suk O Jin, Jeen Sung-Wook, Gillham Robert W, Gui Lai
Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
J Contam Hydrol. 2009 Jan 26;103(3-4):145-56. doi: 10.1016/j.jconhyd.2008.09.013. Epub 2008 Oct 15.
Column experiments and numerical simulation were conducted to test the hypothesis that iron material having a high corrosion rate is not beneficial for the long-term performance of iron permeable reactive barriers (PRBs) because of faster passivation of iron and greater porosity loss close to the influent face of the PRBs. Four iron materials (Connelly, Gotthart-Maier, Peerless, and ISPAT) were used for the column experiments, and the changes in reactivity toward cis-dichloroethene (cis-DCE) degradation in the presence of dissolved CaCO3 were evaluated. The experimental results showed that the difference in distribution of the accumulated precipitates, resulting from differences in iron corrosion rate, caused a difference in the migration rate of the cis-DCE profiles and a significant difference in the pattern of passivation, indicating a faster passivation in the region close to the influent end for the material having a higher corrosion rate. For the numerical simulation, the accumulation of secondary minerals and reactivity loss of iron were coupled using an empirically-derived relationship that was incorporated into a multi-component reactive transport model. The simulation results provided a reasonable representation of the evolution of iron reactivity toward cis-DCE treatment and the changes in geochemical conditions for each material, consistent with the observed data. The simulations for long-term performance were also conducted to further test the hypothesis and predict the differences in performance over a period of 40 years under typical groundwater conditions. The predictions showed that the cases of higher iron corrosion rates had earlier cis-DCE breakthrough and more reduction in porosity starting from near the influent face, due to more accumulation of carbonate minerals in that region. Therefore, both the experimental and simulation results appear to support the hypothesis and suggest that reactivity changes of iron materials resulting from evolution of geochemical conditions should be considered in the design of iron PRBs.
进行了柱实验和数值模拟，以检验以下假设：由于铁的钝化速度更快且在可渗透反应屏障（PRB）进水端附近孔隙率损失更大，具有高腐蚀速率的铁材料对铁可渗透反应屏障的长期性能并无益处。柱实验使用了四种铁材料（康奈利、戈特哈特 - 迈尔、皮尔利斯和伊斯帕特），并评估了在溶解碳酸钙存在下对顺式二氯乙烯（cis - DCE）降解反应性的变化。实验结果表明，由于铁腐蚀速率不同导致的累积沉淀物分布差异，造成了cis - DCE分布曲线迁移速率的差异以及钝化模式的显著差异，这表明对于腐蚀速率较高的材料，在靠近进水端的区域钝化速度更快。对于数值模拟，使用经验推导的关系将次生矿物的积累和铁的反应性损失进行耦合，并将其纳入多组分反应输运模型。模拟结果合理地呈现了铁对cis - DCE处理的反应性演变以及每种材料地球化学条件的变化，与观测数据一致。还进行了长期性能模拟，以进一步检验该假设并预测在典型地下水条件下40年内性能的差异。预测结果表明，铁腐蚀速率较高的情况会出现更早的cis - DCE穿透，并且从进水端附近开始孔隙率降低更多，这是因为该区域碳酸盐矿物积累更多。因此，实验和模拟结果似乎都支持该假设，并表明在设计铁PRB时应考虑地球化学条件演变导致的铁材料反应性变化。
