Publication Date:
2011-08-26
Description:
In order to investigate the anthropogenic activity, namely land use change and reservoirs construction, affects on particulate organic carbon transport, monthly water samples were collected during September 2007-August 2009 from the Longchuanjiang to understand seasonal variations in the concentrations of organic carbon species, and their sources, and the yield of organic and inorganic carbon from the catchment in the Upper Yangtze basin. The contents of riverine particulate organic carbon (POC), total organic carbon (TOC) and total suspended sediment (TSS) changed synchronously with water discharge, while the contents of dissolved organic carbon (DOC) had a small variation. The POC concentration in the suspended sediment decreased non-linearly with increasing TSS concentration. Higher molar C/N ratio of particulate organic matter (average 77) revealed that POC was dominated by terrestrially derived organic matter in the high flows and urban wastewaters in the low flows. The TSS transported by this river was 2.7 × 10 5 t/yr in 2008. The specific fluxes of TOC and dissolved inorganic carbon (DIC) were 5.6 t/km 2 /yr and 6 t/km 2 /yr, respectively, with more than 90% in the high flow period. A high carbon yield in the catchment of the upper Yangtze was due to human-induced land use alterations and urban wastes. Consistent with most rivers in the monsoon climate regions, the DOC/POC ratio of the export flux was low (0.41). 22% (0.9 t/km 2 /yr) POC out of 4 t/km 2 /yr was from autochthonous production and 78% (3.1 t/km 2 /yr) from allochthonous production. The annual sediment load and hence the organic carbon flux, have been affected by environmental alterations of physical, chemical and hydrological conditions in the past 50 years, demonstrating the impacts of human disturbances on the global and local carbon cycling. Finally, we addressed that organic carbon flux should be reassessed using adequate samples (i.e., at least two times in low-flow month, four times in high-flow month and one time per day during the flood period), daily water discharge and sediment loads, and appropriate estimate method. Copyright © 2011 John Wiley & Sons, Ltd.
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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