稻田土壤中有机质结合态铀含量分别增高32.95%、46.86%、30.50%；残渣态铀含量分别增高252.67%、61.90%、98.96%。钝化前，原处于中等风险的池塘底泥、水稻田土壤降为低风险，原处于低风险的溪流沉积物中有效态铀含量占比下降1/3。Ca₃（PO₄）₂能有效降低沉积物中铀的危害，可为放射性核素污染治理和环境修复提供一定参考。

PASSIVATION EFFECT OF CALCIUM PHOSPHATE ON URANIUM IN SEDIMENTS IN DOWNSTREAM WATERS OF A URANIUM MINE

Calcium phosphate was used to solidify the simulated uranium contaminated soil, and its passivation effect on the available uranium in the soil was analyzed. Based on this, the sediment in the downstream of a uranium mine in northern Guangdong was collected, and the occurrence forms of uranium before and after the passivation was carried out by sequential chemical extract method. The results showed that the uranium in the sediments mainly occured in Fe-Mn oxides combining species, and the content of available uranium in the sediments could be reduced by adding calcium phosphate. The exchangeable uranium content in stream sediments, pond sediment and paddy soil decreased by 58.27%, 58.04% and 52.62% respectively, and the carbonate bound uranium content decreased by 33.58%, 47.98% and 32.58% respectively. The content of organic combining species increased by 32.95%, 46.86% and 30.50% respectively in stream sediment, pond sediment and paddy soil, and the content of residual uranium increased by 252.67%, 61.90% and 98.96% respectively. The pond sediment and paddy soil with medium risk to the environment before passivation were reduced to low risk, and the proportion of available uranium in the stream sediment with low risk decreased by 1/3. In this study, the effect of calcium phosphate could effectively reduce the harm of uranium in sediment, which provided some reference for radionuclide pollution control and environmental remediation.