白银市污灌区土壤-小麦系统镉赋存特征及其健康风险评价

为探明白银市有色冶炼污灌区土壤镉(Cd)形态、空间分布特征及小麦中Cd含量对人体健康的影响,采用连续分级提取法和地理信息系统(ArcGIS)空间插值方法,研究污灌区表层土壤和不同污染程度典型土壤剖面Cd赋存形态及其空间分布差异,阐明污灌区Cd在不同生育期春小麦不同器官中分布和富集特征,并利用健康风险模型计算Cd的健康风险水平并进行空间区划。结果表明,表层土壤Cd不同形态平均含量依次为碳酸盐结合态>可交换离子态>铁锰氧化物结合态>残渣态>有机结合态,占全量比例依次为碳酸盐结合态>残渣态>可交换离子态>铁锰氧化物结合态>有机结合态,其空间分布与Cd总量分布相似。Cd的五种形态均与pH呈显著负相关,与土壤有机质(SOM)呈显著正相关。除残渣态外,其他四种Cd形态和阳离子交换量(CEC)呈显著正相关。0~60 cm土壤剖面Cd形态以碳酸盐结合态和铁锰氧化物结合态为主,可交换离子态随污染程度降低而降低,残渣态随污染程度降低而增加。春小麦不同器官的Cd含量随春小麦生长总体表现为根>叶>茎>籽粒。Cd健康风险分布与土壤Cd总量、土壤可交换离子态和碳酸盐结合态Cd的空间分布一致。不同区域居民食用小麦对成人的健康风险指数(HQ)范围在1.2~5.6之间,均大于1,已存在非致癌健康风险。本研究结果为白银市土壤重金属Cd污染综合防控提供了科学依据。

Speciation Features and Health Risk Assessment of Cd in Soil-Wheat System in Baiyin Sewage Irrigation Area in China

In order to detect the chemical speciations and spatial distribution characteristics of Cd in the soil surface in Baiyin sewage irrigation area in China and the effect of the wheat Cd content on human health, sequential extraction procedure and ArcGIS spatial interpolation method were used in Cd speciation features, spatial distribution differences under the different pollution levers in sewage irrigation soil and the distribution and enrichment characteristics of Cd in different organs at different stages of spring wheat. Health risk model was used to calculate the health risk level and spatial division. Results showed that the average contents of Cd in surface soil were carbonate bound state > ion-exchangeable state > Fe-Mn oxides bound state> residue lattice state> organic bound state, and the proportions of different forms of Cd followed the order of carbonate bound state > residue lattice state> ion-exchangeable state> Fe-Mn oxides bound state > organic bound state, and their spatial distribution was similar to that of the total Cd. Except residue lattice Cd, there were significant negative correlation with pH and significant positive correlation with SOM and CEC under other forms of Cd. Cd speciations in the 0-60 cm profiles were mainly composed of carbonate bound state and Fe-Mn oxides binding state, the content of ion-exchangeable state and residue lattice state of Cd decreased and increased with pollution levels decreased, respectively. With the growth spring wheat, the content of Cd increased firstly, then decreased and then increased. The concentration of Cd was different in different organs, following the order of root > leaf > stem > grains. The health risk indexes of Cd consisted with the spatial distribution of total Cd, as well as exchangeable and carbonate bound. The range of residents wheat consumption health risk indexes(HQ) was from 1.2 to 5.6,more than 1.0 in different sewage regions, and belong to a non-carcinogenic health risk. These results provide a scientific basis for the prevention and control of soil heavy metal pollution in Baiyin city.