Influence of Aquifer Properties on Phytoremediation Effectiveness

Abstract

Recent research has shown that planting deep-rooted trees, such as poplar, can take up and degrade important ground water pollutants such as trichloroethylene (TCE) as they transpire water from the capillary fringe of shallow contaminated aquifers. The effect of hydrogeologic factors on the minimum plantation area needed to prevent downgradient migration of contaminated ground water is not well known. Accordingly, the objective of this research was to identify the hydrogeologic parameters that control phytoremediation effectiveness. We used a numerical ground water flow model to evaluate the effect that natural variations in hydrogeologic parameters and growing season duration have on the minimum plantation area required for capture. We found that the plantation area that was needed to completely capture a ground water contamination plume was directly proportional to aquifer horizontal hydraulic conductivity, saturated thickness, and ground water gradient. The plantation area needed for capture increased nonlinearly with increasing plume width, aquifer anisotropy, and decreasing growing season duration. The plantation area needed for capture was generally insensitive to aquifer-specific yield and storativity. Steady-state simulations can be used to predict the plantation area needed for capture in many applications. A particularly important finding of this work is that evapotranspiration fluxes through plantations appropriately sized to contain the plume substantially exceeded the ground water flux through the plume itself.

Introduction to Phytoremediation of Contaminated Groundwater

“…In the groundwater-flow model MODFLOW (McDonald and Harbaugh 1988), loss of water from an aquifer is estimated by using a linear relation between evapotranspiration and water-table depth. MODPATH also can be used to represent a plume of contaminant released from a source area and to determine the final size a phytoremediation planting must be to capture all the contaminant mass and provide maximum hydrologic control (Matthews et al 2003); this is discussed further in Chap. An alternative approach was taken by Matthews et al (2003) in which they simulated evapotranspiration in MODFLOW by using the recharge module, which specified recharge as a negative value.…”

“…Matthews et al (2003) performed numerical simulations of a phytoremediation system based on the removal of groundwater by ET. Matthews et al (2003) performed numerical simulations of a phytoremediation system based on the removal of groundwater by ET.…”

Phytodegradation of organic compounds

“…International interest in using phytoremediation has lead to reviews that discuss both models and processes thought to be important [52], as well as performance evaluations of existing models against experimental datasets [53]. Matthews et al [54] used a numerical groundwater flow model and evaluated how variations in hydrogeologic and seasonal growth parameters influenced the minimum plantation area needed for plume capture. They found that the aquifer horizontal hydraulic conductivity and saturated thickness directly influenced the plantation size.…”

Enhanced Attenuation: A Reference Guide On Approaches To Increase The Natural Treatment Capacity Of A System

“…They recommend that hydrologic factors be considered and that simply calculating plantation size by dividing the contaminated ground water flux by the ET rate will grossly underestimate the water uptake needed to remediate a plume. Matthews et al (2003) also addressed the issue of seasonality of phytoremediation noting that their model simulations show that plantations can be sized to sufficiently depress the water table during the growing season so that groundwater does not bypass the ET pathway.…”

“…They include contaminant levels, position on the landscape, climate, contaminant accessibility, and aquifer properties. Matthews et al (2003) used models developed from MODFLOW and MODPATH to show that evaporation/transpiration from the plantation area required to completely capture a ground water plume is directly proportional to aquifer horizontal hydraulic conductivity, saturated thickness, and hydraulic gradient. Also, plantation area increased nonlinearly with increasing plume width, aquifer anisotropy, and decreasing growing season.…”