Dr. Elizabeth Haack presents

Dr. Elizabeth Haack will be presenting on October 18th at the Association for Environmental Health and Sciences Foundation (AEHS Foundation) Annual East Coast Conference

Event date Monday, October 18, 2021
Event location Virtual Event
Dr. Elizabeth Haack

Elizabeth Haack is presenting the results of a multi-year phytoremediation pilot program that is using hybrid poplars to enhance natural attenuation of a toluene mass in groundwater beneath an area slated for urban renewal. She will discuss the importance of developing a conceptual site model (CSM) of appropriate resolution to support understanding of this nature-based remediation system and its performance, the roles of multiple areas of expertise involved in developing that CSM, and the advances in understanding that this study is contributing.

Abstract: Key Findings on Phyto-Enhanced Petroleum Hydrocarbon Biodegradation in a Fractured Rock Condition

A phytoremediation pilot program was initiated in 2007 at a site located in an area of urban renewal where toluene mass resides in a shallow fractured dolostone aquifer. The fractured bedrock is a dual-porosity, dual permeability system, with the groundwater table positioned at the interface between the bedrock and a native cobbly soil. Hybrid poplars (facultative phreatophytes) were planted to enhance the natural attenuation of residual toluene. Multidisciplinary, high-resolution studies were carried out over four years to characterize the mass and phase distribution of toluene and hydrogeology of the system, and to evaluate the phytoremediation system performance in terms of phytohydraulic control, rhizodegradation, phytodegradation, and phytoextraction. The studies integrated results from rock core, geophysics, multilevel soil vapour probes and groundwater monitoring wells, metagenomic analysis, high-throughput sequencing, DNA stable isotope probing, compound specific stable isotope analysis, and in-planta methods for quantification and transpiration rates.

Key findings have emerged from the work for remediation practitioners. Our work demonstrated that high temporally resolved groundwater monitoring is critical for estimations of biodegradation rates and predictions of plume attenuation. Redox conditions in groundwater at the site were highly dynamic - changing rapidly from oxic to anoxic conditions- as a result of variable recharge and seasonal conditions. Both the plume core and fringe were, thus, temporally replenished with electron acceptors. The extent of biodegradation was influenced significantly; the largest extent of biodegradation observed in the summer under iron reducing conditions while intermediate and low toluene biodegradation were observed in the spring under oxic conditions, and in the fall under mixed degradation conditions (iron, sulfate, manganese reduction, and methanogenesis), respectively. Our work also demonstrated that although the hybrid poplars were phytoextracting toluene, the bulk of mass toluene removal occurs in the (combined) rhizosphere, endosphere and phytosphere. In each of these, biodegradative capacity (measured or predicted) was shown to shift to higher levels with increased toluene exposure. We will present these and other important findings of this work.

Dr. Haack will present during Session 06: Advancing Hydrocarbon Remediation Sites from 1:00 - 1:30pm.