Marine Chemistry最新文献

{"title":"Autonomous high-frequency time-series observations of total alkalinity in dynamic estuarine waters","authors":"Li Qiu ,&nbsp;Mario Esposito ,&nbsp;María Martínez-Cabanas ,&nbsp;Eric P. Achterberg ,&nbsp;Quanlong Li","doi":"10.1016/j.marchem.2023.104332","DOIUrl":"https://doi.org/10.1016/j.marchem.2023.104332","url":null,"abstract":"<div><p>Total alkalinity (TA) is a variable that reflects the acid buffering capacity of seawater, and is key to studies of the global carbon cycle. Daily and seasonal TA variations are poorly constrained due to limitations in observational techniques, and this hampers our understanding of the carbonate system. High quality and high temporal resolution TA observations are required to constrain the controlling factors on TA. Estuarine and coastal waters usually have low TA values and may experience enhanced remineralization of organic matter in response to processes such as eutrophication and terrestrial organic matter input. Therefore, these waters are considered vulnerable to acidification as a consequence of ongoing atmospheric anthropogenic carbon dioxide uptake. An In Situ Analyzer for seawater Total Alkalinity (ISA-TA) was deployed for the first time in low salinity, dynamic estuarine waters (Kiel Fjord, southwestern Baltic Sea). The ISA-TA and a range of additional sensors (for pH, <em>p</em>CO₂, nitrate and temperature, salinity, dissolved oxygen) used to obtain ancillary data to interpret the TA variability, were deployed on a pontoon in the inner Kiel Fjord for approximately four months. Discrete samples (for TA, nutrients including NO₃⁻, soluble reactive phosphorus (SRP) and H₄SiO₄, chlorophyll <em>a</em>) were collected regularly to validate the ISA-TA and to interpret the TA data. The effects on TA in the study area of nitrate uptake and of other processes such as precipitation, run-off and mixing of different waters were observed. The difference between the TA values measured with the ISA-TA and TA of discretely collected samples measured with the Gran titration method was −2.6 ± 0.9 μmol kg⁻¹ (<em>n</em> = 106), demonstrating that the ISA-TA provides stable and accurate TA measurements in dynamic, low salinity (13.2–20.8), estuarine waters. The TA and ancillary data recorded by the sensor suite revealed that physical mixing was the main factor determining the variability in TA in Kiel Fjord during the study period.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"257 ","pages":"Article 104332"},"PeriodicalIF":3.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92065151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparing the isotopic and molecular composition of dissolved organic carbon between the oligotrophic South China Sea and the adjacent North Pacific Ocean: Signals of biodegradation, conservative mixing, and terrestrial input","authors":"Peng Jiang ,&nbsp;Hongmei Chen ,&nbsp;Zhanfei Liu ,&nbsp;Xiaolin Li","doi":"10.1016/j.marchem.2023.104331","DOIUrl":"https://doi.org/10.1016/j.marchem.2023.104331","url":null,"abstract":"<div><p>The cycling of oceanic dissolved organic carbon (DOC) is a crucial component of the global carbon cycle, yet the identification of sources and the mechanisms of its molecular transformation remain poorly understood. This study compared the isotopic and molecular composition of DOC between the oligotrophic South China Sea (SCS) and the adjacent North Pacific Ocean (NPO), and traced both its allochthonous and autochthonous sources as well as its dynamic cycling processes. DOC was collected through solid-phase extraction (SPE) from water samples of both the SCS and NPO. Carbon content, isotopic ratios, and high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) measurements revealed that SPE-DOC contained both labile and refractory fractions. According to our mass balance model, the labile fraction of SPE-DOC exhibited a decline from 11.5 to 12.6 μM in surface waters to a negligible concentration below 1000 m. Conversely, the refractory fraction of SPE-RDOC maintained a relatively consistent value, ranging from 12.7 to 19.0 μM across the entire water column. The vertical distribution patterns of the molecular composition and carbon isotopic ratios jointly indicated that the DOC distributions are shaped by distinct biological and physical processes within different biogeochemical realms of the water column. The production and transformation of the relatively labile DOC fractions were the dominant processes in the epipelagic and mesopelagic zones (upper 1000 m). The extent of diapycnal mixing between the SCS and NPO explained the different vertical distributions of refractory DOC molecules in the bathypelagic oceans. The molecular indices of polyphenol compounds, aromaticity, double bond saturation state, terrestrial mass peaks, and δ¹³C ratios of SPE-DOC indicated contributions from terrestrial sources, likely riverine input, in the SCS. This study sheds light on the molecular evidence of DOC sources, as well as their transformation and conservative mixing processes along the overturning circulation in marginal seas.