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12701. 题目: Cu(II) adsorption on 2-thiouracil-modified Luffa Cylindrica biochar fibres from artificial and real samples, and competition reactions with U(VI)
文章编号: N19080405
期刊: Journal of Hazardous Materials
作者: Ioanna Liatsou, Ioannis Pashalidis, Carsten Dosche
更新时间: 2019-08-04
摘要: The adsorption of Cu(II) ions by biochar fibres prior and after modification with 2-thiouracil on real and artificial samples has been studied by batch-type adsorption experiments, FTIR and XPS spectroscopy and competition reactions using U(VI) ions as competitor cations. The experimental data of the artificial samples clearly show that the modified material presents extraordinary higher affinity for Cu(II) ions even in the acidic pH range, the spectroscopic data indicate the formation of inner-sphere complexes and the competition reactions significantly higher selectivity of the 2-thiouracil modified biochar fibres for Cu(II). The 2-thiouracil-modified biochar fibres have been successfully applied to acid mine drainage (AMD) samples regarding the selective separation of Cu(II) ions from “real” samples. Regarding the desorption of copper from the biochar surface, although 100% copper recovery was achieved by eluting the metal ion using 1 M HNO3, the deterioration of the modified biochar fibers due to extensive 2-thiouracil release from the biochar surface limits the applicability of the present adsorbent in routine and large-scale applications.
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12702. 题目: Cellulose derived carbon nanofiber: A promising biochar support to enhance the catalytic performance of CoFe2O4 in activating peroxymonosulfate for recycled dimethyl phthalate degradation
文章编号: N19080404
期刊: Science of The Total Environment
作者: Lu Gan, Qiang Zhong, Aobo Geng, Linjie Wang, Chi Song, Shuguang Han, Juqing Cui, Lijie Xu
更新时间: 2019-08-04
摘要: We prepared carbon nanofiber (CCNF) using cellulose as the carbon source in this study and utilized for the first time as the support to enhance the catalytic performance of the cobalt ferrite (CoFe2O4) for peroxymonosulfate (PMS) activation. The catalytic capability of the CoFe2O4/CCNF nanocomposites activated PMS was investigated through degrading dimethyl phthalate (DMP), a classical organic pesticide pollutant, in water media. The influence factors like CCNF content, nanocomposite and PMS dosage, DMP content, and pH value on the degradation speed were systematically investigated and analyzed. Since CoFe2O4 is a spinel structured molecule which is magnetically separable, the reusability of the prepared CoFe2O4/CCNF nanocomposites under multiple cycles was also tested. Besides, the degradation intermediates during the catalytic process were also analyzed and identified by liquid chromatography-mass spectrometry (LC-MS) with a possible degradation mechanism. The results indicated that the prepared nanocomposite had promising catalytic capability in degrading DMP, in which the SO4 radicals played the main role as the active oxidation agent. Furthermore, the CoFe2O4/CCNF nanocomposites exhibited very good stability and reusability. The present study provides a clean biochar supported catalyst which could readily enhance the PMS activation efficiency for recycled decontamination of refractory organic pollutants in water media.
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12703. 题目: Enhanced nitrobenzene reduction by modified biochar supported sulfidated nano zerovalent iron: Comparison of surface modification methods
文章编号: N19080403
期刊: Science of The Total Environment
作者: Dejin Zhang, Yang Li, Aiwu Sun, Siqi Tong, Guanyong Su, Xinbai Jiang, Jiansheng Li, Weiqing Han, Xiuyun Sun, Lianjun Wang, Jinyou Shen
更新时间: 2019-08-04
摘要: In our previous study, biochar (BC) supported sulfidated nano zerovalent iron (S-nZVI@BC) was prepared for nitrobenzene (NB) reduction. In this study, in order to further improve the reduction performance of S-nZVI@BC, BC was modified before the loading of S-nZVI through three methods: oxidant (H2O2) pretreatment, alkali (NaOH) pretreatment and acid (HCl) pretreatment. The results indicated that S-nZVI could be evenly distributed onto HCl-BC due to increased surface area, negative surface charge and increased acidic functional groups on HCl-BC. At an initial concentration of 200 mg L−1, NB could be completely removed by S-nZVI@HCl-BC within a reaction time as short as 60 min, indicating rather excellent performance of S-nZVI@HCl-BC. NB reduction performance followed the order: S-nZVI@HCl-BC > S-nZVI@NaOH-BC > S-nZVI@BC > S-nZVI@H2O2-BC. The mass ratio of S-nZVI and HCl-BC was optimized in terms of NB removal efficiency, with 3:1 being identified as the best mass ratio. Furthermore, the mechanism involved in the enhanced NB reduction by S-nZVI@HCl-BC was proposed. This study demonstrated that S-nZVI@HCl-BC is a promising alternative for efficient NB removal from wastewater.
