Leaching risk assessment of pesticides from soil as function of soil properties, pesticide properties and rainfall characteristics using HYDRUS 1D numerical model

Abstract

It has been observed through experiments that many chemicals especially pesticides found in streams and groundwater bodies are transported through surface runoff and/or preferential flow processes. Researchers have also proved that the timing and nature of rainfall since the last pesticide application are often described as significant controls on pesticide transport through flow processes. Rainfall variability is now considered as the climate drivers on contaminant transport. The amount of pesticides transported through surface runoff and/or preferential flow pathways to streams and groundwater respectively has been shown to be strongly correlated with the concentration of that chemical in a thin near-surface layer of the soil immediately prior to such an event. The thin near-surface layer of a soil is regarded as the source where all the dynamics of solute transport starts. The thin near-surface layer is the store of pesticide from which they are leached by both fast episodic as well as slow steady processes. In this research, we seek to better understand the idea of driver-source-trigger concept of pesticide solute transport in the subsurface. The driver (rainfall variability) triggers (surface runoff and/or preferential flow) from the source (a thin near-surface layer) for pesticides transport to stream and/or groundwater. The methodology for this study is by the use of HYDRUS 1D Numerical Model.