河北省保定市典型农业区土壤重金属时空变化特征及来源解析

Spatial-temporal variation and source of soil heavy metals in a typical agricultural region of Baoding City, Hebei Province

关键词:  农业区土壤  重金属  源解析  时空变化  污染

Key words:  agricultural soil  heavy metals  source identification  spatial-temporal variation  pollution

摘要:

土壤重金属污染问题日益严重。为明确河北省典型农业区土壤重金属的富集特征及来源，为当地土壤环境保护和农业生产提供数据支持，文章基于2007年《河北省农业地质调查》项目中的92个历史数据与2021年采集的765个表层土壤样品数据，分析了保定市定兴县8个乡镇内表层土壤样品中Pb、Cd、 As、Zn、Cu、Cr、Ni、Hg重金属元素含量的时空变化特征，并通过单因子污染指数法和内梅罗综合污染指数法分析污染现状，使用主成分分析 （PCA） 结合绝对主成分得分-多元线性回归 （APCS-MLR） 模型，确定土壤中重金属的来源和贡献率。结果表明，该研究区表层土壤中8种重金属元素含量均低于农用地污染风险筛选值，2007—2021年，表层土壤中Cd、As、Hg元素富集现象明显，含量增加的区域分别占研究区总面积的59.13%、83.87%、69.76%。2021年8种重金属元素的污染程度依次为：Hg＞Cd＞ Pb＞Cr＞Zn＞Ni＞Cu＞As。土壤中Cr、Ni元素主要来源于成土母质，Zn、Cu、Pb、Cd、As、Hg元素则有自然及人为活动双重来源，其中，人类活动对表层土壤中Zn、Cu富集的影响小于Pb、Cd、As、Hg，又以对Hg元素的影响最严重。人类活动导致的农业土壤中重金属的长时间积累问题需引起关注。未来研究应关注农业用地重金属污染风险预测，为土壤环境管理提供更具针对性的指导。

Abstract:

Background, aim, and scope The issue of heavy metal contamination in soil is escalating in severity. This research examines the accumulation and origins of heavy metals in the surface soil of typical agricultural regions in Baoding City, Hebei Province, with the objective of providing data support for local soil environmental conservation and agricultural production. Materials and methods In 2021, a total of 765 surface soil samples were collected and analyzed for eight heavy metals (lead (Pb), cadmium (Cd), arsenic (As), zinc (Zn), copper (Cu), chromium (Cr), nickel (Ni), and mercury (Hg)) from eight towns in Dingxing County.Additionally, historical data regarding 92 surface soil samples from 2007, sourced from the Agricultural Geological Survey of Hebei Province project, were also collated. Based on this dataset, the spatiotemporal variations of heavy metals were analyzed. The single-factor pollution index method and the Nemerow comprehensive pollution index method were utilized to evaluate the pollution status of heavy metals in the surface soil. Furthermore, the sources and contribution rates of heavy metals in the soil were determined through the principal component analysis (PCA) combined with the absolute principal component scores-multiple linear regression (APCS-MLR) model. Results The concentrations of eight heavy metals in the surface soil of the agricultural area were lower than the screening values for the pollution risk of agricultural land. However, a notable accumulation of Cd, As, and Hg was detected in the topsoil during the period from 2007 to 2021, with the accumulated areas accounting for 59.13%, 83.87%, and 69.76% of the total study area respectively. The pollution degrees of the eight heavy metals in the top-soil were ranked in the following order: Hg＞Cd＞Pb＞Cr＞Zn＞Ni＞Cu＞ As. Discussion Ni, Cr, Cu, and Zn in surface soils showed weak variability with average concentrations close to the background values of central and southern Hebei Plain. From 2007 to 2021, these elements decreased in more than 50% of the study area, indicating a dominant natural source. Cd, Zn, Cu, and Pb exhibited increased variation coefficients, with mean values near background levels, suggesting enrichment controlled by both parent materials and agricultural activities. As and Pb were more enriched near rivers, related to parent materials and sewage irrigation. Hg increased significantly with strong variability, mainly derived from domestic waste and industrial or mining activities. Conclusions The long-term accumulation of heavy metals in agricultural soil due to anthropogenic activities demands attention. Recommendations and perspectives Future research should focus on the risk prediction of heavy metal pollution in agricultural land to provide more targeted guidance for soil environmental management.