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17501. 题目: Distinct storage mechanisms of soil organic carbon in coniferous forest and evergreen broadleaf forest in tropical China
文章编号: N21062804
期刊: Journal of Environmental Management
作者: Fanglong Su, Shan Xu, Emma J. Sayer, Weibin Chen, Yue Du, Xiankai Lu
更新时间: 2021-06-28
摘要: The impact of human activities on soil carbon (C) storage in tropical forests has aroused wide concern during the past decades, because these ecosystems play a key role in ameliorating global climate change. However, there remain uncertainties about how land-use history alters soil organic carbon (SOC) stability and storage in different forests. In this study, we measured the C content and mass distributions of soil aggregates, density fractions, mineral-bound C and microbial biomass C in the organic horizon, 0-10 cm and 10-20 cm soil layers in coniferous forest and evergreen broadleaf forest at Dinghushan Biosphere Reserve in tropical China. The broadleaf forest had larger SOC stocks than the coniferous forest, but the proportion of SOC stored in different density fractions at 0-10 cm soils was similar between forest types, while a greater proportion of SOC was stored in microaggregates in the coniferous forest. Most of the SOC was held as light fraction C in the organic horizon in the coniferous forest, whereas the concentrations of mineral-bound C were higher in the broadleaf forest. These findings indicate clear differences in the protection of SOC between broadleaf and coniferous forests growing on the same soil type. We propose that historic conversion of broadleaf forest to coniferous forest has reduced soil C sequestration capacity by altering the diversity and quality of plant inputs to the soil, which in turn affected macroaggregate formation, soil chemical properties and microbial biomass. Our results thus demonstrate that changes in forest tree species composition could have long-lasting effects on soil structure and carbon storage, providing crucial evidence for policy decisions on forest carbon sink management.

17502. 题目: The characteristic of N-nitrosodimethylamine precursor release from algal organic matter and degradation performance of UV/H2O2/O3 technology
文章编号: N21062803
期刊: Science of The Total Environment
作者: Zhenqi Du, Ruibao Jia, Wuchang Song, Yonglei Wang, Mengyu Zhang, Zhangbin Pan, Shaohua Sun
更新时间: 2021-06-28
摘要: Seasonal cyanobacterial blooms in eutrophic water releases algal organic matter (AOM), which contains large amount of dissolved organic nitrogen (DON) and is difficult to be removed effectively by conventional treatment processes (e.g., coagulation and sand filtration) because of its high hydrophilicity Moreover, N-nitrosodimethylamine (NDMA) can be generated by the reaction of AOM with disinfectants in the subsequent disinfection process. In this study, the formation of NDMA from different AOM components was explored and the control of algal-derived NDMA precursors by UV/H2O2/O3 was evaluated. The results showed that the hydrophilic and polar components of AOM with the low molecular weight had higher NDMA yields. UV-based advanced oxidation process (AOPs) is effective in degrading NDMA precursors, while the removal rate can be affected greatly by UV doses. The removal rate of NDMA precursors by UV/H2O2/O3 is higher than by UV/H2O2 or UV/O3 which can reach 95% at the UV dose of 400 mJ/cm2. An alkaline environment reduces the oxidation efficiency of UV/H2O2/O3 technology, while an acidic environment is conducive to its function. Inorganic anions such as HCO3−, SO42−, Cl− and NO3− are potential to compete with target algal-derived NDMA precursors for the oxidants reaction and inhibit the degradation/removal of these precursors. The degradation of algal-derived NDMA precursors by UV/H2O2/O3 is mainly accomplished by the oxidation of DON with secondary amide groups, and the main degradation mechanism by UV/H2O2/O3 was through the initial decomposition of macromolecular organic compounds such as biopolymers and humic substances and the further degradation of resulting small molecular components.

17503. 题目: Adsorption and thermal degradation of microplastics from aqueous solutions by Mg/Zn modified magnetic biochars
文章编号: N21062802
期刊: Journal of Hazardous Materials
作者: Jun Wang, Chen Sun, Qun-Xing Huang, Yong Chi, Jian-Hua Yan
更新时间: 2021-06-28
摘要: Microplastics (MPs) derived from plastic wastes have attracted wide attention throughout the world due to the wide distribution, easy transition, and potential threats to organisms. This study proposes efficient Mg/Zn modified magnetic biochar adsorbents for microplastic removal. For polystyrene (PS) microspheres (1 μm, 100mg/mL) in aqueous solution, the removal efficiencies of magnetic biochar (MBC), Mg modified magnetic biochar (Mg-MBC), and Zn modified magnetic biochar (Zn-MBC) were 94.81%, 98.75%, and 99.46%, respectively. It is supposed that the adsorption process was a result of electrostatic interaction and chemical bonding interaction between microplastics and biochar. The coexisting H2PO4- and organic matters in real water significantly affected the removal efficiency of Zn-MBC due to competitive adsorption effect. Microplastic degradation and adsorbent regeneration were accomplished by thermal treatment simultaneously. The degradation of adsorbed MPs was promoted by the catalytic active sites originated from Mg and Zn, releasing adsorption sites. Thermal regeneration maintained the adsorption capability. Even after five adsorption-pyrolysis cycles, MBC (95.02%), Mg-MBC (94.60%), and Zn-MBC (95.79%) showed high microplastic removal efficiency. Therefore, the low-cost, eco-friendly, and robust Mg/Zn-MBCs have promising potential for application in microplastic removal.

17504. 题目: Effective remediation of heavy metals in contaminated soil by electrokinetic technology incorporating reactive filter media
文章编号: N21062801
期刊: Science of The Total Environment
作者: Romina Ghobadi, Ali Altaee, John L. Zhou, Elika Karbassiyazdi, Namuun Ganbat
更新时间: 2021-06-28
摘要: Soil contamination is increasingly a global problem with serious implications for human health. Among different soil decontamination approaches, electrokinetic (EK) remediation is a relatively new technology for treating organic and inorganic contaminants in soil. This research aims to develop an enhanced EK treatment method incorporating a compost-based reactive filter media (RFM) with the advantages of low-cost and strong affinity for heavy metals and test and improve the treatment efficiency for multiple heavy metals in natural soil. A series of EK operations were performed to investigate the performance of EK-RFM under different operating conditions such as the electric current and voltage, processing time, and the amount of RFM. The electric current and treatment time demonstrated a significant positive impact on removing Zn, Cd and Mn ions while changing the amount of RFM had an insignificant impact on the efficiency of heavy metals removal. Overall, 51.6%–72.1% removal of Zn, Cd, and Mn was achieved at 30.00 mA of electric current and 14 days of treatment duration. The energy consumption of the EK process was 0.17 kWh kg−1. The soil organic matter adversely affected the mobilization and migration of heavy metals such as Cu and Pb during EK treatment. The results are valuable in optimizing the design of the EK-RFM system, which will extend its application to field-scale soil decontamination practices.

17505. 题目: Organic matter removal for continuous flow isotope ratio mass spectrometry analysis of carbon and oxygen isotope compositions of calcite or dolomite in organic‐rich samples
文章编号: N21062614
期刊: Limnology and Oceanography: Methods
作者: Carine Chaduteau, Magali Ader, Oanez Lebeau, Guillaume Landais, Vincent Busigny
更新时间: 2021-06-26
摘要: δ13C and δ18O values of carbonate in organic-rich samples such as soils, biofilms, and lake sediments have been scarcely used so far in paleo-environmental, biomineralization, or diagenetic studies because organic matter in high proportions is suspected to alter carbonate isotope analysis. Yet, with the improvement of analytical capabilities and in particular the use of CF-IRMS, this may not be an issue anymore. To evaluate this, δ13C and δ18O values of calcite or dolomite mixed in various proportions with yeast (used here as a model for immature organic matter) were measured. The results indicate that measurements of calcite or dolomite δ13C and δ18O by CF-IRMS require organic matter removal only when its weight proportion exceeds that of carbonates. Yeast generated an unidentified molecule during phosphoric acid digestion at 25°C (none at 80°C), which shifted the carbonate δ18O values for yeast proportions higher than 50%. It also generated CO2, but with a noticeable shift in δ13C and δ18O values only at 80°C (none at 25°C) and for yeast proportions higher than 75%. Three methods of organic matter removal were tested: the well-established NaOCl and H2O2 wet treatments as well as low temperature plasma ashing (LTA) so far seldom examined. LTA removed the isotope shifts, although imperfectly for yeast proportions of 95%, without carbonate dissolution. NaOCl efficiently removed the isotope shifts in all cases but dissolved part of the calcite and dolomite. H2O2 treatment caused severe dissolution of calcite and dolomite while worsening the δ13C and δ18O shifts and should thus be avoided.

17506. 题目: An antagonistic effect of elevated CO2 and warming on soil N2O emissions related to nitrifier and denitrifier communities in a Chinese wheat field
文章编号: N21062613
期刊: Plant and Soil
作者: Yuan Liu, Ke Gao, Zonghao Guo, Xiaoyu Liu, Rongjun Bian, Baobao Sun, Jie Li, Junhui Chen
更新时间: 2021-06-26
摘要: Aims Although elevated atmospheric CO2 and global warming are important climate factors that affect soil carbon sequestration and greenhouse gases emission from agricultural soils, it remains unclear how these factors affect the soil microbial communities that involved in nitrous oxide (N2O) emission. The objectives of this study were to evaluate the interactive effects of elevated CO2 and warming on soil microbial community and its relationship with soil N2O emission. Methods Soil N2O emission was monitored in a Free-Air CO2 Enrichment facility equipped with warming during wheat growth season. The abundance and community composition of ammonia-oxidizing bacteria (AOB) and archaea (AOA) and denitrifiers (nirK, nirS and nosZ) in the rhizosphere were determined using real-time PCR and Illumina MiSeq sequencing technique. Results Elevated CO2 increased N2O emission, the abundance of AOB and nirK, the concentration of rhizospheric soil organic carbon (SOC) and total nitrogen (TN); while it decreased the concentration of soil available phosphorus and potassium. Warming decreased soil pH, and the abundance of AOB, nirK and nosZ; and the effect of warming on soil N2O emission, SOC, TN and AOB abundance was significantly interacted with elevated CO2. Under elevated CO2, warming decreased soil N2O emission but increased the concentration of rhizosphere SOC and TN. Pyrosequencing showed that AOB, nirK, and nosZ community compositions were altered by elevated CO2 levels, and redundancy analyses further showed that variations in SOC, TN and pH determined these community compositions. Soil N2O emission was positively corelated with soil pH, the content of SOC and nitrate, and the abundance of AOB and nirK. Conclusions Our results demonstrated that future climate change of elevated CO2 plus warming will not lead to a significant increase in agricultural soil N2O emission. Ammonia oxidizer (AOB) and denitrifier (nirK) are the key soil microbial community that regulate the response of soil N2O emission to elevated CO2 and warming.

17507. 题目: Effect of EPS and its forms of aerobic granular sludge on sludge aggregation performance during granulation process based on XDLVO theory
文章编号: N21062612
期刊: Science of The Total Environment
作者: Yaying Wang, Jiaqin Wang, Zhiping Liu, Xiaohua Huang, Fang Fang, Jinsong Guo, Peng Yan
更新时间: 2021-06-26
摘要: Different forms of extracellular polymeric substances (EPS) play different roles in the formation process of aerobic granular sludge (AGS). This work focused on the contribution of loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS) and EPS to the aggregation between sludge cells during the start-up of aerobic granular sludge in a sequencing batch reactor. By analyzing the changes of sludge surface characteristics before and after the extraction of each layer of EPS, the contribution of LB-EPS, TB-EPS and EPS to the adhesion and aggregation of sludge cells in the granulation was calculated by surface thermodynamics and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The experimental results showed that AGS reactor basically completed the granulation process and kept stable operation within 40 d. In the process of sludge granulation, the effect of LB-EPS on the aggregation of sludge cells shifted from attraction to repulsion. TB-EPS could improve the surface zeta potential and hydrophobicity and show an attractive effect in the granulation process, which was conducive to the adhesion between sludge cells and was the main contributor to the formation of granules. Additionally, EPS played an apparently positive role in sludge flocculation and could promoted cell aggregation in the whole granulation process.

17508. 题目: Comparison of acidic leaching using a conventional and ultrasound-assisted method for preparation of magnetic-activated biochar
文章编号: N21062611
期刊: Journal of Environmental Chemical Engineering
作者: Diana R. Lima, Eder C. Lima, Pascal S. Thue, Silvio L.P. Dias, Fernando M. Machado, Moaaz K. Seliem, Farooq Sher, Glaydson S. dos Reis, Mohammad Reza Saeb, Jörg Rinklebe
更新时间: 2021-06-26
摘要: Four magnetic biochars (MBs) were prepared from two mixtures of Sappeli sawdust with NiCl2 solution or Sappeli sawdust with NiCl2 plus ZnCl2 solutions. These mixtures formed two pastes that were dried and further pyrolyzed at 700°C under nitrogen flow. The pyrolyzed material was leached out with 0.1M HCl under conventional reflux (AL- 80°C, 2h) or assisted by ultrasound-leaching (US- 15min, 600W), obtaining four biochars: SNiAL, SNiUS, SNiZnAL, SNiZnUS. The biochars were characterized by VSM, XRD, FTIR, isotherms of adsorption and desorption of nitrogen, pHpzc, hydrophobically characteristics (HI), TGA, elemental analysis (CHN/O). The data show that using the leaching process assisted by ultrasound can obtain biochars that present good magnetization saturation, with a lower leaching time than conventional leaching. The four biochar were tested as adsorbents to remove ten emerging contaminants and four dyes of aqueous effluents. It was observed that the impregnation of zinc chloride in the samples led to an increase in the surface areas of the magnetic biochars, which influenced the most of sorption capacities of the adsorbents for the different sorbing species. Making a ratio of sorption capacities of SNiAL/SNiZnAL and SNiUS/SNiZnUS, it was obtained the values, respectively, of 0.9761, and 0.9710 (Acid Red 1), 2.057, and 3.030 (Reactive Blue 4), 4.192, and 1.971 (Basic Violet 3), 3.359, and 1.129 (Basic Green 1), 1.673, and 1.835 (Paracetamol), 3.612, and 3.779 (Propranolol), 5.871, and 5.171 (Sodium Diclofenac), 1.457, and 1.607 (Nicotinamide), 1.094 and 1.093 (Caffeine), 1.167, and 2.398 (4-chloroaniline), 1.009 and 0.9965 (2-nitrophenol), 1.156 and 1.341 (Resorcinol), 1.299 and 1.331 (Hydroquinone), 0.9975 and 1.019 (4-bromophenol).

17509. 题目: Soils and soil organic matter transformations during the two years after a low-intensity surface fire (Subpolar Ural, Russia)
文章编号: N21062610
期刊: Geoderma
作者: A.A. Dymov, V.V. Startsev, E.Yu. Milanovsky, I.A. Valdes-Korovkin, Yu.R. Farkhodov, A.V. Yudina, O. Donnerhack, G. Guggenberger
更新时间: 2021-06-26
摘要: With an rise in temperature in the circumpolar region, an increase in the frequency of fires can be expected. We studied the effects of fire in larch (Lárix sibírica Lebed.) forests on the organic matter composition of topsoils of Leptosols in the Subpolar Ural Mountains (northern taiga, Komi Republic, Russian Federation). We compared topsoils before the fire (BF), during the low-intensity surface fire (DF), one (1AF) and two years (2AF) after the fire. The low intensity surface fire burnt only the upper part of the organic horizon, leading to the formation of a thin pyrogenic horizon. The soil alteration included alkalization of the solution by three pH units, threefold increase in the content of exchangeable forms of cations, a nine times increase in the specific surface area of the solid phase, increase in total carbon and nitrogen contents, and a five-fold increase in the aromaticity of the organic matter. The latter is mirrored by a strong increase in benzene polycarboxylic acids (BPCAs) as marker for pyrogenic carbon (PyC), representing 82 to 97 mg BPCA C g-1C. Two years after the fire, arrival of fresh litter, intensified water regime and soil acidification led to a decline of the surface area of organic horizons. Thus, it was revealed that two years after a low-intensity fire, the soils differed from the initial ones in a total carbon and nitrogen contents, the organic matter aromaticity and the BPCA contents. The content of aromatic fragments in pyrogenic horizon evaluated according 13C NMR spectroscopy decreased after two years after fire, but at the same time, the PyC concentration, estimated on the carbon of BPCAs, remains stable. This indicates that periodically repeating low-intensity fires in boreal northern forests can contribute to the accumulation of stable forms of PyC in soils.

17510. 题目: Enhanced self-powered system with graphene oxide modified electrode for simultaneous remediation of nitrate-contaminated groundwater and river sediment
文章编号: N21062609
期刊: Journal of Cleaner Production
作者: Yilin Yang, Miao Li, Rui Liu, Xuejiao Ma, Jiacheng Li, Wei Li, Xiang Liu, Xin Lu, Xiaohui Lei, Yan Long, Pengwen Wang, Hao Wang
更新时间: 2021-06-26
摘要: Simultaneous in situ remediation of malodorous organic sediment and nitrate-contaminated groundwater was achieved with a novel, enhanced, self-driven three-chamber bio-electrochemical system with Graphene Oxide (GO) modified electrodes. It has been successfully improving the electron transfer efficiency and self-purification ability by the special configuration combining surface water, sediment with underground water. The upper part can be regarded as a Sediment Microbial Fuel Cell (SMFC). The organic sediment serves as available carbon source to provide electrons for the microbes coated on the anode instead of potential pollutants. The lower part is the Biofilm Electrode Reactor (BER). Electrons were synchronously obtained from the loaded biofilm to reduce nitrate. The electricity generated from the upper part was applied directly to the lower part as electrical stimulation to enhance bacterial denitrification of the system. The electron conduction efficiency was further improved by graphene oxide modifying. With a maximum power density of 14.21 W/m2, as well as the voltage outputs ranging from 700 mV to 900 mV, nitrate removal was accelerated with less accumulation of intermediates compared with the controls without graphene oxide. The maximum output power was increased by 1.5 times and the nitrate removal efficiency (in 10 h) was increased from 89.13 ± 1.4% to 99.9 ± 0.1% after the modification. The organic matter in the sediment decreased by 78% after 270 days simultaneously. Sequencing of the microbial community showed that Geobacter and Anaerolinina were enriched in the anode. And theα-proteobacteria were enriched in the four experimental groups and had a good effect on nitrate removal especially in the C-GO-SSG system (Carbon felt anode-Graphene Oxide Modified cathode equipped Surface-water Sediment and Groundwater System) after 270 days operation. These results demonstrate that the C-GO-SSG system can be further used to remediation of sediment and groundwater with improved efficiency.

17511. 题目: Analysis on the removal of emerging contaminant from aqueous solution using biochar derived from soap nut seeds
文章编号: N21062608
期刊: Environmental Pollution
作者: Karthik Velusamy, Selvakumar Periyasamy, Ponnusamy Senthil Kumar, Thanikachalam Jayaraj, Rajasekaran Krishnasamy, Jaisankar Sindhu, Dhanabal Sneka, Balakrishnan Subhashini, Dai-Viet Nguyen Vo
更新时间: 2021-06-26
摘要: For clearing pollutants and emerging contaminants like ciprofloxacin-500mg from wastewaters generated from pharmaceutical industries, soapnut seeds biochar was synthesized and used as an adsorbent for the effective removal process. Tubular furnace operated under nitrogen gas environment was used to synthesize biochar. The batch analysis were carried out successfully to study the removal mechanism and the removal efficiency of the chosen pollutant. The soapnut seeds biochar showed excellent adsorption of ciprofloxacin at pH 6 and temperature 303 K when the dosage was 0.07 g. The Langmuir removal capacity of 33.44 mg/g was received and the Freundlich model provided the best-fits. The ciprofloxacin-500mg adsorption process correlated well with the pseudo-second-order kinetics equation, and the intraparticle diffusion mechanism mainly controlled the process. The characterization of biochar concluded that O–H groups, CO groups, COO−groups and C–F groups, and π-π interactions, pore-filling effect, and cation exchange interactions played a role in the adsorption process. Therefore, the findings of the present work revealed that soapnut seeds biochar would be an excellent low-cost adsorbent for the removal of ciprofloxacin-500mg from wastewater.

17512. 题目: Effect of infiltration hole and mulching in fish‐scale pits on soil water, nitrogen and organic matter contents: Evidence from a four‐year field experiment
文章编号: N21062607
期刊: Land Degradation & Development
作者: Ke Wang, Xiaoyuan Zhang, Gaoliang Li, Jiangbo Ma, Suiqi Zhang, Jiyong Zheng
更新时间: 2021-06-26
摘要: Soil water, nitrogen and organic matter contents are among the main limiting factors for successful vegetation restoration on degraded slopes in arid and semi-arid areas. Combining slope engineering measure to revegetation is considered as an effective eco-rehabilitation practice to restore the degraded slope. However, the single slope measure is insufficient to efficiently utilize runoff and sediments to improve soil water, nitrogen and organic matter for revegetation. In this study, four treatments were implemented on a hilly slope in a temperate continental semi-arid area with fish-scale pits (semicircle-shaped pit, 1.0 m in diameter, 0.5 m in radius, and 0.2 m in deep), namely: with gravel mulching (GM), straw mulching (SM), infiltration hole (IH), and without other measures (CK). The effects of the combined measures on soil water, nitrogen and organic matter contents were analysed over four years. The results showed that the soil water storage (0–100 cm) had no significant differences among all treatments, the one (100–260 cm) of GM/SM/IH increased by 11.65%/8.62%/7.10% compared with CK (P < 0.05). The soil organic matter and nitrogen (0–100 cm) under IH were 73.34%/81.29%/98.32% and 77.37%/80.27%/85.31% higher than CK/SM/GM, respectively (P < 0.05). Overall, IH is the most effective measure for increasing nitrogen and organic matter, and it is equally effective with GM and SM to increase the water replenishment of deep soils in semi-arid areas. Our findings provide the combined measures to combat soil water, nitrogen and organic matter deficits for slope revegetation in arid and semi-arid areas.

17513. 题目: Root-zone carbon and nitrogen pools across two chronosequences of coastal marshes formed using different restoration techniques: Dredge sediment versus river sediment diversion
文章编号: N21062606
期刊: Ecological Engineering
作者: S. Alex McClellan, Tracy Elsey-Quirk, Edward A. Laws, Ronald D. DeLaune
更新时间: 2021-06-26
摘要: Coastal marshes have among the highest rates of soil carbon accumulation of any ecosystem on Earth, yet they are increasingly being lost due to high rates of relative sea-level rise, changes to their hydrology, and other natural and anthropogenic factors. To mitigate some of this wetland loss, restoration strategies in Louisiana have been focused on creating marshes using dredge spoil and diverting river flow into deteriorating wetland basins. Here, we aimed to compare these two different restoration approaches in terms of the development of soil carbon and nitrogen within the root zone (top 30 cm) by examining two chronosequences of newly formed marshes that span 32- and 25-year timeframes—one of which was a series of brackish, created marshes in the Chenier Plain (Sabine; marsh creation), and the other, a series of deltaic, tidal, freshwater marshes in the currently prograding Wax Lake Delta (WLD; sediment diversion). We also assessed the vegetation coverage and the relative chemical stability of the soil organic carbon and nitrogen (refractory versus labile) that has accumulated across these restoration sites. We observed that vegetation coverage initially increased more rapidly in the Sabine marshes, but it was similar to that in the WLD marshes by ~30 years post-establishment. Whereas the soil carbon pool reached similar quantities between the two chronosequences, it increased nearly twice as fast on average in WLD versus Sabine. The density of soil nitrogen closely tracked soil carbon in WLD, but it remained uniform across the Sabine marshes. Refractory soil carbon accounted for 59 ± 12% of the total soil carbon, and the refractory carbon pool increased at a rate that was similar between both chronosequences, despite the characteristic differences in salinity, nutrient input, plant species composition, and mineral sedimentation rates. Overall, our results suggest that marshes formed from sediment diversions in Louisiana have the potential to rival or outpace marshes created using dredge sediment in terms of vegetation and soil organic matter development.

17514. 题目: Production of activated biochar via a self-blowing strategy-supported sulfidated nanoscale zerovalent iron with enhanced reactivity and stability for Cr(VI) reduction
文章编号: N21062605
期刊: Journal of Cleaner Production
作者: Min Zhuang, Hui Wang, Lu Qi, Liqiang Cui, Guixiang Quan, Jinlong Yan
更新时间: 2021-06-26
摘要: Biochar-supported nanoscale zero-valent iron (nZVI) has been unitized for the reduction of Cr(VI). However, the low specific surface area of biochar and the surface oxidation of nZVI limit its contaminant removal efficiency. In this study, activated biochar (ABC) was prepared through a self-blowing strategy and was used as a supporter for sulfidated nZVI (S-nZVI@ABC). The results revealed that S-nZVI@ABC had a significantly increased specific surface area (414 m2 g−1) as compared to S-nZVI supported on commercial biochar (S-nZVI@BC, 62 m2 g−1), and the S-nZVI particles were evenly dispersed. Compared with S-nZVI@BC, the reactivity S-nZVI on ABC increased by 23%. The removal efficiency of Cr(VI) by S-nZVI@ABC was also much higher than the content removed by nZVI, nZVI@ABC. The removal efficiency was nearly doubled when the S/Fe was increased from 0 to 0.5. Higher dosage, lower pH value and Cr(VI) concentration led to an increased Cr(VI) removal efficiency. The retention rate of Cr(VI) removal efficiency was higher than 90% after 10 days of aging. S-nZVI@ABC also showed good reusability in the recycling experiment. The removal process of Cr(VI) was classified as an endothermic process and fitted with the Langmuir adsorption isotherm. Multiple interaction mechanisms including reduction, precipitation, and adsorption were involved in the removal of Cr(VI) by S-nZVI@ABC.

17515. 题目: Understanding the role of cations and hydrogen bonds on the stability of aerobic granules from the perspective of the aggregation and adhesion behavior of extracellular polymeric substances
文章编号: N21062604
期刊: Science of The Total Environment
作者: Zhengwen Li, Huiqi Li, Lianfa Zhao, Xiang Liu, Chunli Wan
更新时间: 2021-06-26
摘要: Extracellular polymeric substances (EPS) were essential for the granulation and stability of aerobic granular sludge (AGS). In this study, the effects of electrostatic interactions, bridging effect of divalent cations, and hydrogen bonds on the EPS-EPS and EPS-surface interaction were verified by enhancing or reducing the specific interaction with the addition of cations or urea. The size and the surface properties of EPS aggregates were investigated, the adhesion behavior and viscoelasticity of EPS were analyzed by quartz crystal microbalance with dissipation monitoring. The changes of EPS in response to the various condition were analyzed by infrared spectroscopy and fluorescence spectrum. The electrostatic repulsion between EPS could be significantly reduced by Ca2+ addition. With the bridging effect, 10 μM of Ca2+ could reduce the negative charge of EPS more effectively than 200 μM of Na+. As Ca2+ could form the complex with the protein and Ca2+ was more inclined to bind with COO−, the Ca2+ took advantage of boosting the EPS-EPS and EPS-surface interaction than Mg2+ at the same ionic strength, which resulted in the denser structure of calcium-treated EPS. The destruction of hydrogen bonds by urea addition reduced the EPS-EPS and EPS-surface interaction, which confirmed the potential existence of hydrogen bonds in the interaction of EPS-EPS and EPS-surface. The removal of hydrogen bonds of EPS destroyed the protein's secondary structure and caused the unfolded state of the protein, which led to the looser structure of the EPS layer.

