Limnology and Oceanography: Methods最新文献

{"title":"Correction to “Estimating ethanol correction factors for δ13C and δ15N isotopic signatures of freshwater zooplankton from multiple lakes”","authors":"","doi":"10.1002/lom3.10647","DOIUrl":"10.1002/lom3.10647","url":null,"abstract":"<p>Blechinger, T., Link, D., Nelson, J.K.R. and Hansen, G.J.A. (2024), Estimating ethanol correction factors for δ¹³C and δ¹⁵N isotopic signatures of freshwater zooplankton from multiple lakes. Limnol Oceanogr Methods, <b>22</b>: 464–472. https://doi.org/10.1002/lom3.10623</p><p>In the author affiliation section, the correct affiliation for the co-author “Jenna K. R. Nelson” is: “Minnesota Department of Natural Resources, Saint Paul, Minnesota, USA.”</p><p>We apologize for this error.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10647","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181773","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":"Multivariate statistical “unmixing” of Indian and Pacific Ocean sediment provenance","authors":"Ann G. Dunlea, Kazutaka Yasukawa, Erika Tanaka, Ingrid L. Hendy","doi":"10.1002/lom3.10645","DOIUrl":"https://doi.org/10.1002/lom3.10645","url":null,"abstract":"The geochemistry of marine sediment is a massive archive of (paleo)oceanographic information. Accessing that information requires “unmixing” the various influences on marine sediment geochemistry to understand individual sources and marine geochemical processes. Q‐mode factor analysis (QFA) and independent component analysis (ICA) are multivariate statistical techniques that have successfully been applied to large datasets of marine sediment element concentrations to identify the number and composition of marine sediment sources or end‐members. In this study, we apply both techniques to two datasets of marine sediment geochemistry, compare the output, and discuss the advantages of each approach. In both datasets, ICA identified a mixing trend between carbonates and dust, whereas QFA represented the end‐members as two separate factors. In the Pacific and Indian Oceans dataset, both techniques produced three factors or independent components involving rare earth elements, but two of the QFA factors explained a small, almost negligible, amount of the variability of the dataset. Also, QFA identified more aluminosilicate end‐members (dust or volcanic ash) than ICA. In the Indian Ocean Sites 738 and 752 dataset, ICA identified two processes affecting Sr and Ba concentrations as separate independent components, while QFA created a factor representing the covariation of Sr and Ba over intervals of the site's paleoceanographic history. The results of this study exemplify that QFA identifies covariances and finds discrete end‐members contributing to the bulk mass of sediment. ICA works best with non‐Gaussian element distributions and finds geochemical signals and mixing trends that constitute the characteristic structure of the multielemental data.","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181774","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":"Assessment of a pH optode for oceanographic moored and profiling applications","authors":"Taylor Wirth, Yuichiro Takeshita, Benjamin Davis, Ellen Park, Irene Hu, Christine L. Huffard, Kenneth S. Johnson, David Nicholson, Christoph Staudinger, Joseph K. Warren, Todd Martz","doi":"10.1002/lom3.10646","DOIUrl":"https://doi.org/10.1002/lom3.10646","url":null,"abstract":"As global ocean monitoring programs and marine carbon dioxide removal methods expand, so does the need for scalable biogeochemical sensors. Currently, pH sensors are widely used to measure the ocean carbonate system on a variety of autonomous platforms. This paper assesses a commercially available optical pH sensor (optode) distributed by PyroScience GmbH for oceanographic applications. Results from this study show that the small, solid‐state pH optode demonstrates a precision of 0.001 pH and relative accuracy of 0.01 pH using an improved calibration routine outlined in the manuscript. A consistent pressure coefficient of 0.029 pH/1000 dbar is observed across multiple pH optodes tested in this study. The response time is investigated for standard and fast‐response versions over a range of temperatures and flow rates. Field deployments include direct comparison to ISFET‐based pH sensor packages for both moored and profiling platforms where the pH optodes experience sensor‐specific drift rates up to 0.006 pH d<jats:sup>−1</jats:sup>. In its current state, the pH optode potentially offers a viable and scalable option for short‐term field deployments and laboratory mesocosm studies, but not for long term deployments with no possibility for recalibration like on profiling floats.","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181775","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":"Evaluating O2 : Ar, N2 : Ar, and 29,30N2 using membrane inlet mass spectrometry configured to minimize oxygen interference","authors":"Ashlynn R. Boedecker, Jason M. Taylor, Tyler H. Tappenbeck, Robert O. Hall, Caleb J. Robbins, J. Thad Scott","doi":"10.1002/lom3.10644","DOIUrl":"https://doi.org/10.1002/lom3.10644","url":null,"abstract":"Membrane inlet mass spectrometry (MIMS) provides