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Gypsum–urea is a kind of urea product with substantially reduced aqueous solubility and lower hygroscopicity that increases the soil retention time of urea and thus enhance its environmental sustainability. Here, gypsum–urea was prepared using bulk industrial solid waste flue gas desulfurization (FGD) gypsum as a raw material in a saturated urea solution via immobilizing urea molecules into the crystal lattice. The preparation process was achieved through a dissolution–recrystallization mechanism during which FGD gypsum dissolved into Ca2+ and SO42−, which then recrystallized with CO(NH2)2 to form gypsum–urea. The preparation process was almost completed within 10 min, and the formed gypsum–urea presented a uniform size distribution of 30–90 μm and a much lower hygroscopicity and nitrogen release efficiency than that of urea. With a high efficiency of synthesis, and sustainable features, and the recyclability of the saturated mother urea solution, the dissolution–recrystallization-based urea immobilization approach is highly promising regarding the preparation of gypsum–urea with the desired environmental sustainability and contributes to the realization of the sustainable reutilization of FGD gypsum. [ABSTRACT FROM AUTHOR]

The palaeoenvironment has an important influence on the formation and evolution of karst geomorphology, and the planation surface at the edge of the karst plateau is one of the important recorders. The Yunnan-Guizhou Plateau is an important karst plateau in China, on the southeast edge of which is located Xiangxi in Hunan Province-a deep cut platform and gorge development area. Xiangxi is also a combination zone of low mountains and middle mountains at the edge of the Yunnan-Guizhou Plateau, in which the high plain transits to the alluvial plain, with rich records of planation surfaces. These planation surfaces are characterized by rapid altitude changes, different weathering crust materials and different types of bedrock lithology. However, the weathering crust properties and palaeoclimate characteristics of these planation surfaces are still unclear. Therefore, we choose two weathering crusts representing the elevation of 1,400 m and 600-700 m of planation surfaces in Luota Period (Luota section) and Zhaoshi Period (Jiaba section) as study objects. In this study, conducting the inversion of palaeoclimate indicated by weathering crusts of planation surfaces through grain size, magnetic susceptibility and sporopollen analyses, we hope to provide more evidence for the development characteristics of planation surfaces and palaeoclimate evolution on the edge of the Yunnan-Guizhou Plateau. Results show that the weathering crust of Luota section is 5.0 m thick and can be divided into 5 layers. The lithology is mainly composed of humus, gravel layer, silt, clay, etc. The content of silt with sizes ranging from 5 to 50 μm is the highest, accounting for 57.6%; the average content of clay is 41.9%; the sand content is the lowest, at 0.56%, all of which are fine sand. The weathering crust in Jiaba section is 3.5 m thick and can be divided into two layers. The lithology is mainly composed of humus, silty, clay and a small amount of gravel. The content of silt with sizes ranging from 5 to 50 μm is also the highest, accounting for 54%; the average content of clay is 39%. In addition, the analyses of Md, Mz, σ, Sk, Kg, SC/D values, magnetic susceptibility and other indicators show that there appear multiple index fluctuations in both Luota and Jiaba sections, but the fluctuation range of Jiaba section is relatively limited. The types of sporopollen in the two sections are different. Luota section is mainly composed of Polypodium and Pinus, with a small number of Abies, Podcarpus and Chenopodium. The main sporopollen components of Jiaba section are Polypodium and Pinus, and a few Gramineae and Carpinipites are found. The types of sporopollen in Jiaba section are fewer than those in Luota section, and the concentrations are also lower. Based on the development of Polypodium in both sections, it is supposed that the climate during the sedimentary period of weathering crust was warm and hot. However, the climate during the sedimentary period of Luota section may have been a warm climate with high humidity, while the climate of Jiaba section may have been a cool and humid climate with low humidity. In addition, according to the analysis of sporopollen and the previous data, it is speculated that the weathering crust of Luota section may have been formed in the early Neogene, and the planation surface may have been formed in the Miocene. The weathering crust of Jiaba section may have been formed in the early Quaternary, and the planation surface may have been formed in the Pleistocene. [ABSTRACT FROM AUTHOR]

