Attention to atmospheric N deposition, as a nutrient resource and as a part of acid deposition, is increasing with the acceleration of global N cycling. However, the information on atmospheric N deposition, especially the spatial and temporal variation of N deposition in the intensive agroecosystems within the North China Plain, is still scarce. Therefore, it is essential to determine the budgets and spatial and temporal variation of atmospheric N deposition in North China Plain in terms of the requirement of integrated N management and the assessment of N deposition effect on surrounding ecosystems.
A monitoring network was established to determine the spatial and temporal variation of atmospheric N deposition in the North China Plain over a 2-year period. The network included 9 monitoring sites: seven in Beijing city, one in Shandong province and one in Hebei province. Except one urban monitoring site in Beijing Academy of Agro-Forestry Sciences (BAAFS), all the other 8 sites were located at typical field areas. Rain gauges (diameter 20 cm, height 80 cm) were installed in all the nine sites for the collection of bulk deposition, and an Automatic Wet-only Sampler (APS-Ⅲ, Wuhan Tianhong Inc.) was installed at Dongbeiwang site, Beijing, for the collection of wet deposition (the sampler opens only when rainfall happens). Rainwater was collected, thoroughly mixed and stored in plastic bottles immediately after each rain event, then was frozen in a refrigerator until analysis by a Continuous Flow Analyzer (TRACC2000, Germany) within three months. Rain gauges and the wet-only sampler were cleaned by deionized water just af ter collection. 
Annual bulk deposition of inorganic N in the North China Plain ranged from 19.2to 38.5 kg/hm^２ and averaged 28.0 kg/hm^２. Concentration of NH^＋_４-N and NO－³-N in rainwater averaged 3.76 and 1.85 mg/L, which were significantly higher than the values in background sites of China. Annual bulk deposition of inorganic N in the Beijing area was as high as 32.5 kg/hm２, while lower annual N deposition of 23.6 kg/hm２ was found in Shandong and Hebei provinces. Bulk deposition of inorganic N showed distinguished monthly variation due to monthly change of precipitation, and 60% of bulk deposition occurred from June to September. Bulk deposition of NH^＋_４-N was 2.0 times of NO^－₃-N deposition in rural monitoring sites. However, the situation was reversed in an urban monitoring site (BAAFS). The results suggest that reduced N in precipitation is dominant in rural region but oxidized N is the major form in urban region. Furthermore, the positive relationship between inorganic N deposition and precipitation can be fitted well by a power equation (r２＝0.67), showing the increase of NH^＋_４-N and NO^－₃-N inputs with increased precipitation. Wet deposition of N accounted for 73% of the corresponding bulk deposition, implying that dry deposition of N particular NH^＋_４-N input from dust is important in the North China Plain.