Search

The magnetic release is a core component of a voltage-independent residual current device (RCD). Due to the sensitivity of magnetic release, it is easy to be interfered with by an external magnetic field. A new magnetic release design with high anti-interference capability is proposed in this work. First, the impact of the interference magnetic field on the magnetic release is analyzed. Second, the proposed magnetic release is detailed illustrated, including the structure and parameter design. Finally, several main factors influencing the anti-interference ability of magnetic release are analyzed, including the right torque arm and right contact area. Both simulation and experimental tests are carried out to verify the effectiveness and superiority of the proposed magnetic release.

As an important contributor to the habitability of our planet, the oxygen cycle is interconnected with the emergence and evolution of complex life and is also the basis to establish Earth system science. Investigating the global oxygen cycle provides valuable information on the evolution of the Earth system, the habitability of our planet in the geologic past, and the future of human life. Numerous investigations have expanded our knowledge of the oxygen cycle in the fields of geology, geochemistry, geobiology, and atmospheric science. However, these studies were conducted separately, which has led to one-sided understandings of this critical scientific issue and an incomplete synthesis of the interactions between the different spheres of the Earth system. This review presents a five-sphere coupled model of the Earth system and clarifies the core position of the oxygen cycle in Earth system science. Based on previous research, this review comprehensively summarizes the evolution of the oxygen cycle in geological time, with a special focus on the Great Oxidation Event (GOE) and the mass extinctions, as well as the possible connections between the oxygen content and biological evolution. The possible links between the oxygen cycle and biodiversity in geologic history have profound implications for exploring the habitability of Earth in history and guiding the future of humanity. Since the Anthropocene, anthropogenic activities have gradually steered the Earth system away from its established trajectory and had a powerful impact on the oxygen cycle. The human-induced disturbance of the global oxygen cycle, if not controlled, could greatly reduce the habitability of our planet.

In this paper, three-dimensional magnetic nitrogen-doped porous carbon modified by EDTA (N-MPC-EDTA) was successfully prepared by two-step method with lignin as the precursor, and was used for the removal of Cd (II). The 3D adsorbents were characterized by SEM, TEM, BET, XRD, XPS, Zeta potential, and element mapping analysis techniques, and the performance of the materials was tested by the batch adsorption method. The influence of experimental parameters such as contact time and pH value on the adsorption capacity of N-MPC-EDTA on Cd (II) was studied. Under the optimal conditions, the equilibrium adsorption capacity of Cd (II) was 43.68 mg∙ L-1 and the adsorption equilibrium was quickly reached within 45 min. A possible adsorption mechanism was proposed, in which the chelation of EDTA as well as the electrostatic attraction of hydroxyl, carboxyl, and nitrogen-containing functional groups dominated the adsorption of Cd (II). The adsorption kinetics and isotherm data fitted well with the pseudo-second-order kinetic model and Freundlich model, respectively. In addition, the good regeneration performance suggested that N-MPC-EDTA will have a broad application prospect in water treatment.

Atmospheric Oxygen (O2) is one of the dominating features that allow the earth to be a habitable planet with advanced civilization and diverse biology. However, since the late 1980s, observational data have indicated a steady decline in O2 content on the scale of parts-per-million level. The current scientific consensus is that the decline is caused by the fossil-fuel combustion; however, few works have been done to quantitatively evaluate the response of O2 cycle under the anthropogenic impact, at both the global and regional scales. This paper manages to quantify the land O2 flux and makes the initial step to quantificationally describe the anthropogenic impacts on the global O2 budget. Our estimation reveals that the global O2 consumption has experienced an increase from 33.69 ± 1.11 to 47.63 ± 0.80 Gt (gigaton, 109 t) O2 yr−1 between 2000 and 2018, while the land production of O2 (totaling 11.34 ± 13.48 Gt O2 yr−1 averaged over the same period) increased only slightly. In 2018, the combustion of fossil-fuel and industrial activities (38.45 ± 0.61 Gt O2 yr−1) contributed the most to consumption, followed by wildfires (4.97 ± 0.48 Gt O2 yr−1) as well as livestock and human respiration processes (2.48 ± 0.16 and 1.73 ± 0.13 Gt O2 yr−1, respectively). Burning of fossil-fuel that causes large O2 fluxes occurs in East Asia, India, North America, and Europe, while wildfires that cause large fluxes in comparable magnitude are mainly distributed in central Africa.

