Earth Science Frontiers ›› 2011, Vol. 18 ›› Issue (6): 161-168.

• Article • Previous Articles     Next Articles

Seasonal variation in the flux and isotopic composition of particulate
 organic carbon along the mainstream of the Changjiang River.

  

  1. 1. Institute of Surficial Geochemistry, Department of Earth Sciences, Nanjing University, Nanjing 210093, China
    2. State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210093， China
    3. China Institute for GeoEnvironmental Monitoring, Beijing 100081, China
    4. College of Environmental Science and Engineering, Hohai University, Nanjing 210098, China
    5. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2011-10-07 Revised:2011-10-20 Online:2011-11-25 Published:2011-12-05

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Abstract:

Suspended particulate matter (SPM) samples were collected along the Changjiang mainstream in summer and winter 2007 to investigate the distribution of organic particulate organic carbon (POC) concentrations and the stable isotopic composition of POC (δ13C) within the river system. The results indicate that the POC% has a range from 0.4% to 1.3% in summer and 0.7% to 2.2% in winter. The mean δ13C values of the POC in winter and summer are -24.74‰，-24.83‰, respectively. The C/N ratio has no significant seasonal variability. The δ13C values of upper reaches are higher than the values of the middle and lower reaches in winter (low flow season). The relative decrease in δ13C values during the low flow season from the upper to lower reaches could be interpreted as the result of an increase in the soil erosion rate and channel erosion in the middle and lower reaches after dam construction, except for flood events during which rivers are also strongly influenced by relative more contribution of phytoplankton from the middle and lower reaches. We got a total organic carbon flux of 1.46 Mt/a after impoundment of the Three Gorges Dam which could have caused a sharp reduction in sediment load of the Changjiang River.

Key words: Changjiang River, organic carbon isotope, seasonal variations, Three Gorges Dam

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