某废弃冶炼场地土壤不同粒径组分重金属的特征及其对修复策略的启示

Characterization of soil heavy metals at an abandoned smelting site based on particle size fraction and its implications for remediation strategy

颗粒粒径组分对土壤重金属的分布与赋存具有重要影响,而当前对受冶炼活动影响的不同区域间土壤各粒径组分重金属分布的比较研究较少。本研究以某废弃铅冶炼场地为研究对象,选取三个土壤剖面(冶炼固废堆存区、交通区和邻近的农田),对比研究了不同土壤颗粒粒径组分(>150、45~150和<45μm)中重金属的地球化学分布特征及赋存形态。结果显示,冶炼场地与周边农田土壤各粒径组分重金属的分布特征具有明显差异。随着粒径的增大,冶炼固废堆存区土壤重金属的富集因子从0.78增至1.14,这与该区粗粒废渣的堆放与机械混合相关;而农田土壤重金属的富集因子从1.49降至0.60,这与冶炼过程释放富集重金属的细颗粒沉降有关。同时,冶炼场地土壤的较粗组分(>45μm)具有较高的重金属质量负载量(>50%),且废渣颗粒对土壤重金属的贡献显著,故物理分离技术可用于该场地的土壤污染修复。此外,石膏和莫来石可能是该场地受冶炼活动影响土壤的指示矿物。本研究将冶炼活动影响与土壤不同粒径组分重金属的赋存形态相关联,对修复策略具有一定的指导意义。

Soil particle size plays a crucial role in the distribution and occurrence of soil heavy metals(HMs).Comparative studies on the distribution of HMs across soil particle sizes of various areas affected by smelting are scarce.Three soil profiles,including smelting slag heap(SH),traffic area(TA),and adjacent farmland(FA),were sampled at an abandoned Pb smelting site,and the geochemical distribution and occurrence of HMs in different soil particle fractions(>150μm,45-150μm,and<45μm)were comparatively investigated.Results showed different distribution of HMs across soil fractions between the smelting site and farmland.Average accumulation factors(FA)of HMs increased from 0.78 to 1.14 as the particle size increased in the SH related to the stockpiling and mechanical mixing of coarse slags,while decreased from 1.49 to 0.60 in the FA related to metal-enriched fine particles released from smelting.The coarser fraction had a higher mass loading of HMs(>50%)in the smelting site soils,where the contribution of waste residues was significant.Therefore,physical separation techniques are recommended in the remediation of soil contamination.The study connected smelting impacts and occurrence of HMs across particle sizes which has implications for remediation strategy.