Although atmospheric greenhouse gas concentrations continuously increased, there was relatively little change in global-averaged surface temperatures from 1998 to 2013, which is known as atmospheric warming slowdown. For further understanding the mechanism involved, we explored the energy redistribution between the atmosphere and ocean in different latitudes and depths by using data analysis as well as simulations of a coupled atmosphere-ocean box model. The results revealed that, compared with observational changes of ocean heat content (OHC) associated with rapid warming, the OHC changes related to warming slowdown are relatively larger in multiple ocean basins, particularly in the deeper layer of the Atlantic. The coupled box model also showed that there is a larger increasing trend of OHC under the warming slowdown scenario than the rapid warming scenario. Particularly, during the warming slowdown period, the heat storage in the deeper ocean increases faster than the ocean heat uptake in the surface ocean. The simulations indicated that the warming patterns under the two scenarios are accompanied by distinct outgoing longwave radiation and atmospheric meridional heat transport, as well as other related processes, thus leading to different characteristics of ocean heat uptake. Due to the global energy balance, we suggest this slowdown has a tight relationship with the accelerated heat transport into the global ocean.

Vivianite crystallization is a promising route for phosphorus (P) recovery from P-rich wastewater. However, organic matter (OM) in wastewater may influence vivianite formation. In this study, the effects of four representative OMs, glucose, bovine serum albumin (BSA), humic acid (HA) and sodium alginate (SA), on P recovery by vivianite were investigated. The results showed that P recovery efficiency was inhibited by HA and SA, declining by 3.7% and 12.1% under HA (100 mg/L) and SA (800 mg/L), respectively. BSA, HA and SA affected the aggregated form of vivianite crystals. Vivianite particle size decreased in the presence of HA and SA. Subsequent mechanistic exploration indicated that the complexation between the OM and Fe2+ was the main cause of P recovery efficiency reduction. The coprecipitation of HA and SA with vivianite could reduce the zeta potential on the crystal surface, resulting in a smaller particle size. The nucleation sites provided by BSA and SA could transfer vivianite from single plate-like agglomerate to multilayer plate-like agglomerate. This study provided a better understanding of P recovery by vivianite from OM-rich wastewater. HIGHLIGHTS Glucose, BSA, HA and SA affected vivianite crystallization from wastewater.; OM might reduce P recovery rate by competition adsorption of Fe2+.; The morphology of vivianite crystals were different under SA and BSA.; Negative correlation presented between OM and Fe/P ratios during crystallization.

PurposeThe purpose of this paper is to analyze the effect of environmental policyChina’s national program to address climate changeon carbon emission efficiency.DesignBased on the directional distance function, the provincial total factor carbon emission efficiency was measured. Then, the authors analyzed the effect of environmental policy on carbon emission efficiency based on a difference in difference model.FindingCarbon emission efficiency has been significantly improved since the environmental policyChina’s national program to address climate changewas put forwarded, but the positive impact in different periods and regions is different. In addition, the environmental policy improves the carbon emission efficiency through the reduction of energy intensity and adjustment of the industrial structure.Originality/valueThis is the first time to use difference in difference model to use a difference in difference model to quantitatively assess the influence of environmental policyChina’s national program to address climate changeon carbon emission efficiency.

Simultaneous removal of sulfur dioxide (SO2) and nitrogen oxides (NOX) is an important research field in air pollution control. The combination application of red mud (RM) with coal mine d...

