论文检索

总访问量：4285366次

总访客量：179930人

所有论文

22721. 题目: Comparison of solid phase extraction methods for the measurement of humic-like substances (HULIS) in atmospheric particles
文章编号: N20022810
期刊: Atmospheric Environment
作者: Chunlin Zou, Meiju Li, Tao Cao, Mengbo Zhu, Xingjun Fan, Shiyun Peng, Jianzhong Song, Bin Jiang, Wanglu Jia, Chiling Yu, Haiyan Song, Zhiqiang Yu, Jun Li, Gan Zhang, Ping'an Peng
更新时间: 2020-02-28
摘要: Humic-like substances (HULIS) constitute a significant fraction of the water-soluble organic compounds in the environment and influence many properties of atmospheric aerosols. In this study, three solid phase extraction (SPE) methods that involve the use of hydrophilic/lipophilic balanced (HLB) resin with pure methanol (HLB-M), HLB resin with 2% (v/v) ammonia/methanol (HLB-N), and Bond Elut PPL (Priority PolLutant) resin with methanol (PPL), were compared for the isolation of HULIS from atmospheric aerosols. The HLB-N and PPL methods efficiently recovered Suwannee River fulvic acid (SRFA) and were excellent for quantifying HULIS at low levels in aerosols. All three SPE methods were favorable for the elution of aromatic and strongly UV-absorbing compounds. However, the chemical structures and molecular compositions of the HULIS isolated by the three methods showed some differences. The HULISHLB-N and HULISPPL fractions contained higher concentrations of aliphatic and aromatic C–H groups than did the HULISHLB-M fraction, indicating that relative higher content of weak polar organic species in HULIS fractions isolated by the HLB-N and PPL methods than those isolated by the HLB-M method. Moreover, the HULISHLB-N and HULISPPL were both characterized by having lower relative abundance-weighted modified aromaticity index values and higher concentrations of S-containing compounds than the HULISHLB-M, as indicated by Fourier transform ion cyclotron resonance mass spectrometry. Some N-containing structures were identified only in the HULISHLB-N, suggesting that some of HULIS molecules were changed during the HLB-N treatment. Based on these comparisons of the three methods, we found that the PPL method serves equally good as compared to other two methods, and therefore, one can utilize PPL method also for HULIS isolation and characterization.

22722. 题目: Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment
文章编号: N20022809
期刊: Global Biogeochemical Cycles
作者: Trista J. Vick‐Majors, Alexander B. Michaud, Mark L. Skidmore, Clara Turetta, Carlo Barbante, Brent C. Christner, John E. Dore, Knut Christianson, Andrew C. Mitchell, Amanda M. Achberger, Jill A. Mikucki, John C. Priscu
更新时间: 2020-02-28
摘要: Although subglacial aquatic environments are widespread beneath the Antarctic ice sheet, subglacial biogeochemistry is not well understood, and the contribution of subglacial water to coastal ocean carbon and nutrient cycling remains poorly constrained. The Whillans Subglacial Lake (SLW) ecosystem is upstream from West Antarctica's Gould‐Siple Coast ~800 m beneath the surface of the Whillans Ice Stream. SLW hosts an active microbial ecosystem and is part of an active hydrological system that drains into the marine cavity beneath the adjacent Ross Ice Shelf. Here we examine sources and sinks for organic matter in the lake and estimate the freshwater carbon and nutrient delivery from discharges into the coastal embayment. Fluorescence‐based characterization of dissolved organic matter revealed microbially driven differences between sediment pore waters and lake water, with an increasing contribution from relict humic‐like dissolved organic matter with sediment depth. Mass balance calculations indicated that the pool of dissolved organic carbon in the SLW water column could be produced in 4.8 to 11.9 yr, which is a time frame similar to that of the lakes' fill‐drain cycle. Based on these estimates, subglacial lake water discharged at the Siple Coast could supply an average of 5,400% more than the heterotrophic carbon demand within Siple Coast embayments (6.5% for the entire Ross Ice Shelf cavity). Our results suggest that subglacial discharge represents a heretofore unappreciated source of microbially processed dissolved organic carbon and other nutrients to the Southern Ocean.

