Project Abstract

Uptake of BTEX Compounds and Metabolites by Hybrid Poplar Trees in Hazardous Waste Remediation

Principal Investigators

J.L. Schnoor
University of Iowa
E-mail: jschnoor@cgrer.uiowa.edu

Joel G. Burken
University of Iowa
E-mail: joel-burken@uiowa.edu

Goal

The goal of this research is to determine feasibility and efficacy of vegetative bioremediation, specifically poplar trees, at sites contaminated with benzene, toluene, ethylbenzene, and xylene (BTEX) compounds.

Rationale

Vegetative remediation has become a promising, inexpensive, publicly accepted, and innovative technique for cleaning contaminated hazardous waste sites. This technique is best suited for sites of shallow contamination that are in the zone of impact for deep-rooted poplar trees. BTEX contamination is ideally suited for vegetative remediation. Being light, nonaqueous phase liquid (LNAPL) contaminants, BTEX compounds are often located near the surface at hazardous waste sites. BTEX contamination is also ubiquitous in today's environment, and many of these sites are located at rural and abandoned sites where little money is available for more expensive traditional remediation techniques.

Approach

This research will attempt to determine whether vegetative remediation with poplar trees is a fundamental approach for remediation of BTEX-contaminated sites. Poplar uptake of BTEX compounds will be monitored and translocation within plant tissues will be studied. Plant tissues and aerial compartments will be examined to measure accumulation in plant tissues and volatilization from leaf surfaces, respectively. Poplars are widely adapted to a wide variety of temperate and boreal environments; they are fast growing, hardy, and easily reproduced from parental cuttings; they are easily rooted at variable and great depths; and they have been successfully grown from tissue cultures.

Status

Work has centered on experimental apparatus design, method development, and experiments utilizing various compounds. Investigators have conducted uptake studies with the majority of these compounds in the reactors designed for this project. These reactors have been designed to contain the individual poplar cuttings and can accommodate growth of the cutting in either hydroponic growth solution or in soil media. The reactors are constructed to contain and collect any VOCs released from the above-ground plant components. Reactors have proven to perform as expected in the laboratory setting. Mass balances for VOC experiments utilizing vigorously-growing cuttings in the reactors have consistently been over 85%. The further improvement of mass balances is a point of focus in future research. Studies to determine structure activity relationships for the leaf volatilization of VOCs by poplar trees are also ongoing, and investigators are examining the impact soil processes have on phytoremediation of VOCs. The overall focus has been the quantification of volatilization, storage, and possible metabolization of specific compounds in poplar tree phytoremediation systems. A study to investigate the impact of soil processes on phytoremediation of VOCs has been started. This project is in its third year.

Clients/Users

This research is of interest to the city of Houston, Texas, which has a petrochemical spill site. It will also be of interest to U.S. Department of Defense and for petrochemical "land farming" sites, U.S. Department of Energy sites, and agricultural locations.

Keywords

Vegetative remediation, poplar trees, BTEX, soil, plants.