Julie K. Chard

Uptake of nonylphenol and nonylphenol ethoxylates by crested wheatgrass

Nonylphenol (NP) and other hydrophobic biodegradation intermediates of nonylphenol ethoxylate (NPE) surfactants have been identified in wastewater treatment biosolids. These biosolids often are land applied, but little is known regarding the potential uptake of biosolid-derived contaminants by plants. Hydroponic experiments, 11 to 14 weeks in duration, were conducted to examine the uptake and translocation of 14C and unlabeled NP, nonylphenol tetraethoxylate (NPE4), and nonylphenol nonylethoxylate (NPE9) by crested wheatgrass (Agropyron cristatum). Phenol also was evaluated for comparison. Plant tissue was analyzed for 14C and for the parent compounds. Volatilization from the hydroponic system and rhizosphere mineralization also were quantified. At the conclusion of the study, most of the plant-associated 14C was found in the roots (NP = 98%, NPE4 = 92%, and NPE9 = 81%). Concentrations of 14C in the foliar tissue ranged from 0.002 to 0.045 mg-equivalent per kg (dry wt), but no parent compounds were detected, implying that the 14C was unextractable or in the form of metabolites. Transpiration stream concentration factors for NP, NPE4, and NPE9, calculated assuming the 14C was parent compound, were 0.012, 0.032, and 0.066, respectively. Little mineralization was observed for NP, NPE4, and NPE9 in the hydroponic system; however, for phenol, 16 to 30% of the added 14C was mineralized.

Volatilization of Trichloroethylene from Trees and Soil: Measurement and Scaling Approaches

Trichloroethylene (TCE) volatilization from leaves, trunk, and soil was measured to assess the significance of these pathways from phytoremediation sites at Travis and Fairchild Air Force Bases. Measurements were scaled temporally and spatially to estimate the annual volatilization of TCE at the Travis (0.82 ± 0.51 kg/yr) and Fairchild sites (0.014 ± 0.008 kg/yr). Volatilization was primarily through the leaf (0.34 ± 0.16 kg/yr at Travis and 0.01 ± 0.06 kg/yr at Fairchild) and soil (0.48 ± 0.36 kg/yr at Travis, 0.003 ± 0.002 kg/yr at Fairchild) pathways. The larger volatilization estimate at Travis was expected because of the sites higher TCE groundwater concentrations. Using groundwater data collected in 2004 and 2009, calculations show that over the 5 year period, 1.7 and 0.015 kg of TCE were removed each year at the Travis and Fairchild sites, respectively. On the basis of the scaled field measurements, volatilization from the leaves and soil may play a significant role in TCE removal at both sites. Daily and seasonal variations were not addressed during the limited daytime sampling events, but the methods described here provide a novel and practical framework for evaluating the potential importance of volatilization of TCE and similar compounds at phytoremediation sites.