50 research outputs found

    Evolution modes of interbedded weathering crust karst: A case study of the 1st and 2nd members of Ordovician Yingshan Formation in EPCC block, Tazhong, Tarim Basin

    No full text
    The evolution of interbedded weathering crust karst on the top of the Ordovician Yingshan Formation were described based on the geological background, oil and gas show while drilling, core, log imaging and seismic reflection features in the Tazhong area. The study shows that: Filling features of dissolved caves near unconformities depend on the hydrodynamic strength, which, together with the vertical lithofacies, determines the development degree of the interbedded karst. Karst units are classified into several first order units, namely highland, sub-high, slope, and sub-sag, and some secondary units such as dissolved peak, cliff, platform, and dissolved mound, stretching like a strip from northwest to southeast on the whole. The surface weathering zone developed only in the north of the EPCC block, the vertical vadose zone has different thickness in south and north, while the seasonal variation zone changes to horizontal vadose zone from south to north. Sedimentary microfacies affects karst development, but it is not the deciding factor of karst cycle classification, the main factors resulting in the karst difference between south and north are structural uplift, climate, and ancient hydrological conditions. Three cycles and eight secondary cycles are identified in the interbedded weathering karst in Member Ying1-Ying2 in the EPCC block, among them, the third cycle, including the fifth to the eighth secondary cycles, remains, and the fifth and eighth secondary cycles show obvious “different facies” features from south to north

    Porous Organic Polymers-Supported Metallocene Catalysts for Ethylene/1-Hexene Copolymerization

    No full text
    Porous organic polymers (POPs) have received much attention in adsorption, separation, and catalysis. In this paper, porous organic polymers with different pore structure were used as metallocene catalyst supports, and ethylene/1-hexene copolymerizations were conducted using the POPs-supported metallocene catalyst. The pore structure of the prepared POPs and the supported metallocene catalyst were characterized by nitrogen sorption porosimetry and non-local density functional theory simulation, and the molecular chain structure of the produced ethylene/1-hexene copolymers were investigated through gel permeation chromatography (GPC), IR analysis, differential scanning calorimetry (DSC), and temperature rising elution fractionation (TREF). The results show that the loading amount of active sites varied with different pore structures of the POP supports, and the active species scattered in different pore sizes had a moderate impact on the molecular chain growth and the molecular weight distribution. The IR, DSC, and TREF analysis revealedthat different branching degree, double bond content, and chemical composition distributions were detected from the molecular chain structure of the ethylene/α-olefin copolymers from different POPs and silica-supported metallocene catalysts, despite their similar IR, DSC, and TREF curves due to the same active species. Scanning electron microscopy (SEM) showed that porous ethylene/α-olefin copolymers with varied surface morphology were obtained from the POPs-supported metallocene catalysts with different pore structure

    Performances of Water Management, Foliage Dressing, and Variation Screening in Controlling the Accumulation of As and Cd and Maintaining the Concentrations of Essential Elements in the Grains of Rice Plant

    No full text
    This study was conducted to understand why and how the technologies of variety screening, foliar dressing, and water management can reduce As/Cd accumulation and affect the concentrations of essential elements in different rice plants. In Trial I (variety screening), the grain As and Cd concentrations in Zhongguyou1361 variety (P3) were both lower than their individual National Food Hygiene Standard of China (NFHSC) under insufficient field drying condition. The P3 also had a relatively high yield and high essential element contents among 15 selected rice varieties. In Trial II (foliar dressing), selenite foliar spray showed a better ability than silicate to reduce the grain As content in Guangliangyou1128 variety (P1). However, spraying Se and Si onto the Fengliangyou1 variety (P2) both showed a limited effect on the grain As and Cd contents, suggesting a different effect of Se on grain As content in various rice varieties. The insufficient field drying in Trial II resulted in the grain Cd content being lower but the grain As content being higher than their individual NFHSC in both P1 and Fengliangyou1 (P2) varieties. Se or Si did not affect the yields and the grain contents of most essential elements in P1 and P2. In Trial III (water management), increasing field drying time enhanced the Cd content but reduced the As content in the grains of P1, P2, and P3, and maintained their yields. Similar to the results of Trial II, the changes in soil pH, organic matter concentration and elemental available concentrations could hardly be used to explain why the contents of corresponding essential elements kept approximately constant in the grains of different rice varieties. Foliar dressing with selenite combined with water regulation can simultaneously reduce the As and Cd contents, and maintain the yields and the essential element contents in the grains of rice plants cultivated in As− and Cd− contaminated soil
    corecore