22723. 题目: Surface soil mixing is more beneficial than the plough layer mixing mode of biochar application for nitrogen retention in a paddy system
文章编号: N20022808
期刊: Science of The Total Environment
作者: Haiying Lu, Yuanyuan Feng, Qian Gao, Jincheng Xing, Yudong Chen, Linzhang Yang, Lihong Xue
更新时间: 2020-02-28
摘要: The benefits of biochar as a soil amendment have been investigated extensively, but few studies have considered the effects of different application modes on nitrogen (N) dynamics. In the present study, a pot experiment was conducted to evaluate the effects of two different biochar application modes [plough layer mixing (PLM) and surface soil mixing (SSM)] on the N dynamics in a paddy system. It was found that biochar application significantly reduced the total N (TN), NH4+-N, and NO3−-N contents of the paddy surface water after fertilization, and that the SSM mode of application was more effective in doing this, particularly for NH4+-N, reducing TN by 11–76%, NH4+-N by 31–77%, and NO3−-N by 31–60% compared with the control at 7 days after fertilizer dressing. By contrast, the effect of biochar application on soil N varied with biochar application mode, N form, and rice growth period. In general, there was no significant effect of biochar type on soil N content, with both types of biochar resulting in a higher TN content of the soil after the tiller stage compared with the control. In addition, the SSM mode of application led to a higher TN content but lower NH4+-N content of the soil than the PLM mode, while the two application modes had varying effects on the NO3−-N content depending on the growing period of the rice. The rice grain yield increased by 25–36% with the SSM application mode and 11–14% with the PLM mode. These findings indicate that the SSM mode of biochar application in paddy soils is a more promising strategy for both reducing the risk of N loss and improving rice yield than PLM mode.

22724. 题目: Biochar retards Al toxicity to maize (Zea mays L.) during soil acidification: The effects and mechanisms
文章编号: N20022807
期刊: Science of The Total Environment
作者: Ren-Yong Shi, Ni Ni, Jackson Nkoh Nkoh, Ying Dong, Wen-Rui Zhao, Xiao-Ying Pan, Jiu-Yu Li, Ren-Kou Xu, Wei Qian
更新时间: 2020-02-28
摘要: Biochar can effectively alleviate the Al phytotoxicity in acidic soils due to its alkaline nature. However, the longevity of this alleviation effect of biochar under re-acidification conditions is still unclear. In the present study, the maize root growth responding to the simulated re-acidification of two acidic soils amended by peanut straw biochar or Ca(OH)2 was investigated to evaluate the long-term effect of biochar on alleviating Al toxicity in acidic soils. Compared with Ca(OH)2 amendment, the application of biochar significantly retarded Al toxicity to plant during soil re-acidification. When 4.0 mM HNO3 was added, the maize seedling root elongation in an Oxisol with biochar was 99% higher than that in the Oxisol with Ca(OH)2. Also, the Evans blue uptake and Al content in the root tip in the biochar treatment were 60% and 51% lower than those in the Ca(OH)2 treatment. The retarding effect was mainly attributed to the slow decrease in soil pH during acidification and the release of dissolved organic carbon (DOC) in the soils amended by biochar. The slower decrease in soil pH resulting from the increased pH buffering capacity after biochar application inhibited the increase of soluble and exchangeable Al during re-acidification. The increased DOC after biochar application decreased the toxic soluble Al speciation at the same pH value and total Al concentration in soil solution. Therefore, given the re-acidification of soils, biochar presented a longer-term effect on alleviating Al toxicity of acidic soil than liming.

