Use of nuclear techniques in soil science: A literature review of the Brazilian contribution

Abstract

This review presents the basic research and some applications of the gamma-ray attenuation, neutron gauges, and 137 Cs fallout techniques for studying soil physical processes and properties. The selected studies aimed to give the readers a general idea of the use of these nuclear techniques carried out by Brazilian researchers in the past decades. It is expected to assist future researchers by identifying knowledge gaps and opportunities for applying the methods presented here. Around 100 studies were selected for this review. The papers dealing with gamma-ray attenuation are mostly related to the analysis of soil radiation interactions, the measurement of basic soil physical properties, the evaluation of hydraulic conductivity, water retention curve, and soil mechanical analysis. Neutron gauge applications are related to monitoring the water distribution and balance at the field scale, procedures for calibrating the existing gauge for the Brazilian soils, and analyzing the spatial and temporal variability of the soil water content. The 137 Cs methodology involves studies about the erosion and sediment deposition in small watersheds and riparian zones, the spatial variability of 137 Cs inventories at reference sites, and the measurement of sediment spatial distributions. Future studies with the gamma-ray attenuation methodology should focus on a better comprehension of the photon interaction with the soil and a correct selection of photon energies to investigate contrasting soils. This is mandatory for adopting it as a reliable tool for soil characterization. This review also revealed that the challenges for the future use of the 137 Cs fallout technique involve the continuous decrease of the 137 Cs activity worldwide, including in Brazil. Advances in detection systems (gamma spectrometers) will be required to overcome this issue. Future studies should focus on the use of correction factors related to the enrichment of fine particles during the transport of sediments to improve the estimates obtained through the conversion models. The use of neutron gauges to detect soil water content at the field scale depends on the adoption of reliable calibration curves. Then, comprehending how soil properties alter this curve and how it affects the water balance is a study of great interest. Motivated by strict regulations on the use of radioactive materials, the adoption of gauges with less activity is becoming a new goal. Thus, the development of more effective systems of neutron detection is crucial.

A novel approach based on X-ray fluorescence and photon attenuation to the analysis of soils for forensic investigation

“…We could see that these differences among soils influenced the radiation interaction parameters. Many authors have described the role of the chemical composition of materials in radiation attenuation (Kucuk et al, 2013;Taqi et al, 2016;Ferreira et al, 2018;Camargo et al, 2021;Pires et al, 2021). Recently, Pires et al (2019) demonstrated the relationship between the soil minerals and radiation interaction parameters, highlighting the particle density importance in the attenuation of the radiation by the matter (Al-Masri et al, 2013).…”