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"257 ","pages":"Article 104331"},"PeriodicalIF":3.0,"publicationDate":"2023-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91964465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variability in zinc:phosphorous and zinc:silicon ratios and zinc isotope fractionation in Southern Ocean diatoms: Observations from laboratory and field experiments","authors":"Robin Grun ,&nbsp;Moneesha Samanta ,&nbsp;Michael J. Ellwood","doi":"10.1016/j.marchem.2023.104330","DOIUrl":"https://doi.org/10.1016/j.marchem.2023.104330","url":null,"abstract":"<div><p>We studied the impact of iron limitation on zinc uptake and the zinc isotope (δ⁶⁶Zn) composition for Southern Ocean phytoplankton. We undertook laboratory culture and field incubation experiments, and linked these to <em>in situ</em> depth profiles of dissolved (dZn) and particulate (pZn) zinc collected from three sites in the Southern Ocean. For the laboratory experiments, diatom growth rates, cellular zinc accumulation, and δ⁶⁶Zn all responded to changes in iron and zinc bioavailability. A significant increase in the cellular quota for zinc (expressed as zinc:phosphorous (Zn:P)) occurred upon iron limitation and zinc enrichment. At the same time, δ⁶⁶Zn for organic tissues became isotopically light under high zinc and low iron concentrations. The opposite occurred for frustule δ⁶⁶Zn values. Here δ⁶⁶Zn_{frustule-organic} for cultured phytoplankton became isotopically heavier under high zinc and low iron concentrations. For senescing and dead cells, Zn:P declined and δ⁶⁶Zn increased, indicating a loss of isotopically light zinc from organic matter. For field incubation experiments, δ⁶⁶Zn_frustule was isotopically heavier than seawater, except for added zinc treatments. The percentage of zinc associated with frustule material for laboratory and field incubations encompassed a wide range with values between 1 and 57%. Depth profiles of δ⁶⁶Zn for dZn and pZn varied, with dZn being isotopically lighter than pZn in low dZn concentration subantarctic waters, whereas the opposite occurred in polar waters where dZn was isotopically heavier than pZn at higher dZn concentrations. Our results show that iron and zinc availability regulates the zinc content of phytoplankton and the δ⁶⁶Zn composition of the Southern Ocean, which is propagated to other parts of the world ocean.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"257 ","pages":"Article 104330"},"PeriodicalIF":3.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0304420323001263/pdfft?md5=a5d7dffbe00a8bf67d2848a633f42864&pid=1-s2.0-S0304420323001263-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92100705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of chromophoric dissolved organic matter in a highly productive Amundsen Sea polynya","authors":"Ji Hu ,&nbsp;Siyou Xue ,&nbsp;Jun Zhao ,&nbsp;Zhengbing Han ,&nbsp;Dong Li ,&nbsp;Haifeng Zhang ,&nbsp;Peisong Yu ,&nbsp;Minhui Zheng ,&nbsp;Jianming Pan ,&nbsp;Yongge Sun","doi":"10.1016/j.marchem.2023.104329","DOIUrl":"https://doi.org/10.1016/j.marchem.2023.104329","url":null,"abstract":"<div><p>Dissolved organic carbon (DOC) is the largest organic carbon pool in the ocean, and is the most active component in respect to the ocean carbon cycling. However, its study in Antarctica has been limited due to challenges associated with sample collection. In this study, we conduct an investigation on the chromophoric dissolved organic matter (CDOM) in a highly productive Amundsen Sea Polynya (ASP), where phytoplankton blooms occur annually during the austral summer, serving as the primary source of DOC and CDOM. The relative abundances of CDOM, as indicated by the absorption coefficient at 254 nm (a₂₅₄), exhibit significant variability, reaching up to 6.34 m⁻¹. Four fluorescent components, including two humic-like components (C1 and C4) and two protein-like components (C2 and C3), are identified by excitation emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Our findings suggest that heterotrophic metabolism primarily contributes to the formation of humic-like fluorescent components and DOC removal. Water mass, solar radiation, primary productivity as well as microbial degradation are identified as the main factors influencing CDOM dynamics in ASP. This study bears significant implications for advancing our understandings of the CDOM and DOC dynamics in the coastal polynyas of Antarctica, thus facilitating improved evaluation of carbon cycle in the Antarctica.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"257 ","pages":"Article 104329"},"PeriodicalIF":3.