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Phosphorus (P) is an essential biogenic element in aquatic ecosystem, and its speciation in sediment may influence the water quality. The composition of P in suspended particular matters (SPM) and sediments were analyzed. Metal ions bonding PO43- and chelating organic P (OP) were explored by Visual MINTEQ simulation and infrared spectroscopy. Inorganic P (IP) mainly comprises orthophosphate and pyrophosphate in SPM. OP mainly includes α-glycerol phosphate, β-Gly, monophosphate, and mononucleotides from aquatic plants in SPM. Cyclotella, Nitzschia, Amphiprore, and terrestrial C3 plants are the main source of aquatic plants in JH, while they are from Oscillatoria and Merismopedia in JL. These aquatic plants directly determine whether OP or IP is taken to surface sediments during the setting of SPM. The bonding between PO43− and Ca is more preferential than Al and Fe, so the excess PO43− makes Ca compounds bonding IP (Ca-IP) and Al/Fe/Mn (hydr) oxides associated IP (Al/Fe/Mn-IP) dominant, but limited PO43− preferentially contributes more Ca-IP. Metal ions in saline water can firmly cheat with OP via P-OH and/or P=O groups to promote the burial of OP.

The development of highly conductive biofilms is a key strategy to enhance antibiotic removal in bioelectrochemical systems (BESs) with biocathodes. In this study, Au nanoparticles (Au-NPs) were in situ fabricated in a biocathode (Au biocathode) to enhance the removal of chloramphenicol (CAP) in BESs. The concentration of Au(III) was determined to be 5 mg/L. CAP was effectively removed in the BES containing a Au biocathode with a removal percentage of 94.0% within 48 h; this result was 1.8-fold greater than that obtained using a biocathode without Au-NPs (51.7%). The Au-NPs significantly reduced the charge transfer resistance and promoted the electrochemical activity of the biocathode. In addition, the Au biocathode showed a specifical enrichment of Dokdonella, Bosea, Achromobacter, Bacteroides and Petrimonas, all of which are associated with electron transfer and contaminant degradation. This study provides a new strategy for enhancing CAP removal in BESs through a simple and eco-friendly electrode design.

In this study, the impacts of dissolved oxygen (DO) on dynamics concentrations of heavy metals (Cu, Cd, Cr, and Pb) from estuary sediments were investigated in a 49-day laboratory simulation. The exchange flux method, Bureau Communautaire de Référence (BCR) sequential extraction procedure, and risk assessment code (RAC) were used to analyze the behavior of heavy metals. The results indicated that oxic environments promoted the concentrations of Cu and Cd in overlying water compared to the anoxic environments. The exchange fluxes showed that the diffusion of Cu, Cd, Cr, and Pb from sediments was the predominant process in the first 9 days, and a metastable equilibrium state was gradually reached in the later period under anoxic conditions. However, oxic conditions extended the time required to reach metastable equilibrium for Cu over the sediment-water (overlying water) interface (SWI). Although the reducible fractions of Cu, Cd, and Pb accounted for a large proportion of their total levels, the release ability of Cu, Cd, and Pb was limited by the high content of sulfide under anoxic conditions. The RAC values indicated that anoxic environments increased the proportion of acid-soluble fraction. The information obtained from this study highlights the potential risk for re-release of heavy metal from sediments under different redox conditions.

