基于贝叶斯最大熵和辅助信息的土壤重金属含量空间预测

Prediction of soil heavy metal content under spatial scale based on Bayesian maximum entropy and auxiliary information

预测土壤重金属空间分布对于识别高污染区域、进行污染来源解析和制定预防控制策略具有重要意义。本文选取浙江省杭州市为研究区,以土壤母质类型作为辅助信息,通过贝叶斯最大熵(Bayesian maximum entropy,BME)法,预测土壤重金属的空间分布,并与传统的克里金方法的预测结果进行比较。结果表明:BME在土壤重金属含量空间预测方面精度更高,其残差分布区间、平均绝对误差和均方根误差更小。研究区内重金属污染风险相对较低,其平均值均低于二级土壤环境质量标准值,但镉和砷的含量高于当地背景值,分别是背景值的1.59倍和1.31倍。铅和汞在该研究区东北部的城市地区含量较高,城市化、工业化和交通运输可能是其污染来源;镉和砷在西南部和中西部农村地区含量较高,农业活动可能是其污染来源。此外,镉在中东部还存在一块明显的高含量区域,这与当地矿业活动密切相关。铬主要受自然因素的影响。

With the rapid urbanization and industrialization process in recent decades,soil heavy metal pollution has been a serious threat to the development of society and human health in China.Mapping the spatial heavy metal distribution is an efficient way to identify high pollution areas,facilitate pollution source apportionment,and formulate prevention and control strategies.Selecting Hangzhou City as a case study,the spatial distribution of heavy metals was predicted by Bayesian maximum entropy(BME)method using the soil parent material as auxiliary information,and the estimation accuracy was compared with the traditional Kriging technique.The results showed that BME method has higher prediction accuracy than Kriging method,which was supported by narrower error distribution,smaller mean absolute error and root mean square error.Although the pollution risk of heavy metals in the study area was relatively low(their mean values were lower than the corresponding secondary soil environmental quality standard values),the contents of cadmium(Cd)and arsenium(As)were significantly higher than their local background values,which were 1.59 and 1.31 times of their corresponding background values,respectively.The contents of lead(Pb)and mercury(Hg)were high in the northeastern urban areas,implying that urbanization,industrialization and transportation may be the pollution sources;Cd and As were relatively high in the southwestern and mid-western rural areas,implying that agricultural activities may be responsible for the pollution source.In addition,Cd also showed some high content areas in the mid-eastern part of the city,which could be attributed to local mining activities.Chromium was mainly affected by natural sources.