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22781. 题目: A quantitative assessment of amino sugars in soil profiles
文章编号: N20022202
期刊: Soil Biology and Biochemistry
作者: Xiangyin Ni, Shu Liao, Siyi Tan, Dingyi Wang, Yan Peng, Kai Yue, Fuzhong Wu, Yusheng Yang
更新时间: 2020-02-22
摘要: Recent evidence suggests that a significant proportion of stable soil organic matter is derived from microbial necromass, which can be evaluated by measuring biomarker amino sugars. However, our understanding of the vertical distribution and control of amino sugars in soil profiles at the global scale is still limited. Here, we synthesized the concentrations of amino sugars relative to soil mass (mg/g soil) and to soil organic carbon (C) concentration (mg/g C) in various soil horizons (litter layer, O horizon soil and mineral soil at 0–20, 20–50, 50–100 and > 100 cm depths) from 131 forest, grassland and cropland sites. We found that the concentration of soil amino sugars declined with soil depth, ranging from 5.90 mg/g soil in O horizon soil and 1.56 mg/g soil at 0–20 cm depth to 0.24 mg/g soil at >100 cm depth. However, the proportion of amino sugars in soil organic C significantly increased from 18.1 mg/g C in O horizon soil to 61.9–83.3 mg/g C in mineral soil. The concentration of amino sugars was positively correlated with soil organic C and microbial biomass C concentrations. The proportion of amino sugars in soil organic C was significantly higher in microaggregates (<2 μm) and in soil with low carbon to nitrogen ratios. Microbial biomass carbon and soil pH had positive and negative effects, respectively, on the concentration of amino sugars in topsoil, and together explained 58.8% of the total variation in the concentration of amino sugars. These results suggest that soil biogeochemical properties are more important than climatic variables and latitude in determining the long-term persistence of microbial residues in soils.

22782. 题目: Carbon doped Fe₃O₄ peroxidase-like nanozyme for mitigating the membrane fouling by NOM at neutral pH
文章编号: N20022201
期刊: Water Research
作者: Hankun Yang, Wu Xue, Mengjie Liu, Kai Yu, Wenzheng Yu
更新时间: 2020-02-22
摘要: Oxidation is a widely used method in drinking water treatment to mitigate the membrane fouling caused by the natural organic matters (NOM) from the surface water during ultra-filtration (UF) and nano-filtration (NF) processes, and H₂O₂ is one of the common oxidants for it. However, the oxidation capability of H₂O₂ at neutral pH is lower, compared to the acidic and alkaline conditions. In order to improve the efficiency of NOM oxidation at neutral pH, a carbon-doped Fe₃O₄ peroxidase-like nanozyme (CFPN) was synthesized in this study and used as a high-performance catalyst for H₂O₂ to generate hydroxyl radical. The oxygen-containing groups on the carbon structure of CFPN can form an acidic microenvironment, allowing H₂O₂ to produce hydroxyl radical by catalysis in neutral conditions. The results of hydrophilicity analysis, zeta potential, high-performance liquid size exclusion chromatography (HPSEC), Fourier transform infrared spectrum (FTIR) and flux indicated that the hydroxyl radical can oxidize the hydrophobic matters of humic acid (HA) into hydrophilic matters by Fenton reaction or electrophilic addition reaction, which can mitigate the fouling of NF membranes. The results of the same test for the bovine serum albumin (BSA) indicated that the hydroxyl radical can mitigate the fouling of UF membranes by degrading the tertiary and secondary structures of BSA and partly oxidizing the side chain groups. In addition, two types of surface water samples were used to verify the above mechanism, and the results indicated that the hydroxyl radical treatment at neutral pH is a new viable and effective strategy to significantly mitigate the NOM fouling of UF and NF membranes.
