Exergy assessment of topsoil fertility

Soil degradation, affecting around 38% of the world''s cropland, threatens the global food supply. Due to the soil''s complexity, the measure of soil degradation that involves the loss of soil fertility due to crop system management processes represents an unsolved problem. Exergy is a property with the potential to be used in soil fertility and/or degradation analysis. A methodology to determine the exergy value fenced in a fertile soil due to its inorganic and organic components is established in this study and will be applied to evaluate soil fertility, degradation, and quality. As a first step, the exergy of perfect topsoil with optimum characteristics called "OptSOIL" is determined. The "OptSOIL" is established by agronomic expertise and will allow establishing a general theoretical reference suitable to execute exergy assessments of soils and compare the degradation grade of any soil concerning the best possible. Consequently, we introduce a perfect fertile planetary crust made of “OptNUT” and “OptSOM” invariant and independent of the different local textures, but not independent of their water content and aeration. We call this imaginary crust -copiously fertile- Pristinia as opposed to Thanatia, a dead state referring to abiotic resources. Thus, any real agricultural soil will be an intermediate soil between Pristinia and Thanatia. This idea might serve to quantitatively diagnose an assessment of all the concepts by which soil is degraded. The methodology has been validated through laboratory agronomic tests for different soils, concluding that exergy is a rigorous indicator to measure topsoil fertility. © 2021 The Author

Recent high resolution laboratory determinations of line broadening and intensity parameters: PH3, CH3D, and CO2

Recent unpublished laboratory work on rovibrational line strengths and broadening coefficients which is of interest in the study of planetary atmospheres was reviewed. The molecules discussed are PH3, CH3D and CO2

Interfacial velocity estimation in highly aerated stepped spillway flows with a single tip fibre optical probe and Artificial Neural Networks

peer reviewedAir-water flows can be found in different engineering applications: from nuclear engineering to huge hydraulic structures. In this paper, a single tip fibre optical probe has been used to record high frequency (over 1 MHz) phase functions at different locations of a stepped spillway. These phase functions have been related to the interfacial velocities by means of Artificial Neural Networks (ANN) and the measurements of a classical double tip conductivity probe. Special attention has been put to the input selection and the ANN dimensions. Finally, ANN have shown to be able to link the signal rising times and plateau shapes to the air-water interfacial velocity

Robust estimators for turbulence properties assessment

Robust estimators and different filtering techniques are proposed and their impact on the determination of a wide range of turbulence quantities is analysed. High-frequency water level measurements in a stepped spillway are used as a case study. The studied variables contemplated: the expected free surface level, the expected fluctuation intensity, the depth skewness, the autocorrelation timescales, the vertical velocity fluctuation intensity, the perturbations celerity and the one-dimensional free surface turbulence spectrum. When compared to classic techniques, the robust estimators allowed a more accurate prediction of turbulence quantities notwithstanding the filtering technique used

On the estimation of free-surface turbulence using ultrasonic sensors

Accurate determination of free-surface dynamics has attracted much research attention during the past decade and has important applications in many environmental and water related areas. In this study, the free-surface dynamics in several turbulent flows commonly found in nature were investigated using a synchronised setup consisting of an ultrasonic sensor and a high-speed video camera. Basic sensor capabilities were examined in dry conditions to allow for a better characterisation of the present sensor model. The ultrasonic sensor was found to adequately reproduce free-surface dynamics up to the second order, especially in two-dimensional scenarios with the most energetic modes in the low frequency range. The sensor frequency response was satisfactory in the sub-20 Hz band, and its signal quality may be further improved by low-pass filtering prior to digitisation. The application of the USS to characterise entrapped air in high-velocity flows is also discussed

Surface velocity and ice discharge of the ice cap on King George Island, Antarctica

Glaciers on King George Island, Antarctica, have shown retreat and surface lowering in recent decades, concurrent with increasing air temperatures. A large portion of the glacier perimeter is ocean-terminating, suggesting possible large mass losses due to calving and submarine melting. Here we estimate the ice discharge into the ocean for the King George Island ice cap. L-band synthetic aperture radar images covering the time-span January 2008 to January 2011 over King George Island are processed using an intensity-tracking algorithm to obtain surface velocity measurements. Pixel offsets from 40 pairs of radar images are analysed and inverted to estimate a weighted average surface velocity field. Ice thicknesses are derived from simple principles of ice flow mechanics using the computed surface velocity fields and in situ thickness data. The maximum ice surface speeds reach mayor que 225 m/yr, and the total ice discharge for the analysed flux gates of King George Island is estimated to be 0.720+/-0.428 Gt/yr, corresponding to a specific mass loss of 0.64+/-0.38 m w.e./yr over the area of the entire ice cap (1127 km2)