Characterization of the Potential Use of Salix Nigra and Populus Balsamifera for the Phytoremediation of 1,4-Dioxane
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Phytoremediation is a viable technology that provides a cost-effective and aesthetically pleasing alternative to traditional remediation technologies. The objective of this study was to compare the effectiveness of Salix nigra and Populus balsamifera in the phytovolatilization of 1,4-dioxane. In the growth studies, P. balsamifera had a significantly decreased growth rate in high concentrations of both 1,4-dioxane and ethylene glycol, while S. nigra showed no significant difference. No significant change in growth was noted between the amended and non-amended soil treatments; however S. nigra trees had a significantly larger size in the amended treatment. S. nigra had a higher survival rate than P. balsamifera with survival rates of 71% and 19% respectively. Total tree evapotranspiration rates were significantly higher in S. nigra than P. balsamifera whereas evapotranspiration rates per m2 of leaf surface area showed the opposite trend. Variations in seasonal precipitation were seen to affect evapotranspiration rates. During the dry 2007 season evapotranspiration rates were significantly higher in P. balsamifera and significantly lower in S. nigra. The opposite trend in evapotranspiration rates was observed in the wet 2008 season. Amendment of the soil was seen to significantly increase rates of evapotranspiration in S. nigra. Total tree dioxane removal was significantly greater in S. nigra than P. balsamifera, while the opposite was observed when removal was calculated per m2 of leaf surface area. Seasonal variations in precipitation exhibited the same trend on dioxane removal as was observed with evapotranspiration. Laboratory studies confirmed S. nigra as an effective species at the phytovolatilization of both dioxane and MTBE. In conclusion, S. nigra was a more effective species in field trials than P. balsamifera for both phytocontainment and phytovolatilization.