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25901. 题目: Redox state of microbial extracellular polymeric substances regulates reduction of selenite to elemental selenium accompanying with enhancing microbial detoxification in aquatic environments
文章编号: N20013104
期刊: Water Research
作者: Xin Zhang, Wen-Yuan Fan, Mu-Cen Yao, Chuan-Wang Yang, Guo-Ping Sheng
更新时间: 2020-01-31
摘要: In nature, many microorganisms show resistance to toxic selenite by reducing selenite to non-soluble and low toxic elemental selenium. Extracellular polymeric substances (EPS), a high-molecular-weight biopolymers originated from microbial metabolism, contain many reducing groups and can induce reductive transformation of pollutants. However, the roles of EPS and its redox state in reductive detoxification or reduction removal of selenite, respectively, remain unknown yet. Herein, the reduction of selenite by different sources of EPS was investigated. Selenite was proved to be reduced by EPS and partly transformed to elemental selenium. The formed elemental selenium was mainly selenium nanoparticles confirmed by transmission electron microscopy coupled with energy dispersive spectroscopy. The redox state of EPS governed selenite reduction and elemental selenium formation, and the reduced state of EPS was in favor of selenite reduction. Dissolved oxygen concentration in water regulated EPS redox state and influenced selenite reduction. The thiols, aldehyde and phenolic groups in EPS were responsible for selenite reduction. Under selenite stress, EPS was capable of increasing cell survivability by enhancing microorganisms-mediated selenite reduction. This work revealed the previously undiscovered roles of EPS in selenite reduction and elemental selenium formation in aquatic environments and also suggested a possible crucial role of EPS in selenium biogeochemical cycle.
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25902. 题目: Impact of groundwater quality and associated byproduct formation during UV/hydrogen peroxide treatment of 1,4-dioxane
文章编号: N20013103
期刊: Water Research
作者: Cheng-Shiuan Lee, Arjun K. Venkatesan, Harold W. Walker, Christopher J. Gobler
更新时间: 2020-01-31
摘要: In this study, a semi-batch, bench-scale UV/hydrogen peroxide (UV/H₂O₂) advanced oxidation process system was used to investigate how typical groundwater quality parameters (pH, alkalinity, natural organic matter (NOM), nitrate, and iron) influence the treatment of 1,4-dioxane. Deionized (DI) water spiked with 1,4-dioxane (100 μg L⁻¹), treated using H₂O₂ (10 mg L⁻¹) in a commercially available UV system (40 W low-pressure lamp) showed an UV fluence-based first-order rate constant (k’) and electrical energy-per-order (EEO) of 4.32✕10⁻³ cm²-mJ⁻¹ and 0.15 kWh-m⁻³-order⁻¹, respectively. The most abundant byproduct generated in spiked-DI water was oxalic acid (up to 55 μg L⁻¹), followed by formic and acetic acids. The k’ showed no significant difference at pH ranging from 5 to 7 and at low alkalinity concentrations (<20 mg-CaCO₃ L⁻¹), typical of sandy aquifers. The k’ declined by up to 85% with increasing NOM concentration. Elevated production (up to ∼400% increase) of aldehydes and organic acids was observed in NOM-spiked water, implying that NOM is a significant byproduct precursor during UV/H₂O₂ treatment. High NO₃⁻ concentration (10 mg-N L⁻¹) in source water reduced the k’ by 25%, while no significant impact was observed at lower concentrations (<2 mg-N L⁻¹). Addition of Fe(II) at 0.5 mg-L⁻¹ resulted in an instantaneous Fenton-reaction-assisted removal of ∼10% 1,4-dioxane in the presence of H₂O₂, but did not enhance the performance of UV/H₂O₂ treatment over time. In contrast, both Fe(II) and Fe(III) addition lowered the k’ by 15–27%. The decline of k’ observed in these experiments was attributed to reduced UVT (Fe), ^.OH radical scavenging (pH), or both (NO₃⁻, NOM). Treatment of groundwater samples collected from three 1,4-dioxane-contaminated wells located in Long Island, NY, showed k’ values of 13–40% lower than what was observed for DI water due to radical scavenging from a combination of high NO₃⁻ and NOM in the samples. A multiple linear-regression model, developed using water quality data as model input, showed good agreement with field observations (paired t-test: p > 0.05) in predicting k’ for the removal of 1,4-dioxane from groundwater. This study provides the first systematic evaluation of the impacts of groundwater quality on UV/H₂O₂ process to remove environmentally relevant levels of 1,4-dioxane and reports standardized performance-related parameters to aid in the design and evaluation of full-scale systems.
