|Rochette, Elizabeth - FORMER USDA EMPLOYEE|
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 1997
Publication Date: N/A
Technical Abstract: Methods commonly used to determine sorption coefficients require that the soils be above field capacity moisture so that the aqueous phase containing the herbicides to be quantified can be separated from the soil. Low- density supercritical CO2 (SF-CO2) was used to remove atrazine from soil solution without first removing the solution from the soil. Atrazine sorption coefficients determined using the SF-CO2 technique increased in a sand as moisture content increased from 4.0 to 16 percent and in a silt loam as moisture increased from 9.6 to 27 percent. Sorption coefficients increased with soil organic carbon and clay contents for three field-moist soils. Isoteric heats of sorption for atrazine ranged from minus 10 to minus 20 kcal mol**-1. Sorption coefficients in field-moist soils were much greater than are typically obtained with the batch slurry technique, while heats of sorption were much more negative, indicating greater atrazine sorption at low moisture contents. Atrazine desorption was rapid equilibrium was reattained within 7 min. Desorption coefficients were constant for successive desorption equilibrations, through removal of difference 25 percent of the applied atrazine from the system. The SF-CO2 technique is a promising method to characterize herbicide sorption- desorption in field-moist soils.