Few studies have investigated the effects of structural heterogeneity (particularly the interactions of silicon and carbon) on the mechanisms for the recalcitrance of biochar. In this study, the molecular mechanisms for the recalcitrance of biochars derived from rice straw at 300, 500, and 700 °C (named RS300, RS500, and RS700, respectively) were elucidated. Short-term (24 h) and long-term (240 h) oxidation kinetics experiments were conducted under different concentrations of H2O2 to distinguish the stable carbon pools in the biochars. We discovered that the stabilities of the biochars were influenced not only by their aromaticity but also through possible protection by silicon encapsulation, which is regulated by pyrolysis temperatures. The aromatic components and recalcitrance of the biochars increased with increasing pyrolysis temperatures. The morphologies of the carbon forms in all of the biochars were also greatly associated with those of silica. Silica-encapsulation protection only occurred for RS500, not for RS300 and RS700. In RS300, carbon and silica were both amorphous, and they were easily decomposed by H2O2. The separation of crystalline silica from condensed aromatic carbon in RS700 eliminated the protective role of silicon on carbon. The effect of the biochar particle size on the stability of the biochar was greatly influenced by C-Si interactions and by the oxidation intensities. A novel silicon-and-carbon-coupled framework model was proposed to guide biochar carbon sequestration.

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Thallium (Tl) is an extremely harmful metal that is substantially distributed in the environment. It can threaten human health via consumption of food potentially derived from Tl-contaminated agricultural production. Little information is available on how to utilize biochar to remediate Tl contamination in agricultural soils. More efforts are urgently needed to be devoted to developing effective techniques to empower biochar with high selectivity of Tl in agricultural soils. In this review, we provided comprehensive information on Tl contamination in agricultural soils. We also discussed recent developments and assessed the current status of biochar applications. We briefly reviewed the bridge between biochar preparation technology and utilization wherein further developments can exhibit potential in terms of Tl remediation. Hence, biochar is expected to exhibit excellent Tl remediation performance in contaminated agricultural soils with promising application prospects. The obtained knowledge provides further insights into the remediation of Tl contamination in agricultural soils.

The purpose of this research was to examine paleoenvironments, hydrothermal activity, and seawater restriction of the lower Cambrian Niutitang Formation shale gas reservoir in the eastern Xuefeng Uplift and to determine factors affecting organic matter (OM) enrichment. In the studied borehole (X1) in western Hunan Province, the Niutitang Formation can be subdivided into the Niu1, Niu2, and Niu3 members based on geological and geochemical features, including trace element enrichment, lithology and fossil content. Total organic carbon (TOC) values of the Niutitang Formation are variable, averaging 1.5 wt.% in the Niu1 Member, 12.7 wt.% in the Niu2 Member, and 5.1 wt.% in the Niu3 Member. Paleoclimatic changes were responsible for changes in biota, which impacted patterns of OM enrichment. Climate proxies (Chemical Index of Alteration (CIA)), and productivity proxies (Babio, Cu/Al, and Ni/Al) consistently indicate higher paleoproductivity in the Niu2 Member. The Niu1 and Niu2 members were possibly affected by hydrothermal events, whereas hydrothermal activity was absent during deposition of the Niu3 Member.Hydrothermal activity may not only provide nutrients and silica but alsoenhance the reducing condition of the water column. In addition, hydrothermal events may have possibly influenced biological survival in the different environments, which in turn increased their reproduction within the early Cambrian ocean and affected OM production. Redox proxies (MoEF and UEF) imply that the Niu1, Niu2, and Niu3 members were deposited in suboxic, euxinic, and ferruginous environments, respectively. Redox conditions, strongly restricted water environments, and

Fissured expansive soils were widely distributed in the South-to-North Water Transfer Project. Most of the fissures were filled with clay, which controlled the stability of the slope. With the method of layered filling—bevel cutting—refilling and a modular design idea, the sample with a filled fissure preparation device for triaxial test was designed. After setting the filled fissures of gray-green clay in the expansive soil, triaxial tests were carried out for the samples with no filled fissures and with filled fissures with inclination angles of 15°, 30°, and 45°. Then, considering the spatial distribution and the strength of the filled fissures in the slope, the stability analysis method for the expansive soil slope with filled fissures was proposed. The stability of a typical slope in Nanyang was analyzed. The results show that the c of expansive soil with filled fissures was about 12 to 15 kPa and the φ was 3° to 6°. Filled fissures had an attenuation effect on the strength of the expansive soil. The larger the inclination of filled fissures, the more significant the effect of soil strength attenuation. The fissured slope stability was controlled by the filled fissures. The sliding surface was affected by the vertical fissures on the top of the slope and the slow-inclined long-large fissures in the slope, and the shape of the sliding surface was a broken line, which was basically consistent with the actual landslide.

The accumulation and productivity of shale gas are mainly controlled by the characteristics of shale reservoirs; study of these characteristics forms the basis for the shale gas exploitation of the Lower Cambrian Niutitang Formation (Fm), Southern China. In this study, core observation and lithology study were conducted along with X‐ray diffraction (XRD) and electronic scanning microscopy (SEM) examinations and liquid nitrogen (N2) adsorption/desorption and CH4 isothermal adsorption experiments for several exploration wells in northwestern Hunan Province, China. The results show that one or two intervals with high‐quality source rocks (TOC>2 wt%) were deposited in the deep‐shelf facies. The source rocks, which were mainly composed of carbonaceous shales and siliceous shales, had high quartz contents (>40 wt%) and low clay mineral (<30 wt%, mainly illites) and carbonate mineral (<20 wt%) contents. The SEM observations and liquid nitrogen (N2) adsorption/desorption experiments showed that the shale is tight, and nanoscale pores and microscale fractures are well developed. BJH volume (VBJH) of shale ranged from 2.144×10–3 to 20.07×10–3 cm3/g, with an average of 11.752×10–3 cm3/g. Pores mainly consisted of opened and interconnected mesopores (2–50 nm in diameter) or macropores (>50 nm in diameter). The shale reservoir has strong adsorption capacity for CH4. The Langmuir volume (VL) varied from 1.63 to 7.39 cm3/g, with an average of 3.95 cm3/g. The characteristics of shale reservoir are controlled by several factors: (1) A deep muddy continental shelf is the most favorable environment for the development of shale reservoirs, which is controlled by the development of basic materials. (2) The storage capacity of the shale reservoir is positively related to the TOC contents and plastic minerals and negatively related to cement minerals. (3) High maturity or overmaturity leads to the growth of organic pores and microfractures, thereby improving the reservoir storage capacity. It can be deduced that the high percentage of residual gas in Niutitang Fm results from the strong reservoir storage capacity of adsorbed gas. Two layers of sweet spots with strong storage capacity of free gas, and they are characterized by the relatively high TOC contents ranging from 4 wt% to 8 wt%.