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25903. 题目: Dissolved organic matter in a tropical saline-alkaline lake of the East African Rift Valley.
文章编号: N20013102
期刊: Water Research
作者: A. Butturini, P. Herzsprung, J. Lechtenfeld O, S. Venturi, S. Amalfitano, Vazquez E, N. Pacini, D.M. Harper, F. Tassi, S. Fazi
更新时间: 2020-01-31
摘要: Saline-alkaline lakes of the East African Rift are known to have an extremely high primary production supporting a potent carbon cycle. To date, a full description of carbon pools in these lakes is still missing. More specifically, there is not detailed information on the quality of dissolved organic matter (DOM), the main carbon energy source for heterotrophs prokaryotes. We report the first exhaustive description of DOM molecular properties in the water column of a meromictic saline-alkaline lake of the East African Rift. DOM availability, fate and origin were studied either quantitatively, in terms of dissolved organic carbon (DOC) and nitrogen (DON) or qualitatively, in terms of optical properties (absorbance) and molecular characterization of solid-phase extracted DOM (SPE-DOM) through negative electrospray ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). DOM availability was high (DOC ∼ 8.1 mM in surface waters) and meromixis imprinted a severe quantitative and qualitative change on DOM pool. At the surface, DOM was rich in aliphatic and moderately in aromatic molecules and thus mirroring autochthonous microbial production together to photodegradation. At the bottom changes were extreme: DOC increased up to 5 times (up to 50 mM) and, molecular signature drifted to saturated, reduced and non-aromatic DOM suggesting intense microbial activity within organic sediments. At the chemocline, DOC was retained indicating that this interface is a highly reactive layer in terms of DOM processing. These findings underline that saline-alkaline lakes of the East African Rift are carbon processing hot spots and their investigation may broaden our understanding of carbon cycling in inland waters at large.

25904. 题目: Photochemical degradation of nebivolol in different natural organic matter solutions under simulated sunlight irradiation: Kinetics, mechanism and degradation pathway
文章编号: N20013101
期刊: Water Research
作者: Jieqiong Wang, Kai Wang, Yuchen Guo, Junfeng Niu
更新时间: 2020-01-31
摘要: Nebivolol (NEB) is widely used for the treatment of hypertension and chronic heart failure and has become an ubiquitous emerging organic pollutant. It has been shown to undergo direct photolysis, but the role of DOM in its degradation kinetics and mechanism is not well understood. In this study, we studied the photochemical behavior of NEB in the presence of seawater DOM (SW-DOM) and freshwater DOM (SRNOM) under simulated sunlight irradiation. SW-DOM had a promotion effect on NEB photodegradation, whereas SRNOM retarded its photolytic transformation. After eliminating the influence of light screening, we found that the indirect photodegradation rate of NEB in the presence of SRNOM was lower than that in the presence of SW-DOM. Results show that the indirect photodegradation pathway occurred by reaction with triplet-excited DOM (³DOM*). The second-order rate constants for ³SW-DOM* and ³SRNOM* reaction with NEB are 3.7 × 10⁹ M⁻¹ s⁻¹ and 3.7 × 10⁸ M⁻¹ s⁻¹, respectively. The electron donating capacity of SRNOM is higher than that of SW-DOM, indicating that SRNOM may contain more activated phenolic moieties. SRNOM may thus have higher antioxidant activity, leading a higher inhibitory effect on NEB photodegradation. A total of six degradation products were identified in the absence and presence of DOM by HPLC-ESI-MS/MS. The substitution of F by OH-groups and further oxidation a OH-group in the lateral chain to a ketone, and cleavage of N–C bond by the attack of ³DOM* are here proposed as the main degradation pathways.
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25905. 题目: Spatiotemporal Patterns of Mineral and Organic Matter Deposition Across Two San Francisco Bay-Delta Tidal Marshes
文章编号: N20013013
期刊: Wetlands
作者: Kevin J. Buffington
更新时间: 2020-01-30
摘要: Sediment deposition in tidal wetlands is a critical process that determines whether vertical growth will keep pace with sea-level rise. However, more information is needed on how sediment deposition varies spatially and temporally across wetlands, including the effects of elevation, tidal inundation, vegetation, and weather. We investigated variation in sediment deposition due to season, distance from channel, channel size, and vegetation composition at low and high salinity tidal marshes in the San Francisco Bay-Delta Estuary, California using sediment traps deployed monthly between December 2015 and November 2016. Over the course of the year, sediment deposition ranged widely (1.4 – 174.0 kg m−2 yr−1) and averaged 19.5 ± 3.5 kg m−2 yr−1. Deposition increased with flooding duration, decreased with increasing distance from channels, and was highest during the spring and early summer. Higher wind speeds during the spring may have driven re-suspension from mudflats, promoting deposition. Ratios of organic-to-mineral deposition were twice as high at the fresher site and were correlated with differences in vegetation composition between sites. Our results suggest that seasonality, distance from sediment source, salinity regime, and channel size are important sources of spatiotemporal variation in deposition. These results are relevant to accretion sampling and wetland restoration design.

