Concentrations of dissolved nitrite plus nitrate increased fairly steadily in samples from four shallow groundwater monitoring wells after biosolids applications to nonirrigated farmland began in 1993. The U.S. Geological Survey began a preliminary assess
Yager, Tracy J.B.,McMahon, Peter B. pmcmahon@usgs.gov. Preliminary assessment of sources of nitrogen in groundwater at a biosolids-application area near Deer Trail. 2012-01-01.