A 20-Year Observation (1991-2009) Of Wet Nitrogen (N) Deposition In Megacity Shanghai

We present measurements of wet deposition of inorganic N (AIN, including NO3- -N and NO4+ -N) in Shanghai over the period 1991-2009. These data series are obtained from the Shanghai Weather monitoring network which consists of nine monitoring stations which are homogeneously spread over the Shanghai. These long-term measurements allow for a trend analysis over this period, which are to a large extent not influenced by the year to year variations in meteorological circumstances. The wet deposition flux of NO3- -N and NO4+ -N increased from 1991 to 1998, and then decreased from 1999 to 2009. Average annual wet N deposition fluxes appeared to vary with season, 40% occurred in the hot season (from June to August), and exhibited a good correlation with the precipitation depth. Wet N deposition in precipitation can provide a useful dataset to assess atmospheric environment and its impacts on ecosystem in Shanghai.