Study Of Atmospheric Wet Deposition Of Nitrogen In Tibetan Plateau

Atmospheric nitrogen (N) deposition, as both a component of acid deposition and a nutrient source, is of increasing interest. Most research on N deposition mainly focuses on sensitive natural ecosystems such as forests and in developed countries. Information on N deposition in important ecosystems such as the Qinghai-Tibet Plateau is scarce. Although we might expect less impact from anthropogenic deposition compared with other regions of China, the ecological environment there is fragile. A study of atmospheric N input in this region would not only indicate N deposition in remote areas of high altitude, but also provide a scientific basis for understanding the N cycle in such natural ecosystems.A monitoring network was established to determine the spatial and temporal variation of atmospheric N deposition in the Tibetan Plateau over a 3-year period. The network included 4 monitoring sites: one in Shannan Area, one in Linzhi Area one in Changdu and one in one in Naqu Area,Except one monitoring site in Academy of Agro- Animal Husbandry,all the other 3 sites were located in County Town. Automatic Wet-only Sampler (APS- 1II, Wuhan Tianhong Inc)was installed at 4 sites, for the collection of wet deposition(the sampler opens only when rainfall happens).Rairnvater was collected,thoroughly mixed and stored in plastic bottles irnrnediately after each rain event, then was frozen in a refrigerator until analysis bya Continuous flow Analyzer (TRACC2000, Germany) within three months. Rain gauges and the wet-only sampler were,leaned bydeionized water just after collection.The research was carried out at the Ecology Research Institute in Tibet.Rain and snow samples were collected and analysed and N concentration and deposition calculated for 2005 and 2007. Annual wet deposition of TN averaged 5.54 kg hm-2 a-1, TIN averaged 2.27 kg hm-2 a-1, TON averaged 3.27 kg hm-2 a-1. Volume-weighted concentrations of NH4+-N,NO3--N,TIN,TON,TN were 0.238 mg L-1,0.070 mg L-1, 0.308 mg L-1, 0.603 mg L-1, 0.911 mg L-1. respectively, and varied throughout the year. The range of NH4+-N/ NO3--N is 0.75 ~ 3.86,averaged 1.68,TIN / TON is 0.53 ~ 1.75,averaged 0.70。Higher values of N concentration in rain were found in winter and summer, while lower values were found in autumn and Higher values of N deposition in rain were found in spring and summer,while lower values were found in winter. the NH4+-N,NO3--N,TIN,TON,TN deposition significantly increased with the increased precipitation (p<0.01), and N concentrations significantly decreased with precipitation, fitting a power equation (p<0.05). N deposition was highest in wet season; the lowest value was found in dry season (only 12.90% of total annual deposition). NH4+-N was the dominant species in TIN wet deposition, comprising 68 % of total wet inorganic N deposition, TON was the dominant species in TN wet deposition, comprising 60 % of total wet N deposition. Statistic analysis showed that only NO3--N concentration in wet deposition was significant differences in diffenrence month and NH4+-N,NO3--N concentration in wet deposition was significant differences in diffenrence season;the different N deposition were significant differences of month 12,1 and 5 ~ 8,deposition significantly precipitation (p<0.01)in winter and summer The effect factors of Wet Deposition of Nitrogen in Tibetan Plateau is NH4+-N,TIN,TN>Rainfall>TON >NO3--N。...