Assessing the Deep Carbon Release in an Active Volcanic Field Using Hydrochemistry, δ¹³C_DIC and Δ¹⁴C_DIC

Abstract

A quantification of the input of deep carbon to the Earth's surface is crucial to understand the carbon budget and carbon biogeochemical processes in active volcanic zone (Caudron et al., 2012;Chiodini et al., 2020;Rivé et al., 2013). It is commonly known that the volcanic eruptions would release a large amount of CO 2 into the atmosphere, which can regulate the climate at the geological timescales (Berner & Caldeira, 1997;Hilton & West, 2020). Recently, it has been recognized that

Temporal variations of chemical and isotopic compositions in the river draining the Changbaishan volcanic area: The role of hydrological changes and volcanic activities

“…The basement of the Changbaishan area is Archean‐Proterozoic metamorphic rocks, with shield basalt. There are no evaporite and carbonate outcroppings in this study area (Hahm et al, 2008; Zhong et al, 2023). The volcanic activities of Changbaishan are concentrated in Tianchi volcano.…”

“…The low Δ 14 C DIC values (Figure 4a) observed in the Erdaobai River suggest that DIC was significantly contributed by hydrothermal fluids (Carapezza & Granieri, 2004). We assumed the biogenic DIC had a concentration of 573 μmol L −1 , as reported by Zhong et al (2023), because it closely matched the Δ 14 C value of the atmosphere reported by Hua et al (2021). We considered a Δ 14 C sur value of 0‰ to estimate the isotopic composition of DIC, which represented modern carbon and served as endmember 1 (E1) for our analysis.…”

“…As mentioned earlier, Cl − is a powerful tracer for hydrothermal fluids, and we supposed that ions in the hydrothermal fluids mixed proportionally into the rivers. Therefore, the cation/chloride ratios in the Julong hot springs (data from Zhong et al, 2023) can be as an endmember to quantify the cation content from the hydrothermal source for EDBH: $$$$ {X}_{\mathrm{Hyd}}=\left({\mathrm{Cl}}_{\mathrm{River}}^{-}{\mathrm{Cl}}_{\mathrm{Atm}}^{-}\right)\times {X}_{\mathrm{JL}}/{\mathrm{Cl}}_{\mathrm{JL}}^{-} $$$$ where X Hyd and X Atm are concentrations of major ions derived from the hydrothermal fluids and atmosphere, respectively, while X JL is the measured concentration of major ions in Julong hot springs. We assumed that the concentration of Cl − in the hydrothermal fluids was 3527 μmol L −1 according to the data from Julong hot springs (Zhong et al, 2023).…”

“…We considered a Δ 14 C sur value of 0‰ to estimate the isotopic composition of DIC, which represented modern carbon and served as endmember 1 (E1) for our analysis. DIC concentration of hydrothermal endmember (endmember 2; E2) was assumed to be 18 853 μmol L −1 (data from Zhong et al, 2023), and its Δ 14 C Hyd value was −1000‰ (dead carbon), which was according to the values of the Julong hot springs. The theoretical mixing curve of DIC from surface water and hydrothermal fluids was shown in Figure 4b.…”

“…Helium and carbon isotopes from the hot springs of the Changbaishan volcanic area showed volatile sources are mantle fluids and slab‐derived fluids (Hahm et al, 2008; Wei et al, 2016). Previous studies have shown that the Changbaishan volcanic area released a large amount of deep carbon in the form of diffusion degassing (Hahm et al, 2008; Sun et al, 2020; Zhong et al, 2023). However, the effect of deep carbon release on the river carbon budget under varying hydrological conditions has not been determined.…”