δ¹³C tracing of dissolved inorganic carbon sources in Patagonian rivers (Argentina)

Abstract

Abstract: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 υ 13 C isotopic signature. The υ 13 C DIC values vary between 12Ð8 and 1Ð8‰ 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, υ 13 C DIC is mainly controlled by important exchanges between the river waters and atmospheric CO 2 , due to the presence of lakes and dams. For the second group, υ 13 C DIC also appears to be controlled by the oxidation of organic carbon, showing a negative relationship between υ 13 C DIC 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 υ 13 C DIC alone to distinguish these contributions. The annual DIC flux exported by Patagonian Rivers to the South Atlantic Ocean averages 621 ð 10 9 g. of C, i.e. a specific yield of 2Ð7 g m 2 year 1 . The mean υ 13 C DIC can be estimated to 4Ð9‰, which is high compared with other rivers of the world.

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

“…TA originates from atmospheric CO 2 through the weathering of carbonates, silicates and other rocks (Meybeck, 1987;Amiotte-Suchet et al, 2003;Cai et al, 2008). The stable isotope composition of DIC (d 13 C-DIC) is controlled by both the signature of the carbon sources and the in-stream fractionating processes that change the d 13 C signature downstream (Brunet et al, 2005;Doctor et al, 2008;Polsenaere and Abril, 2012). On the one hand, oxidation of terrestrial organic matter liberates DIC with a quite negative d 13 C signal, close to that of the dominating plants and soils in the watershed, i.e., between À22 and À34‰ for C 3 plants and À12 to À16‰ for C 4 plants (O'Leary, 1988;Vogel et al, 1993;Diefendorf et al, 2010;Kohn, 2010).…”

Spatial Pattern and Habitat Requirements of Galaxias maculatus in the Last Un-Interrupted Large River of Patagonia: A Baseline for Management

“…The Santa Cruz River (50°S; 70°W) originates in two oligotrophic to ultra-oligotrophic large glacial lakes, Viedma and Argentino, and flows uninterrupted for 382 km across the Patagonian plateau to drain into the Atlantic Ocean (Figure 1; Brunet et al, 2005). The river has an average discharge of 691 m 3 s -1 (min.…”

Sources and Dynamics of Dissolved Inorganic Carbon, Nitrogen, and Phosphorus in a Large Agricultural River Basin in Arid Northwestern China

“…Dissolved inorganic carbon (DIC) is the most abundant carbon pool in many inland waterways and aquifers, being actively incorporated into aquatic food webs and playing an important part in regulating carbon fluxes between terrestrial, aquatic, and atmospheric reservoirs [1,2]. Inorganic N and P are important regulators of water and ecosystem integrity, controlling biomass abundance and biological community structures of aquatic environments [3].…”

“…Inorganic N and P are important regulators of water and ecosystem integrity, controlling biomass abundance and biological community structures of aquatic environments [3]. Establishing a thorough understanding of nutrient fluxes linking terrestrial and aquatic systems is particularly important in large arid basins, where scarce water resources require managers to balance the needs of agricultural use versus ecosystem conservation [2,4,5]. To date, most studies on this topic have been conducted in small, humid watersheds [2,[6][7][8].…”

“…Establishing a thorough understanding of nutrient fluxes linking terrestrial and aquatic systems is particularly important in large arid basins, where scarce water resources require managers to balance the needs of agricultural use versus ecosystem conservation [2,4,5]. To date, most studies on this topic have been conducted in small, humid watersheds [2,[6][7][8]. Fewer studies were performed in large agricultural basins where fertilizer use and irrigation have substantial impacts on watershed-scale nutrient dynamics [1,2,5,9].…”