A STUDY OF THE TEMPORAL VARIABILITY OF ATRAZINE IN PRIVATE WELL WATER.1. STUDY DESIGN, IMPLEMENTATION, AND DATABASE DEVELOPMENT

In 1988, the Iowa Department of Natural Resources, along with the Univ ersity of Iowa conducted the Statewide Rural Well Water Survey, common ly known as SWRL. A total of 686 private rural drinking water wells wa s selected by use of a probability sample and tested for pesticides an d nitrates. Sixty-eight of these wells, the '10% repeat' wells, were a dditionally sampled in October, 1990 and June, 1991. Starting in Novem ber, 1991, the University of Iowa, with sponsorship from the United St ates Environmental Protection Agency, revisited these wells to begin a study of the temporal variability of atrazine and nitrates in wells. Other wells, which had originally tested positive for atrazine in SWRL but were not in the 10% repeat population, were added to the study po pulation. Temporal sampling for a year-long period began in February o f 1992 and concluded in January of 1993. All wells were sampled monthl y, one subset was sampled weekly, and a second subset was sampled for 14-day consecutive periods. Two unique aspects of this study were the use of an immunoassay technique to screen for triazines before gas chr omatography/mass spectrometry (GC/MS) analysis and quantification of a trazine, and the use of well owners to sample the wells. A total of 17 71 samples from 83 wells are in the final data base for this study. Th is paper reviews the study design, the analytical methodologies, and d evelopment of the data base. A companion paper (Pinsky et al., 1997) d iscusses the analysis of the data from this survey.