HR: 1330h
AN: H32A-0515    [PDF]
TI: Vadose Zone Sampling Methods for Detection of Preferential Pesticides Transport
AU: * Peranginangin, N
EM: np34@cornell.edu
AF: Dept. of Biological and Environmental Engineering, Riley Robb Hall, Cornell University, Ithaca, NY 14853 United States
AU: Richards, B K
EM: bkr2@cornell.edu
AF: Dept. of Biological and Environmental Engineering, Riley Robb Hall, Cornell University, Ithaca, NY 14853 United States
AU: Steenhuis, T S
EM: tss1@cornell.edu
AF: Dept. of Biological and Environmental Engineering, Riley Robb Hall, Cornell University, Ithaca, NY 14853 United States
AB: Leaching of agricultural applied chemicals through the vadose zone is a major cause for the occurrence of agrichemicals in groundwater. Accurate soil water sampling methods are needed to ensure meaningful monitoring results, especially for soils that have significant preferential flow paths. The purpose of this study was to assess the capability and the effectiveness of various soil water sampling methods in detecting preferential transport of pesticides in a strongly-structured silty clay loam (Hudson series) soil. Soil water sampling devices tested were wick pan and gravity pan lysimeters, tile lines, porous ceramic cups, and pipe lysimeters; all installed at 45 to105 cm depth below the ground surface. A reasonable worse-case scenario was tested by applying a simulated rain storm soon after pesticides were sprayed at agronomic rates. Herbicides atrazine (6-chloro-N$^{2}$-ethyl-N$^{4}$-isopropyl-1,3,5-triazine-2,4-diamine) and 2,4-D (2,4-dichloro-phenoxyacetic acid) were chosen as model compounds. Chloride (KCl) tracer was used to determine spatial and temporal distribution of non-reactive solute and water as well as a basis for determining the retardation in pesticides movement. Results show that observed pesticide mobility was much greater than would be predicted by uniform flow. Under relatively high soil moisture conditions, gravity and wick pan lysimeters had comparably good collection efficiencies, whereas the wick samplers had an advantage over gravity driven sampler when the soil moisture content was below field capacity. Pipe lysimeters had breakthrough patterns that were similar to pan samplers. At small plot scale, tile line samplers tended to underestimate solute concentration because of water dilution around the samplers. The use of porous cup samplers performed poorly because of their sensitivity to local profile characteristics: only by chance can they intercept and sample the preferential flow paths that are critical to transport. Wick sampler had the least variation, followed (in order) by pipe, tile, and cup samplers. This study has implications on determining best sampling method for monitoring agrichemicals where preferential flow paths are present.
DE: 1831 Groundwater quality
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting