Determining tolerance limits for restoration and phytoremediation with Spartina patens in crude oil-contaminated sediment in greenhouse

Abstract

Oil spills may detrimentally damage sensitive coastal habitats, such as coastal wetlands. Successful restoration of oiled habitats primarily depends on the tolerance of vegetation transplants to oil. In this study, tolerance limits of the dominant coastal brackish marsh plant Spartina patens to South Louisiana crude (SLC) oil and its phytoremediation effectiveness on petroleum hydrocarbons in wetland sediments were investigated in the greenhouse environment. Spartina patens was transplanted into brackish marsh sediments contaminated with SLC oil at concentrations of 0, 40, 80, 160, 320, 640 and 800 mg SLC oil g−1 dry sediment. High oil concentrations adversely affected plant stem density, aboveground biomass and belowground biomass even one year after transplantation. At the 320 mg g−1 oil dosage, plant belowground biomass was significantly lower than the control although aboveground variables were not significantly different from the control. All plant parameters mentioned above at the 640 mg g−1 oil dosage were less than 50% of the control. Spartina patens did not survive the 800 mg g−1 oil dosage. The tolerance limit of S. patens to SLC was estimated about 320 mg oil g−1 dry sediment. In addition, S. patens transplants enhanced oil degradation in the sediment; concentrations of residual total petroleum hydrocarbons (TPH) in the sediments vegetated by S. patens were significantly lower than those of un-vegetated sediments for both the surface and subsurface sediment at the 40 and 160 mg g−1 SLC oil dosages. Decreases in the concentrations of polycyclic aromatic hydrocarbons (PAHs) further demonstrated the capacity of S. patens to phytoremediate residual oil; residual total targeted PAHs in the phytoremediation treatment were less than 20% of the un-vegetated treatment at the 40 mg g−1 oil dosage. These results demonstrated the potential of phytoremediation with S. patens to simultaneously restore and remediate petroleum-contaminated coastal marsh habitats.