Evaluation of phytoremediation for field-scale degradation of total petroleum hydrocarbons

Laboratory studies have shown phytoremediation to be a feasible method for remediating surface soils contaminated with organic compounds. Evaluation of this technology in the field is difficult because of the inherent spatial heterogeneity in the hydraulic and chemical properties of the soil. In this study, total petroleum hydrocarbon (TPH) degradation was monitored in a field site with three vegetative treatment plots, and one control plot undergoing natural attenuation. Within each treatment, TPH concentrations were monitored at 20 locations over time to study the phytoremediation potential of the different vegetative treatments. For comparing the performance of these treatments in a quantitative manner, first-order kinetics were assumed to be applicable at the local scale. The degradation rates and the initial contaminant concentrations were treated as spatially correlated random fields. Field-scale behavior was evaluated based on temporal variations of the means and variances of concentrations. Our results indicate the importance of spatial variability for an accurate assessment of phytoremediation in the field. From the degradation rate constants and mean reduction in TPH, rye grass and St. Augustine grass appear to be superior to sorghum and the unvegetated control in reducing contaminant concentrations in the field.