生态保护和环境治理企业周边土壤-稻米镉污染特征

Characteristics of Soil-Rice Cadmium Pollution Around Ecological Protection and Environmental Treatment Enterprises

分析评价生态保护和环境治理企业对土壤环境和稻米质量影响,对加强企业用地环境风险管控,实施耕地重金属污染精准防控,进一步保障稻米质量安全具有重要意义。以生态保护和环境治理企业周边土壤-稻米为研究对象,对82家企业共444个企业周边表层土壤(0~20 cm)和稻米样品的土壤全镉(Cd)、有效态Cd、稻米Cd含量以及土壤理化性质进行了测定,通过统计土壤和稻米Cd元素随距离企业远近的变化规律,并采用分类与回归树方法探索了影响稻米Cd含量的关键因素。结果表明:①土壤-稻米Cd存在一定程度的污染,土壤全Cd均值超过GB 15618-2018筛选值的1.75倍,样品超过筛选值的比例达到56.5%;稻米Cd含量均值超过GB 2762-2017标准的1.35倍,样品超过标准限值的比例达到44.3%;②稻米Cd与土壤全Cd和有效Cd间均呈显著正相关关系,且土壤全Cd和有效Cd含量的相关性更高,土壤-稻米Cd含量随着土壤酸碱度的升高不断降低;③土壤全Cd、有效Cd、稻米Cd含量随距企业距离变化规律表明,有效Cd含量变化规律与稻米Cd相似,在距企业1 km范围内土壤-稻米Cd含量较高,可以确定稻米的安全种植距离;④分类与回归树结果表明不同距离段影响稻米Cd含量的因素不同,其含量不仅受到土壤全Cd、有效Cd含量、土壤酸碱度的影响,还受到企业密度、土壤母质等因素的影响。可见,生态保护和环境治理企业周边土壤-稻米Cd在一定距离内存在污染,需要加强监测和管控。

The analysis and evaluation of the impact of ecological protection and environmental treatment enterprises on soil environment and rice quality are of great significance for strengthening the environmental risk control of land use by enterprises,implementing precise prevention and control of heavy metal pollution in cultivated land,and further guaranteeing the quality and safety of rice.In this study,soil-rice surrounding ecological protection and environmental treatment enterprises(EPETE)were selected as the research object.The contents of total soil and rice grains cadmium(Cd),available Cd and soil physical and chemical properties of 444 topsoil(0-20 cm)and rice samples around 82 EPETE enterprises were determined.The variation of Cd elements in soil and rice grains with distance from enterprises was analyzed and the key factors affecting Cd content in rice grains were explored by classification and regression tree method.The results showed that:①there was a certain degree of contamination of soil-rice Cd.The mean value of total Cd in soil was more than 1.75 times of the screening value of GB 15618-2018,and the proportion of samples exceeding the screening value reached 56.5%.The average Cd content of rice grains was 1.35 times higher than that of GB 2762-2017 standard,and 44.3%of samples exceeded the standard limit;②There was a significant positive correlation between Cd in rice grains and total Cd and available Cd in soil,and the correlation between total Cd and available Cd in soil was higher.The Cd content in soil-rice decreased with the increase of soil pH;③The variation of total Cd,available Cd and rice Cd contents with the distance from the enterprise showed that the variation of effective Cd content was similar to that of rice Cd.The soil and rice Cd contents were higher within 1 km from the enterprises,which could determine the safe planting distance around enterprises;④The results of classification and regression tree showed that the factors affecting the Cd content of rice grains were different at different distances.The Cd content of rice grains was not only affected by the total Cd content of soil,the available Cd content of soil and the soil pH,but also affected by enterprise density,soil parent material and other factors.It can be seen that soil-rice Cd is polluted in a certain distance around EPETE enterprises,so monitoring and control should be strengthened.