Biodegradation, sorption and transport of 2,4-D under saturated and unsaturated soil conditions

Abstract

Researchers have traditionally viewed sorption, degradation and transport as separate processes and only recently have these processes viewed as coupled. 2,4-D was chosen as a model system to study the interaction between these processes. A series of laboratory batch and column experiments with a sandy loam soil were conducted to determine the relative contributions of sorption and degradation to transport of 2,4-D under both saturated and unsaturated conditions. The sorption contribution to 2,4-D transport was not significant under saturated (Kd = 0.249 mg/g) nor unsaturated conditions (Kd = 0.566 mg/g). Degradation however, was very significant, specially under unsaturated conditions where the estimated first order biodegradation rate (μ) constant was 4.39 d-1. Rate constants under the saturated transport experiment were restricted by oxygen limitations. There was an order of magnitude difference between μ of batch and column experiments which were attributed to differences in aeration and mixing conditions.