PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM067) Contaminants on fine particles in highway storm water runoff.
Young, T1, Green, P1, Hwang, H1, Kayhanian, M1, 1 University of California, Davis, CA, USA
ABSTRACT- The majority of contaminants (e.g., Cu, Zn, Ni, Pb, PAHs) found along highways are associated with particles of a wide range of sizes (<0.1 
m to > 2 mm) but regulatory requirements and toxicity typically center on the dissolved constituents. Improved understanding of the dynamics of the wash off, dissolution/desorption and transport of particle associated contaminants is the goal of this project. Time resolved particle size distributions have been collected during field sampling of storm events and have been related to dissolved constituent concentrations. In one experiment runoff samples were collected at 15-minute intervals at the pavement edge on Interstate 680 in Cordelia, CA. After filtration, the dissolved and particulate phases were extracted and analyzed by GC-MS for PAHs and ICP-MS for metals. Particle concentrations were counted by laser light scattering in 15 size bins ranging from 0.5 to 20 
m. Total PAH concentrations in particles varied from 1,090 to 39,600 ng/L and showed a strong positive relationship with flow rates and the amount of total suspended solids. Distribution patterns of alkylated PAHs, alkanes and hopanes confirmed that significant amounts of petroleum products like vehicular fuels (e.g., gasoline and diesel) were in the runoff samples. The concentrations of dissolved metals generally decreased over time and did not exclusively correlate with flow rates or total suspended solids, although different metals did associate reasonably with different size-bin counts. Detailed size resolved chemical characterization of fine particles in runoff has also been performed on a number of runoff samples using a sorting flow cytometer, indicating the utility of the technique and confirming the importance of the finest solids in particle-facilitated contaminant transport. Contaminant desorption from these particles has been studied under varied solution conditions including dissolved organic carbon concentrations, which have been correlated with higher dissolved Cu and Zn concentrations in previous field sampling.
Key words: colloid, desorption, PAH, metals