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22783. 题目: Optical Properties of Soil Dissolved Organic Matter Are Related to Acidic Functions of Its Components as Revealed by Fractionation, Selective Deuteromethylation, and Ultrahigh Resolution Mass Spectrometry
文章编号: N20022113
期刊: Environmental Science & Technology
作者: Alexander Zherebker, Evgeny Shirshin, Anna Rubekina, Oleg Kharybin, Alexey Kononikhin, Natalia A. Kulikova, Kirill V. Zaitsev, Vitaliy A Roznyatovsky, Yuri K. Grishin, Irina V. Perminova, Evgeny N. Nikolaev
更新时间: 2020-02-21
摘要: The goal of this study was to establish a relationship between the optical properties of soil dissolved organic matter (DOM) and acidic functions carried out by its individual constituents. We obtained 12 fractions of DOM samples using sequential solid phase extraction on nonionic sorbent at steadily lowered pH values: 7, 5, 3, 2, which correspond to low bounds of pKa values of phenols, aliphatic, and aromatic carboxylic acids, and ketoacids. The structural studies were conducted with the use of NMR and selective deuteromethylation of isolated fractions coupled to ultrahigh resolution mass spectrometry. First, a gradual shift of molecular compositions was observed from reduced components to aromatic oxidized compounds isolated at pH 7 and 2, respectively. Changes in molecular compositions were accompanied by a red shift of fluorescence spectra. Further application of deuteromethylation enabled us to distinguish DOM constituents with different amounts of carboxylic groups. Moreover, identification of structural isomers in a single DOM sample was achieved. Statistical analysis revealed that red shift of fluorescence is facilitated by the increase of a contribution of aromatic poly(carboxylic acid)s with high conjugation lengths. Additionally, analysis of the labeled fractionated permafrost thaw DOM directly showed carboxyl-rich alicyclic molecules, while the same components from lower-latitude DOM were assigned to lignin-like species.

22784. 题目: Model study of organic carbon attenuation and oxygen mass transfer in persistent aggregate layers in the deep sea
文章编号: N20022112
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Timothy J. Shaw, Corrianna Boucher, Christine L. Huffard, Kenneth L. Smith
更新时间: 2020-02-21
摘要: A time series study from 1989 to 2017 indicates that, increasingly, carbon export to abyssal sediments in the California Current Ecosystem (CCE), 220 km west of the central California coast (Sta. M), occurs as rapidly sinking pulses of particulate organic carbon (POC). Nearly continuous sediment trap collections confirm that POC export to 3400 m increased significantly after 2011 with carbon attenuation (as fraction of POC remineralized) ranging from a low of 57% to a high of 77% during periods of pulsed flux. All of the major pulse events for the period resulted in the delivery of detrital aggregates that covered part or all of the sediment surface as an organic carbon rich layer at ∼4000 m depth. However, the magnitude of the measured Sediment Community Oxygen Consumption (SCOC) did not increase proportionally to the organic carbon inventory change. Here, a model of oxygen consumption informed by the time series data at Sta. M in the CCE suggest that aggregate flocs constitute a major source for benthic carbon and a barrier to mass transport of oxygen to surface sediments leading to increased carbon attenuation in surface sediment layers. The correlation of POC delivery with aggregate coverage shows that the majority of POC delivery during pulse events is likely to consume all of the oxygen within the aggregates. Results indicate that an increasing fraction of POC reaching the abyssal sediments at Sta. M under conditions that support increased net burial of carbon. This finding is significant in the context of the fraction of the total POC flux that occurs as pulse events in this important upwelling region. During the period from 2011 to 2017, a third of the total POC flux resulted in aggregate flocs that covered a significant portion of the sediment surface (>47%). Following the 2015–2016 El Nino period the flocs became a dominant feature of the sediment surface. More than 80% of the POC flux to near bottom sediment traps in 2017 occurred coincident with aggregate floc cover of more than 90% of the sediments. The resultant physical barrier to oxygen transport and relatively low consumption of newly delivered carbon indicate conditions that are more typical of environments having low oxygen bottom waters.

22785. 题目: Estimating biogenic silica production of Rhizaria in the global ocean
文章编号: N20022111
期刊: Global Biogeochemical Cycles
作者: Natalia Llopis Monferrer, Demetrio Boltovskoy, Paul Tréguer, Miguel Méndez Sandin, Fabrice Not, Aude Leynaert
更新时间: 2020-02-21
摘要: Siliceous polycystines and phaeodarians are open‐ocean planktonic protists found throughout the water column and characterized by complex siliceous skeletons that are formed, at least partly, through the uptake of silicic acid. These protists contribute to the marine organic carbon (C) and biogenic silica (bSi) pools but little is known about their contribution to the silica (Si) biogeochemical cycle. Here we report the first measurements of the Si uptake rate of polycystine and phaeodarian cells from samples collected in the Mediterranean Sea using the 32Si based method. The elementary composition (bSi, particulate organic carbon and nitrogen) of these organisms was also measured. Combining our results with published data on the distribution and abundance of Polycystina and Phaeodaria in the global ocean, we conclude that these organisms could contribute from 0.2 to 2.2 mmol Si m‐2 of the marine standing stock of bSi and from 2 to 58 Tmol Si yr‐1 (1 to 19%) of the global oceanic biogenic silica production. The implications for the global marine Si cycle are discussed.