17516. 题目: Response of exoelectrogens centered consortium to nitrate on collaborative metabolism, microbial community, and spatial structure
文章编号: N21062603
期刊: Chemical Engineering Journal
作者: Dandan Liang, Chao Li, Weihua He, Zeng Li, Yujie Feng
更新时间: 2021-06-26
摘要: Exoelectrogens are widespread and participate in building up interspecies electron-sharing network between anaerobic microbes. However, the exoelectrogens-centered electron-sharing networks might be affected by over-released nitrate, which competes with solid minerals or electrodes as the electron acceptor. The knowledge on the mechanism on the response of exoelectrogens-centered community to nitrate disturbance is still limited. This study applied the microbial electrochemical system as a platform and provided insights into the response of electroactive biofilm to nitrate under a constant potential of +0.2 V. Under a fixed carbon-nitrogen ratio of 6, the biofilm partially processed dissimilatory nitrate reduction to ammonium (DNRA) transitorily and gradually loses electron-output capability. After sufficient succession, the biofilm achieved complete denitrification without ammonia accumulation and started to acquire electrons from the electrode. With nitrate disturbance, the exoelectrogens-centered biofilm dominated by Geobacter sp. preferred to cooperate with highly enriched hydrogenotrophic denitrifiers for mutualistic growth with hydrogen as the electron mediator. Different scan rates of CVs also suggested the mediated electron transfer process. The extracellular polymer substrate (EPS) serving as a network contributed to aggregates formation. The enhanced humic acid and protein secretion in the EPS of nitrate-affected biofilm suggested frequent interactions between cells. Therefore, a mutualistic interaction was established between exoelectrogens and denitrifiers under nitrate stress.

17517. 题目: Quantitative analysis on the mechanism of Cd2+ removal by MgCl2-modified biochar in aqueous solutions
文章编号: N21062602
期刊: Journal of Hazardous Materials
作者: Guangcai Yin, Lin Tao, Xinglin Chen, Nanthi S. Bolan, Binoy Sarkar, Qintie Lin, Hailong Wang
更新时间: 2021-06-26
摘要: In this study, a pristine biochar (BC) and MgCl2-modified biochar (MBC) were prepared using Pennisetum sp. straw for removing Cd2+ from aqueous solutions. Scanning electron microscope (SEM) imaging combined with energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), as well as the surface area and porosity analyses were used to reveal the physico-chemical characteristics of the pristine and modified adsorbents. Results suggested that MgCl2 impregnation during the synthesis had enhanced the specific surface area and pore volume of the biochar. Batch adsorption experiments indicated that the Cd2+ adsorption data of MBC fitted the Langmuir isothermal and pseudo-second order kinetic models better, indicating a chemical adsorption was undergoing in the system. The maximum adsorption capacity of Cd2+ on MBC was 763.12mg/g, which was 11.15 times higher than that of the pristine BC. The Cd2+ removal by MBC was mainly attributed to the mechanisms in an order: Cd(OH)2 precipitation (73.43%) > ion exchange (22.67%) > Cd2+-π interaction (3.88%), with negligible contributions from functional group complexation, electrostatic attraction and physical adsorption. The MBC could thus be used as a promising adsorbent for Cd2+ removal from aqueous solutions.

