Bulk Deposition and Main Ionic Composition in a Remote Tropical Region: Nevado de Toluca, Mexico
2020
Ibarra-Morales, Diana | Alcocer, Javier | Oseguera, Luis A. | Sosa-Echeverría, Rodolfo
The Nevado de Toluca Natural Protected Area (Zona de Protección de Flora y Fauna Nevado de Toluca, ZPFFNT), Central Mexico, encompasses one of the four highest (> 4000 m a.s.l.) volcanoes in Mexico, Nevado de Toluca; an extended area of woodland surrounds this volcano. Although identified as a remote area based on its high altitude, the ZPFFNT is not far from the urban and industrial zones of Toluca (~20 km) and Mexico (~72 km) cities, which potentially threatens the environmental health of the ZPFFNT by emitting SO₂ and NOX. Acid precipitation falling on areas with low alkaline reserve leads to environmental acidification and land degradation. To provide reliable data on the air pollution reaching the ZPFFNT and the related potential risks, our study analyzed the bulk atmospheric deposition chemistry and its temporal dynamics throughout an annual cycle. There are two well-defined seasons: (a) cold/dry with SW–NE wind direction and (b) warm/rainy with NE–SW wind direction. The pH, electric conductivity (K₂₅), cations, Cl⁻, and HCO₃⁻ were statistically higher in the cold/dry period. Differently, NO₃⁻ and SO₄²⁻ showed steadier behavior. Bulk deposition pH remained acidic at all times but reached extreme low values from July to September during the warm/rainy season. In the cold/dry season, alkaline cations were important in partially neutralizing the acidic compounds from the urban and industrial zones of Toluca and Mexico cities. Previously assumed to be safe based on its remoteness, the ZPFFNT is threatened by acid precipitation, which demand the implementation of preventative and mitigating actions as part of a management plan to avoid environmental deterioration.
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