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Atmospheric nitrogen species distribution under influence of agricultural sources in a Brazilian region
* 1 , 1 , 1 , 2 , * 1
1  Universidade Federal de Lavras
2  Universidade de São Paulo
Academic Editor: Anthony Lupo (registering DOI)

Atmospheric deposition is a key process to improve the understanding of human impacts on the nitrogen biogeochemical cycle and its processes. In order to evaluate the nitrogen atmospheric deposition species we quantified the dissolved inorganic nitrogen (DIN = NH4+ + NO3-) and dissolved organic nitrogen (DON) fluxes in Lavras, Minas Gerais, Brazil from May 2018 until April 2019. Our sampling site region in Minas Gerais has a strong influence of local sources, such as fertilizers production and application. Moreover, Lavras has 19% (107 km2) of its total area associated with crops plantation. We collected wet and bulk atmospheric deposition samples (n = 50) and analyzed by Kjeldahl method (Total Dissolved Nitrogen – TDN) and ionic chromatography (Dissolved Inorganic Nitrogen – DIN) analysis, respectively. Overall, our results showed that wet deposition of DON was dominant, accounting for 7.34 kg.ha−1.yr−1, while NH4+ and NO3- fluxes were of 1.39 and 3.94 kg.ha−1.yr−1, respectively. In addition, the NO3-/NH4+ molar ratio ranged from 1.33 to 33.7 and the pH values ranged from 5.66 to 6.08. The lower values of NO3-/NH4+ were associated with an alkaline behavior, suggesting dominance of NH3 in the atmosphere neutralization processes. We noted that DIN species fluxes, NH4+ and NO3-, were concentrated between October 2018 and March 2019, thus less than 14% of NH4+ and NO3- annual deposition were observed in the dry period (April to September). This pattern was associated with seasonal rainfall distribution in Lavras, and with the volatilization of NH3 and NOx species due to fertilizers applications. Regarding DON annual deposition, we observed that such distribution was also present, whereas in a less pronounced percentage (64% in the wet period), suggesting that different processes also play role in Lavras.

Keywords: Nitrogen atmospheric deposition; NO3-/NH4+ ratio; Dissolved organic nitrogen; Dissolved inorganic nitrogen; Agricultural sources; Rainfall distribution.
Comments on this paper
Anthony Lupo
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Interesting work. Based on your results is there a difference for the results in Brazil versus the Northern Hemisphere?