摘要
为了解重金属Cd、Pb在土壤团聚体中的分布、赋存形态及其影响因素,以辽宁省葫芦岛市锌冶炼厂周边农田土壤为研究对象,采用Tessier五步提取法测定土壤各级团聚体中Cd、Pb形态,利用地累积指数法(Igeo)、原生相与次生相比值法(RSP)和风险评估编码法(RAC)评价其环境风险,并利用相关性与冗余分析明确影响Cd、Pb分布与形态的关键因素。结果表明,土壤Cd、Pb含量在水平方向上呈现以锌冶炼厂为中心,随中心距离的增加呈现先增加后降低的变化趋势;垂直方向上,表层土Cd、Pb含量分别为57.40、219.56 mg·kg^(-1),显著高于亚表层(55.06、135.99 mg·kg^(-1))。随着团聚体粒径的减小,Cd、Pb更趋向于在小粒径团聚体中富集,Cd富集能力强于Pb。重金属形态分布特征表明,Cd主要以可交换态和碳酸盐结合态赋存,占总Cd量的60%~94%,Pb主要以铁锰氧化物结合态和碳酸盐结合态赋存,占总Pb量的45%~93%。粒径为<0.002 mm的团聚体组分中可交换态和碳酸盐结合态Cd及铁锰氧化物结合态和碳酸盐结合态Pb含量占比显著高于其他三个粒径团聚体组分。三种评价方法均显示小粒径团聚体中重金属污染风险较高。RAC风险评估方法既考虑了重金属形态又考虑了重金属总量,评价结果更为准确。RAC结果表明研究区Cd污染为极高风险,Pb污染为中等风险。有机质(SOM)、表面积(SA)、阳离子交换量(CEC)和铁锰氧化物是粒径<0.002 mm团聚体组分产生特性差异的主要因素。SOM对粒径为0.25~2.00、0.053~<0.25 mm和0.002~<0.053 mm团聚体中残渣态和有机结合态Cd、Pb均有极显著影响。CEC对粒径为<0.002 mm团聚体组分中可交换态Cd分布具有显著的影响。铁锰氧化物对粒径为0.053~<0.25 mm和<0.002 mm团聚体组分中Cd、Pb形态具有一定影响,且对可交换态、碳酸盐结合态和铁锰氧化物结合态影响较大。Cd、Pb在污染农田中较高活性形态易在粒径为<0.002 mm团聚体组分中富集分布,具有较高环境风险,SOM、CEC和铁锰氧化物为Cd、Pb富集过程主要影响因素。
To understand the distribution and chemical speciation of heavy metals(Cd and Pb)in soil aggregates and factors affecting these processes,agricultural soil surrounding a zinc smelter in Huludao,Liaoning Province,China,was analyzed.Five-step sequential extraction based on the Tessier method was used to determine the chemical speciation of Cd and Pb in soil aggregates in different size classes.The index of geo-accumulation(Igeo),ratios of secondary and primary phases(RSP),and risk assessment coding(RAC)methods were used to evaluate the environmental risk of heavy metal contamination of soil.Correlation and redundancy analyses were applied to determine the key factors affecting the distribution and speciation of Cd and Pb in soil aggregates.Cd and Pb contents in soil increased initially,followed by a decrease,with increasing distance from the center of the zinc smelter.Cd and Pb contents in the topsoil were 57.40 mg·kg^(-1)and 219.56 mg·kg^(-1),respectively,which were significantly higher than those in the subsurface layer(55.06 mg·kg^(-1)and 135.99 mg·kg^(-1),respectively).With decreasing aggregate particle size,Cd and Pb contents tended to increase,with Cd showing greater enrichment than Pb.Cd was predominantly detected in exchangeable and carbonate-bound forms,accounting for 60%–94%of the total Cd.Meanwhile,Pb was predominantly detected in Fe–Mn oxide-and carbonate-bound forms,accounting for 45%–93%of the total Pb.The proportions of exchangeable and carbonate-bound Cd forms as well as of Fe-Mn oxide-and carbonate-bound Pb forms in aggregates fractions with particle size<0.002 mm were significantly higher than those in the remaining aggregate fractions with larger particle sizes.The three independent evaluation methods yielded consistent results that the risk of heavy metal contamination was higher in aggregates with smaller particle size.The RAC method considered both speciation and total amount of heavy metals;thus,its evaluation results were the most accurate.RAC results indicated that Cd contamination in the study area poses a very high risk,whereas Pb contamination poses a moderate risk.Soil organic matter(SOM),surface area(SA),cation exchange capacity(CEC),and Fe–Mn oxides were the major factors underlying differences in the characteristics of aggregate fractions with particle size<0.002 mm.SOM exerted a highly significant effect on both residual and organically bound Cd and Pb in aggregates with particle sizes of 0.25–2.00,0.053–<0.25 mm,and 0.002–<0.053 mm.CEC exerted a significant effect on the distribution of exchangeable Cd in aggregate fractions with particle size<0.002 mm.Fe–Mn oxides exerted a certain effect on Cd and Pb speciation in aggregate fractions with particle sizes of 0.25–<0.053 mm and<0.002 mm and a greater effect on exchangeable,carbonate-bound,and Fe-Mn oxide-bound forms.The higher active forms of Cd and Pb in contaminated farmlands can be easily enriched and distributed in aggregates of particle size<0.002 mm,posing a high environmental risk,and SOM,CEC,and Fe–Mn oxides are the key factors affecting these Cd and Pb enrichment processes.
作者
魏晓莉
张珊
张玉龙
叶子豪
陈华毅
李永涛
李文彦
WEI Xiaoli;ZHANG Shan;ZHANG Yulong;YE Zihao;CHEN Huayi;LI Yongtao;LI Wenyan(College of Nature Resources and Environment,South China Agricultural University,Guangzhou 510642,China)
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2023年第4期820-832,共13页
Journal of Agro-Environment Science
基金
国家重点研发计划项目(2019YFC1804400)
国家自然科学基金项目(41977126)
广东省基础与应用基础研究基金项目(2020A1515010556,2021A1515011283)。
关键词
锌冶炼厂
农田土壤团聚体
镉
铅
土壤理化性质
形态分布
环境污染风险
zinc smelter
agricultural soil aggregate
cadmium
lead
soil physicochemical property
speciation
environmental pollution risk