22725. 题目: Leachable soil black carbon after biochar application
文章编号: N20022806
期刊: Organic Geochemistry
作者: Melanie Braun, Arne Kappenberg, Alexandra Sandhage-Hofmann, Eva Lehndorff
更新时间: 2020-02-28
摘要: Black carbon (BC) enters soil via deposition of emissions and nowadays also via application of biochar. Recent studies indicate that a yet not quantified part of BC is lost from soil by leaching, which implies that BC exists in water-transportable form (so-called water-extractable BC; WEBC). We aim at quantifying the amount of WEBC in soil and at elucidating whether it relates to biochar application. The composition of WEBC was further tested to evaluate the degree of BC weathering over time after application, hypothesizing that BC degrades into smaller polyaromatic units. We analysed total BC and WEBC in topsoil (0-10 cm) of a field trial with application of 0, 4.5, and 9 Mg biochar ha-1 using the benzene polycarboxylic acid method. To see if there is a temporal relation between BC input and WEBC formation, we took samples directly after biochar application and three years later. Bulk BC and also WEBC concentrations increased with increasing biochar application rates. In contrast, portions of WEBC of bulk BC decreased with increasing amount of applied biochar. On average, we found between 7.56±2.50 and 12.56±1.34 mg WEBC per kg agricultural soil, making up 0.6 to 1.84% of bulk BC. Over time, no loss or accumulation of either component was observed. However, we found that the composition of WEBC differed from bulk BC; i.e. WEBC consisted of less condensed aromatic structures than bulk BC indicating that de-condensation processes are involved in the formation of leachable BC.

22726. 题目: Refining benchmarks for soil organic carbon in Australia’s temperate forests
文章编号: N20022805
期刊: Geoderma
作者: Lauren T. Bennett, Nina Hinko-Najera, Cristina Aponte, Craig R. Nitschke, Thomas A. Fairman, Melissa Fedrigo, Sabine Kasel
更新时间: 2020-02-28
摘要: Soil organic carbon (SOC) stocks in Australia's temperate forests have been overlooked in national soil databases and in global SOC analyses of natural ecosystems despite the importance of temperate forests to the global terrestrial carbon balance. This limits the potential to both predict change in SOC stocks in temperate Australia and to identify where and how SOC stocks can be managed to mitigate climate change. Based on data from 707 sites, we examine variations in SOC concentrations and stocks across a range of natural temperate broadleaf forests in south-eastern Australia. Comparisons with current Australia-wide databases highlight previous under-estimation of forest SOC concentrations, leading to substantial underprediction of SOC stocks in the most productive forests (e.g. this study's mean of 207 Mg C ha−1 compared with a database mean estimate of 141 Mg C ha−1 for Tall open-forests to 30-cm soil depth). Random Forest models involving 27 environmental variables (representing climate, terrain, parent material, soil attributes, vegetation, and fire history) explained up to 79% of the variation in SOC concentrations and 77% of the variation in SOC stocks to 30-cm depth. Climate variables (precipitation, temperature) were of greatest importance to the prediction of both SOC concentrations and SOC stocks, tending to override the importance of terrain and fire-history variables at this study's regional scale. While patterns in SOC concentrations and stocks were correlated, SOC concentrations were not a reliable proxy for SOC stocks to 10-cm depth, reiterating the importance of mass equivalent measures (i.e. soil bulk density) to assessing changes in soil carbon storage. Our study provides a timely check of the model-based estimates of SOC concentrations and stocks in Australia's temperate forests that are currently available in nation-wide databases and improves the available information for defining benchmarks, and for identifying potential areas of SOC loss and gain, in programs that aim to mitigate climate change.