25906. 题目: Soil organic matter attenuates the efficacy of flavonoid-based plant-microbe communication
文章编号: N20013012
期刊: Science Advances
作者: Ilenne Del Valle, Tara M. Webster, Hsiao-Ying Cheng, Janice E. Thies, André Kessler, Mary Kaitlyn Miller, Zachary T. Ball, Kevin R. MacKenzie, Caroline A. Masiello, Jonathan J. Silberg, Johannes Lehmann
更新时间: 2020-01-30
摘要: Plant-microbe interactions are mediated by signaling compounds that control vital plant functions, such as nodulation, defense, and allelopathy. While interruption of signaling is typically attributed to biological processes, potential abiotic controls remain less studied. Here, we show that higher organic carbon (OC) contents in soils repress flavonoid signals by up to 70%. Furthermore, the magnitude of repression is differentially dependent on the chemical structure of the signaling molecule, the availability of metal ions, and the source of the plant-derived OC. Up to 63% of the signaling repression occurs between dissolved OC and flavonoids rather than through flavonoid sorption to particulate OC. In plant experiments, OC interrupts the signaling between a legume and a nitrogen-fixing microbial symbiont, resulting in a 75% decrease in nodule formation. Our results suggest that soil OC decreases the lifetime of flavonoids underlying plant-microbe interactions.

25907. 题目: Effects of long‐term straw return on soil organic carbon storage and sequestration rate in North China upland crops: A meta‐analysis
文章编号: N20013011
期刊: Global Change Biology
作者: Medhn Berhane Hagos, Miao Xu, Zhiying Liang, Jianglan Shi, Gehong Wei, Xiaohong Tian
更新时间: 2020-01-30
摘要: Soil organic carbon (SOC) is essential for soil fertility and climate change mitigation, and carbon can be sequestered in soil through proper soil management, including straw return. However, results of studies of long‐term straw return on SOC are contradictory and increasing SOC stocks in upland soils is challenging. This study of North China upland agricultural fields quantified the effects of several fertilizer and straw return treatments on SOC storage changes and crop yields, considering different cropping duration periods, soil types, and cropping systems to establish the relationships of SOC sequestration rates with initial SOC stocks and annual straw C inputs. Our meta‐analysis using long‐term field experiments showed that SOC stock responses to straw return was greater than that of mineral fertilizers alone. Black soils with higher initial SOC stocks also had lower SOC stock increases than did soils with low initial SOC stocks (fluvo‐aquic and loessial soils) following applications of nitrogen‐phosphorous‐potassium (NPK) fertilizer and NPK+S (straw). Soil C stocks under the NPK and NPK+S treatments increased in the greater‐than‐20‐year duration period, while significant SOC stock increases in the NP and NP+S treatment groups was limited to the 11‐20‐year period. Annual crop productivity was higher in double‐cropped wheat and maize under all fertilization treatments, including control (no fertilization), than in the single‐crop systems (wheat or maize). Also, the annual soil sequestration rates and annual straw C inputs of the treatments with straw return (NP+S and NPK+S) were significantly positively related. Moreover, initial SOC stocks and SOC sequestration rates of those treatments were highly negatively correlated. Thus, long‐term straw return integrated with mineral fertilization in upland wheat and maize croplands leads to increased crop yields and SOC stocks. However, those effects of straw return are highly dependent on fertilizer management, cropping system, soil type, duration period, and the initial SOC content.

