Simulation of 2,4-D herbicide transport through the unsaturated zone using an analytical model

Pesticide movement through the unsaturated zone of the subsurface environment is a complex process. Agricultural practices, soil properties, and climatic conditions among others, constitute the most important aspects to be considered. To simulate the transport and fate of the herbicide 2,4-D under real agricultural conditions, the Hantush-Marino (1996) model has been applied. The model is a physically based analytical model that simulates pesticide transport in soils and groundwater. In the unsaturated zone, the model simulates one-dimensional pesticide movement based on the concept of complete mixing, adsorption, volatilization, and degradation. Linear equilibrium liquid-vapor partition is considered based on Henry's law and linear equilibrium adsorption is assumed for sorption and desorption in soil. The simulation model is applied to a study area located in a newly built golf course (Baix Emporda-Gerona, Spain), where 2,4-D is currently applied. Results show that with current agricultural practices, 2,4-D can be still detected at a depth of 2 m at concentrations greater than 0.1 mug/L.