Atmospheric Nitrogen Deposition at Two Sites in an Arid Environment of Central Asia

Arid areas play a significant role in the global nitrogen cycle. Dry and wet deposition of inorganic nitrogen (N) species were monitored at one urban (SDS) and one suburban (TFS) site at Urumqi in a semi-arid region of central Asia. Atmospheric concentrations of NH₃, NO₂, HNO₃, particulate ammonium and nitrate (pNH₄⁺ and pNO₃⁻) concentrations and NH₄-N and NO₃-N concentrations in precipitation showed large monthly variations and averaged 7.1, 26.6, 2.4, 6.6, 2.7 µg N m⁻³ and 1.3, 1.0 mg N L⁻¹ at both SDS and TFS. Nitrogen dry deposition fluxes were 40.7 and 36.0 kg N ha⁻¹ yr⁻¹ while wet deposition of N fluxes were 6.0 and 8.8 kg N ha⁻¹ yr⁻¹ at SDS and TFS, respectively. Total N deposition averaged 45.8 kg N ha⁻¹ yr⁻¹at both sites. Our results indicate that N dry deposition has been a major part of total N deposition (83.8% on average) in an arid region of central Asia. Such high N deposition implies heavy environmental pollution and an important nutrient resource in arid regions.