Contribution: This paper qualitative research delineates the thinking and behavioral patterns that reflect students’ advanced level of epistemological thinking in project-based learning (PBL) activities and the associated impact factors. Background: PBL has been widely adopted in engineering education for its effectiveness in improving students’ problem-solving abilities, collaboration skills, and academic achievement. The four stages of Perry’s theory—Dualism, Multiplicity, Relativism, and Commitment (within Relativism)—depict students’ epistemological development from dualistic to contextual relativistic thinking. Prior research suggested that participation in PBL could benefit students’ development to relativistic thinking—the most revolutionary change in Perry’s model. Nevertheless, how epistemological thinking was exhibited in the context of PBL, and the relationship between students’ epistemological thinking and PBL learning activities both remain unclear. Research Questions: 1) What are demonstrations of students’ relativistic thinking in PBL activities? and 2) What are the factors in regard to students’ relativistic thinking in PBL activities? Methodology: Built upon quantitative results obtained using a modified Zhang’s cognitive development inventory (ZCDI) developed in the context of Perry’s theory, this paper explored demonstrations of students’ relativistic thinking in PBL in a qualitative manner, and analyzed the associated factors based upon one-on-one interviews with 17 engineering students. Findings: In PBL activities, students’ epistemological thinking is reflected in their solving problems within constraints, conducting feasibility analyses, exhibiting commercial awareness, having their thinking broadened, and more. Their epistemological thinking can be impacted by factors, such as guidance from professors, collaborations with peers, communications with other stakeholders, and complexity level of projects.

1-phenylethanol (1-PEA) is a flavor extensively used in the production of cosmetics, beverages, and food. The release of 1-PEA into coastal environments has aroused great concern. However, its potential effects on marine organisms are still unknown. In order to provide a better understanding of the ecological risks of 1-PEA in marine environments, this study determined the toxic effects of 1-PEA on two marine diatoms (Phaeodactylum tricornutum and Skeletonema costatum). The diatoms were grown in culture medium containing different concentrations of 1-PEA for 96 h. The contents of chlorophyll a, chlorophyll c, glutathione (GSH), malondialdehyde (MDA) and the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), were measured at the end of the exposure period. 1-PEA was shown to significantly inhibit the growth of diatoms, with 96-h EC50 values of 257.14 mg/L and 126.46 mg/L in P. tricornutum and S. costatum, respectively. In P. tricornutum, the levels of SOD, CAT, GPx, GSH, and MDA were stimulated only when 1-PEA concentrations were close to or greater than the 96 h EC50 value. However, in S. costatum, the activities of SOD and CAT, and the syntheses of two chlorophylls were inhibited even at an exposure concentration below the 96 h EC50 value. Taken together, these findings indicate a potential ecological risk by discharging 1-PEA into coastal areas and its species-specific toxic effects on marine organisms.

Effective remediation of Cd polluted sediment is imperative for its potential damages to aquatic ecosystem. Biochar (BC) and nano-Fe

Accurate source identification is the first step of pollution control in environmental emergency management, especially in marine pollution events. Dissolved organic matter (DOM) absorption and fluorescence (excitation-emission matrices, EEMs) analyses were applied to trace contaminant sources for a pollution event that occurred along the coast of Laizhou Bay, Bohai Sea. Parallel factor analysis (PARAFAC) of the EEMs identified four fluorescent components: terrestrial humic-like (C1), tryptophan-like (C2), and a mixture of terrestrial and marine humic-like (C3) and tyrosine-like (C4) components. The relationships among C1 to C4 and quality indices indicated that the DOM originated from terrestrial input and biological activity. The EEMs-PARAFAC results accompanied by the optical characteristics of DOM and fingerprinting demonstrated that the marine pollution event occurred was from enterprise emissions. The numerical simulation confirmed the reliability of EEMs-PARAFAC modeling for DOM fingerprinting of pollution sources in polluted regions. This study provided a feasible method for source recognition in marine pollution events.

Geochemical processes of sulfur (S) in river aquatic systems play a crucial role in environmental evolution. In this study, the distributions and sources of reduced inorganic sulfur (RIS) and organic sulfur (OS) in coastal river surface sediments were investigated. The results indicated that OS dominated total S (80%), and OS (i.e., humic acid sulfur, HAS; fulvic acid sulfur, FAS) correlated with the availability of labile organic matter (OM) and reactive iron (Fe). Terrigenous inputs and sulfurization contributed to the enrichment of FAS through the S reduction. Autochthonous biological inputs were potential sources of HAS from S oxidization. The X-ray photoelectron spectroscopy showed that the main sources of S in surface sediments were deposited as the form of organic ester-sulfate. Aquatic life could break S down further, producing reduced S compounds accumulated as thiols and RIS in anoxic sediments. RIS was dominated by acid volatile sulfur (AVS) and chromium (II)-reducible sulfur (CRS). Reactive Fe oxides were major control factors for the conversation from hydrogen sulfide (H2S) to AVS, whereas elemental sulfide (ES) controlled the conversion from AVS into CRS in coastal rivers.