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12704. 题目: Comparison of coagulative colloidal microbubbles with monomeric and polymeric inorganic coagulants for tertiary treatment of distillery wastewater
文章编号: N19080402
期刊: Science of The Total Environment
作者: Ming Zhang, Zhongxia Cai, Li Xie, Yin Zhang, Linfeng Tang, Qi Zhou, Zhimin Qiang, Hua Zhang, Daoyong Zhang, Xiangliang Pan
更新时间: 2019-08-04
摘要: The flotation using coagulative colloidal gas aphrons (CCGAs) is of great potential in effectively removing the recalcitrant dissolved organic matter (DOM) and colorants from the bio-chemically treated cassava distillery wastewater. As bubble modifier, the monomeric and polymeric inorganic coagulants need to be studied considering their distinct influence on the surfactant/coagulant complex, the properties of colloidal aphrons as well as the process performance and mechanisms. Such studies help to create robust CCGAs with high flotation potential. In this work, the commonly-used monomeric and polymeric Al(III)- and Fe(III)-coagulants were combined with the cationic surfactant – cetyl trimethylammonium bromide (CTAB) to generate CCGAs. The CCGAs functionalized with Al(III)-coagulants (both monomeric and polymeric ones) were featured as small bubble size, strong stability and high air content. Particularly, the monomeric Al(III)-coagulant (AlCl3 in this work) resulted in low surface tension and high foamability when being mixed with CTAB in the bubble generation solution. Those CCGAs achieved high removal efficiencies of DOM and colorants at low coagulant concentrations. The molecular weight of DOM in effluent was well controlled below 1 kDa by CCGAs. For the flocs obtained from CCGA-flotation, the characteristic Raman band of DOM and colorants showed the layer-by-layer variation of Raman intensity which decreased from the outer layer to the center. In contrast with the conventional coagulation-flotation, the reduction of coagulant dosage by CCGAs was 67% (AlCl3), 25% (polyaluminum chloride), 60% (Fe2(SO4)3) and 40% (polyferric sulfate). The sludge production could then be largely reduced, and meanwhile, the retention time was shortened by 9.5 min.
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12705. 题目: Solubilization and characterization of extracellular proteins from anammox granular sludge
文章编号: N19080401
期刊: Water Research
作者: Marissa Boleij, Thomas Seviour, Lan Li Wong, Mark C.M. van Loosdrecht, Yuemei Lin
更新时间: 2019-08-04
摘要: Elucidating the extracellular polymeric substances (EPS) of anammox granular sludge is important for stable nitrogen removal processes in wastewater treatment. However, due to a lack of standardized methods for extraction and characterization, the composition of anammox granule EPS remains mostly unknown. In this study, alkaline (NaOH) and ionic liquid (IL) extractions were compared in terms of the proteins they extracted from different “Candidatus Brocadia” cultures. We aimed to identify structural proteins and evaluated to which extend these extraction methods bias the outcome of EPS characterization. Extraction was focussed on solubilization of the EPS matrix, and the NaOH and IL extraction recovered on average 20% and 26% of the VSS, respectively. Using two extraction methods targeting different intermolecular interactions increased the possibility of identifying structural extracellular proteins. Of the extracted proteins, ∼40% were common between the extraction methods. The high number of common abundant proteins between the extraction methods, illustrated how extraction biases can be reduced when solubility of the granular sludge is enhanced. Physicochemical analyses of the granules indicated that extracellular structural matrix proteins likely have β-sheet dominated secondary structures. These β-sheet structures were measured in EPS extracted with both methods. The high number of uncharacterized and possible moonlighting proteins confounded identifying structural (i.e. β-sheet dominant) proteins. Nonetheless, new candidates for structural matrix proteins are described. Further current bottlenecks in assigning specific proteins to key extracellular functions in anammox granular sludge are discussed.
