Dry and Wet Deposition of Inorganic Nitrogen at Urban and Rural Sites in a Semi-arid Environment

Dry and wet deposition of inorganic nitrogen species were monitored at one urban (SDS) and one rural (TFS) site during September 2009 and August 2010 at Urumqi in a semi-arid region. 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 7.0, 18.2, 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 32.8 and 28.9 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. Our results indicate that N dry deposition has been a major part of total N deposition (80.6% on average) in the semi-arid region. Such high N deposition implied the heavy environmental pollution and an important nutrient resource in arid and semi-arid regions.