资源环境科技发展态势分析平台

Few related studies have been carried out for northwest China's the inland, although the increasing inorganic reactive nitrogen (Nr) deposition and severe air pollution in China have attracted considerable attention. Based on eight-year measurements of the concentrations of NH₃, HNO₃, particulate (p) NH₄⁺, pNO₃⁻, and NO₂ in the air and inorganic nitrogen (NH₄⁺, NO₃⁻) in the precipitation at a rural site in Wuwei, Gansu Province, we quantified the dry and bulk/wet Nr deposition fluxes and analyzed their temporal trends in combination with air pollution data (2015–2018). The concentrations of the single Nr species in the air did not exhibit significant seasonal variations, except for that of pNO₃⁻ which were the highest in summer and the lowest in winter. The average annual total Nr (dry + bulk) deposition was 27.2 ± 6.7 kg N ha⁻¹ with a significant (p < .05) annual increase rate of 10%, which was dominated by the dry deposition flux (20.8 ± 7.1 kg N ha⁻¹ yr⁻¹) during the entire period. The NH₄⁺-N and NO₃⁻-N deposition fluxes in the precipitation were significantly (p < .05) higher in the summer than in the other three seasons owing to the heavy rainfall. The reduced N (NH₃, pNH₄⁺, and NH₄⁺) deposition flux was 4.7 times that of the oxidized N (HNO₃, pNO₃⁻, NO₂, and NO₃⁻), which increased with a high annual rate (25%). The annual mean concentrations of the main air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, and CO) significantly decreased by 15%–76%; in contrast, increasing trends of the O₃ and NH₃ concentrations were observed. Our results highlight the importance of the control of NH₃ emissions and O₃ pollution to comprehensively mitigate N deposition and improve air quality in the considered region.