Chemical characterization of dry atmospheric deposition in a natural protected area impacted by an oil-fired power plant in Mexico

摘要

Dry deposition rates of Na~+, K~+, Ca~(2+) , Mg~(2+), NH_4~+, Cl~-, NO_3~-, and SO_4~(2-), are reported for the biosphere reserve named "Los Petenes" in Campeche, Mexico from September to December 2009. Dry deposition samples were taken using nylon filters as surrogate surfaces for one-week long exposure periods. Nitrate levels exceeded the background hemispheric value reported for remote sites. NO_3~- showed good correlation with SO_4~(2-), suggesting that both ions had a common source, probably combustion sources. From backward trajectories analysis, the origin of the air masses during the study period was traced, identifying local sources (Lerma power plant and biomass burning) located at the East from the study site as the main sources contributing to the acidity. In spite of nitrate and sulfate levels were elevated, pH values obtained showed that the site had enough buffer capacity to neutralize the acidity. From Pearson correlation analysis, it could be observed that alkaline ions like Ca~(2+) and Mg~(2+) derived from crustal played an important role in this neutralization process.