Raw data on trace element concentrations in seawater of the Hellenic Volcanic Arc

This dataset contains raw trace element concentration data from seawater samples collected during scientific missions of the nexus monARC project. The data were generated to support marine environmental monitoring and the future validation of citizen science data related to marine environmental quality. Sampling was conducted during multiple field campaigns between 2023 and 2025 in the Hellenic Volcanic Arc (Aegean Sea). Sampling locations were accessed either by sailing vessel or from land. Seawater samples were collected at depths ranging from 0 to 500 m across 30 sampling stations. Geographic coordinates and sampling depths are provided for each sample. Samples were collected using Niskin bottles or polypropylene containers, filtered through 0.20 μm cellulose filters, and preserved by acidification with suprapure nitric acid, following established trace-metal clean protocols. Samples were stored at 4 °C until analysis. Trace element concentrations were determined using ICP-MS (Agilent 7900). Calibration was performed using internal standards. Analytical bias was assessed through the analysis of three reference materials, and analytical precision was evaluated by duplicate analyses of selected samples. The dataset contains raw analytical outputs and has not been further corrected or interpreted beyond standard instrumental processing. The data files are provided in XLSX format and include sample identifiers, geographic coordinates, sampling depth, physicochemical in situ measurements, and elemental concentrations, reported in μg L⁻¹. Missing values are indicated as empty cells. These data are released to support open science, method development, and future integration into marine environmental assessment frameworks, including those developed within the nexus monARC project. Users are advised to consider the raw nature of the dataset and associated methodological constraints when reusing the data.