22727. 题目: Sources and transformation processes of proteinaceous matter and free amino acids in PM2.5
文章编号: N20022804
期刊: Journal of Geophysical Research: Atmospheres
作者: Ren‐guo Zhu, Hua-Yun Xiao, Yuwen Zhu, Zequn Wen, Xiaozheng Fang, Yuanyuan Pan
更新时间: 2020-02-28
摘要: Amino acids is an important organic nitrogen compound class in aerosol. Its origins and transformation in the atmosphere remain poorly understood. The concentrations of free amino acids (FAAs) and combined amino acids (CAAs) and δ15N values of free and combined Glycine (Gly) in PM2.5 and main emission sources (plant, soil and aerosol from biomass burning) were investigated from five sampling sites in Nanchang area (Jiangxi Province, China). Our results showed that the composition profiles of CAAs and FAAs were quite different from each other in PM2.5. For CAAs, percentages of individual combined amino acids were different between biomass burning sources and plant or soil sources, and we found that the composition profiles of aerosol CAAs could reflect the contribution of the main emission sources. For FAAs, a predominance of free Gly was observed in aerosol FAAs pool because atmospheric photooxidative processes could increase free Gly and decrease other reactive FAAs. This implied that the composition of aerosol FAAs could not reflect their origins. A strong correlation between δ15NF‐Gly values in aerosols or sources and the δ15NC‐Gly values in their parent CAAs was observed, indicating that the isotope effect associated with Gly transformation in aerosols may be small. Additionally, we found more positive δ15NGly in aerosols emitted by biomass burning, which was likely due to 15N‐depleted amino‐N loss from Gly molecule. The results suggested that δ15NGly values in aerosols might be used to identify biomass burning sources.

22728. 题目: Pb and Cd chemisorption by acid mineral soils with variable Mn and organic matter contents
文章编号: N20022803
期刊: Geoderma
作者: Yuting Zhou, Sonam Sherpa, M.B. McBride
更新时间: 2020-02-28
摘要: Adsorption of Pb2+ and Cd2+ on acidic A and B horizon mineral soils of New York (MP) and Vermont (BH) were determined in 0.2 M Na acetate buffered at pH 5.5 to determine strength and capacity of the soils for chemisorption of these trace metal ions. Adsorption isotherms over a very wide concentration range were better modeled using the linearized Freundlich compared to the linearized Langmuir equation. Adsorption of Pb was much stronger than that of Cd for all soils, and A horizon soils adsorbed Pb and Cd more strongly than their B horizon counterparts. The logarithms of the Freundlich binding coefficients (log KF) were greater by about 1.0 unit for Pb than for Cd for all but the B-horizon of the MP soil, which was the least strongly adsorptive of all soils tested. Pb binding constants were significantly correlated to hydroxylamine- and NH4 oxalate-extractable Fe and Mn in addition to soil CEC, but the Cd binding constants were correlated significantly to extractable Fe only. Partition coefficients (KP) were calculated for Pb and Cd from the adsorption experiments, and for the lowest additions of Pb to the A-horizon soils, ranged from more than 4000 L kg−1 in the BH soils to about 300 in the more acidic MP soils. Cd partition coefficients were much lower than those of Pb in all soils, and the MP soils retained Cd particularly weakly, with a KP in the range of 3–20 for the A-horizon and even lower for the B-horizon. Pb and Cd were adsorbed more strongly on A-horizon than B-horizon soils, indicating the importance of organic matter in both Pb and Cd retention by chemisorption at low pH. For both Pb and Cd, partition coefficients diminished markedly with increasing metal addition levels. Adsorption of Pb and Cd ions caused release of alkaline earth metals and Mn into solution during the adsorption process on the high-Mn BH soils, whereas the more strongly acidic MP soils released Al. Decreasing solubility of P and S corresponding to increasing Pb adsorption on the soils suggested that, in addition to chemisorption, precipitation of Pb phosphate and Pb sulfate may have been involved in Pb removal from solution.

