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 NH
₄
-N, NO
₂
-N and NO
₃
-N. The average annual concentrations of NH
₄
-N, NO
₂
-N and NO
₃
-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 NH
₄
-N, NO
₂
-N and NO
₃
-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 NH
₄
-N, NO
₂
-N and NO
₃
-N of each station occurred mostly in dry season. With the increasing flow in the upper reaches of the Daling River, the concentrations of NH
₄
-N, NO
₂
-N and NO
₃
-N decreased except NH
₄
-N and NO
₂
-N increased in the Chaoyang station.