detailed measures of dissolved <jats:sup>28,29,30</jats:sup>N<jats:sub>2</jats:sub>, O<jats:sub>2</jats:sub>, and argon (Ar) for estimating important gas fluxes and concentrations in aquatic ecosystems. Previous studies demonstrated a large O<jats:sub>2</jats:sub> scavenging effect while using a MIMS, where varying concentrations of O<jats:sub>2</jats:sub> can affect measured N<jats:sub>2</jats:sub> : Ar because O<jats:sub>2</jats:sub> interacts with N<jats:sub>2</jats:sub> in the ion source to produce NO<jats:sup>+</jats:sup> (<jats:italic>m</jats:italic>/<jats:italic>z</jats:italic> = 30), potentially decreasing the detected current for <jats:sup>28,29</jats:sup>N<jats:sub>2</jats:sub> and increasing the detected current for <jats:sup>30</jats:sup>N<jats:sub>2</jats:sub>. A common solution is to use a muffle furnace heated to 600°C with a copper reduction column to reduce the concentration of O<jats:sub>2</jats:sub> to minimal levels and accurately measure <jats:sup>28,29,30</jats:sup>N<jats:sub>2</jats:sub>. However, this solution eliminates the detection of O<jats:sub>2</jats:sub> in environmental samples, which is a major benefit of using a MIMS. We questioned whether the MIMS was sensitive enough to provide accurate O<jats:sub>2</jats:sub> estimates when using the furnace and whether the O<jats:sub>2</jats:sub> scavenging effect was real and consistent among MIMS. We conducted four separate experiments on three different MIMS to test the O<jats:sub>2</jats:sub> scavenging effect and the potential detection of O<jats:sub>2</jats:sub> when using a MIMS with furnace. The furnace removed ~ 99% of O<jats:sub>2</jats:sub>, and O<jats:sub>2</jats:sub> scavenging had little to no detectable effect on N<jats:sub>2</jats:sub> : Ar and an unclear effect on <jats:sup>29</jats:sup>N<jats:sub>2</jats:sub> : <jats:sup>28</jats:sup>N<jats:sub>2</jats:sub>, but increased <jats:sup>30</jats:sup>N<jats:sub>2</jats:sub> : <jats:sup>28</jats:sup>N<jats:sub>2</jats:sub>. In most cases, accurate O<jats:sub>2</jats:sub> data could be retrieved despite using the furnace. The need for O<jats:sub>2</jats:sub> reduction may be limited to measuring accurate <jats:sup>30</jats:sup>N<jats:sub>2</jats:sub> : <jats:sup>28</jats:sup>N<jats:sub>2</jats:sub> in isotope pairing studies, but without substantial loss of MIMS measurements used to describe O<jats:sub>2</jats:sub> dynamics.","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181785","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":"Optimizing observational arrays for biogeochemistry in the tropical Pacific by estimating correlation lengths","authors":"Winnie U. Chu, Matthew R. Mazloff, Ariane Verdy, Sarah G. Purkey, Bruce D. Cornuelle","doi":"10.1002/lom3.10641","DOIUrl":"https://doi.org/10.1002/lom3.10641","url":null,"abstract":"Global climate change has impacted ocean biogeochemistry and physical dynamics, causing increases in acidity and temperature, among other phenomena. These changes can lead to deleterious effects on marine ecosystems and communities that rely on these ecosystems for their livelihoods. To better quantify these changes, an array of floats fitted with biogeochemical sensors (BGC‐Argo) is being deployed throughout the ocean. This paper presents an algorithm for deriving a deployment strategy that maximizes the information captured by each float. The process involves using a model solution as a proxy for the true ocean state and carrying out an iterative process to identify optimal float deployment locations for constraining the model variance. As an example, we use the algorithm to optimize the array for observing ocean surface dissolved carbon dioxide concentrations (pCO<jats:sub>2</jats:sub>) in a region of strong air–sea gas exchange currently being targeted for BGC‐Argo float deployment. We conclude that 54% of the pCO<jats:sub>2</jats:sub> variability in the analysis region could be sampled by an array of 50 Argo floats deployed in specified locations. This implies a relatively coarse average spacing, though we find the optimal spacing is nonuniform, with a denser sampling being required in the eastern equatorial Pacific. We also show that this method could be applied to determine the optimal float deployment along ship tracks, matching the logistics of real float deployment. We envision this software package to be a helpful resource in ocean observational design anywhere in the global oceans.","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181786","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":"Simultaneous onboard analysis of seawater dissolved inorganic carbon (DIC) concentration and stable isotope ratio (δ13C‐DIC)","authors":"Zhentao Sun, Xinyu Li, Zhangxian Ouyang, Charles Featherstone, Eliot A. Atekwana, Najid Hussain, Wei‐Jun Cai","doi":"10.1002/lom3.10642","DOIUrl":"https://doi.org/10.1002/lom3.10642","url":null,"abstract":"Dissolved inorganic carbon (DIC) and its stable carbon isotope (<jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC) are valuable parameters for studying the aquatic carbon cycle and quantifying ocean anthropogenic carbon accumulation rates. However, the potential of this coupled pair is underexploited as only 15% or less of cruise samples have been analyzed