Atmospheric deposition of nitrogen emitted in the Metropolitan Area of Buenos Aires to coastal waters of de la Plata River

The Metropolitan Area of Buenos Aires (MABA) is the third mega-city in Latin America. Atmospheric N emitted in the area deposits to coastal waters of de la Plata River. This study describes the parameterizations included in DAUMOD-RD (v.3) model to evaluate concentrations of nitrogen compounds (nitrogen dioxide, gaseous nitric acid and nitrate aerosol) and their total (dry and wet) deposition to a water surface. This model is applied to area sources and CALPUFF model to point sources of NOx in the MABA. The models are run for 3 years of hourly meteorological data, with a spatial resolution of 1 km2. Mean annual deposition is 69, 728 kg-N year−1 over 2 339 km2 of river. Dry deposition contributions of N-NO2, N-HNO3 and N-NO3− to this value are 44%, 22% and 20%, respectively. Wet deposition of N-HNO3 and N-NO3− represents 3% and 11% of total annual value, respectively. This very low contribution results from the rare occurrence of rainy hours with wind blowing from the city to the river. Monthly dry deposition flux estimated for coastal waters of MABA varies between 7 and 13 kg-N km−2 month−1. These results are comparable to values reported for other coastal zones in the world.