Using radium isotopes to characterize water ages and coastal mixing rates: A sensitivity analysis

Knee, Karen L.; García-Solsona, Ester; García-Orellana, Jordi; Boehm, Alexandria B.; Paytan, Adina

doi:10.4319/lom.2011.9.380

Cited by 37 publications

(10 citation statements)

References 66 publications

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“…This suggests that the mean radium derived age of system water masses can be used henceforth as a realistic integrative measure of the timescale of exposure of Kinvara Bay to freshwater inputs. In addition, even considering method uncertainties (Knee et al 2011) the radium activity ratios (RAs) results may reveal important features of circulation and mixing within the bay that were not available to other scholars researching Kinvara before (Cave and Henry 2011;Einsiedl 2012;Smith and Cave 2012;McCormack et al 2014). Indeed, since the ARs of 224 Ra and 223 Ra where not derived from individual measurements of each isotope in single water samples, but instead measured as a ratio (hence incorporating both uncertainties in the final result) in radium-accumulating MnO 2 fibres exposed to local water masses at fixed locations in the bay over a period of [24 h (therefore integrating local variability due to circulation over this time span), we are able to draw some useful insights from the relative age distribution across Kinvara Bay (Fig.…”

Section: Freshwater Retention Timescalementioning

confidence: 98%

Retention and fate of groundwater-borne nitrogen in a coastal bay (Kinvara Bay, Western Ireland) during summer

Rocha

Wilson

Scholten³

et al. 2015

Biogeochemistry

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The magnitude of submarine groundwater discharge (SGD) and its contribution to nitrogen biogeochemistry in a small embayment in the Western Coast of Ireland subject to occasional hypoxia were investigated during summer. Time series (24 h) of 222 Rn, NO 3 -, NO 2 -, NH 4 ?, dissolved reactive silicate (DRSi) and salinity (and dissolved organic nitrogen (DON) (July 2013) were measured at the mouth of the bay and coupled with relevant sediment-water fluxes and input loadings to derive nutrient budgets. In-situ activity ratios of the naturally occurring radium isotopes 224 Ra and 223 Ra were employed in parallel to the freshwater fraction method to determine the timescale of freshwater retention in the system. Based on 222 Rn mass balances (n = 4), the mean groundwater (±SE) discharge into Kinvara Bay was 10.4 ± 6.3910 4 m 3 days -1 , delivering average loads of 376 ± 67 kg Si day -1 (as DRSi), 1.6 ± 0.2 kg P day -1 (as TDP) and *280 kg N day -1 of dissolved nitrogen (272 ± 49 DIN, essentially as NO 3 -, and 8.2 ± 1.6 DON), which correspond to *98.8, 49.1 and *93.5 % of total allochthonous nutrient inputs respectively. Expressed on an areal basis and annual scale the exogenous N summer loading of Kinvara is equivalent to 25.9 g N m -2 year -1 . Our biogeochemical budgets indicate that tight benthicpelagic coupling contributes to the very high retention levels of N within the bay with subtidal sediments acting as a link in the internal N cycle via DNRA, while *18 % of the exogenous N load is removed by benthic denitrification. Rapid cycling of DON into bioavailable forms of N within the timescale of freshwater retention in the system (*7 days) contributes *50 % to local biological N fixation. Nutrient availability ratios are N:P *173 and Si:P *503, indicating that primary production is P-limited while the carbon yield (*3.01 9 10 5 mol C day -1 , or *0.313 kg C m -2 year -1 ) suggests the bay is eutrophic during the summer. SGD-borne Nitrogen loading is therefore the major driver of eutrophication in Kinvara Bay. Our biogeochemical characterization is consistent with the observed phytoplankton community composition and species succession and justifies the local observation of HAB's. In addition, the relative magnitude of DNRA-promoted N retention compared to N removal by denitrification, coupled with seasonal hypoxia, suggests that the system is advanced in Responsible Editor:

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Section: Freshwater Retention Timescalementioning

confidence: 98%

Retention and fate of groundwater-borne nitrogen in a coastal bay (Kinvara Bay, Western Ireland) during summer

Rocha

Wilson

Scholten³

et al. 2015

Biogeochemistry

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“…Radium is adsorbed onto the particles present in fresh water, but undergoes essentially complete desorption in contact with brackish water at salinities >5 ppt (Krest et al, 1999). The enrichment in groundwater and the different half-lives of the four radium isotopes allows for the quantifying SGD and estimating of the residence time of the coastal water (Moore, 1996;Charette et al, 2001;Hwang et al, 2005;Moore, 2006;Knee et al, 2011).…”