Phosphorus (P) is an essential biogenic element in aquatic ecosystem, and its speciation in sediment may influence the water quality. The composition of P in suspended particular matters (SPM) and sediments were analyzed. Metal ions bonding PO

To evaluate the integrated toxicity of metals in sediments of Jiaozhou Bay, we exposed clam (Ruditapes philippinarum) to sediments extracts obtained using of sediment extraction with deionised water adjusted to pH 4 which simulated the weak acidity in the digestive juice of clams and tested the selected biomarkers responses in clams for exposure over 15 days. At the same time, the contents of metals in sediments were assessed with method of the mean sediment quality guideline quotient (SQG-Q). The integrated biomarker response version 2 (IBRv2) was used to assess the integrated toxicity induced by metals in sediment extracts based on biomarkers response in clams: the results demonstrated that site S7 located in the mouth of Nanxin'an River show higher IBRv2 values compared to the other sites. The IBRv2 values exhibited the good consistency with SQG-Q values.

Isochrysis galbana MACC/H59 was screened from eight strains of marine microalgae to investigate its capability for phenol biodegradation. Batch incubation experiments were performed for 25 to 200 mg L−1 initial phenol concentrations. Five growth inhibitory kinetic models were used to fit the experimental data. The specific activities of phenol hydroxylase and catechol dioxygenase in I. galbana are measured. The results showed that phenol, at concentrations of less than 100 mg L−1, could be completely degraded in 4 days. The growth kinetics of I. galbana under different phenol concentrations were best fitted with a Yano model among five kinetics models tested. The values of substrate inhibition constant (117.59 mg L−1), limiting substrate concentration (183.90 mg L−1) and optimal substrate concentration (81.46 mg L−1) for phenol biodegradation of I. galbana were also obtained with the Yano model. The phenol biodegradation in I. galbana was mainly catalysed by intracellular enzymes. The ortho-pathway is significantly predominant over the meta-pathway in phenol metabolism in I. galbana. High concentrations of phenol significantly inhibited the activity of phenol hydroxylase, but had no obvious effect on catechol dioxygenase. Isochrysis galbana may be a suitable marine microalgal species for use in environmental restoration operations after accidental spills of phenol at sea.

Surface sediments and clam Meretrix meretrix were collected from a northern estuarine region in Dongying City, China. Sediments were analysed for heavy metals (Hg, As, Cd, Cr, Cu, Pb, and Zn) and the clams were tested for metallothioneins (MTs) and lysosomal membrane stability (LMS). The heavy metal total concentrations decreased in the order of Cr > Zn > Cu > Pb > As > Cd > Hg. The results of Bureau Communautaire de Reference (BCR) sequential extraction of heavy metals showed that the geochemical speciation of all heavy metals was dominated by residual fraction. According to the responses of biomarkers in M. meretrix, the modified potential ecological risk index (PERI-B) can more accurately reflect heavy metals pollution. PERI-B showed all sediment samples have low or moderate risk, except at site S10 (considerable risk), and the main contribution of ecological risk heavy metals were Cd and Hg.

