Search

• Environmental risk caused by groundwater exploitation was investigated. • Ecosystem services related to groundwater was evaluated. • Hydro-economic assessment for alluvial aquifer management in arid river basin was developed. Groundwater has resource, ecology, economy and society attributes. In recent years, ecological degradation caused by intensive groundwater exploitation to support socio-economic development has been of growing concern in arid and semiarid regions. To protect the groundwater sustained ecosystem, this paper developed a novel environmental risk-based hydroeconomic model to evaluate the tradeoff between groundwater utilization and ecological environmental protection in Golmud river catchment of Qaidam basin, a typical inland river watershed and alluvial aquifer, in northwestern China. Field survey, remote sensing and groundwater level monitor were conducted to obtain the threshold of groundwater dependent ecosystem. Results show that depth to groundwater table should be larger than 25.5 m in alluvial plain to prevent downstream Golmud city urban waterlogging, depth to groundwater table should be smaller than 10 m in groundwater overflow zone and fine soil plain to sustain groundwater dependent vegetation survive, and groundwater recharge to the terminal lake should be larger than 282.0 hm3 yr−1 to maintain the minimum water surface area. Meanwhile, ecosystem services value was established according to equivalent value factors per unit area provided by different types of ecosystem in Golmud river catchment. Numerical simulations model was applied to evaluate the potential environment risk, cost and benefit of ecosystem services under different groundwater demand. The investigation results show that groundwater exploitation in 2030 with 240.9 hm3 yr−1 will cause environment risk, which is terminal lake surface area smaller than permitted minimum threshold. And the recommended maximum amount of groundwater exploitation is 219.0 hm3 yr−1. This study provides guidance for regional groundwater management to maintain environment protection and socio-economy development, especially in arid regions. [ABSTRACT FROM AUTHOR]

Adsorption and desorption processes of shale gas possess particular characteristics compared to conventional natural gas. Previous studies conducted desorption experiments on fresh core samples to investigate the isotope and chemical fractionations during the desorption process. However, complete chemical and isotope fractionations cannot be obtained due to the loss of gases during the coring process. In this study, we utilized a modified experimental apparatus based on the fixed adsorption bed to conduct systematic desorption experiments in confined systems with different proportions of free and adsorbed gases. The results show that different adsorption capacities and non-synchronous desorption for alkane gas components are leading factors influencing chemical fractionation during the desorption process. Meanwhile, C 1 /C 2 and C 1 /(C 1 +C 2) vary with different proportions of adsorbed gases in the same adsorption matrix. Generally, isotope fractionation between the adsorbed and free phases during desorption follows the Rayleigh fractionation model. The linear correlations between proportions of adsorbed CH 4 and isotope fractionation factors can be applied to predict the proportions of adsorbed gases. Calculations show that on average 55% of hydrocarbon gases exist at adsorbed state in shale gas from Yanchang Formation of Ordos Basin. • A modified experimental apparatus was firstly applied to study the chemical and isotope fractionations during desorption. • Isotope fractionation between the adsorbed and free phases during desorption follows the Rayleigh fractionation model. • Established mathematical model can be applied to predict the proportion of adsorbed gas in shale. [ABSTRACT FROM AUTHOR]

Soil respiration (Rs) plays a critical role in the global carbon (C) balance, especially in the context of globally increasing nitrogen (N) deposition. However, how N-addition influences C cycle remains unclear. Here, we applied seven levels of N application (0 (N0), 54 (N1), 90 (N2), 126 (N3), 144 (N4), 180 (N5) and 216 kg N ha−1 yr−1 (N6)) to quantify their impacts on Rs and its components (autotrophic respiration (Ra) and heterotrophic respiration (Rh)) and C and N storage in vegetation and soil in alpine meadow on the northeast margin of the Qinghai-Tibetan Plateau. We used a structural equation model (SEM) to explore the relative contributions of C and N storage, soil temperature and soil moisture and their direct and indirect pathways in regulating soil respiration. Our results revealed that the Rs, Ra and Rh, C and N storage in plant, root and soil (0–10 cm and 10–20 cm) all showed initial increases and then tended to decrease at the threshold level of 180 kg N ha−1 yr−1. The SEM results indicated that soil temperature had a greater impact on Rs than did volumetric soil moisture. Moreover, SEM also showed that C storage (in root, 0–10 and 10–20 cm soil layers) was the most important factor driving Rs. Furthermore, multiple linear regression model showed that the combined root C storage, 0–10 cm and 10–20 cm soil layer C storage explained 97.4–97.6% variations in Rs; explained 94.5–96% variations in Ra; and explained 96.3–98.1% in Rh. Therefore, the growing season soil respiration and its components can be well predicted by the organic C storage in root and topsoil in alpine meadow of the north-eastern Qinghai-Tibetan Plateau. Our study reveals the importance of topsoil and root C storage in driving growing season Rs in alpine meadow on the northeast margin of Qinghai-Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Summary Receptor clustering on the cell membrane is critical in the signaling of many immunoreceptors, and this mechanism has previously been attributed to the extracellular and/or the intracellular interactions. Here, we report an unexpected finding that for death receptor 5 (DR5), a receptor in the tumor necrosis factor receptor superfamily, the transmembrane helix (TMH) alone in the receptor directly assembles a higher-order structure to drive signaling and that this structure is inhibited by the unliganded ectodomain. Nuclear magnetic resonance structure of the TMH in bicelles shows distinct trimerization and dimerization faces, allowing formation of dimer-trimer interaction networks. Single-TMH mutations that disrupt either trimerization or dimerization abolish ligand-induced receptor activation. Surprisingly, proteolytic removal of the DR5 ectodomain can fully activate downstream signaling in the absence of ligand. Our data suggest a receptor activation mechanism in which binding of ligand or antibodies to overcome the pre-ligand autoinhibition allows TMH clustering and thus signaling. Graphical Abstract Highlights • Transmembrane helix of death receptor 5 oligomerizes to drive downstream signaling • The transmembrane helix in lipid bilayer forms dimer-trimer interaction network • Receptor ectodomain in pre-ligand state inhibits receptor clustering and activation • Ligand binding overcomes the pre-ligand autoinhibition Unlike traditional receptor clustering mediated by intracellular and extracellular domain oligomerization, the transmembrane domain alone of some TNF family receptors can form higher-order structures competent to drive signaling, basally inhibited by the unliganded ectodomain. [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) are responsible for devastating impact and mass losses. Consequently, it is essential to diagnose all components of risk in order to quantitatively estimate how the TC-induced direct economic losses (DELs) respond to the changes in hazard, exposure and vulnerability. The probability distribution of TC-induced DEL records over the period 2000−2015 for the mainland of China appears to be a negative binomial. This paper quantifies the relationship between TC-induced DELs (L), maximum sustained wind (MSW), asset value (K) and per capita GDP (I) based on the economic concept of elasticity by the generalized linear model. The coefficients on three terms indicate that a doubling in MSW increases the DEL by 303%, a doubling in asset value exposure increases the DEL by 65%, while a doubling in per capita GDP leads to a 53% decrease in DEL. The results can be used for loss assessment of disasters that occur afterwards. The elasticity values suggest that continuing economic growth will take a heavy toll on TC-prone regions assuming no changes in mitigation and adaptation efforts. From another perspective, the results emphasize that human behavior matters to the formation of disasters and disaster risk reduction. [ABSTRACT FROM AUTHOR]