Wet atmospheric deposition of nitrogen: 20 years measurement in Shenzhen City, China.

We presented measurements of wet deposition of NH(4)(+)-N and NO(3)(-)-N from 1986 to 2006 in Shenzhen City, China. Over the past 20 years, NO(3)(-)-N concentration had significantly increased, but a reverse trend was found for NH(4)(+)-N. The main form of total inorganic nitrogen (TIN) was NH(4)(+)-N and the average NH(4)(+)-N/NO(3)(-)-N ratio was 1.57 in this area. The contribution of NO(3)(-)-N to TIN increased from 28-42% in the period of 1986-2000 to 50-63% during 2001-2006. The increased deposition flux of NO(3)(-)-N resulted in the increasing trend of TIN, although NH(4)(+)-N showed a decreasing trend over time. Average deposition flux of TIN during 1986-2006 was 13.24 kg/ha/year, with a minimum value of 6.03kg/ha/year in 1988 and a maximum value of 20.52 kg/ha/year in 1997. Wet deposition fluxes of N appeared to vary with season, 81% occurred in the warm season (from April to September). The wet deposition of TIN to the Shenzhen Reservoir reached 8,902 kg in 2006, which contributed 9.95% of the total nonpoint pollution to the reservoir and will be increased in the future.