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    江苏典型污染耕地土壤有效Cd与稻米Cd相关性及其健康风险

    Correlation between available Cd in the typical contaminated farmland soil and Cd in rice seeds and its health risk in Jiangsu Province

    • 摘要:研究目的】为探明江苏典型耕地Cd污染的健康风险,了解其稻米Cd吸收的主要地球化学控制因素,帮助科学防治耕地Cd污染。【研究方法】系统采集江苏典型Cd污染耕地及其相关地区的水稻籽粒-土壤样品1330套,测定稻米Cd、土壤有效Cd(氯化钙提取法)、Cd、Pb、Hg、As、Cr、Cu、Zn、Sb、pH、TOC、CEC等元素含量,对所获取的土壤有效Cd与稻米Cd等环境地球化学数据进行统计归纳、元素相关性分析及R型聚类分析等,确定影响稻米Cd吸收的主要环境因子,评价局地镉污染健康风险。【研究结果】研究区土壤有效Cd含量为0.0018~1.44mg.kg-1、均量0.265mg.kg-1,土壤Cd含量为0.13~30.0mg.kg-1、均量2.11 mg.kg-1,稻米Cd含量为0.0053~2.58mg.kg-1、均量0.478 mg.kg-1。土壤有效Cd是控制稻米Cd的最主要因子,局部Cd污染已扩散到食物链与人发中。【结论】 1)稻米Cd与土壤有效Cd之间存在显著的正相关性,全部样本参与统计所得到的稻米Cd和土壤有效Cd的相关系数r=0.54,当土壤pH=6.5~7.5时、稻米Cd同土壤有效Cd的相关系数(r)拥有最大值、r=0.86。除了有效Cd外,土壤Cd、TOC、CEC、pH等也是影响稻米Cd的环境因子,稻米Cd同土壤Cd多呈显著或较显著正相关性,同土壤pH、TOC、CEC多呈显著或较显著负相关性,影响稻米Cd的因子排序依次为土壤有效Cd﹥ Cd﹥ pH﹥ TOC≈CEC; 2)相比无污染耕地,耕地污染区的Cd致癌健康风险指数CR值增长了85倍多、食用Cd超标稻米的人发样品Cd均量增加了1.09倍、土壤溶液Cd浓度明显偏高,污染耕地的稻米Cd及其健康风险评价对土壤有效Cd依赖程度更高,指示局部耕地Cd污染区存在更高健康风险; 3)土壤有效Cd同土壤Cd、pH、TOC、CEC、Se等因子之间存在显著相关性或复杂的拮抗作用,综合调控稻米的Cd吸收; 4)江苏耕地Cd污染总体轻微,局部的污染风险等级以轻度为主。若能从实情出发,采取合适的修复治理措施(深翻耕等)降低耕地Cd或有效Cd含量,合理增加土壤有机质、提高土壤pH等,完全可以阻断耕地土壤Cd向食物链迁移、生产合格稻米,满足社会需求。

       

      Abstract: Objective In order to prove the health risk from the Cd pollution in typical cultivated soils in Jiangsu province, and understand the main geochemical factors to control rice seeds uptake of Cd in soil, and provide scientific evidences to cure Cd pollution.Method 1330 sets of rice-soil samples were systematically collected in the studied areas, and Cd, Pb, Hg, As, Cr, Cu, Zn, Se, Sb, TOC(Total Organic Carbon), pH, and CEC (Cation Exchange Capacity) in soil and Cd in rice seeds were determined by advanced testing methods such as ICP-MS, etc, the available Cd in soil was determined by calcium chloride extraction, and mastering the actual distribution data related to rice seeds Cd contents and elemental concentrations in soil. By the means of calculating their geochemical parameters and comparing its difference, developing correlation analysis and R-type cluster analysis, etc., and exploring main geochemical controlling factors to impact rice seeds uptake of Cd in soil, evaluating healthy risk in the local Cd polluted farmland.Results The available Cd concentrations are 0.0018~1.44mg.kg-1, their mean value is 0.265mg.kg-1, and the Cd concentrations are 0.13~30.0mg.kg-1 with an average amount of 2.11 mg.kg-1 in soil, and the rice seeds Cd contents are 0.0053~2.58mg.kg-1 with the mean amount of 0.478 mg.kg-1 in the studied areas. The available Cd in soil is the most important factor to control the rice seeds uptake of Cd, and the local Cd pollutants have spread to the food chain and human hairs in the farmland.Conclusion 1) there are significant positive correlations between rice seeds Cd contents and the available Cd in soil, and its correlated coefficient (named r)is 0.54 without deleting anyone in the 1330 sets samples, if pH values being from 6.5 to 7.5 in soil, the positive correlated relationship between rice seeds Cd contents and the available Cd in soil is best with correlated coefficient maximum value of r=0.86. In addition to the available Cd, the following geochemical factors as to Cd, TOC, CEC, and pH of soil are also important to control rice seeds uptake of Cd, and there exist some significant or more significant positive correlation between rice seeds Cd contents and Cd concentrations too, and similar significant or more significant negative correlation between rice seeds Cd contents and pH, TOC and CEC in soil. In general, the factors order to impact rice seeds Cd absorption is the available Cd﹥ Cd﹥ pH﹥ TOC≈CEC in soil; 2) as to pollution-free Cd farmland, the Cd carcinogenic health risk index (simplified CR value) increased by more than 85 times, the average amount of Cd concentration in the human hair samples increased by 1.09 times because of eating rice seeds with Cd over standard, and the Cd concentration of the soil solution was significantly increased higher in the farmland distributive area contaminated by Cd. Meanwhile, the rice seeds Cd contents and its relative health risk evaluation are more dependent on the soil effective Cd in those areas contaminated by Cd, it means that there are higher health risks or ecological security risks in those local farmland Cd pollution areas; 3) there are too significant correlation or obvious antagonism in soil between the available Cd and other geochemical factors such as Cd, pH, TOC, CEC and Se, and so on, which comprehensively regulate the Cd absorption of rice seeds, but the available Cd in soil is the most main one; 4) the Cd pollution is generally slight, and its healthy risk level is mainly mild from the cultivated land in Jiangsu province, if we can take appropriate restoration and treatment measures (for example deep tillage, etc.) in order to reduce the Cd, especially effective Cd content in soil, reasonably increase soil organic matter, improve soil pH, etc., block the migration of soil Cd to food chain and human bodies, the Cd polluted risk will completely be controlled, and produce qualified rice seeds to meet the social needs at last.

       

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