22786. 题目: Effects of the structures and micropores of sedimentary organic matter on the oxidative degradation of benzo(a)pyrene by Na₂S₂O₈
文章编号: N20022110
期刊: Water Research
作者: Chenya Zhuo, Shujie Hu, Yu Yang, Yong Ran
更新时间: 2020-02-21
摘要: In this study, we investigated how the desorption and degradation processes of radiolabeled benzo[a]pyrene (BaP) that was aged in various marine sediments were influenced by sedimentary organic matter properties. The stable OC fraction (STOC) and the demineralized fraction (DM) were isolated and characterized via advanced solid-state ¹³C nuclear magnetic resonance spectroscopy (NMR) and a CO₂ gas adsorption technique, respectively. Sodium persulfate preferentially removed the unstable OC fractions (USOC) and the aromatic C groups, and the residual STOC fractions were enriched with aliphatic C groups. The aliphatic C showed stronger resistance to degradation by persulfate than that of the aromatic C. A first-order kinetic model described the degradation process by sodium persulfate solutions very well (R² > 0.997). The desorption percentages, degradation percentages and rates k (h⁻¹) of BaP gradually decreased from the estuarine sediments to the offshore marine sediments and were highly significantly and negatively correlated with STOC-bulk, F_aliph-bulk, and V_o-bulk (R²>0.903, p < 0.01). It was demonstrated that sodium persulfate degraded not only desorbed BaP but also a portion of the bound BaP fraction that was difficult to desorb. The BaP fractions that sorbed on USOC were degraded initially; then, the fractions of BaP that were released from STOC were degraded. This study demonstrated the important roles of STOC, aliphatic moieties, and micropores in the degradation process of BaP during the Na₂S₂O₈ treatment of the sediments.
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22787. 题目: An Important Biogeochemical Link between Organic and Inorganic Carbon Cycling: Effects of Organic Alkalinity on Carbonate Chemistry in Coastal Waters Influenced by Intertidal Salt Marshes
文章编号: N20022109
期刊: Geochimica et Cosmochimica Acta
作者: Shuzhen Song, Zhaohui Aleck Wang, Meagan Eagle Gonneea, Kevin D. Kroeger, Sophie N. Chu, Daoji Li, Haorui Liang
更新时间: 2020-02-21
摘要: Dissolved organic carbon (DOC) contains organic acid charge groups that contribute organic alkalinity (OrgAlk) to total alkalinity (TA). These effects are often ignored or treated as a calculation uncertainty in many aquatic CO₂ studies. This study evaluated OrgAlk variability, sources, and characteristics in estuarine waters exchanged tidally with a groundwater-influenced salt marsh in the northeast USA. OrgAlk provided a biogeochemical link between organic and inorganic carbon cycling through its direct effects on pH, and thus CO₂ system speciation and buffer capacity. Two main charge groups were identified including carboxylic and phenolic or amine groups. Terrestrial groundwater and in-situ production within salt marsh peat contributed OrgAlk to the tidal creek, with the former being a more significant source. Groundwater entering the marsh complex contained exceptionally high OrgAlk (> 150 µmol kg^-1), and these compounds were preferentially preserved within the DOC pool during groundwater transport and mixing with coastal water. OrgAlk:DOC ratios in groundwater and marsh-influenced water varied across space and time. This highlights the insufficiency of using a fixed proportion of DOC to account for organic acid charge groups. Accounting for OrgAlk altered H⁺ concentrations by ∼ 1 – 41 nmol kg^-1 (equivalent to a pH change of ∼ 0.03 – 0.26), pCO₂ by ∼ 30 – 1600 μatm and buffer capacity by ∼ 0.00 – 0.14 mmol kg^-1 at the relative OrgAlk contributions of 0.9 – 4.3% of TA observed in the marsh-influenced tidal water. Thus, OrgAlk may have a significant influence on coastal inorganic carbon cycling. Further theoretical calculations confirm that these concentrations of OrgAlk would have sizable impacts on both carbonate speciation and, ultimately, air-sea CO₂ fluxes in different coastal environments, ranging from estuarine to shelf waters. A new conceptual model linking organic and inorganic carbon cycling for coastal waters is proposed to highlight the sources and sinks of organic acid charge groups, as well as their biogeochemical behaviors and mechanistic control on the CO₂ system.

