Introduction
Aquatic organisms are commonly used to monitor the bioaccumulation of persistent environmental contaminants in aquatic systems (Schmitt and Brumbaugh, 1990). For this reason, the U.S. Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) chose aquatic organisms as indicators of the occurrence and distribution of major and minor trace-element concentrations in 47 river basins distributed across the United States (fig. 1). The purpose of this report is to (1) describe the NAWQA tissue-sampling program, (2) present the tissue trace element data, and (3) present sample summaries and concentration statistics (maximum, minimum, and median).
Figure 1. Locations of U.S. Geological Survey National Water-Quality Assessment Program (NAWQA) study units where tissue samples of aquatic organisms were collected, 1992-2000. |