U.S. Geological Survey Open-File Report 09-0346
Trends in Precipitation Chemistry in the United States,
1983-1994: An Analysis of the Effects in 1995 of Phase I of the Clean Air Act Amendments of 1990, Title IV
Table 8. Regional mean departures of 1995 annual and bi-monthly ionic concentrations at NADP/NTN sites with values
predicted by the seasonalized trend model using data from 1983 through 1994.
Annual January- March- May- July- September- November-
Number of Mean February April June August October December
Valid 1995 ----------- ----------- ----------- ----------- ----------- ----------- -----------
Region Estimates µeq/L % µeq/L % µeq/L % µeq/L % µeq/L % µeq/L % µeq/L %
--------------------------------------------------------------------------------------------------------------------
---------------------------------------- Hydrogen Ion -----------------------------------------
East 62 -4.95 -11.7 -5.09 -13.0 0.59 4.3 -7.91 -12.5 -2.66 -3.7 -10.98 -30.2 -3.65 -10.6
NE 47 -5.53 -12.4 -5.92 -15.3 0.23 2.3 -8.05 -10.7 -1.74 -0.3 -12.81 -33.0 -4.91 -15.9
SE 15 -3.13 -9.4 -2.49 -5.7 1.71 10.7 -7.46 -18.0 -5.56 -14.4 -5.27 -21.5 0.28 5.9
West 47 0.76 10.7 -0.67 -1.8 0.19 10.6 -0.03 18.1 1.54 15.9 3.30 31.3 0.24 3.8
Total 109 -2.49 -2.0 -3.18 -8.2 0.42 7.0 -4.51 0.7 -0.85 4.8 -4.82 -3.7 -1.97 -4.4
------------------------------------------- Sulfate -------------------------------------------
East 62 -4.01 -9.8 -3.12 -8.9 1.17 3.1 -7.47 -12.7 -4.14 -6.1 -8.06 -21.4 -2.45 -9.8
NE 47 -4.70 -11.3 -3.99 -12.3 0.99 2.4 -8.04 -13.1 -4.10 -4.7 -9.59 -24.9 -3.49 -14.8
SE 15 -1.85 -5.2 -0.38 1.5 1.72 5.3 -5.68 -11.6 -4.27 -10.3 -3.26 -10.2 0.79 6.0
West 47 1.37 7.5 -0.76 -5.4 -0.91 -6.2 1.71 8.9 1.29 9.4 4.98 31.1 1.92 17.2
Total 109 -1.69 -2.3 -2.10 -7.4 0.27 -0.9 -3.51 -3.4 -1.80 0.6 -2.44 1.3 -0.57 1.9
------------------------------------------- Nitrate -------------------------------------------
East 62 0.97 4.6 -0.04 2.7 3.31 15.4 0.13 0.9 3.20 13.5 -2.82 -14.9 2.04 17.7
NE 47 1.14 4.5 -0.34 -0.8 3.69 15.1 0.56 2.6 4.53 19.2 -3.40 -17.4 1.80 12.9
SE 15 0.44 4.9 0.90 13.8 2.12 16.3 -1.20 -4.5 -1.00 -4.3 -0.99 -7.0 2.80 32.7
West 47 0.76 3.8 0.26 1.3 -0.12 -3.1 -0.68 -3.2 -0.64 -2.1 3.20 27.1 2.54 26.2
Total 109 0.88 4.3 0.09 2.1 1.83 7.4 -0.22 -0.9 1.54 6.8 -0.22 3.2 2.26 21.4
------------------------------------------- Chloride ------------------------------------------
East 62 0.93 21.1 2.66 53.2 0.32 5.7 0.41 7.9 0.38 16.8 0.99 21.1 0.79 24.3
NE 47 0.97 23.6 2.44 55.2 0.36 6.4 0.41 8.2 0.34 15.1 0.97 23.1 1.32 32.2
SE 15 0.77 13.2 3.36 47.0 0.18 3.2 0.44 7.1 0.52 22.3 1.02 14.7 -0.88 -0.6