22788. 题目: Rice waste biochars produced at different pyrolysis temperatures for arsenic and cadmium abatement and detoxification in sediment
文章编号: N20022108
期刊: Chemosphere
作者: Wei Zhang, Xiaofei Tan, Yanling Gu, Shaobo Liu, Yunguo Liu, Xinjiang Hu, Jiang Li, Yahui Zhou, Sijia Liu, Yuan He
更新时间: 2020-02-21
摘要: The effectiveness of rice waste biochars on heavy metal and metalloid abatement and detoxification was investigated using comprehensive studies based on As and Cd immobilization, bioaccumulation in tubifex, and microbial community changes in contaminated sediment. The remediation effects of biochars produced at different pyrolytic temperatures (400–700 °C) were evaluated. Bioaccumulation of heavy metal and metalloid in the tubifex tissue and change of indigenous microbial community under treatment of different biochars were assessed. Biochars produced at 700 °C exhibited greater effect on decreasing the concentrations of As and Cd in aqueous phase, and TCLP extractable and bioavailable metal(loid) in solid phase of sediment. The concentration of As and Cd in water phase decreased by 26%–89% and 22%–71% under the treatment of straw biochar, and decreased by 13%–92% and 5%–64% under the treatment of rice husk biochar, respectively. As and Cd contents in the tubifex tissue were positively correlated with their concentrations in aqueous phase. High-temperature biochars significantly reduced metal(loid) bioaccumulation in tubifex. The richness and biodiversity of microbial community were both greater in all biochars remediated sediment compared to non-treated sediment. These results indicated that rice waste biochars could effectively inhibit the bio-availability and toxicity of heavy metal and metalloid in sediment, and the higher-temperature biochar exhibited better performance.
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22789. 题目: Performance evaluation of a biotrickling filter for the removal of gas-phase 1,2-dichlorobenzene: Influence of rhamnolipid and ferric ions
文章编号: N20022107
期刊: Chemosphere
作者: Kang Li, Bairen Yang, Liping Wang
更新时间: 2020-02-21
摘要: The aim of this study was to evaluate the influence of rhamnolipid (RL) and ferric ions on the performance of a biotrickling filter (BTF) for the removal of gas-phase 1,2-dichlorobenzene (o-DCB). A comprehensive investigation of microbial growth, pollutant solubility, extracellular polymeric substances (EPS) and enzymatic activity in o-DCB degradation by an isolated strain Bacillus cereus DL-1 with/without RL and Fe³⁺ were carried out using batch microcosm experiments. In addition, o-DCB removal performance, biofilm morphology, and microbial community structures in two identical lab-scale biotrickling filters (named BTF1 and BTF2) inoculated with strain DL-1 were studied. The batch microcosm experiments demonstrated that 120 mg L⁻¹ RL and 4 mg L⁻¹ Fe³⁺ could enhance the biodegradation of o-DCB, which may be due to promotion on bacterial growth, o-DCB solubilization, C₁₂O enzyme activity, and polysaccharide (PS) and protein (PN) in EPS. Fourier transform infrared (FTIR) spectra indicated that the addition of RL with Fe³⁺ had notable effects on the functional groups of PS and PN in EPS. The experimental results in BTFs indicate that the removal efficiency of o-DCB decreased from 100% to 56.4% for BTF1, which was not fed with RL and Fe³⁺, and from 100% to 80.3% for BTF2, which was fed with RL and Fe³⁺, when the inlet loading rate increased from 4.88 to 102 g m⁻³ h⁻¹ at an empty bed residence time of 60 s. In addition, the microbial adhesive strength and the microbial community structure were different among both BTFs, highlighting the positive effects of RL and Fe³⁺.

22790. 题目: Application of metallic nanoparticle-biochars with ionic liquids for thermal transfer fluids
文章编号: N20022106
期刊: Chemosphere
作者: Hsin-Liang Huang, Zi-Hao Huang, Yi-Cheng Chu, Hong-Ping Lin, Yun-Jung Chang
更新时间: 2020-02-21
摘要: Ionic liquids (ILs (1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]))) were used as heat transfer fluids for solar thermal collectors. The additive of ILs was biochar containing copper and silver nanoparticles (Cu–Ag/biochar) to improve the adsorption of solar irradiation and thermal conductivities. After impregnation and reduction processes, nanoparticles such as Cu, CuO, Cu(OH)₂, Ag, and Ag₂O were found in the biochar by X-ray powder diffraction (XRD) spectroscopy. With adding 2% Cu–Ag/biochar into the ILs, the thermal conductivities of [C₄mim][Cl] and [C₄mim][BF₄] containing 10% Cu–1% Ag/biochar were individually increased 9.2 and 6.6 times compared to the base ILs due to the high graphitization of biochar and metallic nanoparticles. The ¹H NMR (nuclear magnetic resonance) features of the imidazole ring and methyl group in the ILs were highly disturbed due to the formation of weak or strong hydrogen bonds between the cations in ILs and Cu–Ag/biochar. The high hydrogen bond acceptance of anions in ILs also affected the thermal properties. The thermal properties of the metals/biochar [C₄mim][Cl] were better than those of metals/biochar [C₄mim][BF₄] due to high hydrogen bond acceptance of [Cl]^-. The strong hydrogen bonds between the Cu–Ag/biochar and the cations and anions in ILs result in thermal properties of heat transfer fluids. Under simulated sunlight, the temperatures of [C₄mim][Cl] and [C₄mim][BF₄] containing 10% Cu–1% Ag/biochar rose from 304 to 345 and 340 K within 24 min, respectively. A novel heat transfer fluid was developed for high adsorption of irradiation, high thermal conductivities, and speedy transfer of heat.

