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(46-04) Adsorption of herbicides to soils from highway roadsides. Huang, Xinjiang*,1, Fischer, Michael1, White, Richard1, Lu, Yun1, Young, Thomas1, 1 Civil and Environmental Engineering Dept, University of California at Davis, Davis, CA, USA ABSTRACT- Herbicides are applied by the California Department of Transportation (Caltrans) as part of its highway vegetation management program. Previous study indicated that herbicides were detected in runoff water from highway roadsides, which could negatively impact the environment, in particular aquatic life. To protect adjacent surface waters from herbicide runoff, we need to understand the property of adsorption of herbicides to soils (adsorption coefficient Kd) from highway roadsides since Kd is one of the key factors to control the herbicide runoff. In order to determine Kd and investigate statewide variability in herbicide transport mechanisms, a total of 5 herbicides (isoxaben, diuron, oryzalin, glyphosate, clopyralid) were selected from the 33 herbicides currently used by Cantrans and 10 soils sampled from the representative Caltrans districts. The results showed that isoxaben, diuron, oryzalin, and glyphosate obeyed a linear isotherm relationship within the concentration range investigated and clopyralid had no adsorption to any of the soils, with Kd widely ranging from 0 to near 1000 L/kg. The large Kd variability was highly dependent on not only the herbicides but also the soils. Key words: herbicides , soils, adsorption coefficients, highway roadsides |
