Sources of dissolved inorganic carbon in rivers from the Changbaishan area, an active volcanic zone

• 作者: Xue Bai Benjamin Chetelat Yilong Song
• 学科: 地球科学
• 关键词: Carbon isotopes Dissolved inorganic carbon Rivers Chemical weathering Changbaishan Active volcanic zone
• 年，卷（期）: 2022,（3）
• 页码范围: 410-415
• 页数: 5页
• 语种: 英文
• DOI: 10.1007/s11631-017-0178-y

摘要

Major elements and carbon isotopes of dissolved inorganic carbon (DIC) have been measured in the waters of Changbaishan mountain, a volcanic area in northeastern China, between June and September 2016 to decipher the origin of the CO2 involved in chemical weathering reactions. Spatial variations of major elements ratios measured in water samples can be explained by a change of the chemical composition of the volcanic rocks between the volcanic cone (trachytes) and the basaltic shield as evidenced by the variations in the composition of these rocks. Hence, DIC results from the neutralization of CO2 by silicate rocks. DIC concentrations vary from 0.3 to 2.5 mmol/L and carbon isotopic compositions of DIC measured in rivers vary from -14.2‰ to 3.5‰. At a first order, the DIC transported by rivers is derived from the chemical weathering's consumption of CO2 with a magmatic origin, enriched in 13C (-5%) and biogenic soil CO2 with lower isotopic compositions. The highest δ13C values likely result from C isotopes fractionation during CO2 degassing in rivers. A mass balance based on carbon isotopes suggest that the contribution of magmatic CO2 varied from less than 20% to more than 70%. Uncertainties in this calculation associated with CO2 degassing in rivers are difficult to quantify, and the consequence of CO2 degassing would be an overestimation of the contribution of DIC derived from the neutralization of magmatic CO2 by silicate rocks.