A Comparison of the Ability of Two Lines of Hybrid Poplars (DN34 and NM1) to Phytovolatilize 1,4-Dioxane in Laboratory and Field Settings

Abstract

Phytoremediation technologies offer an economical and practical alternative to traditional remediation technologies. This study attempted to quantify and compare the ability of DN34 and NM1 varieties of hybrid poplars to phytovolatilize the organic contaminant 1,4-dioxane. Research included laboratory experiments and those at an old industrial field site containing 1,4-dioxane and other organic contaminants. Under laboratory conditions it was found that when DN34 was exposed to 36 ppm of 1,4-dioxane in hydroponic solution it had a significantly higher transpiration rate than NM1. There were no toxic effects of the contaminant on the plants. Additionally, the DN34 variety was able to remove 48.7 ± 11.6 % (mean ± standard error) of the dioxane from aqueous solution compared to 41.7 ± 10.0 % removed by NM1. Water availability at the field site had a significant effect on growth rate whereas soil type and contaminant concentration did not appear to have any affect. It was apparent that DN34 had a significantly higher transpiration rates than NM1 in a dry, 2007 season, while the opposite was true during a wet, 2008 season. Interestingly, the DN34 variety had lower transpiration rates in the wet season than in the dry season. The presence of the co-contaminant ethylene glycol affected transpiration rate in the NM1 variety but not the DN34 variety. The NM1 variety had a decrease in transpiration rate of 42 and 30 % when growing in a mid-range concentration (≤ 1000 ppm) of ethylene glycol compared to a low concentration (≤ 100 ppm) of ethylene glycol in the wet and dry seasons, respectively. Unfortunately, detection of 1,4-dioxane removal by trees at the field site was difficult to achieve.