22791. 题目: Coagulation of organo-mineral colloids and formation of low molecular weight organic and metal complexes in boreal humic river water under UV-irradiation
文章编号: N20022105
期刊: Chemosphere
作者: O.Yu. Drozdova, A.R. Aleshina, V.V. Tikhonov, S.A. Lapitskiy, O.S. Pokrovsky
更新时间: 2020-02-21
摘要: Photodegradation of dissolved organic matter (DOM) is highly important in humic waters of peatland regions, yet the coupling between organic and organo-mineral colloids, trace metals and bioavailability of photodegraded products is poorly known. Here we studied photo-destruction of organo-mineral colloids induced by UV-irradiation of sterile-filtered mire water. We revealed two simultaneously occurring processes of transformation of DOM and trace elements speciation: (i) disintegration of high molecular weight organo-mineral colloids into lower molecular weight (<1 kDa) DOM and metal complexes and (ii) formation of particulate (>0.22 μm) aggregates of metals and organic matter. Over 26 days of UV-irradiation, up to 20% of dissolved organic carbon from peat waters was transformed into CO₂. In addition to transformation of organic compounds, sizeable change in speciation and size fractionation of many trace metals such as Fe, Pb, Cd, Co, Zn, Cu, V, La, Ni and Cr occurred. Although short-term (1 day) UV-irradiation of mire water stimulated growth of cultivable Pseudomonas sp. bacterium, the long-term exposure (26 days) of organic substrate had a negative effect on bacterial development. Therefore, while sizeable transformation of the organic and metal colloidal load of peat water may occur over first 10 days of UV-irradiation, the enhanced bioavailability of UV-treated substrate is achieved after first day of exposure. The present study demonstrates the importance of even short-term UV-irradiation on colloidal transformation and potential bioavailability of humic waters from temperate mires and highlights the need for more detailed study of coupled metal-organic matter transformation induced by sunlight exposure of mire waters.
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22792. 题目: Auxiliary voltage enhanced microbial methane oxidation co-driven by nitrite and sulfate reduction
文章编号: N20022104
期刊: Chemosphere
作者: Fengguang Chai, Lin Li, Song Xue, Junxin Liu
更新时间: 2020-02-21
摘要: In this study, single-chamber bioelectrochemical reactors (EMNS) were used to investigate the methane oxidation driven by sulfate and nitrite reduction with the auxiliary voltage. Results showed that the methane oxidation was simultaneously driven by sulfate and nitrite reduction, with more methane being converted using the auxiliary voltage. When the voltage was 1.6 V, the maximum removal rate was achieved at 8.05 mg L⁻¹ d⁻¹. Carbon dioxide and methanol were the main products of methane oxidation. Simultaneously, nitrogen, nitrous oxide, sulfur ions, and hydrogen sulfide were detected as products of sulfate and nitrite reduction. Microbial populations were analyzed by qPCR and high-throughput sequencing. The detected methanotrophs included Methylocaldum sp., Methylocystis sp., Methylobacter sp. and M. oxyfera. The highest abundance of M. oxyfera was (3.97 ± 0.32) × 10⁶ copies L⁻¹ in the EMNS-1.6. The dominant nitrite-reducing bacteria were Ignavibacterium sp., Hyphomicrobium sp., Alicycliphilus sp., and Anammox bacteria. Desulfovibrio sp., Desulfosporosinus sp. and Thiobacillus sp. were related to the sulfur cycle. Ignavibacterium sp., Thiobacillus sp. and Desulfovibrio sp. may transfer electrons with electrodes using humic acids as the electronic shuttle. The possible pathways included (1) Methane was mainly oxidized to carbon dioxide and dissolved organic matters by methanotrophs utilizing the oxygen produced by the disproportionation in the cells of M. oxyfera. (2) Nitrite was reduced to nitrogen by heterotrophic denitrifying bacteria with dissolved organic compounds. (3) Desulfovibrio sp. and Desulfosporosinus sp. reduced sulfate to sulfur ions. Thiobacillus sp. oxidized sulfur ions to sulfur or sulfate using nitrite as the electron acceptor.
