Mercury and its derivatives are hazardous environmental pollutants and could affect the aquatic ecosystems and human health by biomagnification. Lake sediments can provide important historical ...information regarding changes in pollution levels and thus trace anthropogenic or natural influences. This research investigates the 100-year history of mercury (Hg) deposition in sediments from Chao Lake, a shallow eutrophic lake in China. The results indicate that the Hg deposition history can be separated into three stages (pre-1960s, 1960s–1980s, and post-1980s) over the last 100 years. Before the 1960s, Hg concentrations in the sediment cores varied little and had no spatial difference. Since the 1960s, the concentration of Hg began to increase gradually, and showed a higher concentration of contamination in the western half of the lake region than in the eastern half of the lake region due to all kinds of centralized human-input sources. The influences of anthropogenic factors and hydrological change are revealed by analyzing correlations between Hg and heavy metals (Fe, Co, Cr, Cu, Mn, Pb, and Zn), stable carbon and nitrogen isotopes (δ13C and δ15N), nutrients, particle sizes, and meteorological factors. The results show that Hg pollution intensified after the 1960s, mainly due to hydrological change, rapid regional development and urbanization, and the proliferation of anthropogenic Hg sources. Furthermore, the temperature, wind speed, and evaporation are found to interactively influence the environmental behaviors and environmental fate of Hg.
Polycyclic aromatic hydrocarbons (PAHs) are emitted into the environment by daily anthropogenic activities and they potentially threaten human health. Over the past 40 years, the coupling between ...PAHs emissions driven by energy transition and socioeconomic factors has yet to be determined, and future trends between the two parameters are unclear. In China, the emissions of PAHs increased from 1980 to 2016, and the average annual variation rate was 3.5%. After 2016, PAHs emissions were decoupled from socioeconomic growth. PAHs emissions exhibited a change from a developed region (eastern region) to an undeveloped region (central region and western region). The emissions of PAHs, if only driven by energy transition, will reach a peak in 2035 under the shared economic pathways (SSP1, SSP2, SSP4, and SSP5), which are defined to assess sustainable development. The emissions of PAHs will continuously increase by +9.8% under SSP3 during 2020–2050. Comparing these five socioeconomic pathways, SSP1 is the possible choice to achieve the sustainable decoupling of the emissions of PAHs and socioeconomic growth by transforming the drivers of economic growth, thereby optimizing the energy system and cultivating environmentally friendly behaviors.
Plain Language Summary
The widespread occurrences of polycyclic aromatic hydrocarbons (PAHs) in air, surface water, soils, sediments, and biota have been a concern because of their toxic effects on ecosystem and human health. Thus, it is imperative to alleviate emissions of PAHs to reduce human health risks. Significant knowledge gaps exist regarding whether China's PAHs emissions driven by energy transition will decline or continue to increase. In this study, we analyzed the dynamic changes in PAHs emissions from industrial coal combustion, domestic coal combustion, primary aluminum production, gasoline, diesel oil, straw burning, natural gas, and coking coal during the period 1980–2020. Then, a coupling model was employed to explore the coupling relationship between PAHs emissions and socioeconomic growth (gross domestic product and population). Finally, future PAHs emissions were predicted using five shared socioeconomic scenarios (SSP1, SSP2, SSP3, SSP4, and SSP5) during the period 2020–2050. The emissions of PAHs, if only driven by energy transition, will reach a peak in 2035 under the shared economic pathways (SSP1, SSP2, SSP4, and SSP5), which are defined to assess sustainable development. The results will provide a solid basis for policymakers to enact mitigation strategies of PAHs emissions in China.
Key Points
Polycyclic aromatic hydrocarbons (PAHs) emissions exhibited a change from a developed region to an undeveloped region
The emissions of PAHs driven by energy transition will reach a peak in 2035 under the shared economic pathways
SSP1 is the possible choice to achieve the sustainable decoupling of the emissions of PAHs and socioeconomic growth
The development of biofuels, especially liquid hydrocarbon fuels, has been widely concerned due to the depletion of fossil resources. In order to obtain fuel precursors, the reaction of C-C bond ...formation is usually carried out with biomass derived ketones/aldehydes as reactants. Acetoin and 2,3-butanediol are two platform chemicals, which are co-existed in fermentation broth and traditionally separated by distillation, and then acetoin could be use as C4 building block to prepare hydrocarbon fuels. In order to mitigate the process complexity, direct aldol condensation reaction of acetoin in fermentation broth was studied in this work.
