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Reliable estimates of groundwater recharge are crucial for the groundwater resources evaluating and sustainable utilization plans formulating. To protect the precious karst groundwater resources, this paper critically reviewed the previous studies on karst groundwater recharge in northern China karst regions from the perspective of diffuse recharge and focused recharge, and took Niangziguan Spring catchment as a case study. It is concluded that for the 119 karst groundwater systems, 52% occur diffuse recharge through precipitation infiltration, 48% occur both diffuse recharge through precipitation infiltration and focused recharge through surface water leakage. The mean annual precipitation, diffuse recharge and infiltration coefficient (IC, as percentage of precipitation) are 560 mm, 136 mm and 23.1%, respectively. A high correlation was observed between annual precipitation and annual diffuse recharge with a nonlinear relationship. The IC can vary substantially even with the same annual precipitation between 9.3 and 38.0%, with an evidently increasing trend eastward. This reflects a significant difference in the degree of karstification for the northern karst regions. The most commonly applied for recharge assessment in northern China karst regions is equal volume spring flow method, the chloride mass balance method is highly recommended for groundwater recharge estimation of the regions based on the case study. This work provides reference for recharge estimation, assessment and management of karst groundwater resources in northern China. [ABSTRACT FROM AUTHOR]

Crop irrigation based on controlling the matric potential of soil water at the depth of soil fixation in the root zone is more suitable than deficit irrigation for promoting cultivation in arid agricultural areas. However, it remains challenging to determine how controlled irrigation (CI) quantifies crop the response to water limitation and to establish the appropriate CI thresholds based on soil water matric potential. This study was conducted on sunflower fields in Hetao Irrigation District, a typical arid agricultural area in China where this crop is widely grown. Five CI treatments were applied for different soil water matric potentials (-8, -16, -24, -32, and − 40 kPa) to study the effects of CI on the soil environment and the relationship with crop yield. The following conclusions were drawn: (1) after 2 years of CI treatments, secondary salinization was significantly reduced below the defined criteria for saline soils (4 dS/m), achieving desalination of the entire soil profile; (2) the application of CI as an irrigation strategy in the management of sunflower fields significantly improved physiological traits during the crucial period of sunflower yield formation by increasing plant height while reducing stem thickness; (3) two treatments with the greatest difference in the lower limit of control of soil water matric potential under this irrigation strategy exhibited a yield variance ratio that increased from 0.14% in the first year to 15.37% in the second year; and (4) the treatment that controlled soil water matric potential at -24 kPa obtained the highest yield of all treatments in the test cycle, leading to an increase in seed yield of up to 1266.66 kg/ha in 2022 compared to the previous year. [ABSTRACT FROM AUTHOR]

The properties of some types of noncovalent interactions formed by triplet diphenylcarbene (DPC3) have been investigated by means of density functional theory (DFT) calculations and quantum theory of atoms in molecule (QTAIM) studies. The DPC3···LA (LA = AlF3, SiF4, PF5, SF2, ClF) complexes have been analyzed from their equilibrium geometries, binding energies, and properties of electron density. The triel bond in the DPC3···AlF3 complex exhibits a partially covalent nature, with the binding energy − 65.7 kJ/mol. The tetrel bond, pnicogen bond, chalcogen bond, and halogen bond in the DPC3···LA (LA = SiF4, PF5, SF2, ClF) complexes show the character of a weak closed-shell noncovalent interaction. Polarization plays an important role in the formation of the studied complexes. The strength of intermolecular interaction decreases in the order LA = AlF3 > ClF > SF2 > SiF4 > PF5. The electron spin density transfers from the radical DPC3 to ClF and SF2 in the formation of halogen bond and chalcogen bond, but for the DPC3···AlF3/SiF4/PF5 complexes, the transfer of electron spin density is minimal. [ABSTRACT FROM AUTHOR]

The discharge of acid mine drainage from abandoned high sulfur (S) coal mines has caused serious pollution in the Shandi River, Yangquan, Shanxi Province. To determine the impact of long-term acid mine drainage on the microorganisms in the river, we collected river sediments from a polluted tributary (Group P) and the mainstream of Shandi River (Group R) to study the bacterial diversity and community composition. The results showed that the tributary was seriously polluted by acid drainage from abandoned coal mines, with the pH value of the sediment being < 2.5, resulting in the low bacterial richness and diversity of the tributary samples. Acidophillic Fe- and S-metabolizing bacteria, such as Metallibacterium, Acidiphilium, and Acidithiobacillus, were the dominant genera in Group P samples, while the Group R was dominated by the neutral anaerobic iron-reducing bacteria Geothrix and Geobacter. Results of principal co-ordinates analysis (PCoA) revealed that the bacterial communities are significantly different between groups P and R, and the significant different species were mainly attributed to phylum Proteobacteria, Actinobacteria, and Acidobacteria. The distribution of the microbial community is mainly influenced by pH, and the Fe and Cd concentrations. Metallicactrium, the dominant genus, is negatively correlated with pH (R2 = − 0.95) and positively correlated with Fe (R2 = 0.99), while Geothrix and Geobacter, are mainly affected by the heavy metals. This study determined the impact of river pollution caused by abandoned coal mine drainage, especially on the microbial diversity and community composition within the river sediment. [ABSTRACT FROM AUTHOR]

