PREFERENTIAL FLOW AND PESTICIDES

The effect of preferential flow on groundwater quality is much the same whether it occurs in structured soils or homogeneous sandy soils. Both kinds of preferential paths are able to rapidly carry small but significant quantities of pesticides to large distances below the topsoil. Since acceptable maximum concentrations of pesticides are generally in the order of parts per billion (ug/L), even a small amount of water (typicallly less than 1%) moving from a recently-sprayed field surface through preferential flow paths can elevate the groundwater pesticide concentration to detectable levels. Although widespread contamination of wells with several pesticides (i.e. atrazine, alachlor, aldicarb, metolahlor, simazine) has been documented, the significance of these measured concentrations has been subject to debate. Nevertheless, very little attention has been given to the possible cause and effect. A simple mass balance calculation comparing typical pesticide application rates and allowable drinking water thresholds confirms that transport of only a small fraction (well within the margin of error of conventional flow prediction models) of the pesticide-containing percolate to groundwater will be significant. Pesticide contamination of drain tile discharges has also been widespread, affecting surface water quality.

Influence of macropores on biological degradation and transport of pesticides

Biodegradation of 2,4D

Biodegradation of PNP

Published papers