Uptake and Release Kinetics of Sulfolane by Cattail Plants
Sulfolane (tetrahydrothiophene 1,1-dioxide, C4H8O2S) is a highly water-soluble, non-ionizable, organic compound used along with diisopropanolamine in the SulfinolTM process to remove hydrogen sulfide from natural gas. Sulfolane has been identified in wetland vegetation near a sour gas processing facility in Alberta, Canada, and extensive uptake of sulfolane by cattails has also been demonstrated in a laboratory environment. Consequently, it has been suggested that plants could play an important role in the natural attenuation of sulfolane in contaminated wetlands. This assumes that the sulfolane is metabolized and/or sequestered in the plant and not released back into the environment during winter dieback. To address the potential release issue, individual cattails (Typha latifolia) were grown hydroponically in 500-mL glass containers containing one of three initial sulfolane concentrations (8, 40, or 200 mg/L) for a specified duration (7 to 28 days). Half the cattails were used to quantify uptake as a function of time and exposure concentration and the other half were used to evaluate the potential release of sulfolane into the hydroponic solution. Non-exposed cattails and non-planted systems containing sulfolane served as controls. The cattails used to evaluate the potential release of sulfolane were frozen directly in their individual containers at the end of the appropriate exposure period. After being frozen for a minimum of 72 hours, the containers were thawed and the amount of sulfolane released was monitored. At the end of the 28-day uptake period, sulfolane leaf tip tissue concentrations as high as 3600, 1050, and 165 mg/kg dry weight were found for the cattails initially exposed to 200, 40, and 8 mg/L sulfolane, respectively. The percentage of sulfolane subsequently released by the cattails after the freeze-thaw treatment declined as a function of the duration exposed. The percentages of sulfolane released measured in the water after 72 hours in addition to the plant tissue extractions were 71%, 54%, 27%, and 12% for the 40 mg/L concentration at 7-, 14-, 21-, and 28-day exposure periods, respectively. Other concentrations showed the same decreasing trend for increasing exposure periods. The declining release as a function of time suggests metabolism and/or sequestration of the sulfolane within the plant. The significant uptake and limited release of sulfolane from mature plants indicate that wetland plants could play an important role in its natural attenuation.
School:Utah State University
School Location:USA - Utah
Source Type:Master's Thesis
Keywords:cattails sulfolane uptake remediation
Date of Publication:12/01/2008