|Van Genuchten, Martinus|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/1993
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Preleaching of laboratory packed soil columns with non-pesticide solution is a routine procedure used to attain steady-state flow conditions for pesticide leaching experiments. This step may wash out a significant amount of dissolved organic matter (DOM) and inorganic constituents that affect sorption characteristics of the soil. To assess the magnitude of washed out DOM and several constituents and their ultimate impact on napropamide sorption and transport, laboratory batch-equilibrium and soil column experiments were conducted. Batch results with sequentially-washed Tujunga Loamy Sand, indicated a positive relationship between napropamide sorption and number of washings, suggesting that DOM enhanced napropamide partitioning into the liquid phase. Three separate pulses of napropamide injected at three stages of leaching into the same column resulted in different BTC. The second chloride and napropamide observed BTCs were analyzed with CDE and two-site chemical nonequilibrium models. The CDE predictions for chloride were good but were poor for napropamide with the same diffusion coefficient, D values. The two-site model predictions using the same D values were very good. Superimposing the second napropamide two- site model predicted BTC parameters resulted in different BTCs indicating the significance of washed out DOM and other substances on napropamide sorption and transport. The model parameters generated through preleached columns should be used with caution in pesticide behavior prediction.