Acid precipitation in the northeastern United States

Analysis of recent precipitation samples from the northeastern United States has shown a consistent p H of less than 4.4, when the expected p H based upon equilibrium with CO 2 would be 5.6. A stoichiometric formation process being assumed, some 65% of the acidity is due to H 2 SO 4 , 30% to HNO 3 , and less than 5% to HCl. The p H values may be predicted from chemical content and generally agree to within 0.1 p H unit with the observed p H. The distribution of acid precipitation encompasses most of the northeastern United States. This pattern apparently has existed since about 1950–1955, but the intensity of acid deposition, especially that due to HNO 3 , has increased since then. Analysis of prevailing winds indicates that much of the acidity originates as a general source over industrial areas in the Midwest.