22729. 题目: Twentieth Century Black Carbon and Dust Deposition on South Cascade Glacier, Washington State, USA as Reconstructed from a 158 m Long Ice Core
文章编号: N20022802
期刊: Journal of Geophysical Research: Atmospheres
作者: S.D. Kaspari, D. Pittenger, T.M. Jenk, U. Morgenstern, M. Schwikowski, N. Buenning, L. Stott
更新时间: 2020-02-28
摘要: Light absorbing particles (LAP) include black carbon (BC) and mineral dust, and are of interest due to their positive radiative forcing, and contribution to albedo reductions and snow and glacier melt. This study documents historic BC and dust deposition as well as their effect on albedo on South Cascade Glacier (SCG) in Washington State (USA) through the analysis of a 158 m (139.5 m w.e.) ice core extracted in 1994 and spanning the period 1840‐1991. Peak BC deposition occurred between 1940 and 1960, when median BC concentrations were sixteen times higher than background, likely dominated by domestic coal and forest fire emissions. Post 1960 BC concentrations decrease, followed by an increase from 1977 to 1991 due to melt consolidation, and higher emissions. Differences between the SCG record and BC emission inventories, as well as ice core records from other regions, highlights regional differences in the timing of anthropogenic and biomass BC emissions. Dust deposition on SCG is dominated by local sources, and is variable throughout the record. Albedo reductions from LAP are dominated by dust deposition, except during high BC deposition events from forest fires, and during 1940‐1960 when BC and dust similarly contribute to albedo reductions. This study furthers understanding of the factors contributing to historical snow melt and glacier retreat in the Cascades, and demonstrates that ice cores retrieved from temperate glaciers have the potential to provide valuable records of LAP deposition.

22730. 题目: Enhanced cork-boiling wastewater treatment by electro-assisted processes
文章编号: N20022801
期刊: Separation and Purification Technology
作者: Alicia L. Garcia-Costa, Jaime Carbajo, Ramon Masip, Asuncion Quintanilla, Francisco J. Yuste-Córdoba, Jose A. Casas
更新时间: 2020-02-28
摘要: In the cork processing industry, a large amount of highly polluted wastewater is generated during the cork-boiling step. In this work, we propose two novel approaches for the treatment of cork-boiling wastewater (CBW): (i) a sequential electro-coagulation coupled to Fenton oxidation process (EC + Fenton) and (ii) the electro-Fenton process (EF). Both technologies were tested at 80 °C with the stoichiometric dose of H2O2 required for complete mineralization of the organic matter. Both treatments resulted in a high TOC conversion, around 87%, with complete phenolic compounds removal. The resulting effluents were biodegradable (BOD5/COD > 0.65), containing non-toxic carboxylic acids as formic, acetic, oxalic and malonic acids. Regarding the economy of the process, the main cost is related to H2O2 consumption. In this sense, an initial physic-chemical pretreatment diminished the oxidant requirements and thus, the operational costs can be reduced by 40% in the EC + Fenton process.

22731. 题目: Effects of cultivation history in paddy rice on vertical water flows and related soil properties
文章编号: N20022708
期刊: Soil and Tillage Research
作者: Jun Yi, Weiwen Qiu, Wei Hu, Hailin Zhang, Muxing Liu, Dongyou Zhang, Tieniu Wu, Pei Tian, Yan Jiang
更新时间: 2020-02-27
摘要: Soil properties, especially physical properties and macropore characteristics, are controlling factors for vertical water flow in paddy fields. However, the effects of paddy rice cultivation history on vertical water flows and related soil properties have been rarely studied. The objectives were to identify the differences in soil physical properties and macropore parameters and to reveal the effects of these soil properties on vertical water flow patterns in paddy fields under different cultivation times. In this study, soil physical properties in a very young paddy field (2 y, VYPF), a young paddy field (18 y, YPF), and an old paddy field (>100 y, OPF) were analyzed. Meanwhile, macropore parameters (resolution of 0.6 mm) and vertical water flow patterns in these fields were identified by computed tomography and dye tracing experiment, respectively. As cultivation history lengthened in paddy rice, the average content of soil clay and organic carbon in the 80 cm depth soil profile increased, as did the thickness and bulk density of the plow pan. Also, macroporosity, macropore area density, macropore number density, node density, macropore angle, and hydraulic radius significantly decreased as length of cultivation age increased. As a result, differences in these soil propeties affected vertical water flow in three studied paddy fields. Steady-state infiltration rates decreased significantly in accordance with the reduced saturated hydraulic conductivity of soil cores from the plow pan; median values were 9.76 cm d−1, 2.93 cm d−1, and 0.13 cm d−1 for VYPF, YPF, and OPF, respectively. A greater abundance and distribution of a dye tracer and a higher stained area ratio under the plow pan in younger paddy fields indicated that more obvious preferential water flows occurred in VYPF and YPF than in OPF. This implied that the conversion of farmland from upland field to paddy field resulted in greater use of irrigation water and also posed a risk of groundwater pollution through increased percolation. Therefore, a longer puddling time before planting paddy rice should be conducted in paddy fields (i.e. YPF and VYPF) with a short cultivation history, which can reduce water percolation by enhancing bulk density, reducing macropores, and lowering the saturated water conductivity of the plow pan.