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92148908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The roles of carbonate, borate, and bicarbonate ions in affecting zooplankton hatching success under ocean acidification","authors":"John P. Christensen","doi":"10.1016/j.marchem.2023.104269","DOIUrl":"https://doi.org/10.1016/j.marchem.2023.104269","url":null,"abstract":"<div><p><span>Two ocean acidification studies about egg hatching success (HS) in geographically important marine copepods, </span><em>Calanus finmarchicus</em> and <em>C. helgolandicus</em><span><span>, were reanalyzed with improved statistical procedures. The new results at low and moderate levels of seawater<span> acidification showed no HS inhibition at normal habitat temperatures but statistically significant inhibition at warmer and colder temperatures. These HS results were compared with seawater carbonate system and </span></span>borate concentrations from precise seawater measurements. The temperature dependent differences in HS could not be directly explained by changes in the seawater concentrations of either H</span>⁺<span>, bicarbonate (HCO</span>₃⁻), or CO₂* (CO₂* being the sum of unhydrated CO₂ and H₂CO₃). In contrast, HS differences did match trends in seawater carbonate (CO₃²⁻) concentrations. A numerical model was developed which evaluates the concentrations of O₂ or CO₂*, HCO₃⁻, and CO₃²⁻<span> at the cellular level across an egg and embryo by considering both gas diffusion with the seawater and respiration by the embryo. Again, temperature-dependent trends in HS could not be explained changes in intracellular CO</span>₂* or HCO₃⁻ concentrations, but HS did trend with the changes in intracellular CO₃²⁻ concentrations. Carbonate ions form strong coordination complexes with metals, so acidification-driven decreases in external seawater carbonate concentrations, which are amplified at warmer temperatures, could release injurious metals, thus driving the HS inhibition at warmer temperatures. Increases in cytoplasmic carbonate concentrations at warmer temperatures caused by seawater acidification could complex with biochemically-needed nutrient-type metals within the cells, also causing the increased HS inhibition at warmer temperatures. Furthermore, boron is essential in chemically signaling within and between cells. Seawater borate concentrations were closely correlated with HS inhibition via Michaelis-Menton equations, suggesting that acidification-driven decreases in seawater borate concentrations may also inhibit HS. Finally, the acidification-driven increases in CO₂<span> diffusion into cells dramatically increased intracellular bicarbonate concentrations. At mild levels of seawater acidification, an organism might compensate by exporting bicarbonate from the cells to the haemolymph and then to the seawater. Although the energetic<span><span> cost, as percentage of ATP production, might be high, increased respiration rates at warmer temperatures might better allow the organism to survive. However, as temperature is lowered, the cellular respiration rate declines more rapidly with respect to","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"256 ","pages":"Article 104269"},"PeriodicalIF":3.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49743226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distributions of humic substances in an estuarine region (Otsuchi Bay, Japan) determined using electrochemical and optical methods","authors":"Ying Ping Lee ,&nbsp;Kuo Hong Wong ,&nbsp;Hajime Obata ,&nbsp;Keisuke Nishitani ,&nbsp;Hiroshi Ogawa ,&nbsp;Hideki Fukuda ,&nbsp;Chia-Jung Lu","doi":"10.1016/j.marchem.2023.104301","DOIUrl":"10.1016/j.marchem.2023.104301","url":null,"abstract":"<div><p><span><span>Humic substances<span><span> are major components of the dissolved organic carbon pool in aquatic environments that can bind to trace metals like copper and iron as organic ligands. The unique chromophoric and fluorescence properties of humic substances enabled measurements using conventional optical methods but recently a new </span>electrochemical method using </span></span>cathodic stripping voltammetry has emerged. In this study, we employed both methods to measure humic substances and elucidate their distribution patterns in Otsuchi Bay in Japan. The electroactive humic substances (eHS) detected using the electrochemical method were higher in the rivers (range 0.24 to 4.3 mg L</span>⁻¹) than in the coastal bay (range 0.08 to 0.69 mg L⁻¹<span>). Both methods revealed significantly higher humic concentrations in the surrounding rivers than in Otsuchi Bay, indicating that riverine sources are an important source of humic substances to Otsuchi Bay, consistent with previous observations in riverine systems<span> globally. eHS correlated well with optical indices of dissolved organic matter<span> (DOM) including humic and marine humic-like fluorescent DOM and chromophoric DOM. Furthermore, comparison with data from the literature suggests that about 20% of the weaker Cu-binding organic ligand pool in Otsuchi Bay may consist of eHS. As Cu-binding organic ligands, eHS may be important in buffering temporal or seasonal increases in Cu fluxes in estuarine regions, with possible implications for nutrient bioavailability and toxicity for primary producers.