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12706. 题目: Survey of bioaccessible pyrethroid insecticides and sediment toxicity in urban streams of the northeast United States
文章编号: N19080309
期刊: Environmental Pollution
作者: Kara E. Huff Hartz, Samuel A. Nutile, Courtney Y. Fung, Federico L. Sinche, Patrick W. Moran, Peter C. Van Metre, Lisa H. Nowell, Michael J. Lydy
更新时间: 2019-08-03
摘要: Pyrethroids are a class of widely-used insecticides that can be transported from terrestrial applications to aquatic systems via runoff and tend to sorb to organic carbon in sediments. Pyrethroid occurrence is detrimental to stream ecosystems due to toxicity to sediment-dwelling invertebrates which are particularly at risk of pyrethroid exposure in urban streams. In this work, 49 streams located in watersheds in the northeastern United States were surveyed for nine current-use pyrethroids using two extraction methods. Total sediment concentrations were determined by exhaustive chemical extraction, while bioaccessible concentrations were determined by single-point Tenax extraction. Total and bioaccessible pyrethroid concentrations were detected in 76% and 67% of the sites, and the average sum of pyrethroids was 232 ng/g organic carbon (OC) for total and 43.8 ng/g OC for bioaccessible pyrethroids. Bifenthrin was the most commonly detected pyrethroid in streambed sediments. Sediment toxicity was assessed using 10-d Hyalella azteca bioassays, and 28% and 15% of sediments caused a decrease in H. azteca biomass and survival, respectively. A temperature-based focused toxicity identification evaluation was used to assess pyrethroids as the causal factor for toxicity. The concentrations of pyrethroids was only weakly correlated with the degree of urban land use. Sediment toxicity was predicted by total and bioaccessible pyrethroid concentrations expressed as toxic units. This work suggests that bioaccessibility-based methods, such as Tenax extraction, can be a valuable tool in assessing sediment toxicity.
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12707. 题目: Predictive role of spectral slope ratio towards 17α-ethynylestradiol photodegradation sensitized by humic acids
文章编号: N19080308
期刊: Environmental Pollution
作者: Dong Ren, Zhaogang Ren, Fang Chen, Bin Wang, Bin Huang
更新时间: 2019-08-03
摘要: Humic acids (HAs) have been shown to dominate the photodegradation of steroid estrogens in natural waters. Nevertheless, how the photosensitizing ability of HAs relates to their structural and optical characteristics remains largely unknown. In this study, 17α-ethynylestradiol (EE2) was selected as a model compound to study to what extent easily-measurable characteristics of HAs might be used to predict their photosensitization potency. HAs were extracted from sediments of two different sources, and then subjected to structural and optical properties characterization using elemental analyzer, UV–vis spectroscopy and fluorescence spectroscopy. Photochemical experiments show that the HAs from the two sources can effectively meditate EE2 photodegradation. Although with drastically different structural and optical properties, the photosensitizing ability of these HAs towards EE2 can be well described by simple linear regressions using a spectroscopic index, the spectral slope ratio (SR). This optical indicator is correlated with various physicochemical properties of HAs, including the molecular weight, lignin content, charge-transfer interaction potential, photobleaching extent and sources. No universal prediction model could be established for predicting EE2 photodegradation kinetics on the basis of SR, but in specific waters SR could be a powerful indictor for predicting the EE2 photodegradation sensitized by HAs.
