Wu Ming Zhi, Post Vincent E A, Salmon S Ursula, Morway Eric D, Prommer Henning
National Centre for Groundwater Research and Training (NCGRT), University of Western Australia node, Private Bag 5, Wembley, WA 6913, Australia.
School of Earth and Environment, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
Ground Water. 2016 Jan;54(1):23-34. doi: 10.1111/gwat.12318. Epub 2015 Jan 27.
A modified version of the MODFLOW/MT3DMS-based reactive transport model PHT3D was developed to extend current reactive transport capabilities to the variably-saturated component of the subsurface system and incorporate diffusive reactive transport of gaseous species. Referred to as PHT3D-UZF, this code incorporates flux terms calculated by MODFLOW's unsaturated-zone flow (UZF1) package. A volume-averaged approach similar to the method used in UZF-MT3DMS was adopted. The PHREEQC-based computation of chemical processes within PHT3D-UZF in combination with the analytical solution method of UZF1 allows for comprehensive reactive transport investigations (i.e., biogeochemical transformations) that jointly involve saturated and unsaturated zone processes. Intended for regional-scale applications, UZF1 simulates downward-only flux within the unsaturated zone. The model was tested by comparing simulation results with those of existing numerical models. The comparison was performed for several benchmark problems that cover a range of important hydrological and reactive transport processes. A 2D simulation scenario was defined to illustrate the geochemical evolution following dewatering in a sandy acid sulfate soil environment. Other potential applications include the simulation of biogeochemical processes in variably-saturated systems that track the transport and fate of agricultural pollutants, nutrients, natural and xenobiotic organic compounds and micropollutants such as pharmaceuticals, as well as the evolution of isotope patterns.
基于MODFLOW/MT3DMS的反应输运模型PHT3D开发了一个修改版本，以将当前的反应输运能力扩展到地下系统的非饱和组分，并纳入气态物质的扩散反应输运。该代码称为PHT3D-UZF，它纳入了由MODFLOW的非饱和带水流（UZF1）软件包计算的通量项。采用了一种类似于UZF-MT3DMS中使用的体积平均方法。PHT3D-UZF中基于PHREEQC的化学过程计算与UZF1的解析解法相结合，允许进行涉及饱和带和非饱和带过程的综合反应输运研究（即生物地球化学转化）。UZF1旨在用于区域尺度应用，模拟非饱和带内仅向下的通量。通过将模拟结果与现有数值模型的结果进行比较对该模型进行了测试。对涵盖一系列重要水文和反应输运过程的几个基准问题进行了比较。定义了一个二维模拟场景，以说明沙质酸性硫酸盐土壤环境中脱水后的地球化学演化。其他潜在应用包括模拟非饱和系统中的生物地球化学过程，追踪农业污染物、养分、天然和外来有机化合物以及药物等微污染物的迁移和归宿，以及同位素模式的演化。