17518. 题目: Different response pattern of cyanobacteria at development and maintenance stage to potassium permanganate oxidation
文章编号: N21062601
期刊: Journal of Hazardous Materials
作者: Xi Li, Jie Zeng, Xin Yu
更新时间: 2021-06-26
摘要: Occurrence of successive cyanobacterial blooms in source waters can continuously impair drinking water quality. Previous studies have separately investigated potassium permanganate (KMnO4) to treat high-viability cyanobacteria at just one stage of either development or maintenance. However, maintenance stage exhibited significantly higher cell-density and extracellular organic matters (EOMs) than development stage, which may result in a different KMnO4 oxidation pattern. In this study, kinetics of oxidant decay, membrane integrity loss, toxin degradation of high-viability cyanobacteria at both stages were compared. Results showed that cyanobacteria at maintenance stage became more resistant to KMnO4 oxidation than that at development stage, since elevated cell-density and more proteins involved in EOMs resulted in lower oxidant exposure at this stage. Meanwhile, elevated cyanobacterial biomass became the main competitors to decrease toxin degradation efficiency at maintenance stage, leading to incapacity to degrade extracellular toxin to below safety guideline of 1μgL-1. Consequently, comparing with the best strategy for development stage (6mgmin L-1, no membrane damage), a higher oxidant exposure (12mgmin L-1) was recommended to treat cyanobacteria at maintenance stage even with slight membrane damage (19%), since it degraded extracellular toxin to below safety guideline and achieve the highest removal ratio of EOMs. Overall, this study demonstrated that stage of cyanobacteria can strongly affect KMnO4 oxidation pattern, and it is necessary for water supplies to optimize KMnO4 treatments depending on bloom stage.

17519. 题目: Differential impacts of alternate primary producers on carbon cycling
文章编号: N21062525
期刊: Ecology
作者: Khashiff K. Miranda, Brooke L. Weigel, Sophie J. McCoy, Catherine A. Pfister
更新时间: 2021-06-25
摘要: Disturbance impacts the spatial distribution of primary producers, which can have cascading effects on ecosystem function. The lower-intertidal zone on the rocky shores of the Pacific Northwest is one such place where wave energy creates a mosaic-like distribution between two assemblages: surfgrass (Phyllospadix scouleri) meadows and macroalgal forests dominated by kelp. We simulated wave disturbance by experimentally removing patches of surfgrass monocultures, resulting in a macroalgal assemblage with increased diversity, biomass, and net primary productivity in the following year. While surfgrass had a higher C:N compared to macroalgal assemblages, macroalgal assemblages achieved a higher biomass, fixed carbon at a faster rate, and released more dissolved organic carbon (DOC) during photosynthesis. Thus, despite similar standing amounts of carbon, macroalgal assemblages have increased carbon turnover – from fixation to DOC release. Comparative photophysiology indicated that surfgrasses have a competitive advantage over other macrophytes at low-light levels, allowing them to persist when disturbance is reduced. Unexpectedly, disturbance in this system increased the potential for carbon sequestration when surfgrass monocultures were replaced by diverse macroalgae.

17520. 题目: Comparison of retention and output of sulfur in limestone soil and yellow soil and their responses to acid deposition in a small karst catchment of Guizhou Province, Southwest China
文章编号: N21062524
期刊: Environmental Science and Pollution Research
作者: Wei Zhang, Lili Zhang, Jiabin Deng
更新时间: 2021-06-25
摘要: Investigating the responses of retention and output of sulfur (S) is significant to understand the impact of atmospheric S deposition on the S cycling in soils and its environmental effects in the karst catchments of Southwest China. This study analyzed the contents and δ34S values of different S forms (total S, carbon-bonded S, ester-bonded SO42-, SO42-, and total reduced inorganic sulfur [TRIS]), the δ34S values of stream SO42-, the δ13C values of soil organic carbon, and sulfate-reducing bacteria (SRB) quantity in limestone soil and yellow soil profiles in a typical small karst catchment of Southwest China. The results showed that under the same acid deposition level, the limestone soil and yellow soil profiles are significantly different from the distribution of contents and δ34S values of different S forms and the number of SRB. At the same time, more than 70% of the SO42- in the stream water draining the sampling slopes came from soils at different depths in limestone soil and yellow soil profiles. These results indicate the different response of retention and output of S in the limestone soil and yellow soil to S deposition input. The organic S formation and dissimilatory SO42- reduction (DSR) to form TRIS are S retention processes that exist in both limestone soil and yellow soil profiles. There are processes of transport and accumulation of SO42- at the bottom layer in yellow soil profile; therefore, retaining S as absorbed SO42- is also a main S retention process in yellow soil. At present, the output of SO42- through stream water mainly comes from the deposited SO42- which undergoes DSR reaction driven by SRB, not from organic S mineralization and desorption of adsorbed SO42- in the limestone soil and yellow soil profiles. However, organic S is the main S form in limestone soil and yellow soil. After the annual S deposition flux is significantly reduced, organic S mineralization in limestone soil and yellow soil profiles may release a large amount of SO42- into the surface water.