A one-pot process of product separation and acetoin derivative synthesis was proposed based on salting-out extraction (SOE). Aldol condensation reaction of acetoin and 5-methyl furfural in different SOE systems was compared, and the results showed that the synthesis of C
fuel precursors and separation of C
products and 2,3-butanediol from fermentation broth were achieved in one-pot with ethanolammonium butyrate (EOAB) and K
HPO
as SOE reagents and catalysts. The SOE and reaction conditions such as the concentrations of EOAB and K
HPO
, reaction temperature and time were optimized. When the system was composed of 6 wt% EOAB-44 wt% K
HPO
and the mixture was stirred for 6 h at 200 rpm, 40 ℃, the yield of C
products was 80.7%, and 95.5% 2,3-butanediol was distributed to the top EOAB-rich phase. The exploration of reaction mechanism showed that an imine intermediate was rapidly formed and the subsequent C
product formation was the key step for aldol condensation reaction.
With EOAB and K
HPO
as SOE reagents and catalysts, one-pot synthesis of fuel precursor from acetoin fermentation broth was achieved without prior purification. A yield of 80.7% for C
products was obtained which was accumulated at the interface of two aqueous-phase, and 95.5% 2,3-BD was distributed to the top EOAB-rich phase. This work provides a new integration process of product separation and derivative synthesis from fermentation broth based on ionic liquid SOE.
Autophagy has been recognized as a stress tolerance mechanism that maintains cell viability, which contributes to tumor progression, dormancy, and treatment resistance. The inhibition of autophagy in ...cancer has the potential to improve the therapeutic efficacy. It is therefore of great significance to search for new autophagy inhibitors. In the present study, after screening a series of curcumin derivatives synthesized in our laboratory, (E)-3-((E)-4-chlorobenzylidene)-5-((5-methoxy-1H-indol-3-yl)methylene)-1-methylpiperidin-4-one (CB-2) was selected as a candidate for further study. We found that CB-2 increased the LC3B-II and SQSTM1 levels associated with the accumulation of autophagosomes in non-small cell lung cancer (NSCLC) A549 cells. The increased level of LC3B-II induced by CB-2 was neither eliminated when autophagy initiation was suppressed by wortmannin nor further increased when autophagosome degradation was inhibited by chloroquine (CQ). CB-2 enhanced the accumulation of LC3B-II under starvation conditions. Further studies revealed that CB-2 did not affect the levels of the key proteins involved in autophagy induction but significantly blocked the fusion of autophagosomes with lysosomes. High-dose CB-2 induced the apoptosis and necrosis of A549 cells, while a lower dose of CB-2 mainly impaired the migrative capacity of A549 cells, which only slightly induced cell apoptosis. CB-2 increased the levels of mitochondrial-derived reactive oxygen species (ROS) while decreasing the mitochondrial membrane potential (MMP). Scavenging ROS via N-acetylcysteine (NAC) reversed CB-2-induced autophagy inhibition and its inhibitory effect against A549 cells. In conclusion, CB-2 serves as a new late-stage autophagy inhibitor, which has a strong inhibitory potency against A549 cells.
A comprehensive and accurate estimation of water quality in lakes and reservoirs is vital for the protection of the aquatic biota. Research on the spatiotemporal variations of nitrogen (N) and ...phosphorus (P) concentrations in lacustrine systems is typically plagued, however, by a lack of long‐term, spatially continuous monitoring data. This paper assembled a 30‐year (1989–2018) data set of water quality in 586 lakes and reservoirs in China, along with basin characteristics and climate conditions, forming the comprehensive data set available. These data were then used in a stacking model (based on random forest, support vector regression, and K‐nearest neighbor models) to identify the relationships between nutrient concentrations and their influencing factors, including net anthropogenic N/P inputs, geographical position, climate, land use pattern, and soil type. The stacking models were developed using data collected over multiple time scales (annual, seasonal, and monthly), which were then applied to reconstruct TN and TP concentrations during the periods of 1980–2018 and 2020s–2050s under the climate scenarios of RCP 4.5 and RCP 8.5. The accuracy of the stacking models was 99.1% and 98.3% for TN and TP concentrations using ensembled data, respectively. The interannual variations in TN and TP contents in the 586 lakes and reservoirs during 1980–2018 exhibited a non‐monotonic pattern with a peak of 1.12 and 0.049 mg/L in 2007, respectively. This study demonstrates that stacking machine learning models represent a new effective approach for estimating nutrient concentrations in unmonitored lakes and reservoirs across broad spatiotemporal scales.
