Nutrient concentration in seawater samples, collected from the underway supply, CTD and trace metal rosettes in the Southern Ocean during the austral summer of 2016/2017, on board the Antarctic Circumnavigation Expedition (ACE). ***** Dataset abstract ***** This dataset presents concentrations of nutrients (µmol/L): nitrous oxide (NOx), nitrate, nitrite, ammonium (NH4), phosphate (PO4) and silicic acid (Si), measured in samples of seawater during the Antarctic Circumnavigation Expedition (ACE). Samples were collected from CTD and trace metal rosette (TMR) deployments, as well as from the underway water supply on board, then analysed by flow injection following certified standards. This data was collected to support physical, chemical and biological oceanography studies in the Southern Ocean, conducted as part of ACE during the austral summer of 2016/2017. ***** Original data collection ***** Samples were collected in duplicate using polyethylene gloves for all samples from the trace metal rosette and unpowdered latex gloves for all others. 15 mL Falcon tubes and caps were rinsed three times with about 5-10 ml of seawater prior to being filled with 11-12 mL seawater. Samples were stored upright in a freezer until analysis. Samples from each sampling station were gathered in a labelled ziplock bag in the ship’s walk-in freezer (-20 degrees C). TMR sample numbers include the sampling date and time in ship time rather than UTC. The latter is specified within the data file in the "date time of sampling" field. Some sample numbers also include depths that were expected before deployment. Correct sampling depths can be found in the "depth" field. Latitude and longitude of data collection from the quality-checked one-second resolution GPS track of the cruise (Thomas and Pina Estany, 2019) are provided for the date and time of the start of sampling. More information about sampling can be found in the ACE cruise report (Walton and Thomas, 2018). ***** Sample analysis ***** Analyses were carried out between November 2017 and February 2018 using a QuAAtro Seal Analytical autoanalyser, following Seal Analytical methods (listed below). These methods are based on commonly used colorimetric techniques for nutrients in seawater. - Nitrate+phosphate Method No. Q-068-05 Rev. 6 - Nitrite Method No. Q-070-05 Rev. 4 - Phosphate Method No. Q-064-05 Rev. 6 - Silicic acid Method No. Q-066-05 Rev. 3 The calibration is based on Certipur Standard Solutions using the following solutions from MERCK: Nitrite standard solution (Certipur, traceable to Standard Reference Materials (SRM) from the National Institue of Standards and Technology (NIST; www.nist.gov) NaNO2 in H2O, 1000 mg/L) Ammonium standard solution (Certipur, traceable to SRM from NIST NH4Cl in H2O, 1000 mg/L) Nitrate standard solution (Certipur, traceable to SRM from NIST NaNO3 in H2O, 1000 mg/L) Silicon standard solution (Certipur, traceable to SRM from NIST SiO2 in NaOH 0.5 mol/l, 1000 mg/L) Phosphate standard solution (Certipur, traceable to SRM from NIST KH2PO4 in H2O, 1000 mg/L) Based on these standards, the calibration curve was prepared. The first step was to prepare two mixed solutions which were then used to prepare the final 5-point calibration in 50 ml bulbs. Concentrations and pipette volumes are shown below: - Mixed standard 1 - Nitrate 3.2 ml Silicic acid 2.5 ml - Mixed standard 2 - Nitrite 0.1 ml Phosphate 0.6 ml Ammonium 0.15 ml Pipette volumes used from each of the mixed standards: Standard 1 mixed std 1: 0.125 ml mixed std 2: 0.125 ml Standard 2 mixed std 1: 0.25 ml mixed std 2: 0.25 ml Standard 3 mixed std 1: 0.5 ml mixed std 2: 0.5 ml Standard 4 mixed std 1: 1 ml mixed std 2: 0.75 ml Standard 5 mixed std 1: 1.5 ml mixed std 2: 1 ml Concentrations for each of the standards and nutrients can be seen in the file data_analysis_nutrient_concentration_standards.csv These standards are measured in duplicates, r^2 is > 0.999. Limit of detection yielded: 0.16, 0.013, 0.03 and 0.07 umol/L for Nitrate+Nitrite, Phosphate, Nitrite and Silicic acid, respectively. ***** Quality checking ***** In order to evaluate the accuracy of the analysis, KANSO LTD (Japan) Certified Reference Materials (CRMs) were measured during the analysis. CRM information is typically provided (by KANSO) with two types of uncertainty: “expanded uncertainty” and “bottle uncertainty”. With the former being 2x the root sum squared of different uncertainty sources assessed in the production of CRMs. The latter is the standard deviation of measuring 150 bottles in duplicate. The former tends to be higher than the latter, as expected. Here we show the “expanded uncertainty” since we considered it is more representative of the uncertainty we would typically incurred, from collecting a nutrient sample to the moment it is analysed. Typical results of analysis CC CRM can be seen in the file quality_checking_cc_crm_analysis_results.csv One data point (sample AT/ACE/1/15/007/263/ME/Nutrients_15m from event 263, depth of 15m, sampled by the trace metal rosette) was removed because of abnormal concentrations as follows: nitrous oxide -0.17 umol/L, phosphate 73.67, nitrate 42.58 umol/L, silicic acid 0.4 umol/L, ammonium -0.06 umol/L, nitrate -43.93 umol/L. ***** Dataset contents ***** - ace_seawater_nutrient_data.csv, data file, comma-separated values - data_analysis_nutrient_concentration_standards.csv, metadata, comma-separated values - quality_checking_crm_analysis_results.csv, metadata, comma-separated values - nutrient_concentrations_along_track_visualisation.png, metadata, portable network graphics - ace_seawater_nutrients_comparison_plots_tmr_ctd.pdf, metadata, portable document format - data_file_header.txt, metadata, text - README.txt, metadata text - change_log.txt ***** Dataset contact ***** Christel Hassler, University of Geneva, Department of F.-A. Forel for Environmental and Aquatic Sciences, Switzerland. ORCID: 0000-0002-8976-5469. Email: christel.hassler@epfl.ch ***** Dataset license ***** This ACE seawater nutrients dataset from CTD and TMR samples is made available under the Creative Commons Attribution 4.0 International License (CC BY 4.0) whose full text can be found at https://creativecommons.org/licenses/by/4.0/ ***** Dataset citation ***** Please cite this dataset as: Hassler, C. and Ellwood, M. (2020). Nutrient concentration in seawater samples, collected from the underway supply, CTD and trace metal rosettes in the Southern Ocean during the austral summer of 2016/2017, on board the Antarctic Circumnavigation Expedition (ACE). (Version 1.1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3923586