Effective remediation of Cd polluted sediment is imperative for its potential damages to aquatic ecosystem. Biochar (BC) and nano-Fe2O3 modified BC (nFe2O3@BC) were conducted to remedy Cd highly contaminated sediments, and their performances, applicable conditions, and mechanisms were investigated. After 60 d capping, both BC and nFe2O3@BC capping inhibited Cd release from sediment to overlying water and porewater (reduction rates >99%). The released Cd concentrations in overlying water with nFe2O3@BC capping decreased by 1.6-11.0 times compared to those of BC capping, indicating nFe2O3@BC presented a higher capping efficiency. Notably, the increases of acidity and disturbance intensity of overlying water weakened the capping efficiencies of nFe2O3@BC and BC. BC capping was inappropriate in acidic and neutral waters (pH 3, 5, and 7) because Cd maintained a continuous release after 15 d, while nFe2O3@BC capping was valid in all pH treatments. Under 150 rpm stirring treatment, Cd release rates with BC and nFe2O3@BC capping decreased after 15 d and 30 d, respectively. At 0 and 100 rpm treatments, Cd releases treated by nFe2O3@BC capping finally kept a balance, indicating nFe2O3@BC was valid at low disturbance intensity. BC and nFe2O3@BC capping inhibited Cd release via weakening the influences of pH and disturbance on sediment. However, capping layers should be further processed because most adsorbed Cd in capping layers (>98%) would be re-released into overlying water. Meanwhile, excessive application of nFe2O3@BC could increase the risk of Fe release. The results provide novel insights into the potential applications of nFe2O3@BC and BC in situ capping of Cd polluted sediments in field remediation.

With the demand for chemicals and fuels increasing continuously, the occurrence of accidental leakage poses great risks to the aquatic environment. Xylene, a hazardous and noxious substance, has been major concerns with regard to heterogeneity and eco-toxicity towards aquatic organisms. This review focused on the ecotoxicological hazards of m-, o-, and p-xylene, as well as mixed xylene, on aquatic organisms. The mechanism of action of xylenes was also demonstrated in details. The purpose of this review was to further understand transfer and diffusion of toxicity on marine and freshwater organisms of xylene in the aquatic environment. Another aim was to screen sensitive biomarkers which were suitable for ecotoxicological assessment and monitoring in an aquatic system.

The geochemical fractions of heavy metals in sediments are crucial indexes for their mobility and bioavailability evaluations. However, different drying processes of sediment pretreatment could change metal geochemical fractions, especially for Hg, which is potentially volatile. In this study, the influence of pretreatment methods including oven-drying, air-drying, freeze-drying, and fresh sediments on the analysis of Hg fractions in sediments was investigated. Results showed that remarkable differences of Hg concentration were observed between fresh sediments and dried pretreatment sediments (P < 0.05). Briefly, the concentrations of the water-soluble and human stomach acid–soluble fractions in oven-dried and air-dried sediments generally showed significant increasing trends compared with those in the fresh sediments, while the organo-chelated fraction exhibited significant decreasing trends. The cause of this phenomenon was primarily the oxidation of organic matter, aging process, and the diffusion of Hg into micropores. The significant loss was also observed at elemental Hg fraction due to its volatilization effect. The freeze-drying posed minor influence on changes of Hg fraction analysis compared with oven-drying and air-drying. Moreover, the total Hg concentrations in pretreated sediments showed a decline of varying degrees compared with those in fresh sediments ascribing to the volatilization of elemental Hg. Finally, Pearson correlation analysis further confirmed that freeze-drying could minimize the errors of the Hg fraction analysis in sediments.

Recognizing the pollution characteristics and potential risks of trace metals in sediments are important to protect water ecosystem safety. In the present study, a systematic investigation was performed to assess the pollution and risk level of trace metals in river sediments located in the greatest gold production base in China. The geo-accumulation index was used to assess the contamination degree. The sediment quality guidelines and potential ecological risk index were employed to complete an ecological risk assessment. A non-carcinogenic health risk assessment was also carried out to evaluate potential adverse health risks. Correlations and principal component analyses were applied to check relationships among trace metals and ascertain potential pollution sources. The results suggested that the sediments in the river were most polluted by As, Cd, and Hg followed by Cu, Pb, and Zn. The assessment of potential human health risk revealed that there was no significant non-carcinogenic risk to the inhabitants. Gold mining and smelting activities and the long-term excessive application of fertilizers and agrochemicals were identified as the main anthropogenic releases. This study contributed an understanding that possible sources, contamination degree, and ecological risk level of trace metals in riverine surface sediments in a gold mining area.