In order to identify the quality of crude and processed Corydalis Rhizoma decoction pieces, the research established a simple, fast, reliable, and validated near-infrared qualitative and quantitative model combined with chemometrics. 51 batches of crude and 40 batches of processed Corydalis Rhizoma from the Zhejiang and Jiangsu provinces of China were collected and analyzed. Crude and processed Corydalis Rhizoma samples were crushed to obtain NIR spectra. The content of seven alkaloids in crude and processed Corydalis Rhizoma was determined by high-performance liquid chromatography (HPLC). Pretreatment methods were screened such as normalization methods, offset filtering methods, and smoothing. Combined with partial least squares-discriminant analysis (PLS-DA) and partial least squares (PLS), the qualitative and quantitative models of crude and processed Corydalis Rhizoma were established, and the correlation coefficient (R2), root mean square error of calibration (RMSEC), and root mean square error of prediction (RMSEP) were used as evaluation indexes. Tetrahydropalmatine was used as an example for screening pretreatment methods; the results showed that MSC combined with the second derivative and no smoothing and the model with the wavelength range of 10000–5000 cm−1 had the best predictive ability and applied to all seven alkaloid components. Among them, the correlation coefficients were all higher than 0.99, and RMSEC and RMSEP were all less than 1%. The qualitative and quantitative model of the seven alkaloids in Corydalis Rhizoma can effectively identify the crude and processed Corydalis Rhizoma and determine the content of the seven alkaloids. By studying the NIR qualitative and quantitative models of crude and processed Corydalis Rhizoma, we can achieve rapid discrimination and quantitative prediction of crude and processed Corydalis Rhizoma. These methods can greatly improve the efficiency of traditional Chinese medicine analysis and provide a strong scientific basis for the quality identification and control of traditional Chinese medicine.

It has been reported that the transmission of COVID-19 can be influenced by the variation of environmental factors due to the seasonal cycle. However, its underlying mechanism in the current and onward transmission pattern remains unclear owing to the limited data and difficulties in separating the impacts of social distancing. Understanding the role of seasonality in the spread of the COVID-19 pandemic is imperative in formulating public health interventions. Here, the seasonal signals of the COVID-19 time series are extracted using the EEMD method, and a modified Susceptible, Exposed, Infectious, Recovered (SEIR) model incorporated with seasonal factors is introduced to quantify its impact on the current COVID-19 pandemic. Seasonal signals decomposed via the EEMD method indicate that infectivity and mortality of SARS-CoV-2 are both higher in colder climates. The quantitative simulation shows that the cold season in the Southern Hemisphere countries caused a 59.71 ± 8.72% increase of the total infections, while the warm season in the Northern Hemisphere countries contributed to a 46.38 ± 29.10% reduction. COVID-19 seasonality is more pronounced at higher latitudes, where larger seasonal amplitudes of environmental indicators are observed. Seasonality alone is not sufficient to curb the virus transmission to an extent that intervention measures are no longer needed, but health care capacity should be scaled up in preparation for new surges in COVID-19 cases in the upcoming cold season. Our study highlights the necessity of considering seasonal factors when formulating intervention strategies.

Nitrate removal from low carbon water is a problem in the water treatment, especially in the presence of high sulfate. In this work, an up-flow three-dimensional biofilm electrode reactor (3D-BER) was established to remove nitrate and sulfate from low organic carbon water. Results indicated that sulfate negatively affected nitrate removal. Moreover, high electric current and short hydraulic retention time deteriorated the performance of nitrate and sulfate removal. When the influent of SO42− was 150 mg/L, the removal efficiency of NO3−-N and SO42− was 88.49 ± 4.5% and 29.35 ± 5.5%, respectively. The high-throughput sequencing revealed that denitrifying bacteria dominated in the lower part of the reactor while sulfate reducing bacteria dominated in the upper part of the reactor. It was speculated that oxidation products of sulfide could serve as supplementary electron donors to enhance nitrate removal in the 3D-BER.