The Mesozoic rift basins of northeast China are characterized by a significant proportion of basalt due to the progressive emplacement of basalt lava flows. The objective of this study was to construct vesicle distribution models of the basalt lava flowunits, including conceptual geological models and thickness models, to understand the architecture of the basalt and the gas reservoir distribution. The conceptual geological models were constructed based on the characteristics of outcropping basalt lava flows, with supplemental seismic data used to extrapolate the lateral extents of large-scale basalt lava flows. The thickness models were constructed using data on the thicknesses of basalt lava flowunits and vesicle zones. These data were obtained from 27 units in outcrop and 204 units interpreted from well logs in the basin. The conceptual geological models revealed that the shapes of the basalt lava flow units change from braided to tabular with increasing thickness and that their inner structures can be divided into three vesicle zones: the top vesicle zone, the massive core zone, and the base vesicle zone. The thickness models revealed that trends in the thickness of the top vesicle zone relative to the thickness of the basalt lava flow unit can be expressed using a piecewise function that can be separated into a linear fimction and a logarithmic fimction. Similarly, trends in the thickness of the massive core zone and the base vesicle zone relative to the basalt lava flow unit thickness can be expressed by a piecewdse linear fimction. Vesicle distribution models provide an effective means of determining the proportion and distribution of vesicle zones in basalt with limited borehole data. We also constructed a reservoir model based on our vesicle distribution models, and this model revealed that suitable petroleum reservoirs are primarily located in the thinner braided lava flows. Les bassins d'effondrement (Mesozoique) du nord-est de la Chine sont caracterises par une proportion importante de basaltes en raison de la mise en place progressive de coulees de lave basaltique. L'objet de la presente etude est de construire des modeles de distribution des vacuoles des unites de coulees de lave basaltique, incluant des modeles conceptuels de la geologie et de l'epaisseur, afin de comprendre)'architecture des basaltes et la distribution des reservoirs de gaz. Les modeles geologiques conceptuels ont ete construits en se basant sur les caracteristiques des affleurements de coulees de lave basaltique; des donnees sismiques additionnelles ont servi a extrapoler les etendues laterales des coulees de lave basaltique a grande echelle. Les modeles d'epaisseur ont ete construits en utilisant des donnees sur les epaisseurs des unites de coulees de lave basaltique et des zones de vacuoles. Ces donnees ont ete obtenues de 27 unites en affleurement et de 204 unites interpretees a partir de diagraphies de puits dans le bassin. Les modeles geologiques conceptuels revelent que les formes des unites de coulees de lave basaltique changent d'anastomosees a tabulaires en fonction de !'augmentation de l'epaisseur et que leur structure interne peut etre divisee en trois zones vacuolaires : une zone vacuolaire superieure, une zone massive centrale et une zone vacuolaire basale. Les modeles d'epaisseur revelent que les tendances dans l'epaisseur de la zone vacuolaire superieure, par rapport a l'epaisseur de l'unite de coulee de lave basaltique, peuvent etre exprimees au moyen d'une fonction par morceaux, laquelle peut etre separee en une fonction lineaire et une fonction logarithmique. De meme, les tendances dans l'epaisseur de la zone massive centrale et dans la zone vacuolaire basale, par rapport a l'epaisseur de l'unite de coulee de lave basaltique, peuvent etre exprimees par une fonction lineaire par morceaux. Les modeles de distribution des vacuoles fournissent un moyen efficace de determiner la proportion et la distribution des zones de vacuoles dans les basaltes dont les donnees de forage sont limitees. Nous avons aussi construit un modele de reservoir base sur nos modeles de distribution des vacuoles et ce modele a revele que des reseivoirs petroliftres adequats sont principalement situes dans les coulees de lave anastomosees plus minces. [Traduit par la Redaction], Introduction Volcanic successions in the rift basins of northeast China have recently become a focus of geological research owing to the discovery of significant volcanic gas reservoirs in this region [...]