|Pepperman Jr, Armand|
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/1998
Publication Date: N/A
Interpretive Summary: The nation's groundwater resources have become contaminated by man's activities, including those associated with agriculture. Research on the use of controlled-release formulations for pesticides is being conducted to examine the parameters associated with formulations which affect the movement of the pesticide into the soil profile. Using sodium alginate/clay as the incorporating medium for the pesticide produces a granular formulation which slows down release of the herbicide metribuzin into water. Following the kinetics of formulations with and without added linseed oil demonstrated that the dissolution/release of metribuzin was substantially lengthened by addition of 1% and 4% linseed oil to the alginate/clay formulation. By controlling the release of metribuzin, these linseed oil formulations will reduce the movement of pesticides into the ground water. This will preserve the purity of the groundwater and result in healthier drinking water for many Americans.
Technical Abstract: This study was designed to quantify the dissolution/release for metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] from alginate-kaolin controlled release with time and its kinetic retention behavior in soil. We followed a modified batch desorption technique to quantify the release kinetics of metribuzin from control release formulations (CRFs). For CRF with 0% linseed oil, metribuzin released was completed (99%) after 6 days, with 80% of the total released during the first day of desorption. In contrast, CRFs with 1% and 4% linseed oil exhibited strong kinetics with continued metribuzin release at large times. After 59 days, total amounts released from CRFs containing 0%, 1% and 4% linseed oil were 100%, 68% and 12.4%, respectively. This finding was attributed to the incorporation of linseed oil to the CR formula, which acted to slowly release metribuzin from the matrix over extended time periods. Batch results for a range of concentrations (up to 100 mg/L of metribuzin in solution) in a Sharkey clay soil (very-fine, montmorillontic, nonacid, thermic, Vertic Haplaquept) indicated that adsorption kinetics was lacking. Metribuzin adsorption isotherm was linear and reached near equilibrium with two hours. This finding is consistent with metribuzin release from CRF with 0% linseed oil.