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12708. 题目: Mechanisms of carbon sequestration and stabilization by restoration of arable soils after abandonment: A chronosequence study on Phaeozems and Chernozems
文章编号: N19080307
期刊: Geoderma
作者: Irina Kurganova, Agustin Merino, Valentin Lopes de Gerenyu, Nieves Barros, Olga Kalinina, Luise Giani, Yakov Kuzyakov
更新时间: 2019-08-03
摘要: Abandonment of croplands ongoing on 220 million ha worldwide contributes strongly to soil restoration by improvement of degraded properties and medium- and long-term carbon (C) sequestration in post-agricultural ecosystems. Two interrelated processes – decomposition and stabilization of soil organic carbon (SOC) – govern SOC dynamics and affect the C source or sink functions of former croplands. We investigated how the abandonment of arable soils affects (i) accumulation of SOC, its composition, stability, and turnover during the post-agricultural restoration of soils, and (ii) microbial activity parameters. A chronosequence study was carried in two bioclimatic zones of European Russia: deciduous forest (Luvic Phaeozems, PH-chronosequence) and dry steppe (Calcic Chernozems, CH-chronosequence). Each chronosequence included an arable soil, 3–4 soils abandoned at increasing time periods (up to 35 years), and natural soil: never cropped Phaeozem and completely restored Chernozem. We combined the results of nuclear magnetic resonance (NMR), thermal analysis including Differential Scanning Calorimetry and Derivative Thermogravimetry, long-term incubation for SOC mineralization, and microbiological activity (basal respiration and microbial C content). Degraded Phaeozems with low SOC amount had much higher relative increase in SOC content (134%) during the post-agricultural restoration compared to SOC-rich Chernozems (38%). SOC gains were recorded in all organic compound classes identified by NMR and thermal analysis, but the increase of recalcitrant SOC was more pronounced in the post-agricultural Chernozems than in the Phaeozems. The post-agricultural Chernozems were characterized by higher SOC aliphaticity and aromaticity than Phaeozems. Microbial activity and biodegradable SOC increased gradually during post-agricultural restoration. Being mostly a function of climate and vegetation, the soil type was the primary factor explaining the greatest portion (54–88%) of the total variance for most soil and microbial parameters. Concluding, despite SOC content increased in both Chernozems and Phaeozems during the post-agricultural restoration, the mechanisms of C sequestration and stabilization were dependent on climate, vegetation, and on the degradation intensity during the agricultural use. The accumulation of organic compounds was specific for virgin soils dominating in deciduous forest and steppes, and had direct consequences for microbial activities, C turnover and sequestration.
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12709. 题目: Changes in biochar properties in typical loess soil under a 5-year field experiment
文章编号: N19080306
期刊: Journal of Soils and Sediments
作者: Lianshuai Tan, Cengceng Sun, Ying Wang, Tongtong Wang, Gao-Lin Wu, Honghua He, Jiyong Zheng
更新时间: 2019-08-03
摘要: Purpose: After biochar is applied to soil as a sustainable soil amendment and a carbon (C) sequestration technique, its physicochemical properties change over time. However, few studies have reported on the changes of biochar properties over the aging process under field conditions. An understanding of such changes can help us to make full use of biochar as a sustainable soil amendment and C sequestration technique. Materials and methods: We used apple tree branches as the raw material to produce biochar and studied the changes in the physicochemical properties of the biochar over a 5-year field experiment. Scanning electron microscopy (SEM), specific surface area (SSA) and micropore area, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy (XPS) were performed. Results and discussion: After 5 years of aging, the SSA of the biochar had increased by 23.91% relative to that of fresh biochar; however, the SSA initially decreased over the first 3 years and then increased over the next 2 years. The reasons for the initial decrease were the destruction and clogging of the existing pore structure, whereas new micropore formation was responsible for the subsequent increase, as verified by micropore area, SEM and XPS analyses. The C content of the biochar was stable over the 5 years, but the surface O content and quantity of oxygen-containing functional groups increased relative to those of fresh biochar, which impacts the adsorption capacity of the biochar. Conclusions: Our findings illustrate that the SSA of the biochar varied with time during the aging process. The stability of the C illustrated the potential of biochar as a C sequestration technique. The increase in oxygen-containing functional groups of the biochar was responsible for the process of nutrient adsorption.

12710. 题目: Engineering of phosphate-functionalized biochars with highly developed surface area and porosity for efficient and selective extraction of uranium
文章编号: N19080305
期刊: Chemical Engineering Journal
作者: Rui Hu, Jiang Xiao, Tianhui Wang, Guangcai Chen, Lin Chen, Xingyou Tian
更新时间: 2019-08-03
摘要: Properly engineering of surface functionality and structural porosity is critical to improve the sorption performance of biochars. Herein, we report a facile one-pot preparation of phosphate group-functionalized biochars (PBs) derived from bamboo sawdust by engineering with phytic acid prior to pyrolysis. High specific surface areas (629, 1298 and 1109 m2·g−1), large pore volumes (0.332, 0.919 and 0.789 cm3·g−1), and abundant phosphorous contents (1.14, 3.32 and 1.53 at.%) are achieved compatibly for the PBs pyrolyzed at given temperatures (i.e., 300, 450 and 600 °C) which are significantly higher than those of pristine biochars. Phytic acid not only releases hydrogen protons to tailor biochar matrixes to make micropores created and further developed, but also provides organic phosphorous-containing moiety to guarantee the surface phosphate functionality. PBs extract U(VI) from aqueous media efficiently, i.e., equilibrium achieved within 8 h, high sorption capacity of 229.2 mg·g−1 (at pH 4.0, T 298 K), and favorable selectivity towards U(VI) against the interference of coexisting metal ions. PBs can be regenerated by 0.1 mol·L−1 Na2CO3 and reused well after six recycles. This present work provides a path for the design and synthesis of advanced biochars with favorable potentials in the extraction of U(VI)-containing effluents.
