Eastern United States
		Hydro-	Sulfate	Nitrate	Ammon-	Calcium	Precip-
Year	Ph	gen ion	ion	ion	ium ion	ion	itation
	units	ug/l	milligrams per liter				cm
1985	4.43	37.57	2.02	1.25	0.23	0.15	106.70
1986	4.42	38.16	2.14	1.30	0.24	0.13	102.20
1987	4.42	38.06	2.09	1.33	0.26	0.14	100.70
1988	4.43	37.05	2.14	1.33	0.21	0.17	95.90
1989	4.47	34.25	2.01	1.35	0.31	0.15	110.80
1990	4.49	32.71	1.80	1.18	0.27	0.12	122.60
1991	4.47	34.00	1.87	1.27	0.26	0.14	111.00
1992	4.49	32.04	1.77	1.22	0.25	0.12	108.40
1993	4.47	33.64	1.78	1.28	0.26	0.11	113.70
1994	4.48	33.07	1.71	1.24	0.28	0.13	111.90
1995	4.55	28.17	1.47	1.23	0.28	0.13	109.30
1996	4.55	28.01	1.49	1.22	0.28	0.14	123.00
1997	4.52	30.44	1.55	1.28	0.26	0.18	105.80
1998	4.54	28.80	1.60	1.26	0.30	0.13	110.15
	Western United States
		Hydro-	Sulfate	Nitrate	Ammon-	Calcium	Precip-
Year	Ph	gen ion	ion	ion	ium ion	ion	itation
	units	ug/l	milligrams per liter				cm
1985	5.13	7.40	0.82	0.71	0.18	0.23	62.00
1986	5.18	6.57	0.78	0.68	0.17	0.19	72.40
1987	5.11	7.82	0.83	0.83	0.24	0.19	62.20
1988	5.10	7.93	0.93	0.83	0.16	0.27	56.60
1989	5.23	5.84	0.87	0.91	0.29	0.25	56.70
1990	5.21	6.22	0.80	0.87	0.29	0.22	66.20
1991	5.20	6.31	0.77	0.80	0.24	0.21	68.40
1992	5.23	5.86	0.77	0.83	0.28	0.18	65.10
1993	5.27	5.41	0.71	0.76	0.23	0.18	74.40
1994	5.07	8.53	0.76	0.92	0.28	0.20	62.00
1995	5.11	7.73	0.70	0.79	0.27	0.19	77.70
1996	5.15	6.99	0.70	0.86	0.29	0.21	74.50
1997	5.07	8.48	0.67	0.83	0.24	0.18	74.90
1998	5.10	7.92	0.68	0.82	0.26	0.18	75.61
	Entire United States
		Hydro-	Sulfate	Nitrate	Ammon-	Calcium	Precip-
Year	Ph	gen ion	ion	ion	ium ion	ion	itation
	units	ug/l	milligrams per liter				cm
1985	4.57	27.07	1.60	1.06	0.21	0.17	91.10
1986	4.57	27.16	1.67	1.08	0.21	0.15	91.80
1987	4.56	27.53	1.65	1.15	0.25	0.15	87.30
1988	4.57	26.91	1.72	1.16	0.19	0.21	82.20
1989	4.61	24.35	1.61	1.20	0.30	0.19	91.90
1990	4.63	23.49	1.45	1.07	0.28	0.16	102.90
1991	4.61	24.36	1.49	1.11	0.26	0.16	96.10
1992	4.64	22.92	1.42	1.09	0.26	0.14	93.30
1993	4.62	23.81	1.41	1.10	0.25	0.14	100.00
1994	4.61	24.53	1.38	1.13	0.28	0.15	94.50
1995	4.68	21.04	1.20	1.08	0.28	0.15	98.30
1996	4.68	21.13	1.23	1.10	0.28	0.16	107.00
1997	4.64	22.79	1.24	1.13	0.25	0.14	95.10
1998	4.67	21.60	1.28	1.11	0.29	0.15	98.01

Source:  National Trends Network of the National Atmospheric Deposition Program, unpublished, Champaign, IL, 2000.

Notes:  ug/l = micrograms per liter. cm = centimeters. Data are from 73 sites in the eastern United States and 39 sites in the western United States. Sites included in the computations are those where (1) precipitation amounts are available for at least 90% of the summary period and (2) at least 60% of the precipitation during the summary period is represented by valid samples

Last Updated on Monday, May 15, 2000