A Statewide Screening For Acid Rainfall In Iowa

From April through October 1980, a statewide screening for acid rainfall was conducted in Iowa. Ninety-seven National Weather Service observers were provided with pH color-indicating strips and measured and recorded the pH of every precipitation sample. Results of the screening indicate pH values of rainfall ranged from a low of 4.0 to a high of 7.0. The pH values 5.7 and 5.9 were observed most often and represented 66% of the 4,197 values measured. Approximately 80% of the rainfall pH values fell in the 5.7 to 7.0 range and 20% in the acid rainfall range (5.6 or less). Median pH values calculated for the 97 sampling locations ranged from 5.1 to 6.2, with medians of 5.7 and 5.9 occurring most frequently. With the exception of one 3-county area, most of the 11 sampling locations demonstrating acid rainfall (median values 5.6 or less) were widely separated and probably represented localized problems. Three adjacent counties located in southeast Iowa had low median pH values and this area is recommended for future study