Lin Li, Benson Craig H, Lawson Elizabeth M
Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
Ground Water. 2005 Jul-Aug;43(4):582-96. doi: 10.1111/j.1745-6584.2005.0042.x.
This paper describes reactive transport simulations conducted to assess the impact of mineral fouling on the hydraulic behavior of continuous-wall permeable reactive barriers (PRBs) employing granular zero-valent iron (ZVI) in carbonate-rich alluvial aquifers. The reactive transport model included a geochemical algorithm for simulating corrosion and mineral precipitation reactions that have been observed in ZVI PRBs. Results of simulations show that porosity and hydraulic conductivity of the ZVI decrease over time and that flows are redistributed throughout the PRB in response to fouling of the pore space. Under typical conditions, only subtle changes occur within the first 10 years (i.e., duration of the current field experience record with PRBs), and the most significant changes do not occur until the PRB has operated for at least 30 years. However, changes can occur sooner (or later) if the rate at which mineral-forming ions are delivered to the PRB is higher (or lower) than that expected under typical conditions (i.e., due to higher/lower flow rate or inflowing ground water that has higher/lower ionic strength). When the PRB is more permeable than the aquifer, the median Darcy flux in the PRB does not change appreciably over time because the aquifer controls the rate of flow through the PRB. However, seepage velocities in the PRB increase, and residence times decrease, due to porosity reductions caused by accumulation of minerals in the pore space. When fouling becomes extensive, bypassing and reductions in flow rate in the PRB occur.
本文描述了为评估矿物结垢对富含碳酸盐的冲积含水层中采用颗粒状零价铁（ZVI）的连续壁渗透反应屏障（PRB）水力行为的影响而进行的反应输运模拟。反应输运模型包括一个地球化学算法，用于模拟在ZVI PRB中观察到的腐蚀和矿物沉淀反应。模拟结果表明，ZVI的孔隙率和水力传导率随时间降低，并且由于孔隙空间的结垢，水流在整个PRB中重新分布。在典型条件下，最初10年内（即当前PRB现场经验记录的持续时间）仅发生细微变化，直到PRB运行至少30年才会出现最显著的变化。然而，如果输送到PRB的成矿离子速率高于（或低于）典型条件下预期的速率（即由于更高/更低的流速或具有更高/更低离子强度的流入地下水），变化可能会更早（或更晚）发生。当PRB比含水层更具渗透性时，PRB中的平均达西通量随时间变化不大，因为含水层控制着通过PRB的流速。然而，由于孔隙空间中矿物积累导致孔隙率降低，PRB中的渗流速度增加，停留时间减少。当结垢变得广泛时，PRB中会出现旁通和流速降低的情况。