A novel iron nanoparticles encapsulated within nitrogen and sulfur co-doped magnetic porous carbon (Fe-N-S-MPC) was proposed by one-pot pyrolysis strategy to activate peroxymonosulfate (PMS) to degrade 1-naphthol using low-cost lignin as precursors. The Fe-N-S-MPC was characterized for structure and properties by different characterizations. The obtained materials had the morphology of iron nanoparticles encapsulated within nitrogen and sulfur co-doped magnetic porous carbon with rich functional groups and large specific surface area, which made the materials have a good catalytic property. It was proved that the doping of nitrogen and sulfur is pivotal for improving the catalytic performance. The radical quenching experiment confirmed that sulfate radical (SO4− ) and hydroxyl radical (OH ) are two major reactive oxygen groups. The reaction had phenomenon of the free radicals upsurge in the early stage and the shortage in the later stage. Therefore, a mathematical model was put forward to represent the two-stage reaction kinetics. By adding oxidants in batches, the degradation effect could reach nearly 100% within 30 min. The Fe-N-S-MPC were applied to the degradation of 1-naphthol in soil and showed high degradation performance. This work provided a new type of catalytic material by the high-value utilization of waste for the degradation of organic pollutants.

Atmospheric oxygen (O2) is the most crucial element on earth for the aerobic organisms that depend on it to release energy from carbon-based macromolecules. This is the first study to systematically analyze the global O2 budget and its changes over the past 100 years. It is found that anthropogenic fossil fuel combustion is the largest contributor to the current O2 deficit, which consumed 2.0 Gt/a in 1900 and has increased to 38.2 Gt/a by 2015. Under the Representative Concentration Pathways (RCPs) RCP8.5 scenario, approximately 100Gt (gigatonnes) of O2 would be removed from the atmosphere per year until 2100, and the O2 concentration will decrease from its current level of 20.946% to 20.825%. Human activities have caused irreversible decline of atmospheric O2. It is time to take actions to promote O2 production and reduce O2 consumption.

In rhizobia, host specificity is controlled by the nodulation outer proteins (Nops). However, the host genes encoding proteins associated with Nops remain unknown. We constructed a Sinorhizobium fredii HH103ΩnopL mutant and analyzed the nodule number (NN) and nodule dry weight (NDW) of 10 germplasms inoculated with the mutant or wild-type strain. Using recombinant inbred lines (RILs), the conditional and unconditional quantitative trait loci (QTLs) associated with NopL were detected. The regions overlapping conditional and unconditional QTLs were identified. Additionally, the expression levels of selected candidate genes were analyzed by qRT-PCR. Depending on the germplasm, NopL positively or negatively affected NN and NDW. The NN and NDW of ‘Charleston’ and ‘Dongnong 594’ (RIL parents) were lower in samples inoculated with Sinorhizobium fredii HH103ΩnopL than in samples inoculated with the wild-type strain. In soybean inoculated independently with Sinorhizobium fredii HH103 and HH103ΩnopL, 11 and 5 unconditional QTLs were identified for NN and NDW, respectively, while five and two conditional QTLs were identified for NN and NDW, respectively. Two overlapping QTLs were identified among the conditional and unconditional QTLs. Furthermore, the enzymes encoded by Glyma.13g170500 and Glyma.07g099700 likely interacted with NopL. The Glyma.13g170500 and Glyma.07g099700 detected at QTLs represent candidate genes that encode enzymes that interact with NopL to regulate the establishment of symbiotic relationships between rhizobia and soybean.

Based on the data of 30 Chinese provinces from 2011 to 2014, we use a meta-frontier data envelopment analysis model and a symbolic regression method to study wind power generation efficiency and its influencing factors. From our analytical results, the main findings are as follows: (1) The wind power generation efficiency of the eastern region is the highest, followed by the western region, and the wind power generation efficiency of the central region is the lowest. (2) The technology gap ratio of eastern region is at a high level and is stable. In contrast, the technology gap ratios of the central and western regions are at a low level and have a larger fluctuation range. (3) The room for improving internal management is huge in the three regions of China mainland, but the advancement of technical level only in the Central and Western is significant. (4) Geographical location has the most impact on wind power generation efficiency, followed by technical progress and carbon regulation, while wind energy reserve has the least impact on wind power generation efficiency.

