热辐射与灰分耦合对矿区表层土壤Cr、As、Cu和Zn赋存及浸出影响机制研究

Storage and leaching behaviors of Cr,As,Cu and Zn in mine soil under coupling effects of thermal radiation and residual ash

为了解热辐射与灰分耦合对矿区表层土壤理化性质及其重金属Cr、As、Cu、Zn赋存和浸出毒性的影响,采用锥量仪在不同热辐射温度(400℃、600℃、750℃)及生物质负载量(1 kg/m^(2)、3 kg/m^(2)、5 kg/m^(2))下开展室内燃烧试验,对样品理化性质、Cr、As、Cu、Zn质量比和形态进行分析,并通过TCLP法对重金属潜在的浸出风险进行评估。结果表明:热辐射与灰分耦合作用显著改变表层土壤的理化性质。其次,耦合作用使得表层土壤Cr、As、Cu和Zn的总质量比增加,说明生物质燃烧产生的热辐射与灰分是影响矿区林地表层土壤重金属浓度的重要因素。此外,耦合作用使得Cr有效态的比例由50%下降到40%,As有效态的比例由14%增加到22%,对Cu和Zn有效态的作用则不明显,说明其对表层土壤Cr、As的迁移性分别起到了抑制和促进作用。TCLP试验结果表明,仅土壤受热或生物质与土壤共同燃烧都会使土壤中Cr、As、Cu和Zn的浸出水平增大;Cr、As、Cu和Zn浸出质量比最高分别为0.88 mg/kg、0.81 mg/kg、654.13 mg/kg和35.58 mg/kg,其中Cu、Zn均超出监管值。

To identify the coupling effect of thermal radiation and ash on occurrence and leaching behaviors of Cr,As,Cu and Zn,the paper took the area of Huangshi National Mining Park in Huangshi city,Hubei Province,China,as the research object.Vegetation and soil from the park were collected for laboratory simulation combustion.Combustion experiments were conducted at different thermal radiation temperatures(400℃,600℃,750℃)and biomass loadings(1 kg/m^(2),3 kg/m^(2),5 kg/m^(2))by using a cone calorimeter.This paper investigated the physicochemical properties of mine soil,mass ratio,and fractional distribution of Cr,As,Cu and Zn of samples,and then assessed the potential leaching risk of heavy metals by the TCLP method.The results show that residual ash and thermal radiation significantly change the physicochemical properties of the soil.Furthermore,the coupling effect increases the total amount of Cr,As,Cu and Zn in soil,indicating that thermal radiation and ash from biomass combustion play a significant role in affecting the mobilization of Cr,As,Cu and Zn in mine soils.In addition,BCR continuous extraction'results show that the proportion of the available state of Cr decreases from 50%to 40%,and that of As increases from 14%to 22%under the coupling effect in the soil,but not significant for Cu and Zn.It indicates that the coupling effects reduce and promote the mobility of Cr and As,respectively.The TCLP evaluation results indicate that the leaching levels of Cr,As,Cu and Zn in soil both increase by only thermal radiation or by co-combustion of biomass with the soil.The highest leaching contents of Cr,As,Cu and Zn are 0.88 mg/kg,0.81 mg/kg,654.13 mg/kg,and 35.58 mg/kg,respectively,of which Cu and Zn exceed the regulatory levels.The results shown in this study would contribute to understanding the environmental risks of wildfire and prescribed burning in heavy metals contaminated areas.