25908. 题目: Hotspots of biotic compositional change in lakes along vast latitudinal transects in northern Canada
文章编号: N20013010
期刊: Global Change Biology
作者: Émilie Saulnier‐Talbot, Dermot Antoniades, Reinhard Pienitz
更新时间: 2020-01-30
摘要: Ecotones mark zones of rapid change in ecological structure at various spatial scales. They are believed to be particularly susceptible to shifts caused by environmental transformation, making them key regions for studying the effects of global change. Here, we explored the variation in assemblage structure of aquatic primary producer and consumer communities across latitudinal transects in northeastern North America (Québec‐Labrador) to identify spatial patterns in biodiversity that indicated the location of transition zones across the landscape. We analyzed species richness and the cumulative rate of compositional change (expressed as beta‐diversity) of diatoms and chironomids to detect any abrupt shifts in the rate of spatial taxonomic turnover. We used principal coordinates analysis to estimate community turnover with latitude, then applied piecewise linear regression to assess the position of ecotones. Statistically significant changes in assemblage composition occurred at 52°N and 55°N, corresponding to the transition between closed and open crown forest, and to the southern onset of the forest tundra (i.e. the forest limit), respectively. The spatial distribution of ecotones was most strongly related to air temperature for chironomids and to vegetation‐ and soil‐related chemical attributes of lake water for diatoms, including dissolved organic carbon content and water color. Lakes at mid‐ to high latitudes currently face pressures from rapidly rising temperatures, accompanied by large increases in organic carbon inputs from their catchments, often leading to browning and its associated effects. The biota at the base of food webs in lakes located in transition zones are disproportionately affected by the cascading effects of these multi‐factorial changes, concurrent with pronounced terrestrial greening observed in these regions. Similar patterns of biotic shifts have been observed along alpine aquatic transects, indicating the potential for widespread restructuring of cold, high‐altitude and high‐latitude freshwater communities due to global change.

25909. 题目: Particulate organic matter dynamics in a permafrost headwater stream and the Kolyma River mainstem
文章编号: N20013009
期刊: Journal of Geophysical Research: Biogeosciences
作者: Lisa Bröder, Anya Davydova, Sergey Davydov, Nikita Zimov, Negar Haghipour, Timothy I. Eglinton, Jorien E. Vonk
更新时间: 2020-01-30
摘要: Ongoing rapid arctic warming leads to extensive permafrost thaw, which in turn increases the hydrologic connectivity of the landscape by opening up subsurface flow paths. Suspended particulate organic matter (POM) has proven useful to trace permafrost thaw signals in arctic rivers, which may experience higher organic matter loads in the future due to expansion and increasing intensity of thaw processes such as thermokarst and river bank erosion. Here, we focus on the Kolyma River watershed in Northeast Siberia, the world's largest watershed entirely underlain by continuous permafrost. To evaluate and characterize the present‐day fluvial release of POM from permafrost thaw, we collected water samples every 4‐7 days during the 4‐months open water season in 2013 and 2015 from the lower Kolyma River mainstem and from a small nearby headwater stream (Y3) draining an area completely underlain by Yedoma permafrost (Pleistocene ice‐ and organic‐rich deposits). Concentrations of particulate organic carbon generally followed the hydrograph with highest concentrations during the spring flood in late May/early June. For the Kolyma River, concentrations of dissolved organic carbon showed a similar behavior, in contrast to the headwater stream, where DOC values were generally higher and POC concentrations lower than for Kolyma. Carbon isotope analysis (δ¹³C, Δ¹⁴C) suggested Kolyma‐POM to stem from both contemporary and older permafrost sources, while Y3‐POM was more strongly influenced by in‐stream production and recent vegetation. Lipid biomarker concentrations (high‐molecular‐weight n‐alkanoic acids and n‐alkanes) did not display clear seasonal patterns, yet implied Y3‐POM to be more degraded than Kolyma‐POM.

25910. 题目: Specific surface area and electron donating capacity determine biochar's role in methane production during anaerobic digestion
文章编号: N20013008
期刊: Bioresource Technology
作者: Yong Qin, Xiaosi Yin, Xingkun Xu, Xiangrui Yan, Feng Bi, Weixiang Wu
更新时间: 2020-01-30
摘要: The addition of biochar derived from different materials can have varying effects on anaerobic digestion (AD), depending on its physicochemical properties. Physicochemical properties of biochars, biomethanization performance and microbial communities were examined to evaluate the effectiveness of biochars made from different plant wastes on AD in this study. Results showed that all biochars significantly reduce the lag phases during AD, compared with a control treatment (CK). Woody biochars particularly performed much better than herbal ones. Correlation analysis revealed that specific surface area (SSA) and electron donating capacity (EDC) were the key properties of the plant-feedstock-derived biochar in AD enhancement. Microbial community structure analysis showed that higher SSA and EDC are conducive for the growth of bacteria decomposing glucose, further promoting daily methane production in the early AD stage. The results indicate that it is important to select biochar with higher SSA and EDC to enhance biomethanization in AD systems.