Section: Sgd Estimations Using the Radium Quartetmentioning

confidence: 99%

Methodological study of submarine groundwater discharge from a karstic aquifer in the Western Mediterranean Sea

Mejı́as

Ballesteros

Antón-Pacheco

et al. 2012

Journal of Hydrology

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“…Short‐lived Ra isotopes ( 223 Ra, T 1/2 = 11.4 days; 224 Ra, T 1/2 = 3.66 days) have been widely applied to estimate fluxes of submarine groundwater discharge (SGD) (e.g., Burnett et al, 2006; Charette et al, 2013; Garcia‐Orellana et al, 2014), pore‐water exchange (e.g., Alorda‐Kleinglass et al, 2019; Hong et al, 2018; Rodellas et al, 2017), and to determine water residence time and coastal mixing rates (e.g., Knee et al, 2011; Moore, 2000; Moore & Oliveira, 2008).…”

Section: Introductionmentioning

confidence: 99%

Guidelines and Limits for the Quantification of Ra Isotopes and Related Radionuclides With the Radium Delayed Coincidence Counter (RaDeCC)

et al. 2020

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The Radium Delayed Coincidence Counter (RaDeCC) is one of the most extensively used equipment for measuring 223 Ra and 224 Ra activities in water and sediment samples. Samples are placed in a closed He-circulation system that carries the Rn produced by the decay of Ra to a scintillation cell. Each alpha decay recorded in the cell is routed to an electronic delayed coincidence system which enables the discrimination of 223 Ra and 224 Ra. In this study, the measurement and quantification methods using the RaDeCC system are assessed through analyses of registered data in different RaDeCC systems worldwide and a set of simulations. Results of this work indicate that the equations used to correct for 223 Ra and 224 Ra cross-talk interferences are only valid for a given range of activities and ratios between isotopes. Above certain limits that are specified in this study, these corrections may significantly overestimate the quantification of 223 Ra and 224 Ra activities (up to~40% and 30%, respectively), as well as the quantification of their parents 227 Ac and 228 Th. High activities of 226 Ra may also produce an overestimation of 224 Ra activities due to the buildup of 222 Rn, especially when long measurements with low activities of 224 Ra are performed. An improved method to quantify 226 Ra activities from the buildup of 222 Rn with the RaDeCC system is also developed in this study.Wethus provide a new set of guidelines for the appropriate quantification of 223 Ra, 224 Ra, 227 Ac, 228 Th, and 226 Ra with the RaDeCC system.Plain Language Summary In the last decades, there has been a growing interest in using radioactive isotopes to evaluate environmental processes. Their concentrations in environmental settings can reveal information about provenance, path, time, and duration. In this scenario, the research in the techniques to measure isotopes from samples has played a key role. In 1996, the launching of the Radium Delayed Coincidence Counter (RaDeCC) facilitated the fast and precise measurement of Ra isotopes, which provide information on land-ocean interaction processes (e.g., groundwater discharge to the sea and coastal residence times). Nowadays, this detector has become a fundamental tool for oceanographers, geochemist, and hydrologist among other scientific communities. Nevertheless, when the RaDeCC system was released, its quantification limits were not provided, and the recommendations on its use were mostly qualitative. More than 20 years later, we address these questions in a study that contains a comprehensive analysis of the RaDeCC counting mechanism and the determination of the limits of quantification. This study should serve as guidance for the measurement and quantification of Radium isotopes for the scientific community using the RaDeCC system. Key Points: • The maximum quantification limits for 223 Ra and 224 Ra are 200 and 100 cpm in the total channel, respectively • Limits for the quantification of 223 Ra and 224 Ra are provided when measurements are influenced by cross-talk and 222 Rn buildup...

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Using radium isotopes to characterize water ages and coastal mixing rates: A sensitivity analysis

Cited by 37 publications

References 66 publications

Retention and fate of groundwater-borne nitrogen in a coastal bay (Kinvara Bay, Western Ireland) during summer

Retention and fate of groundwater-borne nitrogen in a coastal bay (Kinvara Bay, Western Ireland) during summer

Methodological study of submarine groundwater discharge from a karstic aquifer in the Western Mediterranean Sea

Guidelines and Limits for the Quantification of Ra Isotopes and Related Radionuclides With the Radium Delayed Coincidence Counter (RaDeCC)

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