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22793. 题目: Micron-sized silica particles in wastewater influenced the distribution of organic matters in sludge and their anaerobic degradation
文章编号: N20022103
期刊: Journal of Hazardous Materials
作者: Sisi Chen, Bin Dong, Dianhai Yang, Ning Li, Xiaohu Dai
更新时间: 2020-02-21
摘要: The influence of micron-sized silica particles on the distribution of organic matters in sludge and anaerobic degradation of macromolecular organic components (MOCs) in sludge was investigated. With the addition of micron-sized particles in the influent (VS/TS decreased gradually from 90.46 ± 0.21 % to 33.36 ± 0.17 %), the protein degradation percentage was significantly promoted while the polysaccharides degradation percentage was largely inhibited, resulting in the total MOCs degradation and methane production increasing firstly (with the promotion extent within 10 %) and then declining slightly, with the peak value at VS/TS of 56.03 ± 0.21 %. The shifted degradation percentage of protein and polysaccharides were caused by the significant changed distribution of organic matters in sludge. With the addition of micron-sized silica particles, the MW of EPS and secondary structure of protein in EPS changed little, which brought about little influence. While, the promoted extracellular protein content (so that the total protein content) and declined extracellular carbohydrates content (so that the total protein content), were found to be strongly correlated to the enhanced protein degradation and inhibited polysaccharides degradation. The results suggested that large amounts of grit in sludge might not be the main reason for lower degradability of sewage sludge in China.
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22794. 题目: Fate and role of fluorescence moieties in extracellular polymeric substances during biological wastewater treatment: A review
文章编号: N20022102
期刊: Science of The Total Environment
作者: Tahir Maqbool, Quang Viet Ly, Muhammad Bilal Asif, How Yong Ng, Zhenghua Zhang
更新时间: 2020-02-21
摘要: In biological wastewater treatment systems, extracellular polymeric substances (EPS) are continuously excreted as a response to environmental changes and substrate conditions. It could severely affect the treatment efficacy such as membrane fouling, dewaterability and the formation of carcinogenic disinfection by-products (DBPs). The heterogeneous dissolved organic matter (DOM) with varying size and chemical nature constitute a primary proportion of EPS. In the last few decades, fluorescence spectroscopy has received increasing attention for characterizing these organic substances due to the attractive features of this low-cost spectroscopic approach, including easy sample handling, rapid, non-destructive and highly sensitive nature. In this review, we summarize the application of fluorescence spectroscopy for characterizing EPS and provide the potential implications for online monitoring of water quality along with its limitations. We also link the dynamics of fluorescent dissolved organic matter (FDOM) in EPS with operational and environmental changes in wastewater treatment systems as well as their associations with metal binding, membrane fouling, adsorption, toxicity, and dewaterability. The multiple modes of exploration of fluorescence spectra, such as synchronous spectra with or without coupling with two-dimensional correlation spectroscopy (2D-COS), excitation-emission matrix (EEM) deconvoluted fluorescence regional integration (FRI), and parallel factor analysis (PARAFAC) are also discussed. The potential fluorescence indicators to depict the composition and bulk characteristics of EPS are also of interest. Further studies are highly recommended to expand the application of fluorescence spectroscopy paired with appropriate supplementary techniques to fully unravel the underlying mechanisms associated with EPS.
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22795. 题目: Spatial and seasonal variations of organic carbon distributions in typical intertidal sediments of China
文章编号: N20022101
期刊: Organic Geochemistry
作者: Yushuang Zhang, Xiaotong Xiao, Dongyan Liu, Enhui Wang, Ke Liu, Yang Ding, Peng Yao, Meixun Zhao
更新时间: 2020-02-21
摘要: Intertidal zones are the main sites for land-ocean interaction and play an important role in transporting and accumulating organic carbon (OC). Understanding sources and preservation of sedimentary OC are vital to better evaluate the processes controlling the OC distribution in intertidal zones. In this study, we present bulk parameters of total organic carbon (TOC), δ¹³C_org, grain size and biomarker contents in surface sediments of 14 typical intertidal zones along China’s coastline during both the wet season (WS) and the dry season (DS). Statistical analysis of our data set shows showed that TOC and biomarker contents were generally high in small estuaries, intermediate but more variable in large estuaries and low in non-estuaries; and these distribution patterns broadly correlated with sedimentary clay contents. TOC and biomarker contents were generally higher in the WS than the DS reflecting both OC inputs and preservation. A binary mixing model based on δ¹³C_org and biomarker proxies revealed that large estuaries were characterized by higher terrestrial OC fractions (62–80%) except for the Yellow River Estuary (24%), while lower terrestrial OC fractions occurred in non-estuaries (13–15%). Variable OC contributions were found in small estuaries, with most sites characterized by low terrestrial OC contributions (3–35%), but high terrestrial OC contributions were found at the Qiantang River Estuary site (59%) and the Jiulong River Estuary site (67%). Carbon stocks in Chinese intertidal sediments are comparable with those in marine sediments from shelf areas and the Exclusive Economic Zone (EEZ). This study suggests that intertidal sediments are potentially an important carbon sink.

