scholarly journals Source and flux of POC in a karstic area in the Changjiang River watershed: impacts of reservoirs and extreme drought

2016 ◽  
Vol 13 (12) ◽  
pp. 3687-3699 ◽  
Author(s):  
Hongbing Ji ◽  
Cai Li ◽  
Huaijian Ding ◽  
Yang Gao
Keyword(s):  
Organic Carbon ◽  
Surface Sediments ◽  
Nitrogen Isotopes ◽  
Suspended Sediments ◽  
Extreme Drought ◽  
Changjiang River ◽  
Carbonate Minerals ◽  
The Changjiang River ◽  
Wujiang River ◽  
Tightly Coupled

Abstract. Isotopes of carbon (C) and nitrogen (N) along with C / N ratios of particulate organic carbon (POC) were used to identify source and transformation of organic carbon in the suspended and surface sediments in a typical karstic watershed (the Wujiang River, an important tributary of the Changjiang River). Isotope data for suspended sediments indicate that POC was mainly derived from phytoplankton and C3-dominated soil with an increased contribution of phytoplankton in sites directly affected by the reservoir. In contrast, the POC in surface sediments was mainly derived from C3- and C4-dominated soil with little reservoir influence. The positive correlations of carbon and nitrogen isotopes between suspended and surface sediments indicated that these two carbon pools are tightly coupled. Our conservative estimation suggests that 1.17  ×  1010 g of POC is transported to the Three Gorges Reservoir during the study period in 2013. POC yield in the Wujiang River (0.13 t km−2 yr−1) is much lower than those of large rivers with a high abundance of carbonate minerals. Based on the distribution pattern of POC yield, it is inferred that carbonate minerals (lithology) do not contribute significantly to the riverine POC. The cascade of reservoirs and extreme drought had a significant influence on the POC flux in the Wujiang River.

scholarly journals Source and flux of POC in a karstic area in the Changjiang River watershed: impacts of reservoirs and extreme drought

2016 ◽  
Author(s):  
Hongbing Ji ◽  
Cai Li ◽  
Huaijian Ding ◽  
Yang Gao
Keyword(s):  
Organic Carbon ◽  
Surface Sediments ◽  
Nitrogen Isotopes ◽  
Distribution Patterns ◽  
Extreme Drought ◽  
Changjiang River ◽  
Carbon And Nitrogen ◽  
The Changjiang River ◽  
Wujiang River ◽  
Tightly Coupled

Abstract. Isotopes of carbon and nitrogen along with C / N ratios of particulate organic carbon (POC) were used to identify source and transformation of organic carbon in the suspended and surface sediments in a typical karstic watershed (Wujiang River, an important tributary of the Changjiang River). Isotopic values indicated that POC was mainly derived from C3-dominated soil with increased contribution of phytoplankton in sites directly affected by reservoir. In contrast, the POC in surface sediments was mainly derived from C3- and C4-dominated soil with little reservoir influence. The positive correlations of carbon and nitrogen isotopes between suspended and surface sediments indicated that these two carbon pools were tightly coupled. On basis of the conservative estimation, POC transported 1.17×1010 g to the Three Gorges Reservoir in 2013. POC yield in Wujiang River (0.13 t km−2 yr−1) was much lower than large rivers with high carbonate percentage. Based on the carbonate distribution patterns of POC yield, percentage of carbonate area might not be a significant factor of riverine POC transport. The cascade of reservoir and extreme drought had significant influence on the POC flux in Wujiang River.

scholarly journals The large variation in organic carbon consumption in spring in the East China Sea

2013 ◽  
Vol 10 (5) ◽  
pp. 2931-2943 ◽  
Author(s):  
C.-C. Chen ◽  
G.-C. Gong ◽  
F.-K. Shiah ◽  
W.-C. Chou ◽  
C.-C. Hung
Keyword(s):  
Low Temperature ◽  
Organic Carbon ◽  
East China Sea ◽  
Phytoplankton Growth ◽  
East China ◽  
Changjiang River ◽  
Carbon Consumption ◽  
The East China Sea ◽  
China Sea ◽  
The Changjiang River

