Description of Simazine Transport with Rate‐Limited, Two‐Stage, Linear and Nonlinear Sorption

Abstract

This study was conducted to reconcile an apparent inconsistency between the simazine laboratory sorption isotherm data and the field lysimeter transport experiment reported by Poletika et al. (this issue). In this investigation, linear and nonlinear one-and two-stage simazine sorption models were fitted to the sorption and desorption isotherm laboratory data to obtain parameter estimates for use in the transport model. Once obtained, the calibrated sorption model was combined with the parameterized outflow concentration record from a mobile Br tracer to represent rate-limited sorption and transport of the simazine added simultaneously with the Br. The calil•rated model did an excellent job of representing the final simazine profile in the soil, particularly with the nonlinear model. This is in contrast to a single-stage adsorption model tested by Poletika et al. (this issue), which reached poor agreement with the field profile when laboratorymeasured sorption parameters were used. The results demonstrate the compatibility of field and laboratory experiments on pesticide movement and also indicate that sorption isotherms may require substantially longer to reach equilibrium than is customarily allowed in current protocols. Pignatello, J. J., Sorption dynamics of organic compounds in soils and sediments, in Reactions and Movement of Organic Chemicals in Soils, edited by B. L. Sawhney and K. Brown, pp. 31-44, Soil Science Society of America, Madison, Wisc., 1989. Poletika, N., and W. A. Jury, Effects of soil surface management on water flow distribution and solute dispersion, Soil Sci. Soc. Am. J., 58, 999-1006, 1994. Poletika, N., W. A. Jury, and M. L. Yates, Transport of bromide, simazine, and MS-2 coliphage in a lysimeter containing undisturbed, unsaturated soil, Water Resour. Res., this issue. Press, W. H., B. P. Flannery, S. A. Teukolsky, and W. T. Vetterling, Numerical Recipes in C, The Art of Scientific Computing, Cambridge University Press, New York, 1988. Rao, P.S. C., and J. M. Davidson, Estimation of pesticide retention and transformation parameters required in nonpoint source pollution models, in Environmental Impact of Nonpoint Source Pollution, edited by M. R. Overcash and J. M. Davidson, pp. 23-67, Butterworth, Stoneham, Mass., 1980. Seber, G. A. F., and C. J. Wild, Nonlinear Regression, John Wiley, New York, 1989. Selim, H. M., J. M. Davidson, and R. S. Mansell, Evaluation of a two-site adsorption-desorption model for describing solute transport in soils, paper presented at Summer Computer Simulation Conference, Simul. Counc., Washington, D.C., 1976. Susarla, S., G. V. Bhaskar, and S. M. R. Bhamidimarri, Adsorptiondesorption characteristics of some phenoxyacetic acids and chlorophenols in a volcanic soil, I, Equilibrium and kinetics, Environ. Technol. Lett., 14, 159-166, 1993. Swanson, R. A., and G. R. Dutt, Chemical and physical processes that affect atrazine and distribution in soil systems, Soil Sci. Soc. Am. Proc., 37, 872-876, 1973. Talbert, R. E., and O. H. Fletchall, The adsorption of some s-t...

Single and dual-permeability models of chlorotoluron transport in the soil profile

“…In addition, some transport properties obtained under laboratory and field conditions may be quite different. Streck et al (1995) presented apparent inconsistency between sorption isotherms determined from laboratory and field lysimeter experimental data. Poletika et al (1995) used linear and nonlinear one-and two-stage sorption models to fit the sorption and desorption isotherms.…”

Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreator System

“…These batch sorption results are consistent with our column results showing SMZ does not lose sorption capacity for BTEX over 10 sorption/regeneration cycles (> 4500 PV of exposure to produced water). (Streck et al 1995), destruction of particles while shaking (Schweich et al 1983), reduction in column particle spacing (Celorie et al 1989), and inappropriate application of an equilibrium sorption model (Altfelder et al 2001). The reasons for the discrepancies between batch and column K d s in our experiments are unclear.…”

Statement on the FERA guidance proposal: ‘Guidance on how aged sorption studies for pesticides should be conducted, analysed and used in regulatory assessments’ (FERA, 2012)

“…This would make the estimation of accurate model parameters from the available experiments even more difficult. Both of the two-site models implemented in PEARLNEQ (Leistra et al, 2001;Tiktak et al, 2000) and Streck et al (1995) can be used since they are mathematically equivalent when parameters are converted appropriately.…”

“…Ma and Selim, 1997) and the two-site or multi-site kinetic sorption models (e.g. Streck et al, 1995;Leistra et al, 2001). The draft guidance document recommends using the PEARLNEQ model (Leistra et al, 2001), which is a two-site kinetic sorption model consisting of two sorption sites in parallel, both interacting with the pesticide concentration in the liquid phase.…”