Seeboonruang, Uma
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Seeboonruang, Uma
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Seeboonruang, U.
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uma.se@kmitl.ac.th
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Item type:Publication, Upscaling heterogeneity in aquifer reactivity via exposure-time concept: Forward model(2006-03-20); Ginn, Timothy R.Reactive properties of aquifer solid phase materials play an important role in solute fate and transport in the natural subsurface on time scales ranging from years in contaminant remediation to millennia in dynamics of aqueous geochemistry. Quantitative tools for dealing with the impact of natural heterogeneity in solid phase reactivity on solute fate and transport are limited. Here we describe the use of a structural variable to keep track of solute flux exposure to reactive surfaces. With this approach, we develop a non-reactive tracer model that is useful for determining the signature of multi-scale reactive solid heterogeneity in terms of solute flux distributions at the field scale, given realizations of three-dimensional reactive site density fields. First, a governing Eulerian equation for the non-reactive tracer model is determined by an upscaling technique in which it is found that the exposure time of solution to reactive surface areas evolves via both a macroscopic velocity and a macroscopic dispersion in the artificial dimension of exposure time. Second, we focus on the Lagrangian approach in the context of a streamtube ensemble and demonstrate the use of the distribution of solute flux over the exposure time dimension in modeling two-dimensional transport of a solute undergoing simplified linear reversible reactions, in hypothetical conditions following prior laboratory experiments. The distribution of solute flux over exposure time in a given case is a signature of the impact of heterogeneous aquifer reactivity coupled with a particular physical heterogeneity, boundary conditions, and hydraulic gradient. Rigorous application of this approach in a simulation sense is limited here to linear kinetically controlled reactions. © 2006 Elsevier B.V. All rights reserved. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The effect of acid sulphuric soil restraint by groundwater control in nakhon-nayok province, THAILAND(2007-01-01); Ichikawa, TsutomuNakhon Nayok Province, Thailand, is located in the floodplain area and has severe problems regarding acid soil which contains sulphide bearing material resulting in soil pH below 4.0. The objectives of this study are to investigate the geochemical variation that occurs under a groundwater controlling condition above the acid materials while other field factors are maintained in natural condition and to study the groundwater controlling technique to alleviate the acidic condition. The field experiment is designed in order to control groundwater level within a time period. The effects on the chemistry of groundwater, surface water, porewater and the soil itself are also monitored. The result rev-eals that acidity of the soil increases initially from the soil disturbance and the acidity decreases afterwards as a result of the groundwater controlling condition. This finding is also confirmed by the water chemical changes. Several cations are released into porewater when acidity increases and these metals can be hazardous to plants, foundations, and hu-mans. From this study, we conclude that soil disturbance from any activity can stimulate the acidity of the acid sul-phate soil, and maintaining groundwater level above the parent material can help alleviate the acidity. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Upscaling heterogeneity in aquifer reactivity via the exposure-time concept: Inverse model(2006-03-20); Ginn, Timothy R.A novel inverse technique is proposed to quantitatively characterize macroscopic variability in aquifer reactivity in a Lagrangian representation. Reactivity heterogeneity is expressed in terms of distributions of flux over cumulative time of exposure of the solution to reactive surface area, termed here 'cumulative reactivity'. In cases involving single aqueous species the combined effects of physical and reactivity heterogeneity on reactive solute transport can often be established and further investigated through joint distributions of flux over travel time and cumulative reactivity. The inverse technique requires the breakthrough curve of a passive tracer to determine the distribution of flux over travel time, and additional breakthrough curves of reactive tracers provide additional moments of the distribution of flux over cumulative reactivity given travel time. Thus breakthroughs of one passive and two reactive tracers can provide the mean and variance of the distribution of flux over cumulative reactivity. This Lagrangian characterization is achieved with knowledge of the types of reactive surfaces present, but not their spatial locations. The distributions can subsequently be applied via forward modeling using the same technique to predict breakthrough curves of other solutes undergoing first-order reactions in similar physically and chemically heterogeneous configurations. © 2006 Elsevier B.V. All rights reserved.