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Table 1 Distribution of nitrate concentration in US Geological Survey wells by aquifer type and categories of land use in Lancaster, Lebanon, and Chester Counties, from 1976-2006

From: Modeled nitrate levels in well water supplies and prevalence of abnormal thyroid conditions among the Old Order Amish in Pennsylvania

Well Location Nitrate mg/L (NO3-N)
Aquifer N Median Mean Std. Dev. Minimum Maximum
Piedmont and Blue Ridge crystaline-rock 1676 3.00 4.35 4.88 < .002 52.00
Piedmont and Blue Ridge carbonate rock 1093 6.03 7.88 7.43 0.020 95.50
Early mesozoic basin 469 3.77 4.96 5.28 < .002 45.00
Valley and ridge carbonate rock 241 11.00 13.60 13.39 < .002 90.00
Valley and ridge 134 1.02 2.12 2.86 0.010 16.64
Land use 1992 N Median Mean Std. Dev. Minimum Maximum
Pasture 1756 5.00 6.89 7.37 < .002 90.00
Deciduous forest 674 2.15 3.60 4.46 0.003 45.00
Row crop 399 6.91 9.24 10.79 0.020 95.50
Low intensity residential 289 3.68 4.49 4.91 0.003 52.00
Mixed forest 173 2.50 3.81 3.84 < .002 20.80
Commercial or industrial 130 4.94 5.76 4.66 0.020 22.10
Evergreen forest 121 3.63 4.85 4.37 0.003 21.50
High intensity residential 21 5.95 5.09 2.47 0.690 9.23
Water 17 3.72 4.61 5.39 0.020 22.00
Quarry mine gravel pit 15 0.80 2.02 3.69 0.150 15.00
Transitional 11 1.78 2.34 1.81 0.190 6.13
Urban grasses 4 5.39 4.86 2.68 1.420 7.26
Woody wetland 3 2.48 6.22 8.45 0.280 15.90
Overall 3613 4.12 6.03 7.1 < .002 95.5
  1. Spatial classification is based on the National Land Cover Data Set; 1992, USGS [ref 38].