Plain Language Summary
The current research assembled a 30‐year (1989–2018) data set of 586 lake and reservoir water quality as well as watershed characteristics and climate conditions at a national scale to build the stacking models. As far as we know, this is the most comprehensive data set of Chinese lake and reservoir water quality. Our study first developed models take into account more indicators of the terrestrial ecosystem and consider the impact of spatial attributes and natural background conditions of lakes and reservoirs on TN and TP concentrations. We then applied the stacking model combined the results of various base machine learning algorithms to reduce the variations of the prediction and assimilating the advantages of the base models. Through containing precipitation and temperature variables with various time scales, the models have the ability to estimate and predict the annual, seasonal, and monthly variations in TN and TP concentrations during the period of 1980–2018 and 2020–2050s under different future climate scenarios. The primary target of this paper is to probe the potential benefits of using a stacking model approach to more accurately describe and reconstruct TN and TP concentrations in lakes and reservoirs throughout China over a range of spatiotemporal scales.
Key Points
λ $\lambda $ This study provides spatiotemporal estimates of nutrient concentrations in 586 lakes and reservoirs of China
λ $\lambda $ Spatiotemporal differences of nutrient concentrations and associated drivers have been revealed
λ $\lambda $ Future changes in TN and TP concentrations were estimated for selected climate scenarios
Simulation results from a global magnetohydrodynamic (MHD) model are used to examine whether the bow shock has an indentation and characterize its formation conditions, as well as its physical ...mechanism. The bow shock is identified by an increase in plasma density of the solar wind, and the indentation of the bow shock is determined by the shock flaring angle. It is shown that when the interplanetary magnetic field (IMF) is southward and the Alfvén Mach number (Mα) of solar wind is high (> 5), the bow shock indentation can be clearly determined. The reason is that the outflow region of magnetic reconnection (MR) that occurs in the low latitude area under southward IMF blocks the original flow in the magnetosheath around the magnetopause, forming a high‐speed zone and a low‐speed zone that are upstream and downstream of each other. This structure hinders the surrounding flow in the magnetosheath, and the bow shock behind the structure widens and forms an indentation. WhenMα is low, the magnetosheath is thicker and the disturbing effect of the MR outflow region is less obvious. Under northward IMF, MR occurs at high latitudes, and the outflow region formed by reconnection does not block the flow inside the magnetosheath, thus the indentation is harder to form. The study of the conditions and formation process of the bow shock indentation will help to improve the accuracy of bow shock models.
Key Points
Confirm the indentation of bow shock.
Analyze the formation conditions of the bow shock indentation.
Investigate the physical mechanism of the bow shock indentation.
This study constructs a reinforcement learning-based hybrid algorithm for Aquila Optimizer (AO) and improved Arithmetic Optimization Algorithm (IAOA). The point of the hybrid algorithm is that ...Q-learning can dynamically select the AO and the IAOA at different stages for different problems. In Arithmetic Optimization Algorithm (AOA), the mathematical optimization acceleration (MOA) function is restructured to balance global search and local exploitation, which can effectively stay away from the local optimum. Moreover, an improved reward function is modeled for Q-learning, which makes our hybrid algorithm more efficient and accurate. A set of benchmark functions and two engineering optimization problems are employed to test the performance of the proposed hybrid algorithm in this paper. Compared with other algorithms, the results show that the proposed hybrid algorithm has higher convergence speed and accuracy.
In this paper, the Space Weather Modeling Framework (SWMF) is used to simulate the real-time response of the magnetosphere to a solar wind event on June 5, 1998, in which the interplanetary magnetic ...field shifted its direction from north to south. Since most current models do not take into account convective effects of the inner magnetosphere, we first study the importance of Rice Convection Model (RCM) in the global model. We then focus on the following four aspects of the magnetosphere’s response: the magnetosphere’s density distribution, the structure of its magnetic field lines, the area of the polar cap boundary, and the corresponding ionospheric current change. We find that (1) when the IMF changes from north to south in this event, high magnetosheath density is observed to flow downstream along the magnetopause with the solar wind; low-latitude reconnection at dayside occurs under the southward IMF, while the magnetic field lines in the tail lobe caudal, caused by the nightside high latitude reconnection, extend into the interplanetary space. Open magnetic field lines exist simultaneously at both high and low latitudes at the magnetopause; (2) the area of the polar cap is obviously increased if the IMF turns from the north to the south; this observation is highly consistent with empirical observations; (3) the ionospheric field align current in the northern hemisphere is stronger than in the southern hemisphere and also increases as the IMF changes from north to south. SWMF with the Rice Convection effect provides reliable modeling of the magnetospheric and ionospheric response to this solar wind variation.
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