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A critical evaluation of the local-equilibrium assumption in modeling NAPL-pool dissolution

机译:在模拟NAPL池溶出度中对局部平衡假设的关键评估

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An analytical modeling analysis was used to assess when local equilibrium (LE) and nonequilibrium (NE) modeling approaches may be appropriate for describing nonaqueous-phase liquid (NAPL) pool dissolution. NE mass-transfer between NAPL pools and groundwater is expected to affect the dissolution flux under conditions corresponding to values of Sh'St (the modified Sherwood number (L_x k_l/D_z) multiplied by the Stanton number (k_l/v_x)) < = 400. A small Sh'St can be brought about by one or more of: a large average pore water velocity (v_x), a large transverse dispersivity (a_z), a small pool length (L_x), or a small mass-transfer coefficient (k_l). On the other hand, at Sh'St > ≈ 400, the NE and LE solutions converge, and the LE assumption is appropriate. Based on typical groundwater conditions, many cases of interest are expected tofall in this range. The parameter with the greatest impact on Sh'St is k_1. The NAPL pool mass-transfer coefficient correlation of Pfannkuch [Pfannkuch, H.-O., 1984. Determination of the contaminant source strength from mass exchange processes at the petroleum-ground-water interface in shallow aquifer systems. In f Proceedings of the NWWA/API Conforence on Petroleum Hydrocarbons and Organic Chemicals in Ground Water-Prevention, Detection, and Restoration, Houston, TX. Natl. Water Well Assoc., Worthington, OH, Nov. 1984, pp. 111- 129.] was evaluated using the toluene pool data from Seagren et al.
机译:分析建模分析用于评估局部平衡(LE)和非平衡(NE)建模方法何时适合描述非水相液体(NAPL)库溶解。 NAPL池和地下水之间的NE传质预计将在与Sh'St值(修正的Sherwood数(L_x k_l / D_z)乘以Stanton数(k_l / v_x)的值相对应的条件下,影响溶解通量。<= 400 。较小的Sh'St可由以下一项或多项产生:平均孔隙水速度(v_x)大,横向分散度(a_z)大,池长(L_x)小或传质系数小( k_l)。另一方面,在Sh'St>≈400时,NE和LE解收敛,因此LE假设是合适的。根据典型的地下水条件,预计许多关注案例都将落在该范围内。对Sh'St影响最大的参数是k_1。 Pfannkuch的NAPL池传质系数相关性[Pfannkuch,H.-O.,1984。通过浅层含水层系统中石油-地下水-界面的质量交换过程确定污染物源强度。在德克萨斯州休斯顿的NWWA / API关于地下水中的石油碳氢化合物和有机化学物质的预防,检测和恢复的论文集中。 Natl。 1984年11月,美国俄亥俄州沃辛顿,Water Well Assoc。,第111-129页]使用Seagren等人的甲苯库数据进行了评估。

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