Isotopic composition of dissolved boron and its geochemical behavior in a freshwater-seawater mixture at the estuary of the Changjiang （Yangtze） River

The isotopic composition of dissolved boron, in combination with the elemental concentrations of B, Cl and salinities in freshwater-seawater mixed samples taken from the estuary of the Changjiang River, the largest one in China, was investigated in detail in this study. Brackish water and seawater samples from the estuary of the Changjiang River were collected during low water season in November, 1998. Boron isotopic compositions were determined by the Cs2BO^＋2-graphite technique with a analytical uncertainty of 0.2‰ for NIST SRM 951 and an average analytical uncertainty of 0.8‰ for the samples. The isotopic compositions of boron, expressed in δ^11B, and boron concentrations in the Changjiang River at Nanjing and seawater from the open marine East Sea, China, are characterized by δ^11B values of -5.4‰ and 40.0‰, as well as 0.0272 and 4.43 mg B/L, respectively. Well-defined correlations between δ^11B values, B concentrations and Cl concentrations are interpreted in terms of binary mixing between fiver input water and East Sea seawater by a process of straightforward dilution. The offsets of δ^11B values are not related to the contents of clastic sediment and to the addition of boron. These relationships favor a conservative behavior of boron at the estuarine of the Changjiang River.

Isotopic composition of dissolved boron and its geochemical behavior in a freshwater-seawater mixture at the estuary of the Changjiang (Yangtze) River

The isotopic composition of dissolved boron, in combination with the elemental concentrations of B, Cl and salinities in freshwater-seawater mixed samples taken from the estuary of the Changjiang River, the largest one in China, was investigated in detail in this study. Brackish water and seawater samples from the estuary of the Changjiang River were collected during low water season in November, 1998. Boron isotopic compositions were determined by the Cs₂BO₂ ⁺-graphite technique with a analytical uncertainty of 0.2‰ for NIST SRM 951 and an average analytical uncertainty of 0.8‰ for the samples. The isotopic compositions of boron, expressed in δ¹¹B, and boron concentrations in the Changjiang River at Nanjing and seawater from the open marine East Sea, China, are characterized by δ¹¹B values of −5.4‰ and 40.0‰, as well as 0.0272 and 4.43 mg B/L, respectively. Well-defined correlations between δ¹¹B values, B concentrations and Cl concentrations are interpreted in terms of binary mixing between river input water and East Sea seawater by a process of straightforward dilution. The offsets of δ¹¹B values are not related to the contents of clastic sediment and to the addition of boron. These relationships favor a conservative behavior of boron at the estuarine of the Changjiang River.