Resumo

PADILLA, H. et al. Total peroxides and sulfate in rainwater in the Mexican eastern Pacific Ocean during the Climatic Experiment in the Americas Warm Water Pools. Atmósfera [online]. 2007, vol.20, n.3, pp.299-305. ISSN 0187-6236.

Total peroxides were analyzed in 26 rainwater samples collected on board of the R/V El Puma of the National Autonomous University of México (UNAM) during the Climatic Experiment in the Americas Warm Water Pools (ECAC-1) over the eastern Pacific Ocean between 12 and 14° N, and between 98 and 100° W, from May 23 to 25, 2001. The volume weighted mean concentration of total peroxides was 13.1 ± 1.94 μM. Also, sulfate ion was analyzed. The volume weighted mean concentrations for sulfate and sea-salt sulfate were 0.76 + 0.59 and 0.04 ± 0.06 mg L^-1, respectively. Excess sulfate (non-sea-salt sulfate) represented 95% of the total sulfate. The total peroxides concentration in rainwater correlated significantly with total sulfate and excess sulfate (0.560 and 0.586 at a p < 0.05, respectively) possibly because most of the excess sulfate and hydrogen peroxide, observed in the Mexican eastern Pacific Ocean, could have been produced from the oxidation of biogenic sulfur compounds. The non-significant correlation between sea-salt sulfate and total peroxides was due to the fact that H₂O₂ does not react with the sulfate already present in sea salt aerosols. Also, the concentration of total peroxides did not correlate with rain intensity probably because a significant fraction of H₂O₂ could have been generated within cloud droplets.

Palavras-chave : Total peroxides; sulfates; rainwater.