Speaker
Description
Volcanic activities are known to release a substantial amount of deep carbon to the Earth’s surface, thereby influencing the global carbon cycle on geological timescales. Volcanic activities release CO₂ to the atmosphere not only from the crater, but also from the flank and base of the volcanoes in the form of soil emissions, hot springs, vents, and deep carbon in dissolved state. Carbon isotopes have been widely used to trace deep carbon and processes due to eigenvalue differences among carbon sources. ¹⁴C is more insensitive to CO₂ degassing than ¹³C, so it is less affected by the process and can provide accurate information on carbon sources. Changbaishan volcano is one of the largest active volcanos with the greatest potential for catastrophic eruption in east Asia, which has abundant hydrothermal resources, such as the Julong and Jinjiang hot springs. The deep carbon flux and corresponding climatic and environmental effects need to be clarified in the Changbaishan volcanic area.
We investigated the carbon isotope compositions (δ¹³C and Δ¹⁴C) of hot springs, rivers, groundwater, soil gas, and plants. The results showed that the carbon isotope compositions of different study subjects had been affected by volcanic degassing, for example, The Δ¹⁴C values for riverine and groundwater dissolved inorganic carbon (DIC) are −832‰ to 22‰ and −676‰ to 1‰, respectively. The flux of deep carbon in the dissolved state is 0.33×10⁴ t C yr⁻¹. The minimum flux of deep CO₂ outgassing (i.e. deep carbon release in the gaseous state) from the air-water interface is 1.24×10⁴ t C yr⁻¹. The Changbaishan volcanic area exists as a net carbon source under the control of volcanic degassing and silicate weathering based on existing and this study. In addition, we measured the DIC isotopic compositions of the Erdaobai River in one year, which drains the Changbaishan volcanic area. The isotopic mixing model of ¹⁴C showed that hydrothermal DIC accounted for 40.8±3.7% of the DIC budget and deep carbon exists as a stable carbon source. This study highlights the superiority of ¹⁴C as a tracer in investigating carbon cycling and the impact of deep carbon degassing on the carbon cycle in the volcanic area, which is significant for understanding the global CO₂ balance and climate change.
| Student Submission | Yes |
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