Soils retrospective studies

For a small-scale retrospective study, participants enter and study a field in which a pesticide has been used over a period of time. The purposes of small-scale retrospective studies are to determine whether the pesticide(s) in question has leached to ground water in certain fields, and to characterize the leaching pattern in the soil profile at a given point in time. This section contains discussions on site selection, site characterization, the number and location of observation wells, well construction and sampling, and soil sampling. 

Site Selection and Characterization. The most important criteria for site selection is that there should be no prior use of the pesticide in question on the field site. This demands a landowner/ farmer who keeps careful records of his field and method of application for the pesticide of interest. All other criteria, including hydrogeologic considerations, soil homogeneity, existing well information, and new well construction are similar in the prospective and retrospective study. Characterization of a prospective field site is similar to retrospective field site characterization. 

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