22796. 题目: Sediment and particulate organic carbon budgets of a subarctic estuarine fjard: Lake Melville, Labrador
文章编号: N20022014
期刊: Marine Geology
作者: C. Michelle Kamula, Robie W. Macdonald, Zou Zou A. Kuzyk
更新时间: 2020-02-20
摘要: Sediment and particulate organic carbon (POC) budgets constructed for oceanic regions provide a means to quantify the burial of POC, providing a baseline against which future change can be measured. Here we developed the first mass balance budgets of sediment and POC (terrestrial and marine) for the Lake Melville system (LMS; Goose Bay and Lake Melville) in central Labrador using previously published data (210Pb-based mass accumulation rates, river discharge, and total suspended solids) together with measurements of %OC and δ13C signatures within dated sediment cores collected from the LMS basins and water from main tributaries and Groswater Bay. A two end-member mixing model was used to establish fractions of terrigenous and marine POC. Overall, our mass balance budgets show that the Churchill River is the major supply of sediment (16.7 ± 7.8 × 108 kg y−1) and POCterr (18.4 ± 6.6 × 106 kg y−1) to the LMS, accounting for 47% and 56% of the total input to the system, respectively. Although the Churchill River drains directly into Goose Bay along with the smaller Goose River, the majority of sediment (12.9 ± 7.8 × 108 kg y−1) and POCterr (11.8 ± 7.0 × 106 kg y−1) is transported eastward through the surface water plume into Lake Melville. Inputs of POCmar from autochthonous primary production, estimated by applying an empirical relationship between sediment-surface flux of POCmar and water depth, to Goose Bay (1.8 × 106 kg y−1) and Lake Melville (98.3 ± 4.7 × 106 kg y−1) increase with increasing distance from the Churchill River. To investigate the potential changes to the sediment load of the Churchill River to the LMS following impoundment at Muskrat Falls, we calculated the sediment increase using the median reservoir shoreline erosion potential. This approach showed that the delivery of sediment and POCterr to the LMS by the Churchill River may double during the two years following impoundment of the lower Churchill River.

22797. 题目: Efficiency of crustacean zooplankton in transferring allochthonous carbon in a boreal lake
文章编号: N20022013
期刊: Ecology
作者: Guillaume Grosbois, Dominic Vachon, Paul del Giorgio, Milla Rautio
更新时间: 2020-02-20
摘要: Increased incorporation of terrestrial organic matter (t‐OM) into consumer biomass (allochthony) is believed to reduce growth capacity. In this study, we examined the relationship between crustacean zooplankton allochthony and production in a boreal lake that displays strong seasonal variability in t‐OM inputs. Contrary to our hypotheses, we found no effect of allochthony on production at the community and the species levels. The high frequency seasonal sampling (time‐for‐space) allowed for estimating the efficiency of zooplankton in converting this external carbon source to growth. From the daily t‐OM inputs in the lake (57 – 3027 kg C per day), the zooplankton community transferred 0.2% into biomass (0.01 – 2.36 kg C per day); this level was of the same magnitude as the carbon transfer efficiency for algal‐derived carbon (0.4%). In the context of the boundless carbon cycle which integrates inland waters as a biologically active component of the terrestrial landscape, the use of the time‐for‐space approach for the quantifying of t‐OM trophic transfer efficiency by zooplankton is a critical step toward a better understanding of the effects of increasing external carbon fluxes on pelagic food webs.

22798. 题目: Mechanisms behind soil N dynamics following cover restoration in degraded land in subtropical China
文章编号: N20022012
期刊: Journal of Soils and Sediments
作者: Xiangzhou Zheng, Cheng Lin, Baoling Guo, Juhua Yu, Hong Ding, Shaoyun Peng, Jinbo Zhang, Eric Ireland, Deli Chen, Christoph Müller, Yushu Zhang
更新时间: 2020-02-20
摘要: Purpose: Nitrogen (N) is an important nutrient for re-vegetation during ecosystem restoration, but the effects of cover restoration on soil N transformations are not fully understood. This study was conducted to investigate N transformations in soils with different cover restoration ages in Eastern China. Materials and methods: Soil samples were collected from four degraded and subsequently restored lands with restoration ages of 7, 17, 23, and 35 years along with an adjacent control of degraded land. A ¹⁵N tracing technique was used to quantify gross N transformation rates. Results and discussion: Compared with degraded land, soil organic carbon (SOC) and total N (TN) increased by 1.60–3.97 and 2.49–5.36 times in restoration land. Cover restoration increased ammonium and nitrate immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) by 0.56–0.96, 0.34–2.10, and 0.79–3.45 times, respectively, indicating that restoration was beneficial for N retention. There were positive correlations between SOC content and ammonium and nitrate immobilization and DNRA, indicating that the increase in soil N retention capacity may be ascribed to increasing SOC concentrations. The stimulating effect of SOC on ammonium immobilization was greater than its effect on organic N mineralization, so while SOC and TN increased, inorganic N supply did not increase. Autotrophic and heterotrophic nitrification increased with increasing SOC and TN concentrations. Notably, heterotrophic nitrification was an important source of NO₃⁻−N production, accounting for 47–67% of NO₃⁻−N production among all restoration ages. Conclusions: The capacity of N retention was improved by cover restoration, leading to an increase in soil organic carbon and total N over time, but inorganic N supply capacity did not change with cover restoration age.

