不同土地利用方式土壤重金属赋存与有机碳关联性分析

Correlation analysis between concentrations of soil heavy metal species and organic carbon in different land use types

【目的】评估不同土地利用方式土壤重金属形态与有机碳(SOC)含量的相关性,为深入理解土壤负载SOC和重金属的环境地球化学行为,以及评价土壤环境和人类健康风险提供参考依据。【方法】测定海南省琼海市和定安县3种不同土地利用方式(水田、旱地和抛荒地)中不同形态重金属砷(As)、铬(Cr)、铜(Cu)、锌(Zn)、铅(Pb)以及SOC和矿物结合态有机碳(MAOC)含量,并对重金属形态含量、富集度、生物有效性及重金属与SOC和MAOC之间的关联性进行分析。【结果】不同土地利用方式土壤中重金属含量表现为:水田Cr>Zn>Pb>Cu>As,旱地Cr>Zn>Pb>As>Cu,抛荒地Cr>Zn>Cu>Pb>As;土壤重金属形态以残渣态存在为主;不同土地利用方式下重金属的富集程度存在明显差异,富集指数呈现:水田Cr>As>Cu>Zn>Pb,旱地As>Cr>Cu>Zn>Pb,抛荒地As>Cu>Cr>Zn>Pb;3种土地利用方式土壤中Cr、Cu、Zn和Pb的生物有效性系数较小,处于较稳定的存在状态,生态潜在风险较小,而As对人体健康具有较大的潜在威胁。土壤中SOC和MAOC含量在3种土地利用方式下均表现为水田>抛荒地>旱地,土壤中SOC和MAOC含量与部分形态的Cr、Cu、Zn和Pb之间具有显著(P<0.05)或极显著(P<0.01)相关性。【结论】土地利用方式的改变不仅影响土壤理化性质,还对土壤中重金属的来源和性质以及有机物类型含量产生影响。不同土地利用方式土壤中部分重金属赋存形态含量与SOC和MAOC具有显著或极显著相关性(As除外),对深入理解海南土壤污染状况、土壤自净能力与机制等方面具有重要理论意义,可为海南土壤质量提升及可持续利用提供理论支撑。

【Objective】In order to evaluate the correlation between soil heavy metal forms and organic carbon content(SOC)under different land use types,and to understand the environmental geochemical behavior of soil SOC and heavy metals,it had important theoretical value and practical significance for the risk assessment of soil environment and human health.【Method】The contents of arsenic(As),chromium(Cr),copper(Cu),zinc(Zn)and lead(Pb),SOC and mineral bound organic carbon(MAOC)in soils of three different land use types(paddy field,dry land,abandoned land)in Qionghai City and Ding’an County of Hainan were determined.The morphological content,enrichment,bioeffectiveness and the association between heavy metals and SOC and MAOC were also analyzed.【Result】The results showed that,the contents of heavy metals in soil of different land use types were as follows:paddy field:Cr>Zn>Pb>Cu>As;dry land:Cr>Zn>Pb>As>Cu;abandoned land:Cr>Zn>Cu>Pb>As.The forms of heavy metals in soil were mainly residual;the enrichment degree of heavy metals under different land use types was quite different.The enrichment index showed that,paddy field:Cr>As>Cu>Zn>Pb,dry land:As>Cr>Cu>Zn>Pb,abandoned land:As>Cu>Cr>Zn>Pb.The bioavailability coefficients of Cr,Cu,Zn and Pb were small in the soil,which was in a relatively stable presence,and had less ecological potential risk,while As had large potential threat to human health.The contents of SOC and MAOC in soil showed the following order:paddy field>abandoned land>dry land.The content of SOC and MAOC in soil was significantly(P<0.05)or extremely significantly(P<0.01)correlated with some forms of Cr,Cu,Zn and Pb.【Conclusion】The change of land use types not only affects the physical and chemical properties of soil,but also affects the sources and properties of heavy metals and the content of organic matter in soil.The contents of some heavy metals in soils under different land use typesare significantly or extremely correlated with SOC and MAOC(except As).It has important theoretical significance for the indepth understanding of Hainan’s soil pollution status,ecological and environmental benefits,and its soil self-purification capabilities and mechanisms,in order to provide theoretical support for Hainan’s soil quality improvement and sustainable use.