for <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC because the traditional isotope analysis is labor‐intensive and restricted to onshore laboratories. Here, we improved the analytical precision and reported the protocol of an automated, efficient, and high‐precision method for ship‐based DIC and <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC analysis based on cavity ring‐down spectroscopy (CRDS). We also introduced a set of stable in‐house standards to ensure accurate and consistent DIC and <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC measurements, especially on prolonged cruises. With this method, we analyzed over 1600 discrete seawater samples over a 40‐d cruise along the North American eastern ocean margin in summer 2022, representing the first effort to collect a large dataset of <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC onboard of any oceanographic expedition. We evaluated the method's uncertainty, which was 1.2 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> for the DIC concentration and 0.03‰ for the <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC value (1<jats:italic>σ</jats:italic>). An interlaboratory comparison of onboard DIC concentration analysis revealed an average offset of 2.0 ± 3.8 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> between CRDS and the coulometry‐based results. The cross‐validation of <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C‐DIC in the deep‐ocean data exhibited a mean difference of only −0.03‰ ± 0.07‰, emphasizing the consistency with historical data. Potential applications in aquatic biogeochemistry are discussed.","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181787","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":"Stabilization of nitrite in the presence of the nitrification inhibitor allylthiourea (ATU) in freshwater nitrification rate measurements","authors":"Jade Bosviel,&nbsp;Katharina Kitzinger,&nbsp;Michael Pester","doi":"10.1002/lom3.10643","DOIUrl":"10.1002/lom3.10643","url":null,"abstract":"<p>Nitrification rate measurements provide critical information on the performance of an environmental process central to the N cycle and are best studied using isotope labeling techniques. However, combining the high sensitivity of isotope labeling techniques with selected inhibition of nitrifiers as a whole or of specific nitrifier guilds has not been established in limnology. This can be achieved with different concentrations of the commonly used nitrification inhibitor allylthiourea (ATU). In the ¹⁵N-ammonium oxidation technique, the converted isotope label is typically captured in an excess pool of ¹⁴N-nitrite. Here, we assessed how different storage conditions affect the stability of the nitrite pool in freshwater samples treated with ATU. When stored frozen, the nitrite pool was rapidly destabilized to 25–31% after 7 d of storage and even to less than 5% after storage exceeding 90 d for samples treated with ATU, thus making them unusable for rate determinations in these cost and labor-intensive experiments. In comparison, this was not the case in marine samples or freshwater samples not treated with ATU, where the nitrite pool remained stable. Building on these results, we tested two options to stabilize nitrite during the storage of freshwater samples. The nitrite pool was stable if samples were stored at 4°C instead of freezing. We recommend this option for short-term storage. For long-term storage, samples should be supplemented with 0.5 mmol L⁻¹ NaCl to increase salinity before freezing. As in marine samples, this stabilized the nitrite pool. Our results provide important guidance for the storage of non-saline samples used for nitrification rate measurements in freshwater environments.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10643","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181788","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":"Integrating visual and molecular approaches for fish eggs analysis: A study on formaldehyde fixation and storage procedures","authors":"Bahar Mozfar, Anders Thorsen, Alejandro Mateos‐Rivera, Geir Dahle, Rasmus Skern‐Mauritzen, Henning Wehde, Bjørn A. Krafft","doi":"10.1002/lom3.10640","DOIUrl":"https://doi.org/10.1002/lom3.10640","url":null,"abstract":"Accurate taxonomic classification and developmental stage determination of fish eggs are crucial for ecological monitoring, conservation efforts, and stock assessments. Traditional methods for fish and fisheries rely on visual examination of morphological traits, but they face challenges due to species overlap especially for early stages. Molecular tools, such as DNA barcoding, offer higher resolution in taxonomic identification but may not provide developmental stage information. This study explores the effectiveness of different formaldehyde fixation concentrations and storage procedures on fish eggs collected from Lofoten, Norway, for both visual and molecular analysis. Visual analysis successfully identified developmental stage for all fixation solutions. Molecular barcoding using the 16S rRNA gene identified up to 100% of eggs at the species level, with decreasing success rates over time when stored in formaldehyde fixation. The