Stable carbon isotopes in dissolved inorganic carbon: extraction and implications for quantifying the contributions from silicate and carbonate weathering in the Krishna River system during peak discharge |
| |
Authors: | Amzad H. Laskar Naveen Gandhi Kaustubh Thirumalai Madhusudan G. Yadava Rengaswamy Ramesh Ramakant R. Mahajan |
| |
Affiliation: | 1. Geosciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad, Gujarat, India;2. Research Centre for Environmental Changes, Academia Sinica, Nankang Taipei, Taiwan;3. Indian Institute of Tropical Meteorology, Pune, India;4. Institute for Geophysics, Jackson School of Geosciences, University of Texas, Austin, TX, USA;5. Department of Geological Sciences, Jackson School of Geosciences, University of Texas, Austin, TX, USA |
| |
Abstract: | We present a comparative study of two offline methods, a newly developed method and an existing one, for the measurement of the stable carbon isotopic composition (δ13C) of dissolved inorganic carbon (DIC; δ13CDIC) in natural waters. The measured δ13CDIC values of different water samples, prepared from laboratory Na2CO3, ground and oceanic waters, and a laboratory carbonate isotope standard, are found to be accurate and reproducible to within 0.5 ‰ (1σ). The extraction of CO2 from water samples by these methods does not require pre-treatment or sample poisoning and can be applied to a variety of natural waters to address carbon cycling in the hydrosphere. In addition, we present a simple method (based on a two-end-member mixing model) to estimate the silicate-weathering contribution to DIC in a river system by using the concentration of DIC and its δ13C. This approach is tested with data from the Krishna River system as a case study, thereby quantifying the contribution of silicate and carbonate weathering to DIC, particularly during peak discharge. |
| |
Keywords: | carbon-13 carbonate weathering dissolved inorganic carbon isotope measurements methods and equipment Krishna River mass spectrometry peak discharge |
|
|