Seasonal grain-size measurements of surface sediments off Helgoland@en

All sediment samples were obtained from Helgoland Roads (54.18°N, 7.90°E), which is located between the main island and the dune from Helgoland in the North Sea, German Bight, by scientific divers of the Alfred Wegner Institute (Bremerhaven, Germany) using push cores. Repeated sediment sampling was performed on a total of nineteen sampling dates in 2018 and 2019. Particle-size measurements were performed in the Particle-Size Laboratory at MARUM, University of Bremen with a Beckman Coulter Laser Diffraction Particle Size Analyzer LS 13320. Prior to the measurements, the samples were boiled with approximately 0.3 g tetra-sodium diphosphate decahydrate (Na~4~P~2~O~7~ * 10H~2~O, 3 min) to destroy aggregates. Sample preparation and measurements were carried out with deionized, degassed and filtered water (filter mesh size: 0.2 µm) to reduce the potential influence of gas bubbles or particles within the water. The obtained results provide the particle-size distribution of a sample from 0.04 to 2000 μm divided in 116 size classes. The calculation of the particle sizes relies on the Fraunhofer diffraction theory and the Polarization Intensity Differential Scattering (PIDS) for particles from 0.4 to 2000 µm and from 0.04 to 0.4 µm, respectively. The reproducibility is checked regularly by replicate analyses of three internal glass-bead standards and is found to be better than ±0.7 µm for the mean and ±0.6 µm for the median particle size (1sigma). The average standard deviation integrated over all size classes is better than ±4 vol% (note that the standard deviation of the individual size classes is not distributed uniformly). All provided statistic values are based on a geometric statistic.所有沉积物样品均由德国不来梅港阿尔弗雷德·魏格纳研究所（Alfred Wegner Institute）的科研潜水员采用推式岩心采样器（push cores），采自位于德国北海德国湾黑尔戈兰岛主岛与沙丘之间的黑尔戈兰航道（Helgoland Roads，坐标54.18°N，7.90°E）。研究团队于2018至2019年间共计开展19次重复沉积物采样工作。粒径测量工作于不来梅大学MARUM海洋环境科学中心粒径实验室完成，使用仪器为贝克曼库尔特激光衍射粒径分析仪LS 13320（Beckman Coulter Laser Diffraction Particle Size Analyzer LS 13320）。测试前，需将样品与约0.3g四焦磷酸四钠十水合物（tetra-sodium diphosphate decahydrate，化学式Na₄P₂O₇·10H₂O）一同煮沸3分钟以破坏颗粒聚集体。样品制备与粒径测量均使用经脱气、过滤的去离子水完成（滤膜孔径0.2μm），以降低水中气泡或杂质颗粒对测试结果的潜在干扰。本次测试得到的样品粒径分布数据覆盖0.04μm至2000μm的范围，共划分为116个粒径等级。粒径计算分别采用夫琅禾费衍射理论（Fraunhofer diffraction theory）与偏振强度差散射技术（Polarization Intensity Differential Scattering，PIDS），对应0.4μm至2000μm、0.04μm至0.4μm的粒径区间。本测试的重现性通过对3种内部玻璃微珠标准品的重复分析定期验证，结果显示平均粒径的重现性误差优于±0.7μm，中位粒径的重现性误差优于±0.6μm（1σ标准差）。所有粒径等级的整合平均标准偏差优于±4体积%（需注意单个粒径等级的标准偏差并非均匀分布）。所有给出的统计值均基于几何统计方法计算得到。