Temporal distribution of nitrogen in precipitation in agricultural zone, Pudong, Shanghai

In order to investigate change in nitrogen concentration in precipitation in the agricultural zone of Pudong Shanghai its law and affecting factors and N deposition flux rains were sampled monthly over a year 2008 for analysis of nitrate NO₃ ^--N and ammonia nitrogen NH₄⁺-N concentrations. Results show that nitrogen concentration in rain water and annual N deposition flux were both quite high in the zone with the mean concentration of NO₃^--N being 0. 44 mg L^-1 and of NH₄⁺-N being 1.36 mg L^-1 and the annual deposition flux of NO₃^--N being 5. 19 kg hm^-2 a^-1 and of NH₄⁺-N being 15.91 kg hm^-2 a^-1 making the annual deposition flux of TN up to 21. 10 kg hm^-2 a^-1 of which NH₄⁺N accounted for 75. 4%. The concentrations of NO₃^--N and NH₄⁺-N in rain water were lower in the main growing season April- October than in the main non-growing season November- March. However in terms of deposition flux NH₄⁺-N was higher in the former than in the latter while NO₃^--N did not differ much between the two which was attributed to the comprehensive effect of human activities number of rainy days rainfall wind direction etc.. Generally speaking the nitrogen input with precipitation is of some positive significance to the primary productivity in the study zone the nitrogen concentrations in rainfall have exceeded the threshold value of water eutrophication which may intensify eutrophication of the aquatic systems in the zone.