Dissolved carbon dynamics and exchange in a high permeability beach aquifer

Zhang，Yan1; Guo，Yifan2; Wang，Junjian2; Maher，Damien T.3; Geng，Xiaolong4,5; Wang，Qianqian2; Xiao，Kai2; Ding，Hu6,7; Li，Hailong1,2; Zheng，Chunmiao2; Wang，Zhenyan1; Wang，Xuejing6,7

2024-03-01

10.1016/j.gca.2024.01.014

Geochimica et Cosmochimica Acta   影响因子和分区

0016-7037

The biogeochemical transformation of dissolved carbon in tidal beaches affects the coastal carbon cycle and budget. Yet, the influence of groundwater flow on the behavior of dissolved carbon and CO flux across the different interfaces in these dynamic beach systems remains poorly understood, especially in deep beach aquifers. In this study, we investigated the biogeochemical reactions and origins of dissolved carbon and quantitatively evaluated CO outgassing driven by submarine groundwater discharge (SGD) in a high permeability beach aquifer (9–13 m depth) located in the South China Sea shelf. Results revealed that both dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited non-conservative additions across the salinity gradient. The excess DIC and TA most likely resulted from organic carbon decomposition in the brackish and saline zones. Aerobic respiration (upper saline plume zone), anaerobic reactions, and tidal mixing were identified as the dominant processes controlling DIC and TA dynamics. The mean CO outgassing flux across the beach sediment-air interface was estimated to be 1.05 g m d, significantly higher than the CO flux across the sea-air interface. The outgassing pattern of groundwater CO from beach aquifer appeared to be driven by tidal pumping. Considering the combined effects of SGD-derived dissolved carbon and nutrients, we suggest that SGD yielded a net CO flux, contributing to 45 % of the CO flux across the sea-air interface. SGD directly and indirectly delivered substantial CO from the beach aquifer to the atmosphere, approximately (4.89–9.21) × 10 tons of CO per year along the 76.2 km long sandy coast. These findings demonstrate that intertidal beach aquifers, as active biogeochemical reactors have the strong potential to intensify CO emissions to the atmosphere through both beach sediment-air and sea-air interfaces. This study provides a better understanding of the links between carbon biogeochemical cycles and hydrologic processes in the coastal zones.

CO2 outgassing Different interfaces Dissolved carbon Intertidal beach aquifer Submarine groundwater discharge

SCI

英语

其他

GEOSCIENCES

2-s2.0-85185173004

Scopus

1.MOE Key Laboratory of Groundwater Circulation & Environment Evolution,School of Water Resources and Environment,China University of Geosciences (Beijing),Beijing,100083,China
2.State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control,School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China
3.Southern Cross Geoscience,Southern Cross University,Lismore,PO Box 157,2480,Australia
4.Department of Earth Sciences,University of Hawai‘i at Mānoa,Honolulu,96822,United States
5.Water Resources Research Center,University of Hawai‘i at Mānoa,Honolulu,96822,United States
6.School of Earth System Science,Tianjin University,Tianjin,300072,China
7.Critical Zone Observatory of Bohai Coastal Region,Tianjin Key Laboratory of Earth Critical Zone Science and Sustainable Development in Bohai Rim,Tianjin University,Tianjin,300072,China

Zhang，Yan,Guo，Yifan,Wang，Junjian,et al. Dissolved carbon dynamics and exchange in a high permeability beach aquifer[J]. Geochimica et Cosmochimica Acta,2024,368:64-75.

Zhang，Yan.,Guo，Yifan.,Wang，Junjian.,Maher，Damien T..,Geng，Xiaolong.,...&Wang，Xuejing.(2024).Dissolved carbon dynamics and exchange in a high permeability beach aquifer.Geochimica et Cosmochimica Acta,368,64-75.

Zhang，Yan,et al."Dissolved carbon dynamics and exchange in a high permeability beach aquifer".Geochimica et Cosmochimica Acta 368(2024):64-75.