</span></span></span></p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"256 ","pages":"Article 104301"},"PeriodicalIF":3.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46205246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Method development and quantification of all B vitamins and selected biosynthetic precursors in winter and spring samples from the North Sea and de novo synthesized by Vibrio campbellii","authors":"Stefan Bruns,&nbsp;Gerrit Wienhausen,&nbsp;Barbara Scholz-Böttcher,&nbsp;Simone Heyen,&nbsp;Heinz Wilkes","doi":"10.1016/j.marchem.2023.104300","DOIUrl":"10.1016/j.marchem.2023.104300","url":null,"abstract":"<div><p><span><span>The simultaneous analysis of B vitamins and biosynthetic precursors in </span>seawater<span><span> is of great interest as it gives a better insight into the fluctuations of their availability for marine organisms and thus allows us to better understand the nature of interactions between prototrophic and auxotrophic organisms. The analysis of these micronutrients is challenging, as they are usually present in the marine environment in minuscule quantities only. Additionally, some of them are light- and heat-sensitive which complicates their handling. To meet these circumstances, the presented sample work-up method for seawater started with a freeze-drying step for volume reduction of the sample. This shortened the duration of the subsequent </span>solid phase extraction and resulted in an increase in recovery. When comparing three solid phase extraction materials (C</span></span>₁₈, HLB, PPL), PPL was found to be the most suitable. This method was applied for the quantification of all eleven B vitamins and six precursors in waters from the southern North Sea taken in winter and spring. Quantification was performed by LC-MS. The winter samples showed higher concentrations for nearly all analytes, in contrast to the uptake of most nutrients at the beginning of a potential algal bloom in spring and low analyte concentrations in springtime waters. In addition, the marine bacterium <em>Vibrio campbellii</em>, prototrophic for most B vitamins, was cultivated without the addition of B vitamins in order to measure them intra- and extracellularly during growth. In most cases, intracellular concentrations per cell decreased towards the end of the exponential growth phase, while extracellular concentrations increased. Extracellular B vitamin and precursor concentration measurements show that <em>V. campbellii</em> is in exchange with its environment and thereby possibly enables growth of B vitamin auxotrophs in the environment.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"256 ","pages":"Article 104300"},"PeriodicalIF":3.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45904112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anthropogenic carbon estimation in the surface ocean from atmospheric CO2 fugacity at the BATS (Bermuda Atlantic Time-series Study) station","authors":"Ben Hadid Nadia ,&nbsp;Touratier Franck ,&nbsp;Guglielmi Véronique ,&nbsp;Mouakher Amira ,&nbsp;Goyet Catherine","doi":"10.1016/j.marchem.2023.104310","DOIUrl":"10.1016/j.marchem.2023.104310","url":null,"abstract":"<div><p><span>In surface seawater, it is usually very difficult to quantify anthropogenic carbon concentrations. Many processes (such as air-sea exchanges of gases and heat, biological activity, and mixing of water masses), are at play and often on different timescales. Thus, various hypotheses are used to estimate the anthropogenic concentrations in surface waters. Here, using the relatively long (1980s to present) time series data sets from the Bermuda Atlantic Time-series Study site (BATS; 31</span>^°40′N, 64^°10′W) in the North Atlantic Ocean, we evaluate results based upon two different hypotheses. The results clearly confirm that it is very difficult to assess anthropogenic carbon concentrations in surface waters from sole oceanic properties. However, this study further indicates that at this ocean site, they can be appropriately determined from low-frequency variations of atmospheric CO₂<span> concentrations. Consequently, the impact of anthropogenic carbon penetration in surface waters on their acidification could be predicted.</span></p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"256 ","pages":"Article 104310"},"PeriodicalIF":3.