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12711. 题目: Adsorption and Fenton-like removal of chelated nickel from Zn-Ni alloy electroplating wastewater using activated biochar composite derived from Taihu blue algae
文章编号: N19080304
期刊: Chemical Engineering Journal
作者: He Wang, Han Wang, Hui Zhao, Qun Yan
更新时间: 2019-08-03
摘要: A novel biochar composite impregnated with α-Fe2O3 in hierarchical porous structures (Fe(III)-ABC-20) was synthesized by means of pyrolysis combining with KOH activation using the yearly bloomed Taihu blue algae as resources. It was found that the biochar activated by KOH obtained the specific surface area of 1657.8 m2 g−1, nearly 92.6 times larger than that of the biochar without modification (17.9 m2 g−1). Meanwhile, abundant oxygen-containing functional groups such as COOH, OH, etc. are introduced onto the surface of algae biochar. Besides, Fe(III) was successfully loaded onto the porous structure of biochar from combined characterization of XRD, SEM, TEM, FTIR and XPS. Under the optimized operating conditions of pH at 6, Fe(III)-ABC-20 and H2O2 dosage of 0.5 g and 20 mM, adsorption equilibrium and Fenton-like reaction time at 20 and 60 min respectively, the biochar composite exhibited 98.87% removal rate of chelated nickel in electroplating wastewater. Moreover, the catalyst exerted better stability after four repeated experiments, as which still remained 93.26% of nickel removal. Meanwhile, electrochemical measurements revealed the presence of ligand to metal charge transfer (LMCT), indicating the promoting of Fenton-like reaction. Noticeably, degradation pathways of N,N,N′,N′-Tetrakis(2-hydroxypropyl) ethylenediamine (EDTP), one of the main complexing agents according to the component identification using mass spectrum within electroplating wastewater are proposed. EDTP might be first degraded to 2-hydroxypropanal or 2-Aminoethyl(ethyl) amine, then further degraded to acetaldehyde or ethylene, and finally oxidized to CO2 and H2O. Therefore, the biochar composite developed here could provide a novel route for the resource utilization of blue algae and heavy metal removal in electroplating wastewater containing refractory complexing agent.
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12712. 题目: Revisiting the Great Ordovician Diversification of land plants: Recent data and perspectives
文章编号: N19080303
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Thomas Servais, Borja Cascales-Miñana, Christopher J. Cleal, Philippe Gerrienne, David A.T. Harper, Mareike Neumann
更新时间: 2019-08-03
摘要: Recent molecular clock data suggest with high probability a Cambrian origin of Embryophyta (also called land plants), indicating that their terrestrialization most probably started about 500 Ma. The fossil record of the ‘Cambrian Explosion’ was limited to marine organisms and not visible in the plant fossil record. The most significant changes in early land plant evolution occurred during the Ordovician. For instance, the earliest bryophyte-like cryptospores and the oldest fragments of the earliest land plants come from the Middle and Late Ordovician, respectively. Organic geochemistry studies on biomarker compositions hint at a transition from green algae to land plants during the ‘Great Ordovician Biodiversification Event’ (GOBE). The colonization of the terrestrial realms by land plants clearly had an impact on marine ecosystems. Interactions between the terrestrial and marine biospheres have been proposed and the radiation of land plants potentially impacted on CO2 and O2 concentrations and on global climate. In addition, the shift of strontium isotopes during the Ordovician is probably linked to changing terrestrial landscapes, affected by the first massive land invasion of eukaryotic terrestrial life. The land plants seem unaffected by the first global mass extinction at the end of the Ordovician that eliminated many marine invertebrate taxa.

