Identification of Ion sources in rainwater of a coastal site impacted by the gas and oil industry in the southeast of Mexico

The purpose of this research was to study the chemical composition of rainwater to assess
the impact of marine aerosol and anthropogenic emissions by using back air-mass
trajectories. Fieldwork was done from July to November 2004, in a coastal site probably
impacted by gas and oil industry in Campeche, Mexico: San Antonio Cardenas.
Na+, Cl-, and Mg2+, were the most abundant ions, being sea-salt aerosol their unique source.
A significant portion of K+ and Ca2+ originated from non-sea-salt sources; and the sulphate
excess exceeded the background level reported for remote marine sites, suggesting that
besides of marine aerosol, there was a significant contribution of SO42- from anthropogenic
sources. NO3- concentrations in San Antonio Cardenas exceeded the background level
reported for coastal sites with minimal anthropogenic influence and showed a significant
correlation with SO42-, suggesting a common source. Agricultural practices are null, for this
reason NH4+ levels were low.
Mean pH value was 4.64, this acidity showed a good correlation with SO42- and NO3- levels,
and with the local meteorology. A sour gas recompression plant located 10 km at NE from
San Antonio Cardenas was identified as the main source of this strong acidity.