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25911. 题目: Impact of origin and structure on the aggregation behavior of natural organic matter
文章编号: N20013007
期刊: Chemosphere
作者: Peiyun Wei, Fanchao Xu, Heyun Fu, Xiaolei Qu
更新时间: 2020-01-30
摘要: The intermolecular interactions of natural organic matter (NOM) play a key role in the fate and transport of organic carbon and pollutants in environmental and engineered systems. In this study, the impact of origin and structure on the aggregation behavior of NOM was investigated in the presence of naturally abundant cations. The physicochemical properties of NOM were quantified using a range of indices. Thermodynamic analysis suggests that the colloidal stability of NOM was mainly determined by its hydrophobicity (i.e., Lewis acid-base interactions). All NOM can be coagulated by Ca²⁺ owing to the strong cation-NOM interactions, which lead to bridging effect and lower Lewis acid-base interactions. Terrestrial NOM can be coagulated by Mg²⁺ while aquatic NOM cannot, owing to their different hydrophobicity. The critical coagulation concentrations of tested terrestrial NOM in the presence of Ca²⁺ (CCC–Ca) were quite similar at 1.94–4.88 mM despite their different structural properties. The CCC-Ca of tested aquatic NOM varied significantly from 46.89 mM to 110.40 mM depending on their structure. The optical indices including E₂/E₃, FI, and HIX can be potentially used as convenient indicators for assessing the colloidal stability of aquatic NOM for water treatment and risk assessment purposes.
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25912. 题目: Climate reconstructions based on GDGTs and pollen surface datasets from Mongolia and Siberia: Calibrations and applicability to extremely dry and cold environments
文章编号: N20013006
期刊: Biogeosciences
作者: Lucas Dugerdil, Sébastien Joannin, Odile Peyron, Isabelle Jouffroy-Bapicot, Boris Vannière, Bazartseren Boldgiv, and Guillemette Ménot
更新时间: 2020-01-30
摘要: Our understanding of climate and vegetation changes throughout the Holocene is hampered by biases in the proxy representativeness in sedimentary archives. Such potential biases are identified by comparing proxies to modern environments. Consequently, it becomes important to conduct multi-proxy studies and robust calibrations. The taiga-steppes of the Mongolian plateau, ranging from the extremely cold-dry Baikal basin to the Gobi desert, are characterized by low annual precipitation and continental annual air temperature as well as livestock grazing. The characterization of the climate system of this area is crucial for the understanding of Holocene Monsoon Oscillations. This study focuses on the calibration of proxy-climate relationships for pollen and glycerol dialkyl glycerol tetraethers (GDGTs) by comparing large published Eurasian calibrations with a set of 53 new surface samples (moss, soil and surface sediments). We show that: (1) preserved pollen assemblages are clearly imprinted on the extremities of the ecosystem range but mitigated and unclear on the ecotones; (2) for both proxies, inferred relationships depend on the geographical range covered by the calibration database as well as on the sample nature; (3) local calibrations, even those derived to the low range of climate parameters encompassed in the study area, better reconstruct climatic parameters than the global ones by reducing the limits for saturation impact, and (4) a bias in climatic reconstructions is induced by the over-parameterization of the models by addition of artificial correlation. We encourage the application of this surface calibration method to consolidate our understanding of the Holocene climate and environment variations.

25913. 题目: Decreased N₂O and NO emissions associated with stimulated denitrification following biochar amendment in subtropical tea plantations
文章编号: N20013005
期刊: Geoderma
作者: Cheng Ji, Shuqing Li, Yajun Geng, Yiming Yuan, Junzhang Zhi, Kai Yu, Zhaoqiang Han, Shuang Wu, Shuwei Liu, Jianwen Zou
更新时间: 2020-01-30
摘要: Acidic soils are hotspots of nitrous oxide (N₂O) and nitric oxide (NO) and biochar is documented to have the potential for mitigating N₂O and NO. The N₂O and NO emissions associated with soil functional genes and physicochemical properties under biochar amendment remains unclear in acidic soils. Here, we carried out a two-year field study to examine the responses of soil N₂O and NO emissions to biochar amendment in a subtropical tea plantation in China. Measurements of N₂O and NO fluxes were taken from inter-row soils using the static chamber method. We also measured the seasonal changes in soil key nitrogen (N)-cycling functional genes and physicochemical properties. Annual N₂O and NO emissions averaged 27.31 kg N₂O-N ha⁻¹ yr⁻¹ and 8.75 kg NO-N ha⁻¹ yr⁻¹ for the N fertilizer applied plots, which were decreased by 24% and 16% due to biochar application, respectively. In addition, both potential nitrification (PNR) and denitrification (PDR) rates were stimulated by biochar amendment, which significantly increased the abundances of bacterial amoA (AOB), nirK and nosZ genes. Changes in the composition of the N₂O-related microbial functional community were closely associated with soil PNR, pH, DOC, and NO₃⁻-N contents. The ratios of NO/N₂O were mainly lower than 1, suggesting that N₂O was produced mostly through denitrification rather than nitrification. There were negative correlations between soil N₂O and NO emissions and soil PDR and pH, and soil N₂O emissions were negatively correlated with nosZ gene abundances. Together, the decrease in N₂O and NO emissions following biochar application could be largely attributed to the enhanced denitrification process, in which biochar enriched the nirK and nosZ genes abundance, resulting from the enhancement of soil DOC and pH in acidic soils.

