Simulation of Alachlor fate and transport: Model calibration and sensitivity analysis

Spraying of agricultural chemicals result in their travel downward through the unsaturated zone and adsorption on the surrounding soil. Infiltration from rainfall and irrigation solubilize these chemicals and carry the dissolved components to the ground water. This process can cause soil and ground water contamination the extent of which is greatly influenced by soil characteristics, the rate and method of chemical application. This paper presents experimental and mathematical results describing the transport of the herbicide Alachlor in laboratory soil columns with variable length, initial moisture content, and Alachlor application rate and method. The laboratory time-dependent distribution of Alachlor concentration is used to calibrate a numerical flow and transport model. The model was also used to conduct a sensitivity analysis with respect to soil and chemical properties and identify parameters value ranges controlling Alachlor transport in porous media.