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Micro-near-infrared (Micro-NIR) spectroscopy has emerged as a promising technique for accurate and cost-effective estimation of soil attributes compared to traditional wet chemistry methods and conventional NIR spectroscopy. Despite its potential, the full extent of its capabilities and applications under different soil conditions remained unexplored. This study has evaluated the potential of a low-cost micro-NIR sensor for predicting soil organic carbon (SOC) and clay contents in agricultural soils under dry and fresh conditions. Two sets of soil samples i.e., A (92 samples, Netherlands) and B (92 samples, Belgium, France, and Germany) were collected and analysed for SOC and clay contents using standard laboratory methods. A micro-NIR of 2000 ∼ 2450 nm spectral range with 18–28 nm resolution (NIRONE D2.5, Spectral Engine, Germany) was used to scan both fresh and air-dried soil samples. Partial least squares regression (PLSR) models were developed for each dataset separately with and without feature selection using competitive adaptive reweighted sampling (CARS), successive projections algorithm (SPA), and slime mould algorithm (SMA). Micro-NIR sensor performed differently for the two datasets, predicting SOC and clay contents accurately for the dataset A while failing for the dataset B. The best accuracy achieved for SOC in the dataset A-fresh (coefficient of determination in prediction (R P 2) = 0.76 and root mean square errors in prediction (RMSE P) = 0.27 %) was improved with the dry samples (R P 2 = 0.81 and RMSE P = 0.27 %). The prediction of clay content was rather poor (R P 2 = 0.48 and RMSE P = 5 %). Feature selection by SMA and CARS methods improved SOC prediction for the dataset A of fresh (R p 2 = 0.79 and RMSE P = 0.25 %) and dry soils (R p 2 = 0.84 and RMSE P = 0.25 %), respectively. Using CARS improved the results of clay prediction for the dataset A of dry soil (R p 2 = 0.56; RMSE P = 4.62 %). Poor performance for the dataset B could be attributed to the non-normal data distribution (SOC skewness = 4.30 and clay skewness = 3.05) and the larger soil variability encountered including soil types. Therefore, this study indicates that a micro-NIR sensor is a potential innovation and can predict SOC accurately and clay with rather moderate accuracy for a normally distributed dataset. • Micro-NIR sensor can accurately predict soil organic carbon. • Micro-NIR sensor can predict soil clay content to a certain degree of accuracy. • Feature analysis can enhance the accuracy of micro-NIR for SOC and clay content predictions. • Sample's attributes distribution has influence on the prediction using micro-NIR. [ABSTRACT FROM AUTHOR]

[Display omitted] • - A methdological alternative to handle highly censored As data is developed. • - Higher risk associated with warmer, higher areas with clayey and phosphorus-rich soils. • - Higher As concentrations in Portugal, Spain, Austria, France and Belgium. • - Countries present a non-negligible risk of exceeding the 45 mg/kg limit of action. • - As concentrations exceed background values, but the threshold adopted is uncertain. Arsenic (As) is a versatile heavy metalloid trace element extensively used in industrial applications. As is carcinogen, poses health risks through both inhalation and ingestion, and is associated with an increased risk of liver, kidney, lung, and bladder tumors. In the agricultural context, the repeated application of arsenical products leads to elevated soil concentrations, which are also affected by environmental and management variables. Since exposure to As poses risks, effective assessment tools to support environmental and health policies are needed. However, the most comprehensive soil As data available, the Land Use/Cover Area frame statistical Survey (LUCAS) database, contains severe limitations due to high detection limits. Although within International Organization for Standardization standards, the detection limits preclude the adoption of standard methodologies for data analysis. The present work focused on developing a new method to model As contamination in European soils using LUCAS soil samples. We introduce the GAMLSS-RF model, a novel approach that couples Random Forests with Generalized Additive Models for Location, Scale, and Shape. The semiparametric model can capture non-linear interactions among input variables while accommodating censored and non-censored observations and can be calibrated to include information from other campaign databases. After fitting and validating a spatial model, we produced European-scale As concentration maps at a 250 m spatial resolution and evaluated the patterns against reference values (i.e., two action levels and a background concentration). We found a significant variability of As concentration across the continent, with lower concentrations in Northern countries and higher concentrations in Portugal, Spain, Austria, France and Belgium. By overcoming limitations in existing databases and methodologies, the present approach provides an alternative way to handle highly censored data. The model also consists of a valuable probabilistic tool for assessing As contamination risks in soils, contributing to informed policy-making for environmental and health protection. [ABSTRACT FROM AUTHOR]

