An evaluation of atmospheric Nr pollution and deposition in North China after the Beijing Olympics

Abstract

North China is known for its large population densities and rapid development of industry and agriculture. Air quality around Beijing improved substantially during the 2008 Summer Olympics. We measured atmospheric concentrations of various Nr compounds at three urban sites and three rural sites in North China from 2010 to 2012 and estimated N dry and wet deposition by inferential models and the rain gauge method to determine current air conditions with respect to reactive nitrogen (Nr) compounds and nitrogen (N) deposition in Beijing and the surrounding area. NH3, NO2, and HNO3 and particulate NH4+ and NO3−, and NH4+–N and NO3−–N in precipitation averaged 8.2, 11.5, 1.6, 8.2 and 4.6 μg N m−3, and 2.9 and 1.9 mg N L−1, respectively, with large seasonal and spatial variability. Atmospheric Nr (especially oxidized N) concentrations were highest at urban sites. Dry deposition of Nr ranged from 35.2 to 60.0 kg N ha−1 yr−1, with wet deposition of Nr of 16.3 to 43.2 kg N ha−1 yr−1 and total deposition of 54.4–103.2 kg N ha−1 yr−1. The rates of Nr dry and wet deposition were 36.4 and 33.2% higher, respectively, at the urban sites than at the rural sites. These high levels reflect the occurrence of a wide range of Nr pollution in North China and suggest that further strict air pollution control measures are required.