Acid rain over México City valley and surrounding rural areas

173 determinations of pH were made during sequential rain fractions of single rain events in Mexico City and surrounding rural areas from June to September 1983. Results indicate acidic pH values in the majority of rain samples collected in the urban area, even in those samples taken at mountainous locations (pH values less than 4.5). The variability in the pH values could be attributed to: transport mechanisms of pollutants, prevailing meteorological conditions, geographic location and the rain fraction sequential number.