Sorption of vinclozolin and atrazine on four geosorbents

Abstract

The objectives of this study were to evaluate the magnitude and kinetics of vinclozolin and atrazine sorption on one surface soil and three freshwater sediments using batch and column techniques. Data from miscible displacement column studies were analyzed using a two‐domain, first‐order mass transfer model to obtain the equilibrium sorption constant (K) and the first‐order desorption rate coefficient (k2). In the two‐domain conceptualization and mathematical model, sorption is assumed to be instantaneous (and therefore at equilibrium) in the first domain, and kinetically controlled (modeled as a first‐order reaction) in the second domain. 3H2O used as a conservative tracer to characterize column hydrodynamics yielded breakthrough curves (BTCs) that were all symmetric and the data were described well by the advective‐dispersive local equilibrium solute‐transport model, thus indicating hydrodynamic equilibrium during transport for the column systems. However, vinclozolin and atrazine BTCs exhibited the ‘tailing’ that is characteristic of non‐equilibrium sorption during solute transport. The equilibrium model provided poor fits for all of the vinclozolin and atrazine data except for the least‐sorbing geosorbent and atrazine where BTC symmetry was high. However, when slow sorption kinetics were accounted for, the two‐domain model simulations provided good descriptions of the experimental data. © 1999 Society of Chemical Industry