THE HISTORY AND CHARACTER OF ACID PRECIPTATION IN EASTERN NORTH AMERICA^

The history and present distribution of precipitation acidity in eastern North America is reviewed. Precipitation chemistry from the 1920's indicates heavy ionic deposition, but low acidity (calculated) in Tennessee (pH 7.4) and New York (pH 6.15). However, high acidity was apparently widespread over northeast North America by 1955-56 and measured pH's below 4.5 were observed earlier. The geographic distribution of acid precipitation has spread through the present. Yearly average pH values for 1972-73 are not significantly different in New York and New Hampshire, indicating a regional consis-tency in acid (pH 4.10) deposition. Summer acidity is cur-rently lower in Tennessee than in the Northeast. Precipitation chemistry of individual storms reveals some local variation even within a 3 km range, but a storm in central New York is generally homogenous over 70 km