Focused recharge enhances soil carbon leakage and carbonate weathering in groundwater: Implications for subsurface carbon sinks

Dai，Xin1,2; Liao，Aimin3; Xie，Yueqing1,2; Wang，Chuan1,2; Kuang，Xingxing4; Lin，Jin3; Wu，Jichun1,2

2024

10.1016/j.apgeochem.2023.105878

Applied Geochemistry   影响因子和分区

0883-2927

1872-9134

Soil carbon leakage into groundwater is a crucial and natural carbon sink process in the subsurface carbon cycling. However, the primary driving force for soil carbon downward leakage and the following fate of the carbon in groundwater remains elusive. Here, we investigated multi-seasonal hydrodynamics, hydrogeochemistry and environmental isotopes (δC, δH and δO) in groundwater wells in a humid region. Frequent water-table rise (1 ∼ 3 m) and isotopic signature fluctuation after the concentrated rainfall supported evidence for the occurrence of focused groundwater recharge. We found that focused recharge during the shorter and wetter season induced the increase of groundwater DOC (306.5 ± 231 μmol/L) and CO (2154 ± 726.6 μmol/L), the dilution of CH (1.75 ± 1.2 μmol/L) and DIC (4486 ± 790.8 μmol/L) as well as depleted δC signatures (−17‰ ∼ −18‰). These variations jointly elucidated accelerated soil carbon downward leakage and hydrodynamic mixing driven by focused recharge. Saturation index calculation and PHREEQC simulations confirmed that massive groundwater CO from soil carbon leakage during focused recharge exerted positive perturbations on carbonate weathering, and ultimately stored in a more stable form by transforming into HCO. Carbon isotope analysis further identified carbonate weathering accounted for approximately one third of DIC dynamics compared to biogenic sources. This study highlights that focused recharge has a disproportional contribution to flushing soil-derived carbon into groundwater and activating carbonate weathering in the groundwater, with important implications for temporal variability of non-negligible subsurface carbon sinks in the global carbon budget.

Carbon isotope analysis Carbonate weathering Focused recharge Groundwater carbon sink Soil carbon leakage

SCI ; EI

英语

其他

GEOSCIENCES

2-s2.0-85182440377

Scopus

1.Key Laboratory of Surficial Geochemistry,Ministry of Education,School of Earth Sciences and Engineering,Nanjing University,Nanjing,210023,China
2.Frontiers Science Center for Critical Earth Material Cycling,Nanjing University,Nanjing,210023,China
3.Chuzhou Scientific Hydrology Laboratory,Nanjing Hydraulic Research Institute,Chuzhou,239080,China
4.School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China

Dai，Xin,Liao，Aimin,Xie，Yueqing,et al. Focused recharge enhances soil carbon leakage and carbonate weathering in groundwater: Implications for subsurface carbon sinks[J]. Applied Geochemistry,2024,161.

Dai，Xin.,Liao，Aimin.,Xie，Yueqing.,Wang，Chuan.,Kuang，Xingxing.,...&Wu，Jichun.(2024).Focused recharge enhances soil carbon leakage and carbonate weathering in groundwater: Implications for subsurface carbon sinks.Applied Geochemistry,161.

Dai，Xin,et al."Focused recharge enhances soil carbon leakage and carbonate weathering in groundwater: Implications for subsurface carbon sinks".Applied Geochemistry 161(2024).