In situ immobilization of heavy metals in sediments has been considered as a low-cost and eco-friendly remediation method. In this study, biochar (BC) and BC-nanoscale zero-valent iron composite (nZVI/BC) treatments with different doses were conducted to immobilize Cd in sediments in situ. The performance of BC and nZVI/BC in changing Cd mobility and bacterial community in sediment was investigated, and their remediation efficiencies at various pH values were also explored. After 140 d of remediation, the results showed that the application of BC and nZVI/BC reduced the released Cd concentrations in the overlying water and porewater by 31–69% and 26–73%, respectively. Compared to the control, the labile Cd in treated sediments was transformed to a stable fraction, and the TCLP (toxicity characteristic leaching produce) extracted Cd decreased by 7–29%. The reduction in Cd mobility was closely related to the additional dose of BC or nZVI/BC, and the presence of nZVI greatly enhanced the ability of nZVI/BC to stabilize Cd. Notably, nZVI/BC presented a higher restriction for Cd release from sediment than BC at various pH values, and both BC and nZVI/BC showed the highest remediation effects under alkaline condition. Bacterial community analysis indicated that the richness and diversity of bacterial communities with the low-dose treatments were enhanced, while inhibition was observed at high dose treatments due to changes in the pH and toxicity of BC and nZVI/BC. This study supplies new insights into the potential effects of BC and nZVI/BC application on Cd in situ immobilization in contaminated sediments.

Many abrupt climate change events often cannot be detected timely by conventional abrupt detection methods until a few years after these events have occurred. The reason for this lag in detection is that abundant and long-term observational data are required for accurate abrupt change detection by these methods, especially for the detection of a regime shift. So, these methods cannot help us understand and forecast the evolution of the climate system in a timely manner. Obviously, spatial images, generated by a coupled spatiotemporal dynamical model, contain more information about a dynamic system than a single time series, and we find that spatial images show the fractal properties. The fractal properties of spatial images can be quantitatively characterized by the Hurst exponent, which can be estimated by two-dimensional detrended fluctuation analysis (TD-DFA). Based on this, TD-DFA is used to detect an abrupt dynamic change of a coupled spatiotemporal model. The results show that the TD-DFA method can effectively detect abrupt parameter changes in the coupled model by monitoring the changing in the fractal properties of spatial images. The present method provides a new way for abrupt dynamic change detection, which can achieve timely and efficient abrupt change detection results.

The climate system is a classical spatiotemporal evolutionary dynamic system with spatiotemporal correlation characteristics. Based on this, two-dimensional detrended fluctuation analysis (TD-DFA) is used to estimate the Hurst exponent of two-dimensional images. Then, we monitored the change of the Hurst exponent of the images to identify an abrupt dynamic change. We tested the performance of this method with a coupled spatiotemporal dynamic model and found that it works well. The changes in the Hurst exponents of the spatial images are stable when there is no dynamic change in the system, but there will be a clear non-stationary change of the Hurst exponents; for example, the abrupt mean values change if the dynamics of the system change. Thus, the TD-DFA method is suitable for detecting an abrupt dynamic change from natural and artificial images. The spatial images of the NCEP reanalysis of the daily average temperature exhibited fractality. Based on this, we found three non-stationary changes in the Hurst exponents for the NCEP reanalysis of the daily average temperature or for the annual average temperature in the region (60°S–60°N). It can be concluded that the climate system may have incurred three dynamic changes since 1961 on decadal timescales, i.e., in approximately the mid-1970s, the mid-1980s, and between the late 1990s and the early 2000s.

