1. Nitrate in ground water : using a model to simulate the probability of nitrate contamination of shallow ground water in the conterminous United States Yale Public content 2005. 2009-03-02T21:00:51Z. 2011-03-04T18:50:55Z. Hitt, Kerie J. U.S. Dept. of the Interior, U.S. Geological Survey. English. Public. United States.