**Acknowledgements**

Nitrate did not show a clear seasonal trend and presented a similar pattern along the year representing its local character. However, it was observed a clear spatial pattern with peak values in the surroundings of points 6, 7 and 8. This zone is located at the mangrove forest boundaries and it is characterized by high vehicular traffic since there are not enough roads.

spatial trend which decreased progressively westward. Peak values were centered on the points 1, 2, 3 and 4. An evident seasonal pattern was identified since deposition fluxes were higher during Norths season; it suggests that sulfate levels could be enhanced by large- scale transported emissions from offshore platforms in the Gulf of Campeche demonstrating its

has a local origin, and is mainly distributed along the urban zone, being its deposition higher

the east edge of the island just during the dry season, suggesting a local origin, probably from light- duty vehicles emissions and agricultural activities developed in nearby rural areas.

contribution higher when the Island was subjected to the influence of "Norths". It was quite evident that in addition to local industrial sources in Carmen Island, background levels were enhanced by the long- range transport of SO2 emissions from offshore platforms in the Gulf of

Exceedance of critical loads represents a potential risk indicator of acidification as well as its impacts on ecosystems; therefore, in order to assess the vulnerability of the mangrove ecosystems in Carmen Island, it is necessary to establish the critical loads and to estimate their exceedances. Only then, it will be possible to develop emissions control programs and propose

Interpolation of field measurements is one of the most convincing methods to explore N and S budget, even though the accuracy is limited by the characteristics of measured data and

This research work constitutes the first step to quantify the current status of N and S deposition in the study site. A long- range monitoring network over Mexico will be established in a shorttime for estimating nitrogen and sulfur deposition fluxes and their distribution along the country. A series of monitoring stations should be set down in order to keep the uniformity in the measured data, allowing comparability and considering not only urban and industri‐ alized sites but also rural and remote sites. Maps based on measurements are also required in

Campeche during the "Norths" season when prevailing winds came from NE.

prevention policies and local regulations focused to protect these ecosystems.

Mexico to validate and calibrate three- dimensional transport models.

uncertainties associated with the interpolation technique.

deposition fluxes showed a slight dilution effect, with relatively higher values

2- , deposition fluxes were higher in the east edge of the island with a clear


2- , its deposition has its origin in both, local and regional sources, being this

atmospheric deposition in the study site

<sup>+</sup> highest deposition fluxes were distributed at

Moreover, NO3

160 Current Air Quality Issues

In the case of SO4

regional character.

**5. Conclusions**

Regarding SO4


during dry months, decreasing as rainy season progressed.

Results found in this research work suggest that NO3

during the dry season. On the other hand, NH4

The authors acknowledge the financial support given to this research work by Autonomous University of Carmen through its Postgraduate Department. Thanks to the people, organiza‐ tions, institutions and companies that provided a secure location for the sampling devices used in this study.
