Dissolved Inorganic Nitrogen Changes in Upper Reaches of Daling River in China

Data from 3 monitoring stations in the upper reaches of the Daling River from 1985 to 2007 reveal an obvious increasing trend in the concentrations of NH₄-N, NO₂-N and NO₃-N. The average annual concentrations of NH₄-N, NO₂-N and NO₃-N increased from 0.69 mgL^-1, 0.006mgL^-1, 1.14 mgL^-1 in 1985 to 3.01 mgL^-1, 0.210 mgL^-1, 6.57 mgL^-1 in 2007. The highest concentrations of NH₄-N, NO₂-N and NO₃-N during past 20 years were found in the Habaqi station, being 18.00mgL^-1, 3.230mgL^-1, 16.30mgL^-1. The highest concentrations of NH₄-N, NO₂-N and NO₃-N of each station occurred mostly in dry season. With the increasing flow in the upper reaches of the Daling River, the concentrations of NH₄-N, NO₂-N and NO₃-N decreased except NH₄-N and NO₂-N increased in the Chaoyang station.