• Energy Research
• Chinese Academy of Sciences close

The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’ understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage. In 2016, unconventional oil production in the USA accounted for 41% of the total oil production; and unconventional natural gas production in China accounted for 35% of total gas production, showing strong growth momentum of unconventional hydrocarbons explorations. Unconventional hydrocarbons generally coexist with conventional petroleum resources; they sometimes distribute in a separate system, not coexisting with a conventional system. Identification and prediction of unconventional resources and their potentials are prominent challenges for geologists. This study analyzed the results of 12,237 drilling wells in six representative petroliferous basins in China and studied the correlations and differences between conventional and unconventional hydrocarbons by comparing their geological features. Migration and accumulation of conventional hydrocarbon are caused dominantly by buoyance. We propose a concept of buoyance-driven hydrocarbon accumulation depth to describe the deepest hydrocarbon accumulation depth driven dominantly by buoyance; beyond this depth the buoyance becomes unimportant for hydrocarbon accumulation. We found that the buoyance-driven hydrocarbon accumulation depth in petroliferous basins controls the different oil/gas reservoirs distribution and resource potentials. Hydrocarbon migration and accumulations above this depth is dominated by buoyancy, forming conventional reservoirs in traps with high porosity and permeability, while hydrocarbon migration and accumulation below this depth is dominated by non-buoyancy forces (mainly refers to capillary force, hydrocarbon volume expansion force, etc.), forming unconventional reservoirs in tight layers. The buoyance-driven hydrocarbon accumulation depths in six basins in China range from 1200 m to 4200 m, which become shallower with increasing geothermal gradient, decreasing particle size of sandstone reservoir layers, or an uplift in the whole petroliferous basin. The predicted unconventional resource potential below the buoyance-driven hydrocarbon accumulation depth in six basins in China is more than 15.71 × 109 t oil equivalent, among them 4.71× 109 t reserves have been proved. Worldwide, 94% of 52,926 oil and gas reservoirs in 1186 basins are conventional reservoirs and only 6% of them are unconventional reservoirs. These 94% conventional reservoirs show promising exploration prospects in the deep area below buoyance-driven hydrocarbon accumulation depth.

In the steep mountainous areas in northwest Xinjiang, where rock mass is broken seriously due to intense freeze thaw weathering, rockfall is one of the most common geological hazards on highway high slopes. Engineering geological investigations on geological hazards along a segment of the G219 highway was conducted, indicating that rockfalls on the high slopes threaten the safety of vehicles on the highway seriously. In this study, a combination of field investigations, laboratory experiments and numerical simulation methods was performed to identify unstable high slopes, simulate the rockfall trajectories and assess the rockfall hazard in the study area. The results show that there are five high slopes (i.e., W01, W02, …, W05) where rockfall hazard is extremely serious. Considering both the total kinetic energy and the accumulation rate of blocks, rockfall influence area zonation was performed, leading to the conclusions that the sections of highway on W01 to W05 are located at the medium-intensity low-accumulation zone, high-intensity medium-accumulation zone, high-intensity low-accumulation zone, high-intensity low-accumulation zone and medium-intensity high-accumulation zone, respectively. Based on the analysis, a zonation map was accomplished, which could help engineers select effective mitigation measures against rockfalls to avoid casualty and property losses.

Abstract Buffering is requisite for anaerobic digestion (AD) to maintain suitable pH for methane production. In this study, mesophilic AD of swine manure at total solid (TS) from 4% to 14% was carried out to investigate the formation mechanism of buffer system. Results indicated that the rapid ammonia release (3.5–6.6 g-N L−1) greatly neutralized the accumulated volatile fatty acids (VFAs) (21.4–32.5 g L−1) to prevent pH from lower than 6.4. The released ammonia and accumulated VFAs established the initial stage of buffer system, ensuring suitable acid-base environment for methanogens to acclimate to high ammonia concentration at TS ≥8%. With the consumption of VFAs by acclimated methanogens, more CO2 in biogas was seized and transformed into carbonates to remedy the decreased VFAs for buffering free ammonia from overmuch pH increase. The improved methane production of 303.1 ± 23.0 N mL g-VSadded−1 was obtained at 8% TS under the convoy of ternary buffer system. Meanwhile, the ternary pH buffer system with ammonia-carbonates-VFAs that transformed obeying ionic equilibrium was visually revealed by a simulated ternary contour during overall AD process. Such understanding of buffer system may contribute to develop more effective pH adjustment measures to counter ammonia inhibition on methane production.