12713. 题目: Response of microbes to biochar strengthen nitrogen removal in subsurface flow constructed wetlands: Microbial community structure and metabolite characteristics
文章编号: N19080302
期刊: Science of The Total Environment
作者: Chaoren Deng, Lei Huang, Yinkun Liang, Hongyu Xiang, Jie Jiang, Qinghua Wang, Jie Hou, Yucheng Chen
更新时间: 2019-08-03
摘要: Four subsurface flow constructed wetlands (SFCWs) were constructed on the basis of the volume ratio of biochar in common gravel (0%, 10%, 20%, and 30%) for the evaluation of microbe and metabolite characteristics response to biochar addition. The results showed that the biochar added SFCWs provided higher removal efficiencies for ammonium (49.69%–63.51%) and total nitrogen (81.83%–86.36%), compared with pure gravel packed SFCWs for ammonium (47.40%) and total nitrogen (80.75%), respectively. Illumina MiSeq sequencing results revealed that the dominant phyla were Proteobacteria, Bacteroidetes, and Firmicutes. Biochar addition can improve the removal of nitrogen by altering microbial community and increasing the relative abundance of Thauera, Candidatus Competibacter, Dechloromonas, Desulfobulbus, Chlorobium, and Thiobacillus. Protein and humic substances were the primary components of extracellular polymeric substance (EPS) in SFCWs. The amount of total EPS considerably decreased with biochar addition, which caused a shift in the EPS functional groups including carbonyl of protein, amide, and hydroxyl groups. Moreover, biochar could enhance the high molecular weight compounds metabolized into low molecular compounds. The results can provide new insights into the use of biochar in the enhancement of nitrogen removal by microbial community and metabolic product characteristics.
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12714. 题目: Modifying effect of ant colonization on soil heterogeneity along a chronosequence of tropical forest restoration on slash-burn lands
文章编号: N19080301
期刊: Soil and Tillage Research
作者: Mei Lu, Shaojun Wang, Zhe Zhang, Minkun Chen, Shaohui Li, Run Cao, Qianbin Cao, Qianqian Zuo, Ping Wang
更新时间: 2019-08-03
摘要: Ants act as ecosystem engineers in regulating soil heterogeneities. Little is known about the degree and direction of these modifications on soils across a restoration chronosequence of tropical forests. Our objectives aimed to explore the effect of belowground-nesting ants on soil characteristics across four forest restoration stages (i.e., 12-, 28-, 42- and 53-yr olds) on slash-burn lands in the tropical Xishuangbanna, southwestern China. We confirmed the hypotheses about a positive effect of ant colonization on soil physical characteristics, and on the enrichment of microbial carbon and mineral nutrients in nest soils across the four restoration stages. Ant nests had the highest enrichment of soil organic matter (103%), readily oxidizable carbon (78%), total nitrogen (114%), available nitrogen (126%), NH4+ (133%) and NO3– (140%) at the 12-yr old stage compared with the surrounding soils. In contrast, the highest enrichment of microbial carbon (110%) in nest soils was showed at the 53-yr old stage. The enrichment of microbial carbon in nest soils increased with restoration age, but that of soil mineral nutrients would not follow the forest restorations. A higher enrichment of mineral nutrients in nest soils at the early restoration stage can improve soil fertility, which might promote the spontaneous forest restorations. A higher abundance and area of ant nests at the older restoration stage may create a higher bare space for plant development. Therefore, our results suggest that ant colonization can regulate forest restorations, possibly through creating and maintaining higher soil nutrient heterogeneity at earlier stage, and greatly stirring microbial growth and opening up space for plant development at older stage on slash-burn tropical lands.
