铅锌尾矿中砷的迁移转化特征对比分析

Comparative Analysis of Migration and TransformationCharacteristics of Arsenic in Lead-zinc Tailings

对三铅锌尾矿中砷的含量、形态、环境风险进行分析评价,并结合产酸试验和静态浸出试验研究砷在各铅锌尾矿中的迁移转化特征和影响因素差异。结果表明:1)调查尾矿中砷含量较高,同时砷的形态有明显差异,其中SXD尾矿99%以上为残渣态,而MY尾矿中砷的非残渣态占到54%以上,TD尾矿中虽然残渣态砷占到88%,但由于尾矿中砷含量很高,故其非残渣态总量也较高。2)调查各铅锌尾矿中的砷具有中-重度生态危害,对此类尾矿库后期利用不能直接进行用于农用地用途的开荒复垦,将对农产品带来严重风险。3)结合砷的总量、生物有效性形态、产酸特性和砷的浸出率综合分析,MY尾矿在各尾矿中砷的含量高、活性最高、生物可利用性强,同时该尾矿含硫高,极易产酸,在酸性条件下尾矿中砷的可移动性加强,因而其砷的潜在生态环境风险最高;SXD尾矿砷含量最低,且尾矿中活性砷含量最低、生物可利用性不强,但由于其易产酸特性,在AMD作用下尾矿中砷的可移动性增强,生态环境风险加剧;TD尾矿砷含量最高,同时也具备相当高占比的活性态砷,但是由于其含硫低,酸缓冲能力强,属于不易产酸的尾矿,因而在一定程度上抑制了尾矿中活性砷的迁移转化,但在强碱性条件下,会促进尾矿中相对稳定的硫化砷溶解、解吸,从而向外环境迁移。4)对于不同类型铅锌尾矿中砷污染的防控或生态修复要结合尾矿产酸特性和赋存砷的生物有效性,采取不同的抑酸或固化/稳定化措施;同时考虑到在西南地区地表径流和垂直入渗是砷污染迁移的主要途径,因而必须加强尾矿库的规范设计、建设与管理,必要时采取阻隔措施。

The content,existent morphology,and eco-environmental risk of arsenic in three lead-zinc tailings were analyzed,and the migration and transformation characteristics of arsenic in all lead-zinc tailings and difference in influencing factors combing with acid production test and static leaching test were explored.The results demonstrate that:1)the arsenic content in tailings of study is high,but the existent morphology of arsenic is significantly different.More than 99%of arsenic in SXD tailings occur in residue state,while non-residual arsenic in MY tailings account for more than 54%.Although the residual arsenic in TD tailings account for 88%,the total amount of non-residual arsenic is also high due to the high arsenic content in tailings.2)The arsenic in lead-zinc tailings studied has moderate to severe ecological hazards,and those tailings cannot be directly used for the reclamation of agricultural lands at the late stage,which would pose serious risks to agricultural products.3)Combining with the total quantity of arsenic,the form of bioavailability,the characteristics of acid production,and the comprehensive analysis of arsenic leaching rate,the arsenic content in MY tailings is higher than others and has the highest activity and strong bioavailability compared with other tailings.Besides,MY tailings contain high sulfur which are easy to produce acid.The mobility of arsenic in MY tailings is enhanced under acidic conditions,resulting in the highest potential eco-environmental risk of arsenic.The arsenic content and active arsenic content in SXD tailings was the lowest,and the bioavailability of arsenic is not strong.However,the mobility of arsenic in SXD tailings is enhanced under the action of AMD due to its acid-producing characteristics,which aggravated the eco-environment risk.TD tailings have the highest arsenic content and a relatively high proportion of active arsenic.But with the low sulfur content and strong acid buffering ability,TD tailings are hard to produce acid.That to some extent inhibits the migration and transformation of active arsenic in tailings.Nevertheless,strong alkaline conditions could promote the relatively stable arsenic sulfide in tailings to dissolve and desorption,thus migrating to the external environment.4)For the prevention and control of the arsenic pollution in different types of lead-zinc tailings or ecological restoration,different acid inhibition or solidification/stabilization measures should be taken in combination with the acid-producing characteristics of tailings and the bioavailability of arsenic in tailings.At the same time,considering that surface runoff and vertical infiltration are the main ways of arsenic pollution migration in southwest China,it is imperative to strengthen the normative design,construction and management of tailings pond even take barrier measures if necessary.