In Northern China, karst systems in widely distributed carbonate rocks are one of the most important water supplies for local inhabitants. Constrained by the specific geological and geomorphological conditions, most karst water in this region is discharged as individual or groups of springs. This paper summarizes the characteristics, chemistry, and environmental quality of these karst systems in Northern China. Five structural models of karst water systems were identified based on the relationships between the karst geological strata and karst groundwater flow fields. These specific structural models may closely relate to the attendant environmental geological issues and consistent risks from pollution. Over the past 40 years, the karst water systems in Northern China have suffered from various environmental problems, including deteriorating water quality, the drying up of springs, a continuous decline in the level of karst water, and so on. Based on the field investigation and previous data, a preliminary summary is provided of the environmental problems related to the development and evolutionary trends of karst water in this region. The results highlight the significant challenges associated with karst water, and it is essential that all segments of society be made aware of the situation in order to demand change. In addition, the study provides a scientific basis for the management, protection, and sustainable utilization of karst water resources. [ABSTRACT FROM AUTHOR]

Global land use structure is changing rapidly due to unceasing population growth and accelerated urbanization, which leads to fierce competition between the rigid demand for built-up area and the protection of cultivated land, forest, and grassland. It has been a great challenge to realize the sustainable development of land resources. Based on a computable general equilibrium model of land use change with a social accounting matrix dataset, this study implemented an equilibrium analysis of the land use structure in the Yunnan Province during the period of 2008-2020 under three scenarios, the baseline scenario, low TFP (total factor productivity) scenario, and high TFP scenario. The results indicated that under all three scenarios, area of cultivated land declined significantly along with a remarkable expansion of built-up area, while areas of forest, grassland, and unused land increased slightly. The growth rate of TFP had first negative and then positive effects on the expansion of built-up area and decline of cultivated land as it increased. Moreover, the simulated changes of both cultivated land and built-up area were the biggest under the low TFP scenario, and far exceeded the limit in the Overall Plan for Land Utilization in the Yunnan Province in 2020. The scenario-based simulation results are of important reference value for policy-makers in making land use decisions, balancing the fierce competition between the protection of cultivated land and the increasing demand for built-up area, and guaranteeing food security, ecological security, and the sustainable development of land resources. [ABSTRACT FROM AUTHOR]

Qinghai Province, which is the source of three major rivers (i.e., Yangtze River, Yellow River and Lancang River) in East Asia, has experienced severe grassland degradation in past decades. The aim of this work was to analyze the impacts of climate change and human activities on grassland ecosystem at different spatial and temporal scales. For this purpose, the regression and residual analysis were used based on the data from remote sensing data and meteorological stations. The results show that the effect of climate change was much greater in the areas exhibiting vigorous vegetation growth. The grassland degradation was strongly correlated with the climate factors in the study area except Haixi Prefecture. Temporal and spatial heterogeneity in the quality of grassland were also detected, which was probably mainly because of the effects of human activities. In the 1980s, human activities and grassland vegetation growth were in equilibrium, which means the influence of human activities was in balance with that of climate change. However, in the 1990s, significant grassland degradation linked to human activities was observed, primarily in the Three-River Headwaters Region. Since the 21 century, this adverse trend continued in the Qinghai Lake area and near the northern provincial boundaries, opposite to what were observed in the eastern part of study. These results are consistent with the currently status of grassland degradation in Qinghai Province, which could serve as a basis for the local grassland management and restoration programs. [ABSTRACT FROM AUTHOR]

Characterizing neutralizing antibody (NAb) responses in individuals infected with diverse HIV-1 strains is necessary to reveal the novel targets for regional preventive and therapeutic strategies development. We evaluated the prevalence, breadth, and potency of NAb responses in 98 CRF07_BC-infected individuals using a large, multi-subtype panel of 30 tier 2-3 Env-pseudotyped viruses. Furthermore, we compared the neutralization pattern of CRF07_BC-infected people with that of subtype B'-infected individuals in China. Of the 98 plasma samples tested, 18% neutralized more than 80% of viruses in the panel, and 53% neutralized more than 50%, suggesting the presence of broadly NAbs in these individuals. A preferential intra-subtype neutralization of CRF07_BC was found. Notably, CRF07_BC-infected individuals generated higher neutralization titers against intra-subtype viruses than subtype B'-infected individuals with longer infection length. However, subtype B'-infected individuals mounted broader neutralization responses against inter-subtype viruses than CRF07_BC infection with shorter infection time, indicating the transition from narrow autologous to broad heterologous neutralization over time. Neutralization activity of the top six plasmas from each cohort was attributable to IgG fraction, and half of them developed CD4 binding site antibody reactivity. Heatmap analysis identified three statistically robust clusters of plasmas that offer valuable resources for further in-depth virological and immunological study. [ABSTRACT FROM AUTHOR]