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12715. 题目: The influence of plankton community structure on sinking velocity and remineralization rate of marine aggregates
文章编号: N19080211
期刊: Global Biogeochemical Cycles
作者: L.T. Bach, P. Stange, J. Taucher, E.P. Achterberg, M. Algueró‐Muñiz, H. Horn, M. Esposito, U. Riebesell
更新时间: 2019-08-02
摘要: Gravitational sinking of photosynthetically fixed particulate organic carbon (POC) constitutes a key component of the biological carbon pump. The fraction of POC leaving the surface ocean depends on POC sinking velocity (SV) and remineralization rate (Cremin), both of which depend on plankton community structure. However, the key drivers in plankton communities controlling SV and Cremin are poorly constrained. In fall 2014, we conducted a 6 weeks mesocosm experiment in the subtropical NE Atlantic Ocean to study the influence of plankton community structure on SV and Cremin. Oligotrophic conditions prevailed for the first 3 weeks, until nutrient‐rich deep water injected into all mesocosms stimulated diatom blooms. SV declined steadily over the course of the experiment due to decreasing CaCO3 ballast and – according to an optical proxy proposed herein – due to increasing aggregate porosity mostly during an aggregation event after the diatom bloom. Furthermore, SV was positively correlated with the contribution of picophytoplankton to the total phytoplankton biomass. Cremin was highest during a Synechococcus bloom under oligotrophic conditions and in some mesocosms during the diatom bloom after the deep‐water addition while it was particularly low during harmful algal blooms. The temporal changes were considerably larger in Cremin (max. 15‐fold) than in SV (max. 3‐fold). Accordingly, estimated POC transfer efficiency to 1000 m was mainly dependent on how the plankton community structure affected Cremin. Our approach revealed key players and interactions in the plankton food web influencing POC export efficiency thereby improving our mechanistic understanding of the biological carbon pump.

12716. 题目: Alpine glacier shrinkage drives shift in dissolved organic carbon export from quasi‐chemostasis to transport‐limitation
文章编号: N19080210
期刊: Geophysical Research Letters
作者: Marta Boix Canadell, Nicolas Escoffier, Amber J. Ulseth, Stuart N. Lane, Tom J. Battin
更新时间: 2019-08-02
摘要: The export of dissolved organic carbon (DOC) from catchments is considered as an important energy flux through streams and a major connection between terrestrial and aquatic systems. However, the impact that predicted hydrological changes due to glacier retreat and reduction in snow cover changes will have on DOC export from high‐mountain streams remains unclear. In this study, we measured daily runoff and DOC yield during one year in Alpine streams draining catchments with different levels of glacier coverage. DOC yield showed a varied response to runoff across the catchments and varied seasonally as a function of the degree of glaciation and vegetation cover. Using space‐for‐time substitution, our results indicate that the controls on DOC yield from Alpine catchments change from chemostasis to transport‐limitation as glaciers shrink.

12717. 题目: Effects of eddy‐driven subduction on ocean biological carbon pump
文章编号: N19080209
期刊: Global Biogeochemical Cycles
作者: Laure Resplandy, Marina Lévy, Dennis J. McGillicuddy
更新时间: 2019-08-02
摘要: Estimates of the ocean biological carbon pump are limited by uncertainties in the magnitude of the physical injection of particulate (POC) and dissolved (DOC) organic carbon to the ocean interior. A major challenge is to evaluate the contribution of these physical pumps at small spatial and temporal scales (< 100 km and < 1 month). Here, we use a submesoscale permitting bio‐physical model covering a large domain representative of a subpolar and a subtropical gyre to quantify the impact of small‐scale physical carbon pumps. The model successfully simulates intense eddy‐driven subduction hotspots with a magnitude comparable to what has been observed in nature (1000‐6000 mgC m‐2 d‐1). These eddy‐driven subduction events are able to transfer carbon below the mixed‐layer, down to 500‐1000 m depth. However, they contribute <5% to the annual flux at the scale of the basin, due to strong compensation between upward and downward fluxes. The model also simulates hotspots of export associated with small‐scale heterogeneity of the mixed‐layer, which intermittently export large amounts of suspended POC and DOC. The mixed‐layer pump contributes ~20% to the annual flux. High resolution measurements of export flux are needed to test models such as this one, and to improve our mechanistic understanding of the biological pump and how it will respond to climate change.

