关键词：农药；水质
摘 要：Field replicate water samples ('field Replicates') collected for the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program during 1992 to 1997 were used to assess the variability of pesticide detections and concentrations in environmental water samples collected from the surface and ground-water-quality networks of the NAWQA Program. Field replicates are two or more identically collected, processed, and analyzed environmental water samples that are used to assess the overall variability of field and laboratory procedures. Variability is the degree of random error in independent measurements of the same quantity and is the opposite of precision-the degree of mutual agreement. Information on variability can be used to estimate the reproducibility of individual measurements, the concentration needed to be assured of exceeding a water-quality standard, and the likelihood that two measurements of water quality are different.