Three cascade reservoirs,built in different periods of time in the Wujiang drainage basin,were inves-tigated in this study.Samples were taken at the surface and also at 20,40,60,80 m depths in front of the dams in Apr...Three cascade reservoirs,built in different periods of time in the Wujiang drainage basin,were inves-tigated in this study.Samples were taken at the surface and also at 20,40,60,80 m depths in front of the dams in April,July,October of 2006 and January of 2007.Chemical parameters were calculated and the concentrations of dissolved inorganic carbon DIC and its isotopic composition(δ13CDIC) were de-termined.In surface waters,the δ13CDIC values are high in summer and autumn and low in winter and spring,while the DIC concentrations are relatively low in summer and autumn and relatively high in winter and spring.In the water column,the DIC concentrations increase while δ13CDIC values decrease with water depth.DIC in various reservoirs is significantly different in isotopic composition from that in natural rivers,but is close to that in natural lakes.In addition,in surface waters,the δ13CDIC values tend to become lower whereas the nutrition level tends to become higher with increasing age of the reser-voirs.The conclusion is that after dam blocking,changes took place in the hydrochemical properties of river water,and the impounding rivers developed toward lakes and swamps.In addition,differentiation in DIC isotopic composition may be used to some extent to trace the evolution process of a reservoir.展开更多
To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon(DIC)in the Wujiang River basin,field measurements and samples were collected semimonthly for a year.The surface waters of th...To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon(DIC)in the Wujiang River basin,field measurements and samples were collected semimonthly for a year.The surface waters of the reservoirs contained concentrations of chlorophyll a up to 5.6 times higher than the upstream river.Compared with the entering waters,the contributions of HCO3-and dissolved CO2to DIC decreased,and the contribution of CO32-to DIC and the carbon isotopic composition of DIC(d13CDIC)increased in the surface waters of the reservoirs,while in the waters released,the DIC species showed reverse geochemical behaviors.The d13CDICranged from-10.2%to 2.5%,indicating that significant contributions were from carbonate weathering,photosynthesis,and respiration.After the damming of a river,the bioactivity of phytoplankton was enhanced,and this affected the geochemistry of DIC compared to an unimpacted river and d13CDICcan be used to discern these changes.High-frequency monitoring of river-reservoir systems is necessary to evaluate the efflux of CO2and provide a better understanding of the carbon sinks and sources in the impounded river.展开更多
基金the Ministry of Science and Technology of China (Grant No. 2006CB403205)the National Natural Science Foundation of China (Grant Nos. 90610037, 40571158 and 40721002)
文摘Three cascade reservoirs,built in different periods of time in the Wujiang drainage basin,were inves-tigated in this study.Samples were taken at the surface and also at 20,40,60,80 m depths in front of the dams in April,July,October of 2006 and January of 2007.Chemical parameters were calculated and the concentrations of dissolved inorganic carbon DIC and its isotopic composition(δ13CDIC) were de-termined.In surface waters,the δ13CDIC values are high in summer and autumn and low in winter and spring,while the DIC concentrations are relatively low in summer and autumn and relatively high in winter and spring.In the water column,the DIC concentrations increase while δ13CDIC values decrease with water depth.DIC in various reservoirs is significantly different in isotopic composition from that in natural rivers,but is close to that in natural lakes.In addition,in surface waters,the δ13CDIC values tend to become lower whereas the nutrition level tends to become higher with increasing age of the reser-voirs.The conclusion is that after dam blocking,changes took place in the hydrochemical properties of river water,and the impounding rivers developed toward lakes and swamps.In addition,differentiation in DIC isotopic composition may be used to some extent to trace the evolution process of a reservoir.
基金supported by the National Basic Research Program of China (2013CB956703)the National Natural Science Foundation of China (41021062)
文摘To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon(DIC)in the Wujiang River basin,field measurements and samples were collected semimonthly for a year.The surface waters of the reservoirs contained concentrations of chlorophyll a up to 5.6 times higher than the upstream river.Compared with the entering waters,the contributions of HCO3-and dissolved CO2to DIC decreased,and the contribution of CO32-to DIC and the carbon isotopic composition of DIC(d13CDIC)increased in the surface waters of the reservoirs,while in the waters released,the DIC species showed reverse geochemical behaviors.The d13CDICranged from-10.2%to 2.5%,indicating that significant contributions were from carbonate weathering,photosynthesis,and respiration.After the damming of a river,the bioactivity of phytoplankton was enhanced,and this affected the geochemistry of DIC compared to an unimpacted river and d13CDICcan be used to discern these changes.High-frequency monitoring of river-reservoir systems is necessary to evaluate the efflux of CO2and provide a better understanding of the carbon sinks and sources in the impounded river.
