Title: How do laboratory assessments of S-metolachlor sorption and dissipation agree with field behavior? Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 12, 2011
Publication Date: July 22, 2011
Citation: Papiernik, S.K., Cabrera, A., Koskinen, W.C. 2011. How do laboratory assessments of S-metolachlor sorption and dissipation agree with field behavior? [abstract] Picogram and abstracts, Agrochemicals Division. Vol. 80, p. 81. Technical Abstract: Research has suggested that existing bonds become stronger with aging time, decreasing the extractability and bioavailability of some pesticides in soil. We found that using high-energy extraction conditions (elevated temperature and pressure in ASE) removed a higher proportion of sorbed S-metolachlor, which influenced calculated distribution coefficients and masked the aging effect. The difference in Kd values for manual extraction and ASE did not affect S-metolachlor dissipation rates. High-efficiency methods are advantageous from an analytical standpoint, but the significance of residues removed under harsh conditions in determining pesticide availability for mobility and biological uptake is unknown. The results of these laboratory tests are consistent with companion field studies. Together, they show that despite large differences in soil properties and sorption coefficients, dissipation proceeded at approximately the same rate (and weed control was the same) in soils from different landscape positions. Equilibrium processes may not drive dissipation and bioavailability under field conditions.