The two-dimensional (2D) topological insulator (TI) is a promising material for designing dissipationless spintronic devices. Although many candidates have been found, few of them have a massive spin-orbit coupling (SOC) strength with high stability. In the present work, we demonstrate that h-Ga2Bi2 is a highly stable 2D TI with a massive Eg(Γ) at the Γ point of 1.477 eV, while the global band gap is 0.20 eV, which is sufficiently large for room temperature (∼26 meV). The edge states are greatly affected by the geometrical configuration of ribbon edges. The linear dispersive edge states still hold when the nanoribbon is limited to 1.7 nm, which actually realizes the ideal nanowire as theoretically derived in the field of TI. Most excitingly, an exotic 'O-atom bridge' is proposed here, and resides in the inner part of the nanoribbon, and so is thus highly protected from damage. The corresponding 'O-bridge states' display the interaction of electrons in a clear pattern, which leads to a better understanding of the 2D TI.

Heavy metal sediment quality standards (SQSs) derived from sediment quality guidelines (SQGs) are crucial in risk evaluation and environmental management. However, the establishment of SQSs is quite complex, especially for heavy metals. This study attempted to establish basin-scale SQSs for Cd, Cu, Pb and Zn based on SQGs combined with water quality standards in two coastal rivers in North China, named Jiaolai River (JL) and Jiahe River (JR), respectively. The spatial distribution, fraction, partition coefficients and environmental risk of heavy metals in sediments-porewater were investigated. The results showed that most heavy metals in sediments in JH were higher than those in JL, however, in the porewater, it exhibited an opposite trend. The geochemical fraction showed that most heavy metals in sediments were dominated by residual fraction. The partition of heavy metals between sediment and porewater were mainly affected by both sediment and porewater properties, and exogenous input of heavy metals. Contamination factors showed that Cd in sediment posed high pollution degree; the interstitial water criteria toxicity units and Nemerow Indexes suggested that heavy metal toxicities in porewater were low. The basin-scale heavy metal SQGs were calculated based on porewater quality derived from surface water quality standards using the modified equilibrium partitioning approach. The basin-scale heavy metal SQGs was classified with different grades to deduce the SQSs. Evaluated results of heavy metals in sediments based on SQSs showed lower potential bio-toxic effects in two rivers. In total, basin-scale SQGs for heavy metals were feasible for basin-scale SQSs establishment in coastal rivers.

Although phosphorus (P)-removing materials have been widely used to immobilize orthophosphate in aquatic ecosystems, the immobilization of organic phosphorus (OP) and pyrophosphate (PP) remains unclear. In this study, a unique OP/PP-immobilizing synthetic zeolite loaded with humic acid (HA) and La(OH)3 nanorod composite (ZHLA) is synthesized, and OP/PP-immobilization is examined by means of enzymolysis and photolysis. The results indicate that OP and PP could not be photodegraded into PO43− under natural conditions. Although OP could be degraded into PO43− by enhanced Fenton’s reagent, La3+ and HA could protect OP and PP from degradation. As a result of the colloidal coagulation and photocatalysis of La(OH)3, the activity of phosphatase could be reduced. The PP and phytate become resistant to enzymolysis through the formation of stable HA–La–PP/phytate or La–PP/phytate chelates. However, labile monoester phosphate could not form stable chelates resisting to enzymolysis. This labile monoester phosphate is hydrolyzed into PO43− and thereafter immobilized by ZHLA, which is the main pathway to achieve permanent immobilization. Most release-sensitive P fractions are transferred to the stable P fraction after ZHLA application. The ZHLA is demonstrated to be an economical and effective P-immobilization material and has high potential as a commercial sediment-capping product for eutrophication control.

