Concentrations of size-fractionated particulate thorium and protactinium isotopes (Th-232, Th-230, Pa-231) in seawater collected during the U.S. GEOTRACES Arctic cruise (HLY1502, GN01) on USCGC Healy from August to October 2015

<p>This dataset contains concentrations of size-fractionated particulate thorium and protactinium isotopes (Th-232, Th-230, Pa-231) in seawater collected during the U.S. GEOTRACES Arctic cruise (HLY1502, GN01) on USCGC Healy from August to October 2015. This is compiled data produced by two laboratories with the following associations: Lamont-Doherty Earth Observatory of Columbia University (LDEO) and the University of Minnesota (UMN). All data have been deemed intercalibrated by the International GEOTRACES Standards and Intercalibration (S&amp;I) Committee.</p> <p><strong>Naming Conventions:</strong><br /> Parameter names in the form such as \"Th_232_SPT_CONC_PUMP\" are adopted based on a recommendation from the GEOTRACES community (<a href=\"https://www.geotraces.org/parameter-naming-conventions/\" target=\"_blank\">https://www.geotraces.org/parameter-naming-conventions/</a>).</p> <p>The \"small particulate\" (SPT) data refers to the particle size class 0.8-51 µm and is sometimes also called the \"suspended\" size fraction. The \"large particulate\" (LPT) data refers to particles greater than 51 µm and is sometimes referred to as the \"sinking\" size fraction. The particulate samples were collected by in-situ pumping over two loaded filter holders/flowpaths. One filter holder/flowpath was loaded with paired 0.8 µm Pall Supor800 polyethersulfone filters behind a 51 µm Sefar polyester mesh prefilter (\"Supor-side\") and the other filter holder/flowpath was loaded with paired 1 µm Whatman QMA quartz fiber filters behind a 51 µm Sefar polyester mesh prefilter (\"QMA-side\") (see Xiang and Lam, 2020 for particulate sampling methodology). Analysis of the paired Supor filters represents a particle size class approximating 0.45-51 µm (Bishop et al., 2012), while the top filter alone represents 0.8-51 µm and it is this size class referred to here as the \"small particulate\" fraction. We measured a select number of top and bottom Supor filters separately for radionuclides and found that the bottom filters had radionuclide levels that were indistinguishable from procedural blanks (\"dipped\" filter blanks). Therefore, whether or not samples were analyzed as paired Supor filters, or the top Supor filter alone, we infer the \"small particulate\" data to represent the 0.8-51 µm particle size class or \"suspended\" size fraction. The \"large particulate\" data is based on the analysis of the QMA-side 51 µm Sefar polyester mesh prefilters. Only a selection of \"large particulate\" samples were analyzed and those analyses were all performed at the University of Minnesota (UMN).</p> <p><strong>Units of Measurement:</strong><br /> Radionuclide concentrations are given as micro-Becquerel (10e-6 Bq, µBq or micro-Bq) per kilogram seawater for Th-230 and Pa-231, and picomole (10e-12 mol, pmol) per kilogram seawater for Th-232. A Becquerel is the SI unit for radioactivity and is defined as 1 disintegration per second. These units are recommended by the GEOTRACES community.</p><p>本数据集包含2015年8月至10月期间，在美国海岸警卫队希利号（USCGC Healy）执行的美国GEOTRACES北极科考航次（航次编号HLY1502、GN01）中采集的海水中分级颗粒态钍与镤同位素（Th-232、Th-230、Pa-231）浓度。本数据集由两家合作实验室整合完成，分别为哥伦比亚大学拉蒙特-多尔蒂地球观测站（Lamont-Doherty Earth Observatory, LDEO）与明尼苏达大学（University of Minnesota, UMN）。所有数据均通过国际GEOTRACES标准与互校委员会（Standards and Intercalibration Committee, S&I）的互校认定。</p> <p><strong>命名规范：</strong><br /> 本数据集采用形如"Th_232_SPT_CONC_PUMP"的参数命名规则，该规则参考自GEOTRACES社区的官方建议（<a href="https://www.geotraces.org/parameter-naming-conventions/" target="_blank">https://www.geotraces.org/parameter-naming-conventions/</a>）。</p> <p>“小颗粒态”（SPT）数据对应的粒径范围为0.8~51 µm，有时也被称为“悬浮态”粒径组分；“大颗粒态”（LPT）数据对应的粒径为大于51 µm的颗粒，亦被称为“沉降态”粒径组分。颗粒态样品通过原位泵采法采集，搭载两套预装的滤膜支架/流路系统：其中一套滤膜支架/流路在51 µm Sefar聚酯网预滤膜后方安装配对的0.8 µm Pall Supor800聚醚砜滤膜（记为“Supor侧”）；另一套则在同款51 µm Sefar聚酯网预滤膜后方安装配对的1 µm Whatman QMA石英纤维滤膜（记为“QMA侧”），颗粒态采样方法详见Xiang与Lam于2020年发表的研究。<br /> 对配对Supor滤膜的分析对应近似0.45~51 µm的粒径组分（Bishop等，2012），而仅使用上层滤膜则对应0.8~51 µm的粒径范围，即本研究中定义的“小颗粒态”组分。本研究对部分单独的上层与下层Supor滤膜进行了放射性核素分析，结果显示下层滤膜的放射性核素水平与过程空白（“浸泡式”滤膜空白）无显著差异。因此无论样品采用配对Supor滤膜分析，还是仅使用上层Supor滤膜分析，均可认定“小颗粒态”数据对应0.8~51 µm粒径组分或“悬浮态”粒径组分。<br /> “大颗粒态”数据基于QMA侧的51 µm Sefar聚酯网预滤膜的分析结果，仅对部分“大颗粒态”样品开展了分析，且全部分析工作均在明尼苏达大学（UMN）完成。</p> <p><strong>测量单位：</strong><br /> Th-230与Pa-231的放射性核素浓度单位为每千克海水微贝可（10⁻⁶ Bq，即µBq或micro-Bq）；Th-232的浓度单位为每千克海水皮摩尔（10⁻¹² mol，即pmol）。贝可（Becquerel）是放射性活度的国际单位制（SI）单位，定义为每秒发生一次核衰变。上述单位均为GEOTRACES社区推荐使用的标准单位。</p>