22732. 题目: Recent advances on the development and application of magnetic activated carbon and char for the removal of pharmaceutical compounds from waters: A review
文章编号: N20022707
期刊: Science of The Total Environment
作者: Luciana S. Rocha, Diogo Pereira, Érika Sousa, Marta Otero, Valdemar I. Esteves, Vânia Calisto
更新时间: 2020-02-27
摘要: The adsorption of pharmaceutical substances using carbonaceous materials, such as activated carbon (AC), biochar (BC) and hydrochar (HC), has received substantial attention by researchers working on water treatment, due to the simplicity, low-cost and high performance of this process. In order to widen the potentiality of these carbonaceous materials and to overcome some of their limitations, particularly the inefficient separation of powdered formulations from treated water, the incorporation of magnetic nanoparticles has been explored. The recovery of magnetic carbon materials (MCM) from the treated water can be attained by applying an external magnetic field, avoiding inefficient and costly filtration and centrifugation processes, typically applied in the case of non-magnetic carbonaceous adsorbents. In the last ten years, some work has been devoted to the preparation of MCM specifically from AC (MCACM), biochar (MCBCM) and hydrochar (MCHCM). This review aims to present the different aspects of using MCM in water treatment, namely in the removal of pharmaceutical compounds. The synthesis routes used to produce MCM, their physical, morphologic and chemical features, and their application in the removal of these micro-organic contaminants from water will be assessed. The advantages and disadvantages of using MCM in water treatment, and their comparative performance with the carbonaceous non-magnetic precursors will be also discussed in this review.

22733. 题目: Improvement effect of pyrolyzed agro-food biochar on the properties of magnesium phosphate cement
文章编号: N20022706
期刊: Science of The Total Environment
作者: Muhammad Riaz Ahmad, Bing Chen, Haijuan Duan
更新时间: 2020-02-27
摘要: This study extends the application of pyrolyzed biochar and investigates its influence on the mechanical, sorption and microstructure properties of magnesium phosphate cement mortar. Biochar was produced by the pyrolysis of wheat straw biomass by controlled burning and its replacement level was kept up to 1.5%. At the age of 30 days, the compressive and flexural strength of mortar containing 1.5% biochar was 17.3% and 9.0% higher as compared to the control mortar, which was associated with the micro-filler and internal reservoir effect of biochar particles. Inclusion of biochar considerably improved the resistance of magnesium phosphate cement in the water environment. Sorptivity and water absorption of mortar containing 1.5% biochar was reduced by 33.8% and 25% respectively than the control mortar. Biochar densified the microstructure of mortars by filling the microcracks and blocking the pores. X-ray diffraction and Fourier transform infrared spectroscopy did not provide any information about the formation of new hydration products. Elemental analysis of mortar samples using energy dispersive spectroscopy showed the presence of some elements, which indicates the possibility of new hydration products. Based on the positive results in this study, future study will include the detailed chemical effect of biochar on magnesium phosphate cement.

