National Water-Quality Assessment (NAWQA) Program
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 98-4222
Sacramento, California, 1999
Figure 14. Annual mean detection frequencies for all 46 target compounds for each of the three types of sites during a 1-year period. Each bar represents the mean of the annual detection frequencies for a specific compound at all sites in the group during a 1-year period. Detection frequencies are based on a common reporting level of 0.01 microgram per liter for all compounds.