气化渣提碳灰渣重金属赋存形态特征及生态风险评价

Occurrence form characteristics and ecological risk assessment of heavy metals in carbon extraction ash from gasification slag

气化渣是残碳较为丰富的一般工业固体废弃物,其提碳是高值化利用的重要途径之一,但提碳后残余灰渣的环境效应不明显限制了下游资源化利用。为此,以气化渣提碳灰渣为研究对象,利用BCR连续提取法研究镉(Cd)、镍(Ni)、铜(Cu)、锌(Zn)、砷(As)、铬(Cr)、汞(Hg)、铅(Pb)、铊(Tl)等9种重金属的全量和赋存形态特征,并对气化渣提碳灰渣进行生态风险评价。研究结果表明,气化渣提碳灰渣中除Tl外,其余重金属全量平均值均小于农用地土壤风险筛选值;气化渣提碳灰渣中的重金属(除Ni、Zn和Tl)主要以残渣形式存在;潜在生态风险指数法评价得出气化渣提碳灰渣中9种重金属全量风险等级为中等风险水平;单因子指数法评价得出Tl为中度污染,地质累积指数法评价得出Cd、Zn、Pb、Tl为中度污染;内梅罗综合污染指数法得出,9种重金属的综合污染等级为重度污染,但放大了Tl的影响,去除Tl后的评价结果为清洁水平。

Coal gasification slag is a kind of general industrial solid waste rich in carbon residue,Its carbon extraction is an important way of high value utilization,but the environmental effect of residual ash after carbon extraction is not obvious,limiting the downstream resource utilization.On the basis,the total amount and occurrence form characteristics of cadmium(Cd),nickel(Ni),copper(Cu),zinc(Zn),arsenic(As),chromium(Cr),mercury(Hg),lead(Pb)and thallium(Tl)are investigated by BCR sequential extraction method,and the ecological risk assessment of carbon extraction ash from gasification slag is conducted.The results show that the total average value of heavy metals(except Tl)in the carbon extraction ash from gasification slag is less than the soil risk screening value of agricultural land;the heavy metals(excluding Ni,Zn,and Tl)in the carbon extraction ash from gasification slag mainly exist in the residual state;the potential ecological risk index method evaluates that the total risk level of 9 heavy metals in the carbon extraction ash from gasification slag is at a medium risk level;the single factor index method evaluates Tl as moderate pollution,while the geological accumulation index method evaluates Cd,Zn,Pb,and Tl as moderate pollution;according to the Nemero comprehensive pollution index method,the comprehensive pollution level of 9 heavy metals is severe pollution,but the impact of Tl is amplified,and the evaluation result is cleanliness level after removing the impact of Tl.