DOI: 10.5281/zenodo.18400657
title: Laboratory soil reflectance spectra and Zn, Pb, Cd concentrations (pXRF and ICP-OES) used in hyperspectral soil contamination modelling.

description: This record contains the laboratory spectral and geochemical reference data of Zn, Pb and Cd used in the study “Hyperspectral Soil Heavy Metal Prediction via Privileged-Informed Residual Correction” (Remote Sensing, 2025, 17(12), 1987; DOI: 10.3390/rs17121987). The dataset supports modelling of Zn, Pb, and Cd concentrations in topsoil using laboratory spectroscopy and provides paired reference concentrations measured by portable XRF (pXRF) and ICP-OES. Airborne hyperspectral imagery used in the study is not included.
description: Study context and sampling

Samples originate from agricultural fields east and northeast of Celje, Slovenia, impacted by historical industrial activities. Soil was collected from 0–5 cm depth at georeferenced sites using a triangular incremental design (three subsamples per site, vertices of a ~50 cm triangle; site defined at the centroid). 

Sample preparation and laboratory spectroradiometry

Subsamples were dried at 40 °C for 3 days, cleared of coarse fragments, ground, and sieved to 2 mm. Laboratory reflectance spectra were measured using an ASD FieldSpec III Pro FR. The instrument provides a spectral resolution of approximately 3 nm up to 700 nm and 10 nm above 700 nm, with sampling intervals of 1.4 nm (350–700 nm) and 2.0 nm (700–2500 nm). Radiometric calibration to a Zenit Polymer white reference panel (nominal reflectance 95%) was performed every 10 measurements. For each subsample, three raw spectra were acquired and are provided in this dataset. In the associated article, these spectra were averaged per subsample prior to analysis; no averaging is applied to the spectra distributed here.

Chemical analyses

Zn, Pb, and Cd were measured by:





Portable XRF (Olympus Delta 50) on subsamples (two measurements per sample, 90 s per measurement; instrument Cd detection limit reported as 4.5 ppm).




ICP-OES after microwave-assisted digestion of the aqua regia soluble fraction, reported at the site level (one ICP-OES result per site, representing the mean concentration of the three subsamples).



Handling of Cd values below detection limit

For Cd values reported below the detection limits, Cd is stored as missing (NA) In the associated article, these below-detection observations were replaced by 0.61 ppm, corresponding to the regional median natural background concentration of Cd for the Inner Carniola–Celje Basin, to avoid zeros and retain modelling consistency.

Relationship to the article

These data were used to develop and evaluate the modelling framework described in the associated article, including comparisons between pXRF and ICP-OES reference concentrations and integration of laboratory spectra with downstream spectral feature engineering.
description: Privacy and linkage

To respect landowner and site privacy, geographic coordinates are not provided. Linkage across files is enabled via anonymised identifiers sample_id and subsample_id. Researchers interested in spatially explicit validation or coordinate access for reproducibility may contact the corresponding authors to discuss data access under an appropriate agreement.

Files in this record

spectra_raw.csv

Long format table of laboratory reflectance spectra. Each row represents a single wavelength measurement for a given subsample. Columns include sample_id, subsample_id, wavelength_nm (nm), and reflectance. Raw (non-averaged) spectra are provided.

pxrf_measurements.csv

Subsample level geochemical measurements obtained by portable XRF (pXRF). One row per subsample. Columns include sample_id, subsample_id, and element concentrations in ppm. Cd values below the instrument detection limit are stored as missing (NA); in the associated article these values were imputed for modelling as described in the Methods.

icp_oes_measurements.csv

Sample level geochemical reference measurements obtained by ICP-OES following microwave assisted aqua regia digestion. One row per sample, representing the mean concentration across three subsamples. Columns include sample_id and element concentrations in ppm (at least Zn, Pb, Cd; additional elements may be present depending on laboratory reporting). Cd values stored as missing (NA) correspond to values treated as below detection or imputed in the article, as described in the Methods.

dataset.parquet

Integrated dataset in Apache Parquet format combining laboratory spectra, pXRF measurements, and ICP-OES reference concentrations using sample_id and subsample_id. This file is intended for efficient reuse in data analysis and machine learning workflows and contains the same information as the individual CSV files in a single, columnar dataset.

Additional variables

Additional variables (for example pH, CaCO3, organic matter, total carbon, total nitrogen, plant available phosphorus as P2O5 and potassium as K2O) were measured during the broader study but are not included in this Zenodo record. These data may be made available upon reasonable request for research purposes.
description: Acknowledgements

We acknowledge the Faculty of Chemistry and Chemical Technology, University of Ljubljana, for support with ICP-OES analyses, and the Biotechnical Faculty, University of Ljubljana, for support with soil sampling and pedological work. We further acknowledge the collaborators at the Czech University of Life Sciences, Prague, for support and access to laboratory soil spectroscopy facilities. We would like to thank the Slovenian Research and Innovation Agency (ARIS) for funding this work through the Research Programmes P1-0153 and P2-0406.