Field Investigations and Modeling of Particle‐Facilitated Pesticide Transport in Macroporous Soil

Abstract

Physical and chemical non‐equilibrium processes may facilitate the transport of pesticides and other chemicals through structured and macroporous soils. For sorbing pesticides, transport associated with a mobile colloidal or particulate phase represents an additional transport mechanismin structured soils that is not well understood. We investigated particle‐facilitated transport of a sorbing pesticide (prochloraz, N‐propyl‐N‐[2‐(2,4,6‐trichlorophenoxy)ethyl]imidazole‐1‐carboxamide) in a 5‐ by 5‐m subsurface‐drained field plot in a structured sandy loam in Denmark. Following pesticide application, three simulated rainfall events during an 8‐d period were monitored in terms of drainage flow rate, content of particulate matter (>0.24 µm), and pesticide concentration in the solution and in the particulate phases in the drainage water. The fraction of pesticide loss to the drain was 0.2% of the applied mass, of which 6% was associated with the particulate phase. Macroporous flow paths appeared to be major routes of pesticide and particle transport. Preferential sorption to particles in the drainage water relative to bulk soil, and possibly also slow desorption from the particles, were assumed to influence the pesticide leaching in the particulate fraction. Based on experimental and reported data, the dual‐porosity model MACRO, modified to account for particle mobilization and transport, could be calibrated to simulate the observations. Sensitive parameters for the particle and pesticide descriptions were identified.

Atrazine leaching from biochar-amended soils

“…Previous studies have demonstrated that preferential flow through macro-pores increases contaminant movement through the soil profile (Camobreco et al, 1996;Akhtar et al, 2003). Studies have also shown that colloid-facilitated transport is enhanced by preferential flow through soil macropores (Seta and Karathanasis, 1997;Jacobsen et al, 1997;Villholth et al, 2000). If biochar particles influence atrazine leaching via colloidfacilitated transport, we would expect this effect to be enhanced by the presence of soil macropores.…”

Development of a method for estimating the likelihood of crack flow in Canadian agricultural soils at the landscape scale

“…Briefly, the amount of contaminant transported by PF is affected by its mass and initial position in the soil relative to water, and by the timing, the duration and the intensity of rainfall after the chemical has been applied (Edwards et al 1993;Saini et al 2003;McGrath et al 2008). Preferential flow appears to be one of the most important pathways for the transport of strongly adsorbed and fast degrading agricultural chemicals (Villholth et al 2000;Vereecken 2005), phosphorus (Ga¨chter et al 1998;Jarvis 2007), and pathogens (Jamieson et al 2002;Tallon et al 2007) to tile drains, surface waters and groundwaters.…”

Determinación De La Concentración De Glifosato en Agua Mediante La Técnica De Inmunoabsorción Ligada a Enzimas (Elisa)

“…Estudios de lixiviación y escurrimiento indican que el glifosato puede ser transportado hacia las capas profundas del suelo debido al flujo preferencial por macroporos o hacia cursos de agua superficiales cuando su aplicación se realiza en momentos anteriores a lluvias intensas (Flury 1996, Villholth et al 2000, Jaynes et al 2001, Elliot et al 2002, Petersen et al 2002. En Argentina, la Subsecretaría de Recursos Hídricos de la Nación publicó en el año 2003, los niveles guía nacionales de calidad de agua ambiente correspondientes a glifosato.…”