Abstract: The Boom Clay formation (Oligocene) is studied as a reference host rock for methodological studies on deep geological disposal of radioactive waste. During excavation of galleries within the Clay formation (HADES underground research facility, Mol, Belgium), the physico-chemical conditions are significantly modified as an air–clay interface is created. In order to study the long-term impact of the air–clay contact on the organic matter contained in the Boom Clay, two types of samples were studied: (1) a reference series of clay samples having been in contact with the atmosphere of the HADES gallery for increasing times up to several years and (2) unaltered clay samples submitted to artificial oxidation in a ventilated oven at 80°C. The evolution of geochemical data of the two series was compared using Rock-Eval pyrolysis, GC–MS and size exclusion chromatography. The organic matter of the unaltered clays sampled in the HADES galleries is dominated by type III kerogen (terrestrial) with some contribution of type II (marine) and is thermally immature. The evolution of geochemical parameters during air alteration for the two series are very similar. They show progressive oxidation of kerogen accompanied by the release of bitumen enriched in low molecular weight constituents. Molecular analysis evidences the presence of a complex mixture of aliphatic and aromatic O-bearing compounds, inherited from the degradation of kerogen as well as from the clay catalyzed oxidation of the bitumen. These results show that (1) air oxidation is a major process in the in situ alteration of the organic matter of Boom Clay within the HADES galleries, (2) laboratory oxidation experiments at 80°C yield similar results as in situ air alteration of Boom Clay and (3) artificial air oxidation may be used to assess the long term exposure of the organic matter to air. [Copyright &y& Elsevier]

Boom clay, a stiff clay, has been selected as a potential host formation for the geological disposal of radioactive waste in Belgium. The underground research facility HADES has been constructed to enable various in situ experiments to be performed on Boom clay so as to study the feasibility of high-level radioactive waste disposal, and to provide reliable data on the performance of Boom clay as a host formation. Among the various laboratory studies performed on samples extracted from the HADES facility to investigate the thermo-hydro-mechanical behaviour of Boom clay, relatively few were devoted to the time-dependent behaviour, limiting any relevant analysis of the long-term behaviour of the disposal facility. The present work aims at investigating the time-dependent behaviour of Boom clay under both thermal and mechanical loading. High-pressure triaxial tests at controlled temperatures were carried out for this purpose. The tests started with constant-rate thermal and/or mechanical consolidation and ended with isobar heating and/or isothermal compression at a constant stress rate or by step loading. The results obtained confirmed the effect of the overconsolidation ratio (OCR) on the thermal volume changes (i.e. thermal dilation under high OCRs and thermal contraction with OCR close to unity). Significant effects of temperature as well as of compression and heating rates were also observed on the volume change behaviour. After being loaded to a stress lower than the preconsolidation pressure (5 MPa) at a low temperature of 25°C and at a rate lower than 0.2 kPa/min, the sample volume changes seemed to be quite small, suggesting a full dissipation of pore water pressure. By contrast, after being subjected to high loading and heating rates (including step loading or step heating), the volume changes appeared to be significant, particularly in the case of stresses much higher than the preconsolidation pressure. Because of its low permeability, full consolidation of Boom clay required a long period of time, and it was difficult to distinguish consolidation and creep from the total volume change with time. [ABSTRACT FROM AUTHOR]

The research and development programme on geological disposal for high-level and long-lived waste (HLW) in Belgium was initiated in 1974. A deep tertiary clay formation, the Boom Clay, present under the Mol-Dessel nuclear site, was selected as a reference host formation for experimental purposes. The construction of the underground laboratory HADES (at a depth of 223 m, initiated in 1980 and extended in 2002) allowed the building of a valuable geotechnical database, and led to the development of improved excavation techniques that significantly reduce the excavation-damaged zone (EDZ). Since the operational start of HADES about 25 years ago, many geotechnical measurements have been performed around excavations. Comparison between in situ measurements and modelling results allowed a continuous improvement of our knowledge on the Boom Clay behaviour. Important issues for interpreting the measurements correctly are good control of the excavation parameters and the boundary conditions. An extensive characterisation of the hydromechanical response of Boom Clay around an excavation for short- and long-term conditions has been performed. One important finding was the occurrence of measurable hydraulic effects at a distance of about 60 m (12.5 tunnel diameters) ahead of the tunnel excavation. [ABSTRACT FROM AUTHOR]