Tracing terrestrial groundwater discharge and porewater exchange derived dissolved carbon export in a tropical estuary using multiple isotopes

Wang，Qianqian1,2; Tang，Gang1; Jiang，Shan3; Wang，Xuejing4; Xiao，Kai1; Yu，Shengchao1; Cai，Pinghe5; Kuang，Xingxing1; Li，Hailong1

2023-07-01

10.1016/j.jhydrol.2023.129648

Journal of Hydrology   影响因子和分区

0022-1694

1879-2707

Coastal terrestrial groundwater discharge and porewater exchange are two different submarine groundwater discharge (SGD) pathways. The contribution of both pathways in dissolved carbon export to the coastal water remains almost unknown. Here, we investigated terrestrial groundwater discharge, porewater exchange, and dissolved carbon export in a tropical estuary (Moyangjiang, China) using stable water (δH and δO) and radioactive (Rn, Ra, and Th) isotopes. The average terrestrial groundwater discharge was estimated to be (3.2±0.2) × 10 m d by a three end-member mixing model of δO and salinity. The porewater exchange was estimated to be 11.3±0.14 cm d by the Ra/Th disequilibrium method. Accordingly, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) fluxes from terrestrial groundwater discharge were estimated to be (1.19±0.10) × 10 and (3.23±0.25) × 10 mol d, respectively. In comparison, when upscaling to the whole estuary, DIC and DOC export fluxes from porewater exchange were estimated to be (1.56±0.21) × 10 and (2.12±0.29) × 10 mol d, respectively. Terrestrial groundwater discharge derived DIC flux was two orders of magnitude greater than that from porewater exchange, and was three times greater than that from river discharge. Terrestrial groundwater discharge was recognized as a significant contributor to DIC export. Porewater exchange played a disproportionately important role in the delivery of DOC to the ocean, and its contribution to DOC needed to be emphasized. Overall, both pathways contributed a large amount of dissolved carbon export to the coastal water, and play an important role in delivering terrestrial carbon across land-ocean interface. Evaluating the contributions of different pathways of SGD to terrestrial solutes will help to improve the accuracy of SGD associated terrestrial solute fluxes.

224Ra/228Th disequilibria Dissolved carbon export Radioactive isotopes Stable water isotopes Submarine groundwater discharge

SCI ; EI

英语

第一

National Natural Science Foundation of China["42107055","42130703","92047202"] ; Opening Project of Guangxi Laboratory on the Study of Coral Reefs in the South China Sea[GXLSCRSCS2021003] ; Shenzhen Science and Technology Innovation Committee[20200925174525002]

Engineering ; Geology ; Water Resources

Engineering, Civil ; Geosciences, Multidisciplinary ; Water Resources

WOS:001012284900001

ELSEVIER

20232214151014

Discharge (fluid mechanics) ; Dissolution ; Groundwater ; Isotopes ; Organic carbon ; Radioactivity ; Submarines ; Tropics

Waterways:407.2 ; Meteorology:443 ; Groundwater:444.2 ; Radioactive Materials:622 ; Combat Naval Vessels:672.1 ; Chemical Operations:802.3 ; Organic Compounds:804.1

ENGINEERING

2-s2.0-85160016194

Scopus

1.School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China
2.Guangxi Laboratory on the Study of Coral Reefs in the South China Sea,Guangxi University,Nanning,530004,China
3.State Key Laboratory of Estuarine and Coastal Research,East China Normal University,Shanghai,200241,China
4.School of Earth System Science,Tianjin University,Tianjin,300072,China
5.State Key Laboratory of Marine Environmental Science,Xiamen University,Xiamen,361005,China

Wang，Qianqian,Tang，Gang,Jiang，Shan,et al. Tracing terrestrial groundwater discharge and porewater exchange derived dissolved carbon export in a tropical estuary using multiple isotopes[J]. Journal of Hydrology,2023,622.

Wang，Qianqian.,Tang，Gang.,Jiang，Shan.,Wang，Xuejing.,Xiao，Kai.,...&Li，Hailong.(2023).Tracing terrestrial groundwater discharge and porewater exchange derived dissolved carbon export in a tropical estuary using multiple isotopes.Journal of Hydrology,622.

Wang，Qianqian,et al."Tracing terrestrial groundwater discharge and porewater exchange derived dissolved carbon export in a tropical estuary using multiple isotopes".Journal of Hydrology 622(2023).