Organic and inorganic carbon isotope analysis (δ13C) in aqueous solution is a key technology widely used in environmental science, hydrology, biogeochemistry, ecology, etc. It helps to reveal the source of carbon, transformation process and carbon cycle mechanism.
Alfa Chemistry relies on a complete technical platform and a professional R&D team with global experimental analysis capabilities to provide you with carbon and oxygen isotope analysis in Gases and Carbonates. We are committed to providing customers with accurate and fast analysis results and solving any research problems encountered by customers.
Organic Carbon and Inorganic Carbon
- Organic carbon: usually refers to the carbon in organisms (plants, animals, etc.) and their residues. Its presence in water bodies is usually related to biological processes such as plant photosynthesis and microbial activity.
- Inorganic carbon: generally refers to carbon dioxide (CO2), carbonates (such as HCO3⁻, CO3²⁻) dissolved in water, etc., mainly from natural processes such as rock weathering, soil respiration, and atmospheric exchange.
Carbon in Aqueous Solution
| Type | Main forms | abbreviation | Examples |
|---|
| Inorganic Carbon (DIC) | CO2, (aq), H2CO3, HCO3⁻, CO3²⁻ | Dissolved Inorganic Carbon | Carbonates in groundwater |
| Organic Carbon (DOC) | Carbon-containing organic molecules | Dissolved Organic Carbon | Humic acid, amino acids, sugars |
Isotope Analysis Objectives
- δ13C-DIC: reflects the source of inorganic carbon (such as rock weathering, atmospheric CO2, respiration, etc.).
- δ13C-DOC: reflects the source of organic matter and biological processes (such as plant exudates, microbial metabolism).
Typical δ13C Value Range
| Sources | δ13C value (‰) |
|---|
| Atmospheric CO₂ | ~ -8 |
| Terrestrial C3 plants | -26 ~ -28 |
| Terrestrial C4 plants | -12 ~ -14 |
| Rock weathering (carbonates) | 0 ~ +2 |
| Microbial respiration products | -20 ~ -30 |
| DOC (lakes/rivers) | -26 ~ -28 (Mainly derived from plant humus) |
Analytical methods
- Sampling: Water samples need to be collected from the water body, and care should be taken to avoid contamination and ensure the representativeness of the sample.
- Sample pretreatment: Organic carbon usually needs to be separated and extracted by chemical oxidation (such as using H2O2 or K2Cr2O7) or pyrolysis, while inorganic carbon can be removed by acid titration and other methods.
- Isotope ratio determination: The carbon isotope ratio in the sample is determined using mass spectrometry (such as gas chromatography-mass spectrometry, GC-MS or isotope ratio mass spectrometry, IRMS).
- Data analysis: The δ13C value of the sample is obtained by comparing it with a standard sample (such as the PDB limestone standard) to analyze its source and changes.
Application Examples
Identification of groundwater carbon sources
δ13C-DIC close to 0‰ → source is carbonate rock dissolution.
δ13C-DIC as low as -20‰ → source is soil CO2 (biological respiration).
Lake carbon cycle research
Comparison of δ13C-DOC and δ13C-DIC can reveal the mineralization degree and source of DOC.
Oceanography
δ13C-DIC is used to analyze surface and deep water mixing and carbon pump efficiency.
Instrument Support
- IRMS (Isotope Ratio Mass Spectrometer): stable isotope ratio analysis.
- TOC-IRMS coupling system: DOC analysis.
- GasBench II + IRMS: commonly used for DIC analysis.
Application Areas
- Ecology: Study the effects of phytoplankton and microorganisms in water bodies on carbon isotopes to reveal the carbon cycle process of the ecosystem.
- Geology: Reconstruct ancient environments and ancient climate changes through carbon isotope analysis.
- Archaeology: Analyze ancient human diet and migration patterns and compare them with the age and source of organic materials.
Alfa Chemistry is always happy to assist you set up a follow-up mechanism and interpreting results, particularly if they are unexpected.
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