Glaciers continue to erode and transport material, forming an accumulation area at the front of the glacier. The trunk glacier, which has many tributary glaciers upstream and converges on the main channel, deposits vast amounts of material in the main channel. It blocks the main channel, forming barrier lakes, and eventually turns into mountain disasters, such as debris flows or outburst floods. Therefore, the accumulation rate of the material is a major parameter in such disasters and can determine the frequency of disasters. The material usually comes from bedrock erosion by glaciers, weathering of bedrock walls, and upstream landslides, and the material loss depends on river erosion. Based on this, we set up a method to calculate the material accumulation rate in the glacier front based on satellite images. Then, the Peilong catchment was taken as an example to validate the proposed method. The results indicate that climatic fluctuations may increase landslides, resulting in more actual accumulation than the calculated value according to the average rate of bedrock retreat. The material provided by the retreat of bedrock accounts for 92% of the total volume. Our method provides a practical reference for the mid- and long-term prediction of glacial catastrophic mass movement, as global warming seriously threatens glacier instability and downstream communities.

To evaluate the potential of Chlorococcum pamirum for producing biodiesel, the effects of nitrogen, phosphate, initial cell concentrations and NaCl on lipid accumulation and growth were studied. The highest specific growth rate (μ(max)), biomass productivity and lipid content achieved was 1.888 d(-1), 350.1 mg L(-1) day(-1), and 64.9%, respectively. Under nitrogen-deficient condition, the cells accumulated lipids faster at low initial cell concentration. Additional NaCl to nitrogen-deficient media accelerated the lipid accumulation. When adding 10 g L(-1) NaCl to nitrogen-deficient media, the lipid content and productivity of cells cultured outdoors with high initial cell concentration increased from 38.2% and 153 mg L(-1) day(-1) to 54.3% and 192 mg L(-1) day(-1) respectively. Moreover, NaCl enhanced the saturated fatty acids content from 56.40% to 73.41% of total fatty acids. The results show that C. pamirum is a promising organism for biofuel production.

Industry, transport and unsustainable agriculture result in the increased quantity of wastewater, release of nutrients and emission of carbon dioxide that promotes eutrophication of water bodies and global climate change. the application of microalgae for phycoremediation, their biomass use for human needs may increase sustainability and have a positive effect on the regional development. The experiments were carried out in order to establish the feasibility of treating the local municipal wastewater with microalgae consortia and their biomass potential for biofuel production. The results revealed that Chlorella/Scenedesmus consortium eliminated up to 99.7–99.9% of inorganic phosphorus and up to 88.6–96.4% of inorganic nitrogen from the wastewater within three weeks. The ammonium removal was more efficient than that of nitrate. Chlorella algae grew better in diluted, while Scenedesmus – in the concentrated wastewater. The consortium treated wastewater more efficiently than a single species. The maximum biomass (3.04 g/L) of algal consortium was estimated in concentrated wastewater. Algae accumulated 0.65–1.37 g of CO2/L per day in their biomass. Tus, Chlorella/Scenedesmus consortium is a promising tool for nutrients elimination from the local wastewater under the climatic conditions specific to Lithuania. However, none of the two species were able to accumulate lipids under the nitrogen starvation conditions.

Asbestos is an industrially important microfiber present in cement industries and some mining sites and is very toxic to plant growth and development, but it has been neglected over the years. Therefore, this study was conducted to investigate the hazardous effects of asbestos on the growth and development of two important grass species (switchgrass and timothy grass). In order to mitigate the toxic effects of asbestos, a compost (bio-fertilizer) was also used. The asbestos soil samples were collected within a 10 km area of a cement factory. The results revealed that the asbestos-contaminated soils displayed a considerable increment in heavy metal uptake including chromium (Cr), manganese (Mn), vanadium (V), arsenic (As), and barium (Ba), which led to stunted plant growth. Consequently, the activities of antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) were stimulated to kept the redox balance under control. Among all the contaminated soils, the soil that was taken within a 0 Km area, closest to the cement factory, was the most toxic one. However, a compost amendment (25%) as a bio-fertilizer substantially reduced the toxic effects of asbestos fiber on the overall growth and development of plants, by reducing the metals’ uptake. Moreover, it was found that the roots of both grass species experienced higher heavy metal accumulation relative to the shoots. Collectively, it can be proposed that the studied grass species can be used for phytoextraction purposes, since both of them absorbed the heavy metals from the asbestos-contaminated soils.

Studies have shown that the effectiveness of poverty alleviation funds is not always as intended; hence, there is an urgent need for researchers and policy makers to study the relationship between such funds and their impact on endogenous growth dynamics. This study focuses on the impact of these funds on human capital accumulation, which is an important driver of endogenous economic growth, and analyzes whether there is a threshold level for the efficacy of funds in countering poverty. This study examines the relationship between the Chinese government’s fund transfers to key poverty-stricken counties and the level of human capital in these regions by employing a fixed-effect threshold panel regression model on data from 592 counties from 2002 to 2015. Our study finds that the Chinese government’s fund transfers for poverty alleviation display a significant threshold effect. When funds are less than RMB 1291 per capita, there is a significant effect on local economic development; once this threshold is exceeded, there is a significant inhibitory effect instead. When the amount exceeds RMB 4469 per capita, fund transfers once again stimulate economic growth. This study enriches the theoretical understanding of the complex relationship between the use of funds in poverty-stricken areas and their impact on endogenous growth dynamics. It also provides useful suggestions for the effective use of poverty alleviation funds.