Drylands are one of the most sensitive areas to anthropogenic climate change and are projected to experience accelerated expansion throughout the end of this century. However, the responses of drylands degradation to anthropogenic ecosystem changes remain unclear. This study proposes a new perspective of the ‘oxygen footprint’, defined as the ratio between oxygen consumption and oxygen production, which could be regarded as an indicator in evaluating the effects of anthropogenic climate change on global dryland ecosystems. A global distribution of the trend of oxygen footprint in response to climate change indicators and the transformations for ecosystem functioning is presented. The response of oxygen footprint to human activities and global warming is projected to enhance in the 21st century. Under a high emissions scenario (RCP8.5), linear regression analysis between oxygen footprint and other indicators shows oxygen footprint to increase with the increase of air temperature, precipitation, potential evapotranspiration and dryland areas, respectively. Our study suggests that when oxygen production is unsustainable combined with oxygen consumption, this scenario will accelerate the degradation of dryland ecosystem, with fundamental and negative consequences for the capacity of drylands to supply essential ecosystem services.

The existing white light-emitting diodes (WLEDs) are mostly fabricated with downshifting phosphors and ultraviolet (UV) or blue light LED chips. To achieve unconventional upconversion white-light-emitting phosphors, a novel strategy by encapsulating upconversion nanoparticles and organic dyes into metal–organic frameworks (MOFs) at room temperature is put forward. Herein, lanthanide-doped upconversion nanoparticles (NaYF4:Yb,Tm@NaYF4 core–shell UCNPs), dye 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) and dye Coumarin 6 (C6) with blue, red and green light emission, respectively, are encapsulated together into ZIF-8 through a facile one-pot solid-confinement conversion process. Owing to their appropriate spectral overlaps and efficient energy transfer processes between two pairs of UCNPs/DCM and UCNPs/C6 within ZIF-8, the optimized UCNP/DCM/C6@ZIF-8 thin film exhibits high-quality white-light emission upon a commercial 980 nm LED chip with ideal CIE coordinates of (0.33, 0.33), high color rendering index (CRI) value of 93 and moderate correlated color temperature (CCT) value of 5567 K. This strategy paves the way for other upconversion phosphorous nanoparticles and fluorescent molecules for WLEDs applications excited by near infrared light.

The primary pollutants in reverse-osmosis concentrates (ROC) are the substances with the UV absorbance at 254 nm (UV254), which is closely related to humic substances that can be degraded by humus-reducing bacteria. This work studied the degradation characteristics of humus-reducing bacteria in ROC treatment. The physiological and biochemical characteristics of humus-reducing bacteria were investigated, and the effects of pH values and electron donors on the reduction of humic analog, antraquinone-2, 6-disulfonate were explored to optimize the degradation. Furthermore, the O3-assisted UV-Fenton method was applied for the pretreatment of ROC, and the degradation of UV254 absorbance was apparently promoted with their removal rate, reaching 84.2% after 10 days of degradation by humus-reducing bacteria.