22734. 题目: An automated solid phase extraction procedure for lipid biomarker purification and stable isotope analysis
文章编号: N20022705
期刊: Organic Geochemistry
作者: Oliver Rach, Xennophone Hadeen, Dirk Sachse
更新时间: 2020-02-27
摘要: Effective recovery and high purity of lipid biomarkers are essential for compound-specific stable isotope analysis in a variety of fields ranging from hydrocarbon research, paleoclimatology, food and drug analysis and medicine. Solid-phase extraction (SPE) is the most common method for purifying organic compounds from complex mixtures. SPE constitutes the most labor-intensive part of laboratory work often limiting the number of samples that can be analyzed. Reliable, easy-to-use, automated methods could increase sample throughput as well as reproducibility. Here we introduce such a method using a Gilson ASPEC GX-271 system and test the separation quality, reproducibility, and efficiency in comparison to a classical manual SPE lipid purification procedure. Using multiple extractions of the same natural soil sample we show that the automated SPE is comparable in overall quality and slightly superior in reproducibility to a manual SPE. We demonstrate that stable hydrogen isotope measurements of n-alkanes purified using an automated SPE extraction showed significantly lower standard errors. Furthermore, the unattended operation of the system eases the purification of large sample sets. Generally, the automated SPE using the Gilson ASPEC GX-271 for lipid biomarker separation provides qualitatively and quantitatively accurate and reproducible results with more efficient purification of compounds than the manual method.

22735. 题目: A unique bacteriohopanetetrol stereoisomer of marine anammox
文章编号: N20022704
期刊: Organic Geochemistry
作者: Rachel Schwartz-Narbonne, Philippe Schaeffer, Ellen C. Hopmans, Margot Schenesse, E. Alex Charlton, D. Martin Jones, Jaap S. Sinninghe Damsté, Muhammad Farhan Ul Haque, Mike S.M. Jetten, Sabine K. Lengger, J. Colin Murrell, Philippe Normand, Guylaine H.L. Nuijten, Helen M. Talbot, Darci Rush
更新时间: 2020-02-27
摘要: Anaerobic ammonium oxidation (anammox) is a major process of bioavailable nitrogen removal from marine systems. Previously, a bacteriohopanetetrol (BHT) isomer, with unknown stereochemistry, eluting later than BHT using high performance liquid chromatography (HPLC), was detected in 'Ca. Scalindua profunda' and proposed as a biomarker for anammox in marine paleo-environments. However, the utility of this BHT isomer as an anammox biomarker is hindered by the fact that four other, non-anammox bacteria are also known to produce a late-eluting BHT stereoisomer. The stereochemistry in Acetobacter pasteurianus, Komagataeibacter xylinus and Frankia sp was known to be 17β, 21β(H), 22R, 32R, 33R, 34R (BHT-34R). The stereochemistry of the late-eluting BHT in Methylocella palustris was unknown. To determine if marine anammox bacteria produce a unique BHT isomer, we studied the BHT distributions and stereochemistry of known BHT isomer producers and of previously unscreened marine ('Ca. Scalindua brodeae') and freshwater ('Ca. Brocadia sp.') anammox bacteria using HPLC and gas chromatographic (GC) analysis of acetylated BHTs and ultra high performance liquid chromatography (UHPLC)-high resolution mass spectrometry (HRMS) analysis of non-acetylated BHTs. The 34R stereochemistry was confirmed for the BHT isomers in Ca. Brocadia sp. and Methylocella palustris. However, 'Ca. Scalindua sp.' synthesise a stereochemically distinct BHT isomer, with still unconfirmed stereochemistry (BHT-x). Only GC analysis of acetylated BHT and UHPLC analysis of non-acetylated BHT distinguished between late-eluting BHT isomers. Acetylated BHT-x and BHT-34R co-elute by HPLC. As BHT-x is currently only known to be produced by 'Ca. Scalindua spp.', it may be a biomarker for marine anammox.

22736. 题目: Spatial distribution characteristics and influencing factors of organic carbon in sediments of Tongshun River riparian zone
文章编号: N20022703
期刊: Chemosphere
作者: Yueyong Ma, Zhiqiang Wang, Teng Ma, Shuxian Chen
更新时间: 2020-02-27
摘要: The riparian zone is closely related to the surrounding environment, and it is important to find out the distribution characteristics of organic carbon in the sediment of the riparian zone. In this paper, the distribution of organic carbon in sediments and its influencing factors were analyzed in the riparian zone of small watershed. The results show that the distribution of organic carbon was significantly related to the lithology of sediment, and the sedimentary environment determined the content of organic carbon in sediment. In shallow sediments, organic carbon changed significantly with depth, and redox conditions were the main influencing factors. When the environment changed from oxidation condition to reduction condition, both the mineralization of organic carbon and the change of iron oxide morphology would change the stabilizing effect of organic carbon, thus affecting the distribution of organic carbon. In addition, under the influence of flood, the organic carbon in the riparian sediments changed with the distance to the river in the horizontal direction.

