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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Publications at this Location » Publication #88170
Title: FATE OF METRIBUZIN FROM ALGINATED CONTROLLED RELEASE FORMULATIONS IN A SHARKEY SOIL: 1. COLUMN STUDIES

Author
item SELIM, H - LSU
item MCGOWEN, STEPHEN - LSU
item JOHNSON, RICHARD - TEXAS TECH
item Pepperman Jr, Armand

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/1998
Publication Date: N/A
Citation: 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. Using uniformly packed clay soil columns to compare mobility and breakthrough demonstrated that these parameters were 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: The fate and persistence of alginate-kaolin controlled release formulations (CRFs) for metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] were investigated. Miscible displacement methods using uniformly packed Sharkey clay soil (very-fine, montmorillontic, nonacid, thermic, Vertic Haplaquept) or acid washed sand columns were used. The CRF beads (1.6-1.8 mm in diameter) contained 1% sodium alginate, 10% kaolin; 0.002% charcoal; 0.5% surfactant, and 88% water. Three metribuzin formulations were investigated; CRFs with 0%, 1% and 4% linseed oil. Metribuzin CRFs with 0% linseed oil when compared with liquid pulse applications indicated comparable mobility. In fact, breakthrough curves (BTCs) from pulse applications exhibited symmetry and lack of tailing of the desorption side indicative of dominant equilibrium sorption mechanisms. In contrast, BTCs from columns with CRFs of 1% and 4% linseed oil exhibited extensive tailing of the desorption side. This 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. This finding is consistent with solvent extraction experiments of metribuzin release over time. Three major metribuzin metabolites; diketometribuzin (DK), deaminated diketometribuzin (DADK), and deaminated metribuzin (DA) were detected in the effluent and closely followed metribuzin BTCs for all columns that received CRFs metribuzin. For transport experiments where a pulse or reagent grade metribuzin in solution was applied, metribuzin metabolites in the effluent were not detected.