FORMALDEHYDE IN RAIN WATER IN MEXICO CITY ATMOSPHERE

Measurements of formaldehyde in rain water were performed at the National University of Mexico during the rainy seasons of 1981 and 1982. A total of 71 samples from storms and prolonged rains were analyzed. The results obtained throughtout this study gave an average of 0.479 ± 0.19 mg/l, much higher than those reported in rain water by different authors for maritime and clean coastal air. The statistical program “cross tabulation” applied to CH 2 O concentrations, indicated a liner correlation only between the CH 2 O concentrations, sunshine hours and the time when precipitation began. The high CH 2 O values found in rain water indicated a much greater source tan that provided by the methane oxidation. Motor vehicles emissions and the huge combustion of fuel oil are the obvious candidates for the additional CH 2 O sources in the atmosphere of Mexico City.