The pH of Precipitation in Central Maryland

Abstract

Nineteen precipitation sampling stations were established in Frederick County, Maryland, on a 58-kilometer north-south transect line and maintained from September, 1974, through March, 1975. During this time, 20 precipitation periods were sampled, and pH measurements taken. The data accumulated show a gradually increasing acidity of 2.85 pH points over the seven-month study period. Local sources of atmospheric acid were not determined, while it was possible to identify sources of alkaline influence. The direction from which individual storms came had a noticeable correlation with the pH of the rainfall. Storms moving into the study area from an easterly direction were more acidic than those moving in from a westerly direction. Periodic sampling within a precipitation period indicated no appreciable difference in pH values of rain samples collected. Storage of rainwater samples had no significant effect on measured pH values.