Remediation of Cd pollution in sediments is crucial for the safety of aquatic environments and human health. In this study, four effective, common, and low-cost remediation materials (zeolite, sepiolite, red mud (RM), and biochar (BC)) loaded with nanoscale zero-valent iron (nZVI) and themselves were employed to immobilize Cd in sediments. The effects of different materials on sediment properties, immobilization effectiveness, bacterial communities, enzyme activities, and dissolved organic matter (DOM) were investigated. Results showed that sediment properties were significantly changed by the addition of immobilization materials (P 0.05). The geochemical fraction analysis showed that the labile Cd was partially transformed to the stable fraction after immobilization, with an 11-47% decrease in the acid-soluble fraction and a 50-1000% increase in the residual fraction. The Cd immobilization effectiveness peaked at the nZVI/RM and nZVI/BC treatments, and the Cd toxicity characteristic leaching procedure (TCLP) leachabilities decreased by 42% and 44%, respectively. The modified materials were more effective for immobilizing Cd than the raw materials owing to the presence of nZVI, and the Cd TCLP leachabilities with the modified materials decreased by 15%-22% compared with the raw material treatments. Immobilization-driven reduction of bioavailable Cd enhanced the richness and diversity of bacterial communities and enzyme activities. Moreover, the immobilization treatment promoted the Fe(III)-reducing process by increasing the Fe(III)-reducing bacteria (e.g. Geobacteraceae, Bacillus, and Clostridium), which are conducive to Cd immobilization. Additionally, the DOM composition presented more autogenetic characteristics in treated groups. BC (nZVI/BC) can be selected as the priority material for Cd immobilization in sediments due to higher immobilization effectiveness and lower adverse effects on sediments.

Alkaline phosphatase (AP) is commonly found in aquatic ecosystems as an extracellular enzyme closely related to the biogeochemical cycling of phosphorus. Although the AP activity (APA) is conventionally thought to be a main response to PO43− starvation, significant effects of macro metal elements (Al, Fe, and Ca) and S on the APA were found in this study. The APA was reduced by Al primarily through the adsorption of the enzyme onto AlOOH colloids. Fe2+ inhibited the APA via a mechanism involving free radical oxidation. The main mechanism by which Ca2+ inhibited the APA was by competing with Mg2+ and Zn2+ for the active sites of the enzyme. Excessive S2− could reduce the APA by removing Zn2+ from the active sites of the enzyme. The inhibition of APA could be reversed if some metal ions (e.g., Fe2+) were precipitated by S2− under reducing conditions. Therefore, in anaerobic ecosystems, the effects of macro metals on APA under conditions of sulfide accumulation may have innovative implications for phosphorus management.

In this study, the detrended fluctuation analysis (DFA) method is used to analyse the drought and flood index (DFI) of the past 531 years in 20 stations over east central China. It is found that the variation of the DFI exhibits long-range correlation. The long-range correlation gradually decreases from northwest to southeast over the studied region. Moreover, the recurrence times of droughts or floods also show long-range correlation. The long-range correlation in the DFI data will disappear if the DFI data are randomly shuffled, which was also found in the recurrence time of the randomly shuffled DFI series for each station. The results show that long-range correlation is an intrinsic property of drought or flood events, which could result in the long-range correlation of the corresponding recurrence times. At present, the prediction skill of droughts/floods in Asian-Australian monsoon region is relatively low, particularly in most of China. The long-range correlation of the DFI provides a theoretical basis for climate predictions of droughts/floods and may help improve model performance by amending the model configuration, in terms of addressing parameterization problems and improving atmosphere–ocean coupling.

In this study, the performance of moving cut data-approximate entropy (MC-ApEn) to detect abrupt dynamic changes was investigated. Numerical tests in a time series model indicate that the MC-ApEn method is suitable for the detection of abrupt dynamic changes for three types of meteorological data: daily maximum temperature, daily minimum temperature, and daily precipitation. Additionally, the MC-ApEn method was used to detect abrupt climate changes in daily precipitation data from Northwest China and the Pacific Decadal Oscillation (PDO) index. The results show an abrupt dynamic change in precipitation in 1980 and in the PDO index in 1976. The times indicated for the abrupt changes are identical to those from previous results. Application of the analysis to observational data further confirmed the performance of the MC-ApEn method. Moreover, MC-ApEn outperformed the moving t test (MTT) and the moving detrended fluctuation analysis (MDFA) methods for the detection of abrupt dynamic changes in a simulated 1000-point daily precipitation dataset.

