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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