Dry and Wet Deposition of Nitrogen Emitted in Buenos Aires City to Waters of de la Plata River
2008
Pineda Rojas, Andrea L. | Venegas, Laura E.
Dry and wet deposition of atmospheric nitrogen species (NO₂ and HNO₃) coming from nitrogen oxides emissions in Buenos Aires city to surface waters of de la Plata River were estimated. Atmospheric dispersion models DAUMOD-RD (v.2) and CALPUFF were applied to area and point sources, respectively. These models were run considering 1 year of hourly meteorological data. Emission information included a typical diurnal variation of area source emissions. Annual atmospheric nitrogen (N-NO₂ + N-HNO₃) deposition to 1,763 km² of the river was 35,600 kg-N year⁻¹. Dry deposition processes accounted for 89% of this value. The small contribution of wet deposition was a consequence of the very few cases (5%) of rain events during offshore wind conditions. Monthly dry deposition to 1,763 km² of the river varied from 1,628 kg-N month⁻¹ in February to 3,799 kg-N month⁻¹ in December, following the monthly occurrence of offshore winds. Monthly wet deposition varied from 1 kg-N month⁻¹ in June to 1,162 kg-N month⁻¹ in February. These results came from the combination of favorable conditions for formation of HNO₃ and the occurrence of precipitation during offshore wind situations. Spatial distribution of annual atmospheric N deposition showed a strong coastal gradient. Deposition values reached a maximum of 137.1 kg-N km⁻² year⁻¹ near the shoreline, which was reduced to the half at 4 km from the coast.
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