22799. 题目: Accumulation of germanium (Ge) in plant tissues of grasses is not solely driven by its incorporation in phytoliths
文章编号: N20022011
期刊: Biogeochemistry
作者: Sabine Kaiser, Stephan Wagner, Christin Moschner, Claudia Funke, Oliver Wiche
更新时间: 2020-02-20
摘要: Ge/Si ratios of plant phytoliths have been widely used to trace biogeochemical cycling of Si. However, until recently, information on how much of the Ge and Si transferred from soil to plants is actually stored in phytoliths was lacking. The aim of the present study is to (i) compare the uptake of Si and Ge in three grass species, (ii) localize Ge and Si stored in above-ground plant parts and (iii) evaluate the amounts of Ge and Si sequestrated in phytoliths and plant tissues. Mays (Zea mays), oat (Avena sativa) and reed canary grass (Phalaris arundinacea) were cultivated in the greenhouse on soil and sand to control element supply. Leaf phytoliths were extracted by dry ashing. Total elemental composition of leaves, phytoliths, stems and roots were measured by ICP-MS. For the localization of phytoliths and the determination of Ge and Si within leaf tissues and phytoliths scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was used. The amounts of Si and Ge taken up by the species corresponded with biomass formation and decreased in the order Z. mays > P. arundinacea, A. sativa. Results from LA-ICP-MS revealed that Si was mostly localized in phytoliths, while Ge was disorderly distributed within the leaf tissue. In fact, from the total amounts of Ge accumulated in leaves only 10% was present in phytoliths highlighting the role of organic matter on biogeochemical cycling of Ge and the necessity for using bulk Ge/Si instead of Ge/Si in phytoliths to trace biogeochemical cycling of Si.

22800. 题目: The influence of tree and soil management on soil organic carbon stock and pools in dehesa systems
文章编号: N20022010
期刊: CATENA
作者: Lizardo Reyna-Bowen, Pilar Fernandez-Rebollo, Jesús Fernández-Habas, José A. Gómez
更新时间: 2020-02-20
摘要: This study evaluated the effect on SOC concentration, stock and fractions in a dehesa divided into two areas of similar soil type but different soil management. The first area was a pastured dehesa (P) with young Holm oaks, planted in 1995 (70 trees ha⁻¹, 12 m × 12 m) and, since 2000, grazed by sheep (3 sheep ha⁻¹) with an average period of grazing of six months a year. Prior to this it was managed in the same way as the second adjacent area. The second area was a cropped dehesa (C) with widely spaced mature Holm oak (14 trees in a 12-ha dehesa), on which a mixture of vetch and oats was cultivated every three years and tilled with a chisel plough. After 22 years both dehesas showed similar SOC stock distribution amongst areas with different soil management, with approximately 40 t ha⁻¹ in the top 100 cm of the soil. The P dehesa only showed higher SOC stock than the C dehesa on the surface 0–2 cm (5.86 ± 0.56 t ha^-1vs 3.24 ± 0.37 t ha⁻¹). The influence of the trees, increasing SOC concentration and content when compared to the area outside the canopy projection, was only detected under the mature trees in the C dehesa. In the area outside the tree canopy, both systems showed a similar distribution of soil organic carbon among their different fractions, with the unprotected fraction being the dominant one, followed by the physically and chemically protected fractions. In the C dehesa, the mature trees’ presence significantly modified the distribution of soil organic carbon in their surroundings, increasing the relevance of the unprotected fraction. The distribution of soil organic carbon in the unprotected and physically and chemically protected fractions were strongly correlated to the overall organic carbon concentration in the soil, indicating the rapid response of these three fractions to management, with the biochemically protected fraction showing no correlation, suggesting a high resilience to the changes in carbon budget.