Assessing desorption kinetics of native pyrene from contaminated sediment by time-resolved fluorescence spectroscopy

ENVR 11

Dave T. F. Kuo, tfdkuo@mit.edu1, Rachel Adams2, Steven M. Rudnick, Steven.Rudnick@umb.edu3, Robert F Chen, bob.chen@umb.edu3, and Philip M. Gschwend1. (1) Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, The Ralph M. Parsons Laboratory (Bldg 48), 15 Vassar Street, Cambridge, MA 02139, (2) Department of Civil Engineering and Environmental Sciences, Loyola Marymount University, Los Angeles, CA 90045, (3) Environmental, Earth and Ocean Sciences, UMassBoston, 100 Morrissey Boulevard, Boston, MA 02125
Hydrophobic organic compounds (HOCs) such as PAHs and PCBs in sediment are of great regulatory concern. Knowing their desorption kinetics is necessary to anticipate the bed-to-water transfers in coastal/riverine systems. We present a novel way to investigate desorption kinetics using pyrene, an ubiquitous contaminant that exhibits a long fluorescence lifetime and time-gated laser-induced fluorescence. Batch desorption experiments were conducted at three solid-to-water ratios (20, 70, 280 mgsolids/L) and three sediment size-fractions (38-75, 75-106, 180-250 μm). At realistic suspension conditions, we observed both desorption at minute-resolved timescales and continuing solid-water equilibration for weeks to months. This implied that the desorption time of pyrene and, by inference, other sediment-bound HOCs exceeds the typical characteristic-time for flushing and resuspension. Consequently, assuming local sorption equilibrium would be inappropriate. Box-model simulations using such desorption kinetics indicate resuspension is an important HOC release pathway in coastal/river systems where such events are intense and frequent.
 

Fate of Persistent Organic Pollutants in Urban Systems
8:30 AM-11:30 AM, Sunday, August 19, 2007 Boston Park Plaza -- Beacon Hill Rm, Oral

Division of Environmental Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007