d13C tracing of dissolved inorganic carbon sources in Patagonian Rivers (Argentina)

VF. BRUNET, D. GAIERO, J. L. PROBST, P. J. DEPETRIS, F. GAUTHIER LAFAYE AND P. STILLE

HYDROLOGICAL PROCESSES

John Wiley and Sons, Ltd.

Lugar: Chichester; Año: 2005 vol. 19 p. 3321 - 3344

0885-6087

The main Patagonian rivers (Colorado, Negro, Chubut, Deseado, Coyle, Chico, Santa Cruz and Gallegos) were sampled between September 1995 and November 1998 to determine their chemical and isotopic compositions, the origins of the suspended and dissolved river loads and their inputs to the South Atlantic Ocean. This paper focuses on the dissolved inorganic carbon (DIC) transport and its ¥ô13C isotopic signature. The ¥ô13CDIC values vary between 12¨¢8 and 1¨¢8¢¶ and allow one to distinguish two river groups: (i) the Colorado, Negro, Chubut and Santa Cruz, which display the highest values and the lowest seasonal variations; (ii) the Deseado, Coyle, Chico and Gallegos, which show the lowest values and the highest seasonal variations. For the first group, ¥ô13CDIC is mainly controlled by important exchanges between the river waters and atmospheric CO2, due to the presence of lakes and dams. For the second group, ¥ô13CDIC¥ô13C isotopic signature. The ¥ô13CDIC values vary between 12¨¢8 and 1¨¢8¢¶ and allow one to distinguish two river groups: (i) the Colorado, Negro, Chubut and Santa Cruz, which display the highest values and the lowest seasonal variations; (ii) the Deseado, Coyle, Chico and Gallegos, which show the lowest values and the highest seasonal variations. For the first group, ¥ô13CDIC is mainly controlled by important exchanges between the river waters and atmospheric CO2, due to the presence of lakes and dams. For the second group, ¥ô13CDIC¥ô13CDIC is mainly controlled by important exchanges between the river waters and atmospheric CO2, due to the presence of lakes and dams. For the second group, ¥ô13CDIC2, due to the presence of lakes and dams. For the second group, ¥ô13CDIC also appears to be controlled by the oxidation of organic carbon, showing a negative relationship between ¥ô13CDIC and the dissolved organic carbon. These biogeochemical processes interfere with the contribution of carbonate and silicate weathering to the riverine DIC and do not allow use of ¥ô13CDIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ©£ 109 g. of C, i.e. a specific yield of 2¨¢7¥ô13CDIC and the dissolved organic carbon. These biogeochemical processes interfere with the contribution of carbonate and silicate weathering to the riverine DIC and do not allow use of ¥ô13CDIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ©£ 109 g. of C, i.e. a specific yield of 2¨¢7¥ô13CDIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ©£ 109 g. of C, i.e. a specific yield of 2¨¢7©£ 109 g. of C, i.e. a specific yield of 2¨¢7¨¢7