West 47 0.67 12.4 0.63 4.0 0.90 12.3 1.62 21.4 0.89 23.9 0.43 19.1 -0.45 14.7
Total 109 0.81 17.3 1.78 32.0 0.57 8.5 0.94 13.7 0.60 19.9 0.75 20.2 0.25 20.1
------------------------------------------- Ammonium ------------------------------------------
East 62 1.69 14.3 1.62 23.0 2.71 25.3 1.46 10.8 2.61 20.0 0.06 0.1 1.67 26.6
NE 47 1.71 12.6 1.81 23.0 2.80 26.7 0.96 6.1 3.05 18.2 -0.07 -2.7 1.69 24.3
SE 15 1.63 19.6 1.03 23.1 2.41 20.9 3.03 25.6 1.22 25.7 0.47 8.9 1.59 33.9
West 47 0.62 8.3 -0.41 2.1 -2.42 -8.2 0.29 8.5 1.17 14.8 3.17 34.2 1.94 41.7
Total 109 1.23 11.7 0.75 14.0 0.50 10.8 0.96 9.8 1.99 17.8 1.40 14.8 1.79 33.1
------------------------------------------- Calcium -------------------------------------------
East 62 1.44 30.6 0.88 26.1 1.84 36.6 1.31 26.8 1.42 29.6 1.47 24.1 1.69 66.4
NE 47 1.66 31.4 0.86 20.2 2.20 41.9 1.50 26.3 1.78 33.8 1.72 20.8 1.91 68.8
SE 15 0.73 27.9 0.94 44.9 0.71 20.2 0.74 28.1 0.29 16.6 0.68 34.3 1.02 58.9
West 47 2.33 30.3 1.39 19.4 1.64 18.8 2.74 34.2 1.70 24.0 3.34 63.0 3.15 74.6
Total 109 1.82 30.4 1.10 23.2 1.76 28.9 1.93 30.0 1.54 27.2 2.27 40.8 2.32 69.9
------------------------------------------ Magnesium ------------------------------------------
East 62 0.64 47.9 0.65 65.5 0.71 45.6 0.54 34.4 0.59 49.4 0.84 56.1 0.49 56.0
NE 47 0.72 53.5 0.63 68.5 0.81 53.3 0.63 36.5 0.68 50.4 0.94 64.2 0.62 67.6
SE 15 0.38 30.5 0.72 56.1 0.36 21.4 0.28 27.7 0.31 46.0 0.50 30.9 0.10 19.8
West 47 0.53 37.1 0.25 13.2 0.39 26.9 0.82 38.7 0.69 48.6 0.64 64.5 0.38 78.5
Total 109 0.59 43.3 0.48 42.9 0.57 37.5 0.67 36.2 0.63 49.1 0.75 59.7 0.44 65.7
------------------------------------------ Potassium ------------------------------------------
East 62 0.26 64.8 0.14 64.8 0.17 41.7 0.31 58.5 0.18 50.7 0.60 115.8 0.17 79.6
NE 47 0.24 69.5 0.14 70.6 0.17 46.5 0.29 53.2 0.15 52.5 0.45 120.3 0.21 98.8
SE 15 0.34 50.1 0.11 46.7 0.15 26.8 0.39 75.4 0.26 45.2 1.06 101.8 0.03 19.4
West 47 0.23 51.5 0.05 21.7 0.29 77.8 0.17 25.6 0.43 88.9 0.22 48.5 0.22 119.9
Total 109 0.25 59.1 0.10 46.2 0.22 57.3 0.25 44.3 0.28 67.2 0.43 86.8 0.19 97.0
------------------------------------------- Sodium --------------------------------------------
East 62 1.49 48.7 3.30 87.9 0.71 20.7 1.02 46.9 0.94 59.2 1.64 51.4 1.36 46.6
NE 47 1.50 56.5 2.95 96.7 0.75 25.2 1.07 56.6 0.83 61.2 1.61 57.8 1.81 59.0
SE 15 1.46 24.1 4.40 60.3 0.58 6.9 0.85 16.7 1.31 53.1 1.72 31.2 -0.07 7.7
West 47 1.10 31.6 0.89 20.1 1.08 19.0 1.85 37.3 1.42 51.6 1.16 53.6 0.17 47.6
Total 109 1.32 41.3 2.26 58.7 0.87 20.0 1.38 42.8 1.15 55.9 1.43 52.3 0.85 47.0
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