| Water samples along water column in the front of dams and samples at 0.5 m below surface water from tributary rivers were collected in July and October, 2007. The water chemistry, concentrations of dissolve inorganic carbon and its carbon isotopic compositions were determined, in order to investigate the geochemical behavior of carbon in the Maotiao River. This study aimed to understand the variations of the concentrations of dissolved inorganic carbon(DIC) and δ13CDIC during its transport along the cascade reservoirs and river system. The results showed that DIC concentrations in summer were lower than that in autumn. In summer, the DIC concentrations were 1.35-2.84 mmol/L, with an average value of 2.12 mmol/L; and in autumn they fell into 2.03-3.98 mmol/L, with an average value of 2.67 mmol/L. The δ13CDIC in surface water along Maotiao River ranged from -10.3‰ to -5.1‰ in summer, with a value of -8.6‰ in average, and in autumn, δ13CDIC became more negative, and had a range from -13.0‰ to -6.9‰, with an average value of -9.0‰. Generally, DIC in surface water showed a trend to decrease from the upper reaches to lower reaches along Maotiao River, and δ13CDIC gradually became more negative downstream. On the water column, DIC concentrations were higher in hypolimnion, while δ13CDIC had a reverse trend with higher values occurred in epilimnion. The results indicated that the hydrochemistry of river could be significantly changed by river damming processes. As for carbon, reservoir should be an important place for the transformation among the different carbon species. |
