Resumo

CERON-BRETON, Rosa M. et al. Potential influence of emissions and transport of N and S in the Orizaba Valley, Veracruz, Mexico. Agrociencia [online]. 2018, vol.52, n.5, pp.653-670. ISSN 2521-9766.

There have been few studies in Mexico about the atmospheric deposition of acidified substances that modify the balance of tropical mountain systems, which are highly sensitive to N and S compound deposits. The objective of this study was to evaluate the spatial and temporal distribution of N and S deposits during a year, in the Orizaba Valley, and to estimate the effect produced by the large-scale transport of SO2 regional emissions in S atmospheric deposits. The hypothesis was that N and S deposits in the Orizaba Valley are produced by local and regional sources, respectively. N and S deposits were measured in 2015, using passive collectors with ion-exchange resin (RII) in 10 sites, throughout the Orizaba Valley, Veracruz, Mexico. The ions (${\mathrm{N}\mathrm{O}}_3^{-}$, ${\mathrm{N}\mathrm{H}}_4^{+}$ and ${\mathrm{S}\mathrm{O}}_4^{2-}$) retained in the RII column were extracted using KCl 2 N, analyzed using the indophenol blue method, and subject to a turbidimetric analysis. The annual average N and S deposits were 1.42 and 27.25 kg ha-1 year-1. The S flow exceeded almost sixfold the critical load proposed for sensitive areas. This represents a potential acidification threat for the region. During the rainy and cold fronts (nortes) seasons, large-scale transport was evident. The ${\mathrm{N}\mathrm{O}}_3^{-}$ and ${\mathrm{N}\mathrm{H}}_4^{+}$ and atmospheric deposits had a local origin while ${\mathrm{S}\mathrm{O}}_4^{2-}$ had a regional origin; the contribution was higher when the trade and north winds blew in the Orizaba Valley. The ${\mathrm{S}\mathrm{O}}_4^{2-}$ background levels increased as a result of the transport of emissions released by the platforms in the Sonda de Campeche and by industrial sources in northern Mexico that influence S deposit in that region of Veracruz.

Palavras-chave : atmospheric deposition; N; S; Orizaba Valley; Veracruz.