National Water-Quality Assessment (NAWQA) Program
Carbonate aquifers provide water of acceptable quality for human use and consumption in the majority of about 1,000 wells sampled across the U.S. With few exceptions, chemicals detected in groundwater from carbonate aquifers were low, generally below human-health benchmarks. Radon and nitrate were among the few contaminants with elevated concentrations in samples from wells tapping these important aquifers. Carbonate aquifers with features such as sinkholes, caves, and porous rocks are vulnerable to contamination, particularly aquifers located in intensively farmed areas. Contaminant levels in a few of these areas are among the highest in the Nation.
Findings of this study are available at: http://water.usgs.gov/nawqa/pubs/carbonate/