Dept. of Civil Engineering, University of Concepción, Casilla 160-C, Correo 3, Ciudad Universitaria, Concepción, Chile.
J Contam Hydrol. 2010 Mar 1;112(1-4):155-62. doi: 10.1016/j.jconhyd.2009.12.004. Epub 2009 Dec 23.
Using the biogeochemical model CCBATCH, which we expanded to include transport processes, we study a novel approach for the treatment of aquifers contaminated with toxic concentrations of metals, the diffusion-active permeable reactive barrier (DAPRB), which is based on generation of sulfide by Sulfate Reducing Bacteria (SRB) as the groundwater moves through a layered treatment zone. In the DAPRB, layers of low conductivity (low-K) containing reactive materials are intercalated between layers of high conductivity (high-K) that transport the groundwater across the barrier. Because diffusion dominates transport in the reactive layers, microbial communities can take advantage there of the chemical-gradient mechanism for protection from toxicants. The ideal sulfidic DAPRB design includes particulate organic matter (POM) and solid sulfate mineral inside the reactive (low-K) layer. This leads to sulfate reduction and the formation of sulfide ligands that complex with toxic metals, such as Zn(2+) in the high-K layer. We perform a theoretical biogeochemical analysis of the ideal configuration of a DAPRB for treatment of Zn-contaminated groundwater. Our analysis using the expanded CCBATCH confirms the gradient-resistance mechanism for bio-protection, with the ZnS bio-sink forming at the intersection of the Zn and sulfide plumes inside the high-K layers of the DAPRB. The detailed DAPRB analysis also shows that total alkalinity and pH distributions are representative footprints of the two key biogeochemical processes taking place, sulfidogenesis and Zn immobilization as sulfide mineral. This is so because these two reactions consume or produce acidic hydrogen and alkalinity. Additionally, because Zn immobilization is due to ZnS mineral precipitation, the ZnS mineral distribution is a good indicator for the bio-sink. Bio-sinks are located for the most part within the high-K layers, and their exact position depends on the relative magnitude of metal and sulfide fluxes. Finally, we conduct a practicality analysis that supports the feasibility of implementing the proposed design. For instance, the fraction of reactive material that is consumed during sulfidogenesis is relatively small (including POM and sulfate source), a total volume fraction of less than 6% over a time span of 50years.
利用我们扩展的包含传输过程的生物地球化学模型 CCBATCH，我们研究了一种处理含水层中有毒浓度金属污染的新方法，即扩散活性可渗透反应屏障（DAPRB），该方法基于硫酸盐还原菌（SRB）产生的硫化物作为地下水通过分层处理区移动。在 DAPRB 中，低电导率（低-K）层中含有反应性材料，夹在高电导率（高-K）层之间，这些高-K 层将地下水输送穿过屏障。由于扩散在反应层中占主导地位，微生物群落可以利用化学梯度机制来保护它们免受有毒物质的侵害。理想的含硫 DAPRB 设计包括反应性（低-K）层中的颗粒有机物（POM）和固体硫酸盐矿物。这导致硫酸盐还原和形成硫化物配体，与高-K 层中的有毒金属（如 Zn(2+)）络合。我们对用于处理受 Zn 污染地下水的理想 DAPRB 配置进行了理论生物地球化学分析。我们使用扩展的 CCBATCH 进行的分析证实了生物保护的梯度阻力机制，ZnS 汇在 DAPRB 高-K 层内 Zn 和硫化物羽流的交点处形成。详细的 DAPRB 分析还表明，总碱度和 pH 分布是发生的两个关键生物地球化学过程的代表性特征，即硫化物生成和 Zn 固定为硫化物矿物。这是因为这两个反应消耗或产生酸性氢和碱度。此外，由于 Zn 固定是由于 ZnS 矿物沉淀，因此 ZnS 矿物分布是生物汇的良好指标。生物汇大部分位于高-K 层内，其确切位置取决于金属和硫化物通量的相对大小。最后，我们进行了实用性分析，支持实施所提出设计的可行性。例如，在 50 年内，硫化物生成过程中消耗的反应性材料的分数相对较小（包括 POM 和硫酸盐源），总体积分数小于 6%。
