PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM071) Volatile organic compounds (VOCs) in highway stormwater runoff.
Hwang, H-M1, Young, TM1, 1 Civil & Environmental Engineering, University of California, Davis
ABSTRACT- Watersheds near the highway are vulnerable to highway stormwater runoff, which contains a variety of toxic chemicals. In spite of potential impact of volatile organic compounds (VOCs) on nearby surface waters and groundwater, most studies have mainly focused on metals and hydrophobic organic chemicals such as polycyclic aromatic hydrocarbons. In order to investigate the loadings and sources of VOCs, highway runoff samples were collected at the edge of pavement on Interstate 80 near Davis, CA. VOCs were extracted using a purge and trap and analyzed using a GC/MS. The most frequently detected VOCs were fuel related compounds (BTEX: benzene, toluene, ethylbenzene, xylene) and some chlorinated compounds, including chloromethane, chloroform, trans-1,2-dichloroethene, and 1,1-dichloroehene. Concentrations of BTEX compounds were similar to or slightly lower than those in urban stormwater collected from residential areas. VOCs in stormwater runoff were inversely related to atmospheric temperature. Less photochemical reactions and more biomass burning during the low temperature period may be also responsible for elevated concentrations of VOCs. As temperatures decline the distribution of chemical between air and water is expected to shift in the direction of increasing aqueous concentrations, but the magnitude of this effect should be about 30% over our observed temperature range using typical enthalpies for air-water chemical transfer. Ratios of benzene to other fuel related VOCs in the highway stormwater samples were higher than those in gasoline. It was possibly due to additional input of benzene from other sources like residential wood combustion. At some events, VOCs in time series samples showed the first flush effect. Volume weighted mean concentration of 1,1-dichloroethene in the sample collected in January was 23 times above the ambient water quality guideline level, indicating stormwater runoff from the highway may adversely affect the health of humans and the environment.
Key words: Stormwater runoff, VOCs, Highway