کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4546477 1627033 2015 18 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
On the validity of travel-time based nonlinear bioreactive transport models in steady-state flow
ترجمه فارسی عنوان
در مورد اعتبار زمان حمل و نقل مبتنی بر مدل های بیرونی غیر خطی حمل و نقل در جریان ثابت حالت
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی


• We test whether travel time is a good proxy for reactive-species concentrations.
• The agreement is very good for moderate heterogeneity and steady-state flow.
• Effective longitudinal mixing must adequately be addressed.
• Travel-time based simulations thus simplify nonlinear reactive transport.
• The approach is invalid when macroscopic transverse mixing is relevant.

Travel-time based models simplify the description of reactive transport by replacing the spatial coordinates with the groundwater travel time, posing a quasi one-dimensional (1-D) problem and potentially rendering the determination of multidimensional parameter fields unnecessary. While the approach is exact for strictly advective transport in steady-state flow if the reactive properties of the porous medium are uniform, its validity is unclear when local-scale mixing affects the reactive behavior. We compare a two-dimensional (2-D), spatially explicit, bioreactive, advective–dispersive transport model, considered as “virtual truth”, with three 1-D travel-time based models which differ in the conceptualization of longitudinal dispersion: (i) neglecting dispersive mixing altogether, (ii) introducing a local-scale longitudinal dispersivity constant in time and space, and (iii) using an effective longitudinal dispersivity that increases linearly with distance. The reactive system considers biodegradation of dissolved organic carbon, which is introduced into a hydraulically heterogeneous domain together with oxygen and nitrate. Aerobic and denitrifying bacteria use the energy of the microbial transformations for growth. We analyze six scenarios differing in the variance of log-hydraulic conductivity and in the inflow boundary conditions (constant versus time-varying concentration). The concentrations of the 1-D models are mapped to the 2-D domain by means of the kinematic (for case i), and mean groundwater age (for cases ii & iii), respectively. The comparison between concentrations of the “virtual truth” and the 1-D approaches indicates extremely good agreement when using an effective, linearly increasing longitudinal dispersivity in the majority of the scenarios, while the other two 1-D approaches reproduce at least the concentration tendencies well. At late times, all 1-D models give valid approximations of two-dimensional transport. We conclude that the conceptualization of nonlinear bioreactive transport in complex multidimensional domains by quasi 1-D travel-time models is valid for steady-state flow fields if the reactants are introduced over a wide cross-section, flow is at quasi steady state, and dispersive mixing is adequately parametrized.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Contaminant Hydrology - Volumes 175–176, April–May 2015, Pages 26–43
نویسندگان
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