Journal article
Radium and radon isotopes reveal multi-scale porewater and groundwater nutrient sources in a macrotidal embayment
Geochimica et cosmochimica acta, Vol.418, pp.212-223
01/04/2026
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Abstract
Advective flows in coastal sediments occur on both small scales (centimeters) as porewater exchange (PEX), and large scales (>meters) as fresh groundwater discharge (FSGD) and seawater recirculation (RSGD). Constraining these benthic boundary exchange processes is essential to resolve biogeochemical budgets in global marginal seas. Here, we integrated field data and models to resolve porewater exchange and the different submarine groundwater discharge (SGD) components as nutrient sources in a highly dynamic macrotidal embayment. Small-scale PEX and large-scale RSGD are defined operationally based on the Ra–Rn mass balance model. Using Monte Carlo simulations, radium and radon mass balance models revealed that small-scale PEX 0.50 (0.32 ∼ 0.77) m³/m²/d exceeded large-scale fresh (<0.01 m³/m²/d) and recirculated 0.07 (0.04 ∼ 0.15) m³/m²/d SGD in macrotidal Hangzhou Bay. The seawater-based mass balance model results were corroborated by an independent sediment-based approach using ²²⁴Ra–²²⁸Th disequilibrium. The PEX- and SGD-associated nutrient fluxes in this bay, with extreme tidal ranges of 9 m, are an order of magnitude higher than local riverine loads. PEX accounted for over 90% of total nutrient inputs, highlighting the importance of recycled nutrients at the sediment–water interface. Tidal currents were the main driving forces of porewater exchange, pumping oxygen and organic matter into sediments while releasing nutrient-rich porewater. Resolving multi-scale advective benthic exchange provides deeper insight into complex nutrient sources driving eutrophication in coastal waters.
Details
- Title
- Radium and radon isotopes reveal multi-scale porewater and groundwater nutrient sources in a macrotidal embayment
- Creators
- Wen Liu - Ocean University of ChinaShibin Zhao - Ocean University of ChinaIsaac R. Santos - University of GothenburgNatasha T. Dimova - University of AlabamaTianyi Zhu - Ocean University of ChinaHaowei Xu - Ocean University of ChinaMiaomiao Zhang - Ocean University of ChinaErgang Lian - Ministry of Ecology and EnvironmentPengxia Liu - Ministry of Ecology and EnvironmentZhigang Yu - Ocean University of ChinaBochao Xu - Ocean University of China
- Publication Details
- Geochimica et cosmochimica acta, Vol.418, pp.212-223
- Publisher
- Elsevier Ltd
- Number of pages
- 12
- Grant note
- This work was funded by Natural Science Foundation of China (42425602, 42130410, U22A20580, and 42506040), Fundamental Research Funds for the Central Universities, China (202341002, 202561020), project ZR2023QD035 supported by Shandong Provincial Natural Science Foundation and High-End Foreign Expert Recruitment Program (G2023151003L).
- Identifiers
- 991013370359002368
- Copyright
- © 2026 Elsevier Ltd.
- Academic Unit
- National Marine Science Centre; National Centre for Naturopathic Medicine
- Language
- English
- Resource Type
- Journal article