Rainwater chemistry at the western savannah region of the Lake Maracaibo Basin, Venezuela

The major part of Venezuela oil production is located in and around the Lake Maracaibo Basin. The samples were collected over a 1-year period at Catatumbo and La Esperanza sites. The rainwater was acidic, with a VWA-pH of 4.6 for Catatumbo and 4.2 for La Esperanza. This acidity is made up in 93% by inorganic acids (mainly H2SO4), and NH4+ is the major cation which buffer the acidity of precipitation. An excess of sulfate (SO4*) > 96% was obtained in both sites. Correlation analysis shows that H+ is strongly correlated with SO4*. Anthropogenic air pollution from oil fields (H2S) and the burning of sulphur-bearing fuels (SO2) are probably the dominant sources; however, the lack of correlation between the H+ and NO3- levels would appear to indicate that the SO4* is also of biogenic origin (H2S-DMS from Sinamaica Lagoon-Lake Maracaibo-and the Caribbean). Statistical analysis of the pooled data indicated that the concentration differences between Catatumbo and La Esperanza sites are not significant at 99% confidence level.