Nitrogen atmospheric deposition driven by seasonal processes in a Brazilian region with agricultural background

Abstract

Understanding the seasonal patterns and influencing factors of nitrogen atmospheric deposition is essential to evaluate human impacts on the air quality and nitrogen biogeochemical cycle. However, evaluation of the nitrogen deposition flux, especially in South America agricultural regions, has not been fully investigated. In this paper, we quantified the atmospheric wet deposition fluxes of total dissolved nitrogen (TDN), dissolved organic nitrogen (DON), and dissolved inorganic nitrogen (DIN), in a region with agricultural and livestock predominance in the Southern Minas Gerais region, Brazil, from May 2018 to April 2019. Deposition fluxes of nitrogen species in the wet season (October-March) were on average 4.8-fold higher than those in the dry season, which revealed significant seasonal variations driven largely by the seasonality of rainfall and agricultural operations. We also found high NO₃^-/NH₄⁺ ratios (average = 8.25), with higher values in dry season (NO₃^-/NH₄⁺ = 12.8) in comparison with wet season (NO₃^-/NH₄⁺ = 4.48), which revealed a higher relative contribution of NO_x emissions from traffic sources in dry season. We also estimated the influence of atmospheric deposition of inorganic nitrogen (N-DIN) on environmental ecosystems, being 2.01 kgNha^-1 year^-1 with potential risk of acidification and eutrophication of 30%. Therefore, attention should be paid to the role of wet atmospheric deposition of nitrogen as a source of nitrogen environmental pollution in agricultural regions.

Keywords: Agricultural sources; Atmospheric wet deposition fluxes; Dissolved organic nitrogen; NO3 −/NH4 + ratio; Seasonality; Total dissolved nitrogen.