Abstract. A tremendous amount of organic carbon respired by plankton communities has been found in summer in the East China Sea (ECS), and this rate has been significantly correlated with fluvial discharge from the Changjiang River. However, respiration data has rarely been collected in other seasons. To evaluate and reveal the potential controlling mechanism of organic carbon consumption in spring in the ECS, two cruises covering almost the entire ECS shelf were conducted in the spring of 2009 and 2010. These results showed that although the fluvial discharge rates were comparable to the high riverine flow in summer, the plankton community respiration (CR) varied widely between the two springs. In 2009, the level of CR was double that of 2010, with mean (± SD) values of 111.7 (±76.3) and 50.7 (±62.9) mg C m−3 d−1, respectively. The CR was positively correlated with concentrations of particulate organic carbon and/or chlorophyll a (Chl a) in 2009 (all p < 0.01). These results suggest that the high CR rate in 2009 can be attributed to high planktonic biomasses. During this period, phytoplankton growth flourished due to allochthonous nutrients discharged from the Changjiang River. Furthermore, higher phytoplankton growth led to the absorption of an enormous amount of fugacity of CO2 (fCO2) in the surface waters, even with a significant amount of inorganic carbon regenerated via CR. In 2010, even more riverine runoff nutrients were measured in the ECS than in 2009. Surprisingly, the growth of phytoplankton in 2010 was not stimulated by enriched nutrients, and its growth was likely limited by low water temperature and/or low light intensity. Low temperature might also suppress planktonic metabolism, which could explain why the CR was lower in 2010. During this period, lower surface water fCO2 may have been driven mainly by physical process(es). To conclude, these results indicate that high organic carbon consumption (i.e. CR) in the spring of 2009 could be attributed to high planktonic biomasses, and the lower CR rate during the cold spring of 2010 might be likely limited by low temperature in the ECS. This further suggests that the high inter-annual variability of organic carbon consumption needs to be kept in mind when budgeting the annual carbon balance.

Variation of dissolved organic carbon transported by two Chinese rivers: The Changjiang River and Yellow River

2015 ◽  
Vol 100 (1) ◽  
pp. 60-69 ◽  
Author(s):  
Dong Liu ◽  
Delu Pan ◽  
Yan Bai ◽  
Xianqiang He ◽  
Difeng Wang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Yellow River ◽  
Changjiang River ◽  
The Changjiang River

scholarly journals The large variation in organic carbon consumption in spring in the East China Sea

2012 ◽  
Vol 9 (11) ◽  
pp. 16533-16564
Author(s):  
C.-C. Chen ◽  
G.-C. Gong ◽  
F.-K. Shiah ◽  
W.-C. Chou ◽  
C.-C. Hung
Keyword(s):  
Organic Carbon ◽  
East China Sea ◽  
Phytoplankton Growth ◽  
East China ◽  
Community Respiration ◽  
Changjiang River ◽  
Carbon Consumption ◽  
The East China Sea ◽  
China Sea ◽  
The Changjiang River

Abstract. A tremendous amount of organic carbon respired by planktonic communities has been found in summer in the East China Sea (ECS), and this rate has been significantly correlated with fluvial discharge from the Changjiang River. However, data related to this issue in other seasons have rarely been collected. To evaluate and reveal the potential controlling mechanism of organic carbon consumption in spring in the ECS, research using stations covering almost the entire ECS shelf was conducted in the spring of 2009 and 2010. During both periods, the fluvial discharges were similar, and these rates were comparable to high riverine flow in summer. Interestingly, planktonic community respiration (CR) varied widely in both springs; in 2009, the level of CR was double that of 2010, with mean (± SD) values of 111.7 (± 76.3) and 50.7 (± 62.9) mg C m−3 d−1, respectively. The CR was positively linearly regressed with concentrations of particulate organic carbon and/or chlorophyll a (Chl a) in 2009 (all p< 0.01). These results suggest that the rate was dependent on planktonic activities, especially that of phytoplankton, in 2009. During this period, phytoplankton growth flourished due to allochthonous nutrients discharged from the Changjiang River. Furthermore, higher phytoplankton growth leaded to the absorption of an enormous amount of fugacity of CO2 (fCO2) in the surface waters, even with a significant amount of inorganic carbon regenerated via CR. In 2010, there were even more riverine runoff nutrients into the ECS than in 2009. Surprisingly, the growth of phytoplankton in 2010 was not stimulated by enriched nutrients, and its growth was likely limited by low water temperature and/or low light intensity. Low temperature might also suppress planktonic metabolism, and this could explain why the CR was lower in 2010. During this period, lower surface water fCO2 might have mainly been driven by physical process(es). To conclude, these results indicate that organic carbon consumption (i.e. CR) in the ECS in spring might be controlled by the magnitude of planktonic activities and physical factor (e.g. temperature), and that the latter is especially important during a cold spring season. This further suggests that the high intraseasonal variability of organic carbon consumption needs to be kept in mind when budgeting the annual carbon balance.

Sign in / Sign up

Export Citation Format

Share Document