Influence of Water Content and Plants on the Dissipation of Chlorinated Volatile Organic Compounds in Soil

Abstract

To devise effective procedures for the remediation of soil contaminated by VOCs, an improved understanding of their fate and transport mechanisms in soil is essential. To show the effect of plants on the dissipation of 1,1,1-trichloroethane (TCA), trichloroethylene (TCE) and tetrachloroethylene (PCE), two types of experiments, vial and column, were conducted. The results suggested that keeping the soil moisture content at field capacity is desirable for VOCs dissipation. All VOCs were dissipated quickly in unplanted columns than planted conditions in early periods of the experiment because more volatilization occurred in unplanted conditions. The plants could take up and retard volatile contaminants, and prevent contamination of ambient air. Although the time for acclimation for microbial communities to contaminants for enhanced biodegradation should be considered, phytoremediation is potentially a cost-effective remediation technique for soils contaminated by volatile organic compounds (VOCs).

Effects of Grasses on the Fate of VOCs in Contaminated Soil and Air

“…This result indicates that the soil organic matter content can affect the fate and transport of target contaminants in the soil. This is in agreement with previous soil column studies in which volatilization was thought to be the main mechanism of VOC dissipation (Cho et al 2005).…”

“…Root uptake of water can further retard contaminant migration through soil by slowing or reversing water moving through the root zone. Therefore, VOC concentration in planted soil is thought to be higher than in unplanted soil (Cho et al 2005). With the build-up of rhizosphere microbial biomass, the contaminants are then degraded by soil microorganisms and taken up by plants through extraction from soil and water.…”

On-line screening of soil VOCs exchange responses to moisture, temperature and root presence

“…In parallel, we measured higher CO 2 exchange rates and net photosynthetic rates, corresponding to greater microbial and plant activity. Biodegradation of VOCs by soil microorganisms or roots could be responsible for the soil sink activity (Schade and Custer 2004;Cho et al 2005;Van Roon et al 2005) as well as physical adsorption of VOCs to water, soil particles surface or organic matter and dissolution (partitioning) of VOCs in water (Pignatello and Xing 1996).…”

“…Likewise, roots can also uptake and accumulate or degrade some contaminant organic volatiles from the soil solution (Cho et al 2005) and microorganisms can consume them (Cleveland and Yavitt 1998;Yoo and Day 2002). In addition, there could be interactions between these biological processes, for example, roots activity produces the enhancement of associated microbial populations by releasing carbon-rich exudates on the rhizosphere (Walker et al 2003).…”

“…Both soil moisture and temperature are reported to aVect physical VOC processes in soil (adsorption, dissolution, volatilization) and also biological processes (biodegradation by microorganisms, uptake by plants) (Pignatello and Xing 1996;Cho et al 2005;Johnsen et al 2005), which in turn aVect the VOCs soil exchange rates.…”