Characterizing spectral and geochemical signatures of Armenian top soils through combined proximal visible near infrared and x-ray fluorescence spectroscopy

Soil health and sustainable use of soil resources are directly related to their main characteristics and the level of alteration. Effective soil monitoring in Armenia is currently limited by a scarcity of comprehensive datasets of soil chemical, physical and biological indicators. This pilot study investigates the spectral-geochemical signatures of Armenian soils by integrating proximal VIS–NIR (350–2500 nm) and X-ray fluorescence (Rigaku NEX DE XRF) spectroscopy. Thirty topsoil samples were collected across five regions, representing diverse soil types. Geochemical analysis determined 14 elements and 5 oxides, while mineralogy and Soil Organic Matter (SOM) were assessed via XRD and loss on ignition, respectively. K-means clustering identified three distinct geochemical associations reflecting parent material influences and anthropogenic impacts. Partial Least Squares Regression (PLSR) was employed to model the spectral response of major macrocomponents (SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, K 2 O, and SOM). Results indicated that Al 2 O 3 (R 2 test = 0.484) and Fe 2 O 3 (R 2 test = 0.499) yielded relatively best predictive performance, attributed to their well-defined absorption features. It was found that while SOM showed high calibration accuracy (R 2 train = 0.923), its independent testing performance was moderate (R 2 test = 0.356), suggesting overfitting due to the limited sample size. Models for SiO 2 , CaO, and K 2 O demonstrated limited reliability. This research provides an initial methodological foundation for a national Armenian soil spectral library, confirming the feasibility of proximal sensing for regional soil characterization while highlighting the necessity for larger datasets to improve model generalization. By demonstrating the utility of proximal spectroscopic techniques for rapid soil characterization, this research contributes to Sustainable Development Goal (SDG) 15 (Life on Land) by establishing a methodological foundation for digital soil mapping and land degradation monitoring in Armenia, supporting long-term soils resource and sustainable agricultural management SDG 2 (Zero Hunger).