Abstract
Dry deposition samples were collected in a weekly basis during 2010 in a site located at the Mexican Pacific Coast: Manzanillo, Colima. Samples were collected with an automatic wet/dry deposition sampler using nylon filters as surrogate surfaces. Samples were extracted with deionized water and analyzed for pH, conductivity, Na+, K+, Ca2+, Mg2+, NH4-, NO3-, SO42- and Cl-. Nitrate and sulfate were the most abundant ions, contributing with 53% to the total ionic mass; and their levels exceeded the hemispheric background concentrations proposed for marine remote sites. The influence of the power plants burning combustoleo located upwind the sampling site was completely evident. From meteorological analysis, it could be observed that the sampling site was all time under the influence of power plants as a result of the effect of breezes. However, in spite of the high levels of NO3- and SO42- found in the samples collected, pH value average was almost neutral, with 28% of samples slightly acid. Potassium was the most abundant cation and from the quantification of the neutralization effect of the main alkaline components, the prevalence role of K+ was completely evident, suggesting the influence of the mining complex Pe?a Colorada located upwind the sampling site, where amyl xanthate potassium is used as collector in tailing dams. Dry deposition fluxes were estimated for all ions measured. Nitrogen dry deposition at Manzanillo is already in the upper extreme of the threshold value reported for sensible ecosystems. On the other hand, sulfur deposition exceeded slightly the critical load value reported for some ecosystems in Europe. Even at this moment, nitrogen and sulfur deposition is not a problem, it is necessary to take steps to avoid that total deposition of these elements exceeds critical loads, considering that results reported in this study not include the wet deposition fluxes.
Highlights
Atmospheric deposition is the process by which airborne pollutants are deposited to the terrestrial surface
The analytical data shows that pH of collected dry deposition samples ranged between 5.06 and 6.94, with an average value of 5.76, indicating a neutral nature of dry deposition samples (Figure 5)
In spite of nitrate and sulfate levels were high as a result of the proximity of the sampling site to the power plants, pH values obtained were not acid, it suggests that HNO3 and H2SO4 were subjected to neutralization processes that lead to pH values almost neutral
Summary
Atmospheric deposition is the process by which airborne pollutants are deposited to the terrestrial surface. These pollutants include, but are not limited to, sulfur dioxide, nitrogen oxides, ammonia and mercury. There are two ways that acids fall out of the atmosphere: wet and dry deposition. Dry deposition is responsible for delivering atmospheric loads of compounds such as NO3 and. Wet deposition involves atmospheric hydrometeors which scavenge aerosol particles predominantly by rain and snow, and by clouds and fog. Dry deposition of particles and gases occurs by complex processes such as settling, impactation and adsorption
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