25914. 题目: Insight into the magnetic lime coagulation-membrane distillation process for desulfurization wastewater treatment: from pollutant removal feature to membrane fouling
文章编号: N20013004
期刊: Journal of Hazardous Materials
作者: Libing Zheng, Yunyi Jiao, Hui Zhong, Chun Zhang, Jun Wang, Yuansong Wei
更新时间: 2020-01-30
摘要: The high suspended solid (SS) and salts were main issues for flue gas desulfurization wastewater (FGDW). A magnetic lime coagulation (MLC)-membrane distillation (MD) integrated process was firstly applied with a self-made poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) membrane and the pollutants remove feature and membrane fouling were discussed. The SS was nearly 100% removed and magnetic seed significantly accelerate the settleability. The flux was 43.00 kg/m²·h with a salt rejection>99%. It was higher than 13 kg/m²·h in the first 125 h during the 18d continuous test, and the rejection for all cations, anions, total organic carbon (TOC) and total inorganic carbon (TIC) were higher than 99.95%, 99.00%, 98.81%, and 99.65%, respectively. Humic substances and tryptophan with 100-5000 Da were main dissolved organic matter (DOM), which were significantly removed. However, membrane fouling and wetting happened after 150 h. Scaling was the main foulants, while the organic fouling and biofouling were also detected. A new “bricklaying model” was induced to depict the formation of foulant layer, the colloids, organic matters (OMs) and microbe communities act as the “concrete”, while the inorganic crystals (magnesium and calcium oxysulphides) were the “bricks”. This contribution offers a new method for FGDW treatment and the membrane fouling mechanism of MD process.
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25915. 题目: Investigation into lanthanum-coated biochar obtained from urban dewatered sewage sludge for enhanced phosphate adsorption
文章编号: N20013003
期刊: Science of The Total Environment
作者: Jing Li, Bing Li, Haiming Huang, Ning Zhao, Mingge Zhang, Lu Cao
更新时间: 2020-01-30
摘要: Phosphate adsorption using metal-modified biochar has awakened much attention and triggered extensive research. In this study, the effect of lanthanum (La)-modified sludge using impregnation-co-precipitation was used for phosphate adsorption. Consequently, La-coated biochar at a pyrolysis temperature of 600 °C had the highest phosphate adsorption and the lowest heavy metal leaching potential. The treatment of virgin biochar with alkali before La loading was found to be beneficial for the increase of phosphate adsorption capacity. The adsorption kinetics was well depicted by the pseudo-second-order model, and indicating that intraparticle diffusion played a crucial role in the adsorption process. The good fitness between adsorption data and the Langmuir isotherm model showed a maximal adsorption capacity of 93.91 mg/g, where phosphate absorption was highly correlated to its concentration in the solution. The La-coated biochar showed high adsorption capacity when the solution pH varied from 3.0 to 6.0, and was insensitive to the coexisting chloride, nitrate, sulfate, bicarbonate and citrate. Moreover, the adsorption mechanism was further explored by using Zeta potential analysis, FTIR and XPS, indicating that the phosphate is adsorbed through electrostatic attraction in the form of the inner-sphere complexation. All the results suggested that the sludge-based biochar, as a support material for La, could serve as a promising adsorbent for phosphate in real applications.
