[Change and Influencing Factors of Dissolved Carbon and Dissolved Nitrogen in Water of the Three Gorges Reservoir].

In order to understand the changes of dissolved carbon and dissolved nitrogen in the water of Three Gorges Reservoir,this research was carried out once a week by the bank of Yangtze River in Fuling beach from March 2011 to August 2012,and the variation characteristics of dissolved C,N composition and their source were analyzed.The results showed that the concentration of DOC ranged from 0.64 mg·L ^-1 to 9.07 mg·L ^-1 ,and had obvious seasonal change:summer >spring and autumn >winter.Annual total input of DOC was 1.78×10 ⁹ kg,the seasonal change trend of the total input of DOC was similar to that of the concentration of DOC;The concentration of DTN ranged from 2.59 mg·L ^-1 to 4.35 mg·L ^-1 :spring >winter >summer >autumn,annual total input was 1.32×10 ⁹ kg,the seasonal input changed in the order of summer >autumn >spring >winter,among them DON,NO ₃ ^- -N accounted for 30.35%-63.45% and 35.87%-67.72%,respectively.DOC was affected by precipitation and air temperature,and mainly came from the exogenous input,in the spring and summer its exogenous input increased with the increase of rainfall runoff,but in the autumn and winter the endogenous contribution increased;DTN was relatively affected by human emissions and water dilution.Correlation analysis showed that there was a significant negative correlation between DOC and DON ( P <0.05),DOC/DON ratio usually reflects the source of the DOM,the DOC/DON in the water of three gorges reservoir ranged from 0.35 to 7.28,the source of DOM had obvious seasonal characteristics.DOC/DON was the highest in summer,and the DOM mainly came from watershed erosion;DOC/DON was the lowest in winter,and the DOM mainly came from living sewage and endogenous field;the DOC/DON ratios in spring and autumn were higher than those in winter and lower than those in summer,and the DOM sources included watershed erosion,living sewage and endogenous field.