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This study presents a novel and simple morphology approach to generate two-dimensional air-water distribution in porous media considering Or and Tuller's cavitation mechanism (published in 2002). The connectedness condition for the nonwetting phase is replaced by the Laplace equation. An algorithm is developed to detect the ruptured water spaces that are incorrectly formed in the throat by the morphology approach, but cannot exist in a real thermodynamic equilibrium system. The distributions of soil moisture, water retention curve, and air-liquid interface area at different saturations predicted by this method are in a good quantitative agreement with the experimental observations on glass beads and Ottawa sand from micro X-raycomputed tomography (microXCT). Compared to Lu et al.'s Monte Carlo lattice-gas approach (published in 2010), another computational method to generate the soil moisture distribution, the proposed approach provides better results with significantly less computational power. Key words: unsaturated soil, air-water distribution, morphology, porous media. Cette etude presente une nouvelle et simple approche de morphologie permettant de generer une distribution bidimensionnelle air-eau dans des milieux poreux, en tenant compte du mecanisme de cavitation de Or et Tuller (publie en 2002). La condition de connectivite pour la phase non mouillante est remplacee par l'equation de Laplace. Un algorithme est developpe pour detecter les espaces d'eau rompus qui sont formes de maniere incorrecte dans la gorge par une approche morphologique, mais ne peuvent pas exister dans un systeme d'equilibre thermodynamique reel. Les distributions de l'humidite du sol, de la courbe de retention d'eau et de la surface d'interface air-liquide a differentes saturations predites par cette methode concordent bien avec les observations experimentales sur les billes de verre et le sable d'Ottawa obtenues par micro tomographie par rayons X (microXCT). Comparee a l'approche reseau-gaz de Monte Carlo de Lu et al. (publie en 2010), une autre methode de calcul permettant de generer la distribution de l'humidite du sol, l'approche proposee fournit de meilleurs resultats avec un pouvoir de calcul nettement inferieur. [Traduit par la Redaction] Mots-cles: sol non sature, distribution air-eau, morphologie, milieu poreux., 1. Introduction Water in unsaturated soil can be formed as pendular capillary bridges, funicular bridges or more complicated water clusters depending on various water contents, suctions, and pore structures (Iveson [...]

Sanitary landfills and uncontrolled dumpsites are plastic wastes (PWs) reservoirs containing ∼60% of all the plastics ever made, amounting to 5,000 × 106 tons as of 2017. The distribution, long-term behavior, and release of macro- and microplastics (MPs) from disposal sites are critical to global plastics pollution, but are poorly understood and lack systematic assessments. We review comprehensively the available knowledge in the three aspects herein. The spatial and temporal distribution of PW in 616 municipal solid waste (MSW) samples retrieved from 275 disposal sites in 56 countries are summarized. The weight percentages of PW (%PW) generally decrease with increasing year of disposal and disposal depth. Other influential factors are disposal duration and country income level. The %PW values in different disposal sites show high regionality and spatial variability and heterogeneity. Disposal sites mostly have harsh temperature and stress, reactive liquids, and microbial activities, which are conducive to long-term processes of PW and MPs. The major processes are chemical degradation, dissolution, leaching and adsorption, biological degradation, mechanical wearing, pneumatic and hydrological transport and deposition, and conglomeration. PW leaves disposal sites via recycling, scavenging, mining, wind and surface runoff, coastal erosion and flooding, and slope failure. The release and removal pathways of PW from disposal sites have been recognized only qualitatively. In addition, the sources, presences, and secondary generation of MPs in disposal sites have been studied occasionally, whereas the transport and fate of MPs within and from disposal sites remain largely unstudied. [ABSTRACT FROM AUTHOR]

At present, the dealkalization and comprehensive utilization of red mud is a worldwide problem. Studies on the settling performance and phase transformation of red mud by HCl, CaO, and HO leaching are limited. In this study, the characteristics of red mud were systematically analyzed. The average sizes of graded and initial red mud were 4.11 and 9.20 μm, respectively. X-ray diffraction (XRD), X-ray fluorescence spectra (XRF), and thermogravimetry-differential scanning calorimetry (TG-DSC) results indicated the different mineralogical phases, composition, and thermal behavior. The addition of HCl could neutralize the alkalization in the red mud slurry, and CaO could replace the Na and K. Notably, the pH of the red mud slurry had no obvious change with the increase in water washing times in a certain pH. Interestingly, soluble Al and Fe were not detected in the HCl-red mud and CaO-red mud. In addition, the settling ratio was used to express the settling performance of the red mud slurry. Their interaction mechanisms were proposed, which may include phase transformation and the changing of the size and surface area. The research provided a better understanding of the phase transformation and settling performance in the treatment of red mud by HCl, CaO, and HO leaching. [ABSTRACT FROM AUTHOR]