Atmospheric oxygen (O2) is one of the predominant features that enable Earth as a habitable planet for active and diverse biology. However, observations since the late 1980s indicate that O2 content in the atmosphere is falling steadily at part-per-million level. Although a scientific consensus has emerged that the current decline is generally attributed to the combustion of fossil fuel, a quantitative assessment of the anthropogenic impact on the O2 cycle on both global and regional scale is currently lacking. This paper quantifies the anthropogenic and biological O2 flux over land and provides a quantitative and dynamic description of land O2 budget under impacts of human activities on grid scale. It is found that total anthropogenic O2 flux over land has risen from 35.6 Gt/yr in 2000 to 46.0 Gt/yr in 2013, while the compensation from land (11.5 Gt/yr averaged from 2000 to 2013) displays a faint increase during the same period. High anthropogenic fluxes mainly occur in Eastern Asia, India, North America and Europe caused by fossil fuel combustion and in Central Africa caused by wildfire. Due to strong heterotrophic soil respiration under higher temperature conditions, the positive O2 flux in the tropics is not significant. Instead, boreal forest and Tibetan plateau become the most important sources of atmospheric O2 in the Anthropocene. The anthropogenic oxygen consumption data are publicly available online at https://doi.org/10.1594/PANGAEA.899167.

In some legume&ndash, rhizobium symbioses, host specificity is influenced by rhizobial nodulation outer proteins (Nops). However, the genes encoding host proteins that interact with Nops remain unknown. We generated an Ensifer fredii HH103 NopP mutant (HH103&Omega, NopP), and analyzed the nodule number (NN) and nodule dry weight (NDW) of 10 soybean germplasms inoculated with the wild-type E. fredii HH103 or the mutant strain. An analysis of recombinant inbred lines (RILs) revealed the quantitative trait loci (QTLs) associated with NopP interactions. A soybean genomic region containing two overlapping QTLs was analyzed in greater detail. A transcriptome analysis and qRT-PCR assay were used to identify candidate genes encoding proteins that interact with NopP. In some germplasms, NopP positively and negatively affected the NN and NDW, while NopP had different effects on NN and NDW in other germplasms. The QTL region in chromosome 12 was further analyzed. The expression patterns of candidate genes Glyma.12g031200 and Glyma.12g073000 were determined by qRT-PCR, and were confirmed to be influenced by NopP.

As a new-style solar cell, copper indium gallium selenide (CIGS) thin-film solar cell owns excellent characteristics of solar energy absorption, and it is one of the widely used thin-film solar cells. This paper mainly focuses on the research progress of this type of solar cell. Firstly, its theoretical principles are briefly described. Then, its cell materials, configuration and fabrication procedure are introduced. Subsequently, the remarkable research work about CIGS solar cell are reviewed. Finally, its commercial status is illustrated, followed by the critical issues and future perspectives.

In this paper, we demonstrate the enhanced photodegradation of rhodamine B on polarized ferroelectric KNbO3 (KNO) particles. High-quality KNO samples were prepared using a solid-state reaction and polarized under different electric fields. The variation of XRD and piezoelectric coefficient (d33) suggest an increased intensity of the ferroelectric polarization in the polarized samples. In contrast to the slow photodegradation rate of unpolarized KNO, the normalized photodegradation reaction rate constant was remarkably increased to 0.317 min−1 by the polarized KNO. The longer photoluminescence lifetime indicates that the enhancement of photocatalytic activity in polarized ferroelectric KNO powder is mainly attributed to the enhanced internal field. We believe this work may open up new avenues in photocatalysis using polarized ferroelectric materials.

To evaluate the potential utilization of B40 nano-cluster in the recognition of COS, H2S, SO2, and CS2 gases density functional theory calculations were utilized. Generally, the sequence of stability of interaction for the investigated gases is as below: SO2 > H2S > COS > CS2. It appears that a relationship exists between the absorption energy and the molecules' electric dipole moment. The B40 nano-cluster is Ф-type sensor just for SO2 and an electronic sensor for CS2 and SO2. It can be deduced that B40 nano-cluster can recognize the SO2 at the attendance of H2S, CS2, and COS as a Ф-type sensor. Moreover, it is able to selectively operate between CS2 and SO2 as an electronic sensor due to altering various electrical conductivity values at their attendance. It is neither electronic sensor nor function-type for COS and H2S gases.The B40 nano-cluster for desorption of CS2 and SO2 gases from its surface at room temperature profits from a short recovery time about 29.0 ms and 9.6 s, respectively. It is deduced that this cluster can act at a wet ambient.

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.