土壤调理剂对土壤-水稻系统Cd、Zn迁移累积的影响及健康风险评价

选取湖南省长沙市北山镇某中重度Cd污染稻田,研究了土壤调理剂(石灰石+偏高岭土+钙镁磷肥)对稻田土壤重金属Cd、Zn的钝化效果,以及对水稻各部位累积Cd和Zn的影响,并进行了Cd的健康风险评价.结果表明,使用土壤调理剂提高了稻田土壤p H值.Cd的CaCl_2提取态含量降低了0.9%~24.1%,Zn的CaCl_2提取态含量降低了22.5%~69.6%.土壤调理剂显著降低了水稻糙米中Cd与Zn的含量,与对照相比分别降低了10.8%~47.3%、10.3%~17.5%;土壤调理剂对水稻糙米Cd的吸收和累积的影响要远大于Zn,水稻糙米中的Cd/Zn比随着土壤调理剂施用量的增加而显著降低.研究区大米重金属Cd目标危害系数THQ值大于1,说明当地人群通过食用大米途径摄入重金属Cd存在健康风险.土壤调理剂有效地抑制了水稻植株对土壤中Cd的吸收,并降低了Cd/Zn比,使糙米中的Cd含量显著降低,从而降低了当地人群通过食用大米途径摄入重金属Cd的健康风险.

Effects of combined amendment on transport and accumulation of Cd and Zn in soil-rice system and the related health risk assessment

An in-situ experiment was conducted in Beishan Town, Changsha, Hunan, an area with paddy soil contaminated severely with Cd and partly with Zn, to study the effects of a combined amendment (calcium carbonate + metakaolin + fused calcium-magnesium phosphate) stabilizing Cd and/or Zn and on the accumulation of Cd and/or Zn in rice organs and to evaluate the Cd health risk potential caused from rice consumption. The results showed that application of the combined amendment significantly increased soil pH. The contents of CaCl₂-extractable Cd in soil reduced by 0.9%~24.1%, and the contents of CaCl₂-extractable Zn in soil reduced by 22.5%~69.6%. The contents of Cd and Zn in brown rice decreased by 10.8%~47.3% and 10.3%~17.5%, respectively, due to application of the combined amendment. It was obvious that the effects of the combined amendment on Cd accumulation in rice organs were much greater than those of Zn accumulation, and the Cd/Zn ratios in brown rice were significantly decreased with increasing application amount of the combined amendment. The values of the target hazard THQ for Cd exceeded 1 in the studied area, indicating that intake of Cd through consuming rice would pose potential health risks to the local individuals. Application of the combined amendment inhibited Cd uptake by rice root and reduced Cd contents in brown rice, and therefore declined the Cd/Zn ratios and the health risk of Cd in rice.