highest DNA barcoding success rates were accomplished using 4% formaldehyde fixation for 12‐ or 24‐h following transfer to ethanol. Using 0.5% and 1% formaldehyde fixation up to 8 weeks also resulted in high DNA success rates, but results deteriorated with increasing storage time. This study provides valuable insights for integrating visual and molecular methods for fish egg analysis, with practical implications for sample preservation during marine surveys.","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141885101","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":"Presence of oxygen in diffusive equilibrium in thin films (DET) probes: Effect on phosphate and iron porewater profiles and advice for correct deoxygenation and handling procedures","authors":"Anna-Marie Klamt,&nbsp;Theis Kragh,&nbsp;Ronnie N. Glud,&nbsp;Cecilie M. Wagner,&nbsp;Kasper Reitzel","doi":"10.1002/lom3.10639","DOIUrl":"10.1002/lom3.10639","url":null,"abstract":"<p>Diffusive equilibrium in thin films (DET) probes are passive samplers that are designed to reflect in situ porewater concentrations. In this study, we show that the gel and the plastic housing of DET probes store a substantial amount of oxygen (O₂) that affects the chemical composition of porewater. To ensure complete deoxygenation, DET probes need to be treated for 7 d with continuous nitrogen flow. Such fully deoxygenated probes can be handled in the air (exposure time: &lt; 90 s) and deployed to sediments through oxic water (exposure time: &lt; 2 s) without significant ad(b)sorption of O₂. Furthermore, we deployed a set of untreated (i.e., in equilibrium with atmospheric O₂) and a set of fully deoxygenated DET probes to lake sediments. The O₂ present in untreated DET probes altered iron (Fe) and phosphate (P) porewater profiles significantly. This is caused by the oxidation, immobilization, and accumulation of redox-sensitive Fe (oxyhydr)oxides in the probe over time. Since P has a high binding affinity to Fe (oxyhydr)oxides, it is not in equilibrium with the porewater and is overestimated as well. Our results highlight the importance of thorough deoxygenation of DET probes before deployment in sediments, especially when addressing redox-sensitive porewater species.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10639","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783544","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":"Sample preservation methods for nitrous oxide concentration and isotope ratio measurements in aquatic environments","authors":"Claudia Frey,&nbsp;Weiyi Tang,&nbsp;Bess B. Ward,&nbsp;Moritz F. Lehmann","doi":"10.1002/lom3.10638","DOIUrl":"10.1002/lom3.10638","url":null,"abstract":"&lt;p&gt;The nitrogen (N) and oxygen (O) stable isotope analysis of dissolved nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O) can provide important constraints on the sources and cycling of N&lt;sub&gt;2&lt;/sub&gt;O in aquatic environments. The isotopic composition of aqueous N&lt;sub&gt;2&lt;/sub&gt;O, both in field (natural abundance) or experimental (&lt;sup&gt;15&lt;/sup&gt;N-labeling) samples, however, may be altered by abiotic reactions involving nitrite (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;NO&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;&lt;/math&gt;) or hydroxylamine (NH&lt;sub&gt;2&lt;/sub&gt;OH) and microbial activity during sample storage, if samples are not adequately preserved. Here we tested five different preservatives, mercuric chloride (HgCl&lt;sub&gt;2&lt;/sub&gt;), copper sulfate (CuSO&lt;sub&gt;4&lt;/sub&gt;), zinc chloride (ZnCl&lt;sub&gt;2&lt;/sub&gt;), hydrochloric acid (HCl) mixed with sulfamic acid (SFA), and sodium hydroxide (NaOH), for fixing natural water samples from an estuary and a lake with different &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;NO&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;&lt;/math&gt; concentrations over a range of different storage times for N&lt;sub&gt;2&lt;/sub&gt;O analyses. ZnCl&lt;sub&gt;2&lt;/sub&gt; and CuSO&lt;sub&gt;4&lt;/sub&gt; decreased the pH, and led to abiotic N&lt;sub&gt;2&lt;/sub&gt;O production from &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt; &lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mn&gt;15&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;&lt;/math&gt;, shifting the N&lt;sub&gt;2&lt;/sub&gt;O isotopic composition significantly. Removal of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;NO&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;&lt;/math&gt; with a mixture of SFA and HCl did not always prevent the alteration of the original N and O isotope composition of N&lt;sub&gt;2&lt;/sub&gt;O, confirming the requirement for complete &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;NO&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;&lt;/math&gt; removal, and underscoring the biasing effects of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;NO&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;&lt;/math&gt; at very low pH, even at trace levels. At low &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10638","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783849","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}