12718. 题目: Bioretention cell incorporating Fe-biochar and saturated zones for enhanced stormwater runoff treatment
文章编号: N19080208
期刊: Chemosphere
作者: Jiaqing Xiong, Sihui Ren, Yifan He, Xiaochang C. Wang, Xuechen Bai, Jiaxuan Wang, Mawuli Dzakpasu
更新时间: 2019-08-02
摘要: Nitrogen (N) and phosphorus (P) removal in conventional bioretention systems is highly variable. Therefore, five novel experimental columns with different media configurations and constituents, and incorporating a saturated zone were developed and assessed to optimize the removal of N, P and other nutrients. Three types of media composed of the conventional mixed sand and soil media (T1), biochar-amended media (T2), and iron-coated biochar (ICB)-amended media (T3) were evaluated. Two of the experimental columns were designed with double-layer configurations, while the other three were of a single-layer structure. Removal efficiencies of nutrients in the experimental columns were evaluated and compared using simulated runoff. Also, the effect of media depth on the retention of P and denitrifying enzyme activity (DEA) in the bioretention columns were evaluated. The experimental column only filled with T3 showed the best performance for COD, ammonia (NH4+-N) and total phosphorus (TP) removal (94.6%, 98.3% and 93.70%, respectively), whereas columns filled with T2 performed poorly for TP removal (57.36%). For the removal of nitrate (NO3-N) and total nitrogen (TN), the columns using a single-layer and only filled with either T3 or T2 exhibited the best performance (93% and 97% TN removal, respectively). Overall, this study demonstrates that our proposed single-layered bioretention cell only filled with T3 and incorporating a saturated zone effectively improves the runoff quality, and can provide a new bioretention cell configuration for efficient stormwater treatment.

12719. 题目: Soil organic matter amount determines the behavior of iron and arsenic in paddy soil with microbial fuel cells
文章编号: N19080207
期刊: Chemosphere
作者: Williamson Gustave, Zhao-Feng Yuan, Raju Sekar, Yu-Xiang Ren, Jinjing-Yuan Liu, Jun Zhang, Zheng Chen
更新时间: 2019-08-02
摘要: Arsenic (As) mobility in paddy soils is mainly controlled by iron (Fe) oxides and iron reducing bacteria (IBR). The Fe reducing bacteria are also considered to be enriched on the anode of soil microbial fuel cells (sMFC). Thus, the sMFC may have an impact on elements’ behavior, especially Fe and As, mobilization and immobilization in paddy soils. In this study, we found dissolved organic matter (DOC) abundance was a major determinate for the sMFC impact on Fe and As. In the constructed sMFCs with and without water management, distinctive behaviors of Fe and As in paddy soil were observed, which can be explained by the low or high DOC content under different water management. When the sMFC was deployed without water management, i.e. DOC was abundant, the sMFC promoted Fe and As movement into the soil porewater. The As release into the porewater was associated with the enhanced Fe reduction by the sMFC. This was ascribed to the acidification effect of sMFC anode and the increase of Fe reducing bacteria in the sMFC anode vicinity and associated bulk soil. However, when the sMFC was coupled with alternating dry-wet cycles, i.e. DOC was limited, the Fe and As concentrations in the soil porewater dramatically decreased by up to 2.3 and 1.6 fold, respectively, compared to the controls under the same water management regime. This study implies an environmental risk for the in-situ application of sMFC in organic matter rich wetlands and also points out a new mitigation strategy for As management in paddy soils.
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12720. 题目: Biochar particle aggregation in soil pore water: influence of ionic strength and interactions with pyrene
文章编号: N19080206
期刊: Environmental Science: Processes Impacts
作者: Stephanie Castan, Gabriel Sigmund, Thorsten Hüffer, Thilo Hofmann
更新时间: 2019-08-02
摘要: The beneficial properties of biochar have led to its increasing application to soils for environmental management. Despite its stability in soil, biochar can physically disintegrate into smaller particles, which can then be relocated from the application area. Biochar transport is strongly dependent on the biochar particle size and aggregation, with the extent of aggregation depending on the chemistry of the soil pore water. Biochar has a strong sorption affinity for polyaromatic hydrocarbons (PAHs) such as pyrene, which can also affect its transport. We therefore investigated biochar particle aggregation in solutions of different ionic strengths (ultrapure water, 0.01 M CaCl2, and 0.1 M CaCl2) with suspensions of biochar particles, and with suspensions of biochar particles loaded with pyrene (0.2, and 3.6 g/kg). Increasing the pyrene concentration in ultrapure water resulted in an increase in biochar particle size, an effect that was more pronounced following equilibration for 28 days than following equilibration for only 24 hours. Biochar particle aggregation in solutions containing both pyrene and 0.01 M CaCl2 was greatly enhanced compared to aggregation in similar solutions with no pyrene. However, the influence of pyrene became negligible at high CaCl2 concentrations (0.1 M CaCl2). To determine fate of biochar in soil the presence of PAHs and the influence of the pore water's ionic strength therefore both need to be taken into account.

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