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25916. 题目: Removal of methylene blue from aqueous solutions by biochar prepared from the pyrolysis of mixed municipal discarded material
文章编号: N20013002
期刊: Science of The Total Environment
作者: John Hoslett, Heba Ghazal, Nour Mohamad, Hussam Jouhara
更新时间: 2020-01-30
摘要: This paper investigates the adsorption of organic compounds in aqueous solution to biochar adsorbent, using methylene blue as an indicator for adsorption. Biochar was produced by the pyrolysis of mixed municipal discarded material in an innovative heat pipe reactor, the pyrolysis temperature was held at 300°C for 12 h. Biochar produced under these conditions was found to have oxygen containing functional groups that are beneficial to the adsorption of methylene blue as well as graphitic structures suggesting potential sites for π-π interactions with methylene blue. Methylene Blue followed the pseudo second order kinetic model with higher R² values than both the pseudo first order kinetic and intraparticle diffusion models. The adsorption also closely fit the Langmuir isotherm rather than the Freundlich model, suggesting monolayer adsorption rather than multilayer adsorption. Maximum adsorption capacity was observed at 7.2 mg/g for initial concentration of 100 mg/l Methylene blue in aqueous solution. The amount of Methylene blue adsorbed increased with increasing initial concentration as expected. The adsorption mechanisms are likely π-π interactions between methylene blue and the graphitic structures in the biochar which are shown to be present in Raman spectroscopy, as well as electrostatic attraction and ionic bonding between negatively charged surface sites on the char and the positive charge on the dissolved methylene blue molecules. The results show that biochar obtained from mixed waste could be employed as a low-cost and effective tool in water treatment for the removal of basic dyes and potentially other organic impurities.
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25917. 题目: A meta-analysis on biochar's effects on soil water properties – New insights and future research challenges
文章编号: N20013001
期刊: Science of The Total Environment
作者: Ifeoma G. Edeh, Ondřej Mašek, Wolfram Buss
更新时间: 2020-01-30
摘要: Biochar can significantly alter water relations in soil and therefore, can play an important part in increasing the resilience of agricultural systems to drought conditions. To enable matching of biochar to soil constraints and application needs, a thorough understanding of the impact of biochar properties on relevant soil parameters is necessary. This meta-analysis of the available literature for the first time quantitatively assess the effect of not just biochar application, but different biochar properties on the full sets of key soil hydraulic parameters, i.e., the available water content (AWC), saturated hydraulic conductivity (K_sat), field capacity (FC), permanent wilting point (PWP) and total porosity (TP). The review shows that biochar increased soil water retention and decreased K_sat in sandy soils and increased K_sat and hence decreased runoff in clayey soils. On average, regardless of soil type, biochar application increased AWC (28.5%), FC (20.4%), PWP (16.7%) and TP (9.1%), while it reduced K_sat (38.7%) and BD (0.8%). Biochar was most effective in improving soil water properties in coarse-textured soils with application rates between 30 and 70 t/ha. The key factors influencing biochar performance were particle size, specific surface area and porosity indicating that both soil-biochar inter-particle and biochar intra-particle pores are important factors. To achieve optimum water relations in sandy soils (>60% sand and <20% clay), biochar with a small particle size (<2 mm) and high specific surface area and porosity should be applied. In clayey soil (>50% clay), <30 t/ha of a high surface area biochar is ideal.
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25918. 题目: Understanding the remote influences of ocean weather on the episodic pulses of particulate organic carbon flux
文章编号: N20012921
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Henry A. Ruhl, Frederick L. Bahr, Stephanie A. Henson, W. Brett Hosking, Benoit Espinola, Mati Kahru, Patrick Daniel, Patrick Drake, Christopher A. Edwards
更新时间: 2020-01-29
摘要: The biological carbon pump has been estimated to export ∼5–15 Gt C yr−1 into the deep ocean, and forms the principal deep-sea food resource. Irregular, intense pulses of particulate organic carbon (POC) have been found to make up about one-third of the overall POC fluxes at a long-term deep-sea research station influenced by coastal upwelling of the California Current, Station M (34°50′N, 123° W, 4000 m depth). However, the drivers of these pulses have been challenging to quantify. It has long been recognized that ocean currents can result in particles being advected while sinking to the point of collection by a sediment trap. Thus, a sediment trap time series can incorporate material from a dynamic catchment area, a concept sometimes referred to as a statistical funnel. This concept raises many questions including: what are the day-to-day conditions at the source locations of the sinking POC And, how might such 'ocean weather' and related ecosystem factors influence the intense variation seen at the seafloor Here we analyzed three-dimensional ocean currents from a Regional Ocean Modeling System (ROMS) model from 2011 to 2017 to trace the potential source locations of particles sinking at 1000, 100, and 50 m d−1 from an export depth of 100 m. We then used regionally tailored satellite data products to estimate export flux of POC from these locations. For the 100 m d−1 speed, the particles had origins of up to ∼300 km horizontal distance from the sediment trap location, moored at Station M at 3400 m depth., and nearly 1000 km for the 50 m d−1 speed. Particle tracking indicated that, there was considerable inter-annual variation in source locations. Particle source locations tended to originate from the east in the summer months, with higher export and POC fluxes. Occasionally these locations were in the vicinity of highly productive ocean features nearer to the coast. We found significant correlations between export flux of organic carbon from the estimated source locations at 100 m depth to trap-estimated POC fluxes at 3400 m depth. These results set the stage for further investigation into sinking speed distributions, conditions at the source locations, and comparisons with mechanistic biogeochemical models and between particle tracking model frameworks.

