Akter et al. (2025) Comparing the Accuracy of Soil Moisture Estimates Derived from Bulk and Energy-Resolved Gamma Radiation Measurements

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Identification

• Journal: Sensors
• Year: 2025
• Date: 2025-07-17
• Authors: Sonia Akter, Johan Alexander Huisman, Heye Bogena
• DOI: 10.3390/s25144453

Research Groups

Not specified in the provided text.

Short Summary

This study compares the accuracy of soil moisture (SM) estimation using bulk environmental gamma radiation (EGR) from a Geiger-Mueller counter against specific $^{40}\text{K}$ radiation measurements. The results demonstrate that $^{40}\text{K}$ measurements provide significantly higher accuracy because they are less susceptible to interference from radon and biomass.

Objective

• To evaluate the extent to which confounding factors, specifically soil radon emanation and biomass shielding, deteriorate the accuracy of SM estimates derived from bulk EGR compared to reference $^{40}\text{K}$ gamma radiation measurements.

Study Configuration

• Spatial Scale: Local (single agricultural field).
• Temporal Scale: Seasonal (analysis includes winter and summer periods).

Methodology and Data

• Models used: Theoretical functional relationship for SM estimation; Wavelet coherence analysis.
• Data sources: In situ soil moisture sensors, a Geiger-Mueller counter ($\text{EGR}_{\text{G-M}}$), a gamma spectrometer ($^{40}\text{K}$), and a meteorological station.

Main Results

• $^{40}\text{K}$ measurements yielded a higher SM prediction accuracy with a Root Mean Square Error (RMSE) of 3.39 vol. % (using a theoretical $\alpha$ value of 1.11).
• $\text{EGR}_{\text{G-M}}$ measurements showed lower accuracy with an RMSE of 6.90 vol. %.
• Wavelet coherence analysis identified that $\text{EGR}_{\text{G-M}}$ accuracy was reduced by radon-induced noise during winter and biomass shielding during summer.

Contributions

• The study quantifies the accuracy gap between bulk EGR and specific $^{40}\text{K}$ radiation for soil moisture monitoring.
• It identifies the specific seasonal confounding factors (radon and biomass) affecting G-M counters and suggests that biomass correction can improve the utility of operational radioactivity monitoring networks for SM estimation.

Funding

Not specified in the provided text.

Citation

@article{Akter2025Comparing,
  author = {Akter, Sonia and Huisman, Johan Alexander and Bogena, Heye},
  title = {Comparing the Accuracy of Soil Moisture Estimates Derived from Bulk and Energy-Resolved Gamma Radiation Measurements},
  journal = {Sensors},
  year = {2025},
  doi = {10.3390/s25144453},
  url = {https://doi.org/10.3390/s25144453}
}