The two-dimensional (2D) topological insulator (TI) is a promising material for designing dissipationless spintronic devices. Although many candidates have been found, few of them have a massive spin-orbit coupling (SOC) strength with high stability. In the present work, we demonstrate that h-Ga

In the present work, we demonstrate that both GaBi3 and InBi3 monolayers are Quantum Spin Hall insulators. Here, the electronic band structures and edge states of the two novel monolayers are systematically investigated by first principle calculation. Our analysis of the band inversion and Z2 number demonstrate that both GaBi3 and InBi3 are promising 2D TIs with large gaps of 283meV and 247meV, respectively. Taking GaBi3 as example, it is illustrated that the edge states are impacted by SOC and finite size effect. In addition, it is found that the compression and tension totally affect differently on the edge states. Finally, the electron velocity is studied in detail, which is highly important in the manufacturing of spintronics device.

Higher education institutions are facing unprecedented opportunities and challenges due to the rapid development of global contexts. With the momentum of higher education internationalization, leading universities in China began to launch international summer programs. These summer programs offer multiple benefits to university stakeholders, especially students. This chapter reviews the context and characteristics for international programs in leading Chinese universities. The significant role these programs play in designing an innovative learning platform were argued by reviewing and analyzing the trends among sample programs on aspects of curriculum design and implementation. The authors provide an in-depth understanding of students' learning outcomes during these programs by conducting a qualitative study utilizing sample summer programs. Last but not least, the opportunities and challenges concerning the organization and implementation of programs were analyzed and possible recommendations were proposed for future study abroad improvements.

This paper explores the possible application of recurrence quantification analysis in the detection of abrupt change of the dynamic structure of the climate system. It is discovered in the recurrence quantification analysis of the typical chaotic system-logistic model that the method may well distinguish the state of logistic model with different parameters, demonstrating its potential value in identifying the dynamic change of the system. When recurrence quantification analysis is later applied to the detection of abrupt change of average daily precipitation of all regions in China, the result indicates that the abrupt change of the dynamic structure corresponding to the precipitation of China in recent 50 years occurred in the late 1970s and the early 1980s. It is in agreement with the Chinese commonly recognized years of abruption; therefore the effectiveness is further demonstrated regarding the recognition of complexity of dynamical system.

An abrupt climate change means that the climate system shifts from a steady state to another steady state. Study on the phenomenon and theory of the abrupt climate change is a new research field of modern climatology, and it is of great significance for the prediction of future climate change. The climate regime shift is one of the most common forms of abrupt climate change, which mainly refers to the statistical significant changes on the variable of climate system at one time scale. These detection methods can be roughly divided into five categories based on different types of abrupt changes, namely, abrupt mean value change, abrupt variance change, abrupt frequency change, abrupt probability density change, and the multivariable analysis. The main research progress of abrupt climate change detection methods is reviewed. What is more, some actual applications of those methods in observational data are provided. With the development of nonlinear science, many new methods have been presented for detecting an abrupt dynamic change in recent years, which is useful supplement for the abrupt change detection methods.

Two-dimensional (2D) transition metal compound (TMC) monolayers, as well as their van der Waals heterostructures with unique properties, are fundamentally and technologically intriguing. Here, heterostructures consisting of a MoS2 monolayer and TM2CO2 (TM = Ti, Zr or Hf) monolayers are systematically researched by means of the density functional theory (DFT). Different from semiconductor/metal contacts, MoS2 and TM2CO2 monolayers are all semiconductors with band gaps ranging from 0.25-1.67 eV. According to rigorous screening of stacking patterns, MoS2/Zr2CO2 is shown to be an indirect type-II semiconductor with the maximum valence and minimum conduction bands spatially separated on opposite monolayers. Simultaneously, the interface charges transfer from Zr2CO2 to MoS2 results in a built-in field that separates the electrons and holes efficiently. Also, the smaller effective masses of electrons and the holes of band edges indicate the higher carrier mobility. Moreover, strain regulation can make the hetero-bilayer's character a semiconductor-semimetal-metal transition. The physical insights pave the way for the good performance of MoS2/TM2CO2 in next-generation electronic devices and photocatalysts.