U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993,
Water-Resources Investigations Report 94-4015
Vulnerability of Water from Public Supply Wells to Contamination
by Pesticides, Potomac-Raritan-Magothy Aquifer System, New Jersey Coastal
Eric F. Vowinkel (U.S. Geological Survey, West Trenton, N.J.
A numerical rating model used in conjunction with hydrogeologic, land-use,
and water-quality data stored in a geographic information system was developed
to rank 558 public supply wells screened in the Potomac-Raritan-Magothy
aquifer system in the New Jersey Coastal Plain into groups of high, medium,
and low vulnerability to contamination by pesticides. The vulnerability
of water from public supply wells to contamination by pesticides is defined
by variables describing the (1) sensitivity of the aquifer to contamination
and (2) intensity of pesticide use in areas where the aquifer is sensitive.
The results of the model indicated that 305 wells were of low vulnerability,
237 were moderately vulnerable, and 16 were highly vulnerable to contamination.
Because analyses for pesticides in water samples are scarce, the concentration
of nitrate in water samples was used as a surrogate to develop and test
the accuracy of the model. Results of statistical tests indicate that the
concentration of nitrate is a significant indicator of aquifer sensitivity,
pesticide-use intensity, and the presence of pesticides in ground water.
Results of the rating model indicate that water from only 1 of the 138 sampled
wells that were ranked as low vulnerability contained nitrate as nitrogen
in concentrations larger than 0.5 milligrams/L. Concentrations of nitrate
in water samples were significantly larger in the medium- and high-vulnerability
groups than in the low-vulnerability group.