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46258276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regulated vs. unregulated rivers: Impacts on CDOM dynamics in the eastern James Bay","authors":"Amélie Évrard,&nbsp;Caroline Fink-Mercier,&nbsp;Virginie Galindo ,&nbsp;Urs Neumeier,&nbsp;Michel Gosselin,&nbsp;Huixiang Xie","doi":"10.1016/j.marchem.2023.104309","DOIUrl":"10.1016/j.marchem.2023.104309","url":null,"abstract":"<div><p>The eastern James Bay (EJB) coast harbors numerous rivers, but there is a dearth of knowledge concerning dissolved organic matter (DOM) in the downstream coastal water. Here we report a four-year (2018–2021) and multi-seasons field study on the mixing behavior and characteristics of the chromophoric DOM (CDOM) in the nearshore EJB. Freshwater discharged from the extensively regulated La Grande River (LGR) was constantly depleted in DOM compared with the unregulated rivers (URRs), being on average 3.35 times lower in CDOM absorption coefficient at 440 nm (<em>a</em>_CDOM(440)) and 2.50 times lower in dissolved organic carbon (DOC). In contrast, the absorption spectral slope between 275 and 295 nm (<em>S</em>_275–295, a proxy of molecular weight) and the specific absorption coefficient at 254 nm (<em>a</em>*_CDOM(254), an indicator of aromaticity) of the LGR CDOM were only 10.6% lower and 11.7% higher than those of the URRs CDOM, respectively. Riverine input was found to be the dominant source of CDOM in the study area, with little influence from sea ice formation or melting. CDOM distribution fell into two distinct regimes: the LGR-influenced low-CDOM area in the north and the URRs-influenced high-CDOM area in the south. The two areas showed strong conservative but separate <em>a</em>_CDOM(440)–salinity relationships converging at a common marine endmember (salinity ∼25) with little seasonality. The composite data combing both areas and all seasons and years exhibited non-linear relationships between <em>S</em>_275–295, <em>a</em>*_CDOM(254) and <em>a</em>_CDOM(440) and a robust simple linear correlation of DOC to <em>a</em>_CDOM(440). This study suggests a strong impact of river regulation on CDOM input into the EJB, reveals low seasonal variability of CDOM mixing dynamics and characteristics, and demonstrates the feasibility of using remote sensing from space for real-time and synoptical assessment of DOM dynamics and the associated biogeochemical cycles in the EJB.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"256 ","pages":"Article 104309"},"PeriodicalIF":3.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44411196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of methods to determine extraction efficiencies of Ra isotopes and 227Ac from large volume seawater samples","authors":"Morgane Léon ,&nbsp;Pieter van Beek ,&nbsp;Virginie Sanial ,&nbsp;Marc Souhaut ,&nbsp;Paul Henderson ,&nbsp;Matthew A. Charette","doi":"10.1016/j.marchem.2023.104328","DOIUrl":"10.1016/j.marchem.2023.104328","url":null,"abstract":"<div><p><span>Radium isotopes, other than </span>²²⁶Ra, and ²²⁷<span><span><span>Ac are typically present at low activities in the open ocean. The analysis of these isotopes thus requires the collection of large volumes of </span>seawater and high sensitivity, low background instruments. To obtain the required large volumes (hundreds to thousands of liters), these </span>radionuclides are typically preconcentrated on cartridge-style filters impregnated with MnO</span>₂<span> (Mn-cartridges) deployed on in-situ pumps. This technique, however, requires the determination of the extraction efficiency of the Mn-cartridges for the radionuclides of interest. For Ra isotopes, we used two methods to estimate the extraction efficiency of these Mn-cartridges at two stations on the South-West Indian Ridge in the Southern Ocean (GEOTRACES GS02). Method (1) compares the </span>²²⁶<span>Ra activities recovered on the Mn-cartridges versus the activities determined in Mn-fibers, through which seawater was passed at a flow rate &lt; 1 L min</span>⁻¹ to quantitatively sorb Ra (Mn-fiber method) while method (2) combines the ²²⁶Ra activities determined from two Mn-cartridges placed in series on in-situ pumps (A-B method). The second method is also applied to determine the ²²⁷Ac extraction efficiency. We find a relatively wide-range of Ra and ²²⁷Ac extraction efficiencies across the dataset (from 44.8% to 99.6% for Ra, and from 23.7% to 77.5% for ²²⁷Ac). Overall, the yield of ²²⁷Ac extraction is lower than that of Ra (mean value of 49.3 ± 19.0% for ²²⁷Ac, <em>n</em> = 10, mean value of 79.2 ± 10.3% for Ra, <em>n</em> = 13, using the Mn-fiber method; and a mean value of 63.9 ± 12.5%, <em>n</em> = 11 using the A-B method). Our dataset suggests that the Ra extraction efficiencies using either the A-B method or the Mn-fiber method are in relatively good agreement. Consequently, the ²²³Ra_ex, ²²⁴Ra_ex and ²²⁸Ra activities determined from the Mn-cartridges by applying the two Ra extraction yields are similar. We also show that the ²²⁷Ac extraction efficiency can be estimated from the Ra extraction efficiency allowing the use of a single Mn-cartridge. Finally, we recommend to determine the Ra and ²²⁷Ac extraction efficiencies in each individual Mn-cartridge, rather than applying a single extraction efficiency to all the Mn-cartridges, since a significant variability in the extraction efficiencies was observed between the different Mn-cartridges.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"258 ","pages":"Article 104328"},"PeriodicalIF":3.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135963768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}