25919. 题目: Non-linear temperature sensitivity of litter component decomposition under warming gradient with precipitation addition on the Tibetan plateau
文章编号: N20012920
期刊: Plant and Soil
作者: Wangwang Lv, Lirong Zhang, Haishan Niu, Bowen Li, Qi Wang, Yang Zhou, Yanfen Wang, Lili Jiang, Peipei Liu, Huan Hong, Shugang Jia, Caiyun Luo, Dorji Tsechoe, Huakun Zhou, Shiping Wang
更新时间: 2020-01-29
摘要: Background and aims: Interactive effect of warming and precipitation addition on litter decomposition is still scarce. Moreover, nonlinear response of its temperature sensitivity to warming is not demonstrated due to lack of warming gradient experiment in situ. Methods: we performed a warming gradient experiment (0, ~0.25–0.5, ~1, ~2, and ~4 °C, respectively) using infrared heaters and a precipitation addition treatment in a fully-factorial design for 2-years on the Tibetan Plateau. The responses of mass loss of litter components (i.e. organic matter (OM), soluble cell content (SCC), lignin, cellulose (Ce), hemi-cellulose (Hce), total organic carbon (OC)) and nutrients (total nitrogen (TN) and total phosphorus (TP)) to warming and precipitation addition were determined over 2-years. Results: We found that warming significantly increased annual mass losses of all litter components in both treatment years. Precipitation addition significantly increased annual mass losses of OM, SCC, OC, TN and TP only in the first year due to drought. There were no interactive effects between warming and precipitation addition on litter component decomposition in the semi-arid alpine region. Temperature sensitivities were lowest when soil temperature increased by a mean of about 2.3 °C. There was an inverse relationship between the temperature sensitivity of organic matter decomposition and quality of litter carbon compounds. Conclusions: Our results suggest that soil temperature effects may override soil moisture effects on litter decomposition in the alpine region, and the nonlinear temperature sensitivity of litter decomposition should be estimated using warming gradients. Lower quality of litter carbon compounds had higher temperature sensitivity of organic matter decomposition.

25920. 题目: Changes in soil organic matter and microbial communities after fine and coarse residues inputs from Mediterranean tree species
文章编号: N20012919
期刊: Applied Soil Ecology
作者: Caroline Brunel, Raphael Gros, Thomas Z. Lerch, Anne Marie Farnet Da Silva
更新时间: 2020-01-29
摘要: Trees residues decomposition is a key step in forested ecosystems. In the context of sclerophyllous Mediterranean forests, the effects of residue quality on soil organic matter and microbial communities is still poorly documented. Using a mesocosm experiment, we explored microbial responses (enzyme activities, basal respiration, molecular fingerprints and catabolic profiles) and variations in soil chemical properties (pH, CaCO₃, organic C and N contents, quality of soil organic matter via ¹³C CP/MAS NMR) induced by coarse woody debris (W) or fine residues (i.e. twigs -leaves/needles, hereafter TL) from mono-specific or mixed stands of Pinus halepensis and Quercus ilex, P. sylvestris and Q. pubescens. After a nineteen-month incubation period, we found that the origin of residues (Pinus spp. stand, Quercus spp. stand or mixed stand) shaped the genetic structure of both fungal and bacterial communities. TL inputs led to higher soil N content and increased enzyme activities and bacterial biomass. Aromatic compounds and C to N ratio increased with W inputs, strongly shaped fungal communities and increased tyrosinase activity. Thus, the type of residue and the tree species identity (Quercus spp. vs Pinus spp.) appeared to modulate the balance between fungal and bacterial biomass and soil microbial diversity. Our results revealed that logging residues management, by modulating the type of residues remaining on forest floor, could have significant impacts on soil functioning by modifying both chemical properties (e.g. soil C/N ratio) and microbial structure and functions. These findings need to be supported by in natura studies since deciphering such mechanisms controlling C fluxes in forest soils has important consequences under the context of climate change.