Improving Environmental Fate Models for Agrochemicals

The standard models assume that sorption is due only to binding to the organic matter in the soil.  In lower horizons of soil, the organic matter is approximately zero, and thus no sorption is assumed.  In reality this may not be entirely correct when other mechanisms of sorption are taken into consideration. 

Battelle looked at one of the standard scenarios used to assess pesticide leaching, the “Borstel” model.  This is considered to be one of the more critical scenarios, as it is a very sandy soil and represents a greater risk for leaching into groundwater.  To provide data to refine the simulation, Battelle collected “Borstel” soil as a core down to 1m.  The core was segmented and each horizon analyzed to confirm its similarity to the soil characterization data used in the computer simulation.  Each soil horizon was then used in an adsorption/desorption study to determine the actual sorption of the chemical.  The measured sorption in the deeper soil horizons was found to be greater than predicted by assuming organic matter binding as the sole mechanism, leading to a more favorable leaching risk assessment.