22737. 题目: Emerging investigator series: formation of brominated haloacetamides from trihalomethanes during zero-valent iron reduction and subsequent booster chlorination in drinking water distribution
文章编号: N20022702
期刊: Environmental Science: Water Research & Technology
作者: Pengzhou Luo, FeiFei Wang, Stuart W. Krasner, Chao Fang, Shenghua Chen, Wenhai Chu
更新时间: 2020-02-27
摘要: Iron materials and booster chlorination in drinking water distribution pipe networks could impact disinfection by-product (DBP) transformation. This study investigated trihalomethane (THM) mixture degradation and brominated haloacetamide (Br-HAM) formation during zero-valent iron (ZVI) reduction and booster chlorination. The toxicity change resulting from the formation of the higher toxicity species, Br-HAMs, in drinking water distribution systems was explored for the first time. The results from tribromomethane (TBM) reduction experiments showed that the ZVI dosage and the water matrix enhanced TBM reduction by ZVI. The higher the ZVI dosage and the lower the pH, the more TBM was reduced by ZVI. Coexisting ions, SO42− and HCO3−, promoted TBM reduction slightly. The humic acid-like component of natural organic matter was conjectured to dominate the coordination complex generation through reacting with Fe2+ and therefore greatly inhibited TBM reduction. During the subsequent booster chlorination, brominated THM yields increased with time, while a sharp increase in Br-HAMs was observed before it decreased. Under the drinking water distribution system conditions with an environmentally relevant concentration ratio of the THM mixture, most THMs were reduced greatly by ZVI. Subsequently, the following booster chlorination produced Br-THMs and Br-HAMs instead of haloacetonitriles (HANs). Generally, THMs slightly increased with time (except for trichloromethane [TCM]), while Br-HAMs exhibited a sharp formation at 0.5 h after booster chlorination and then decreased gradually. This resulted in an increase in the cytotoxicity and genotoxicity index, indicating that booster chlorination should not be too close to residential areas in iron pipe networks. Overall, the toxicity risk caused by Br-HAM formation through ZVI reduction and booster chlorination increased.

22738. 题目: Carbon monoxide reduction in the flue gas during biochar production from oil palm empty fruit bunch
文章编号: N20022701
期刊: Journal of Cleaner Production
作者: Mohammed Abdillah Ahmad Farid, Mohd Ali Hassan, Ahmad Muhaimin Roslan, Mohd Hafif Samsudin, Zarry Jay Jay Mohamad, Mohd Ridzuan Othman, Yoshihito Shirai
更新时间: 2020-02-27
摘要: Biomass carbonization technology is implemented to produce charcoal with high-calorific content. However, this technology releases pollutant gases, which adversely affect ambient environment and human health. This study proposed a catalytic gas treatment method using platinum-supported alumina catalyst (Pt/γ-Al2O3) for carbon monoxide emission reduction in oil palm empty fruit bunch carbonization. Carbonization released a rather high carbon monoxide concentration of 5558 ± 53 mg m−3 in the flue gas, exceeding the permissible limit of 1000 mg m−3. At 2.5 wt% of catalyst dosage, the carbon monoxide emission substantially was reduced to 595 ± 9 mg m−3, achieving 89.3% carbon monoxide removal efficiency. This was due to oxidation by the platinum-supported alumina catalyst (Pt/γ-Al2O3), which was done at low temperature, thus transforming carbon monoxide into carbon dioxide. The catalyst demonstrated reusability, attaining >80% carbon monoxide removal efficiency for 5 consecutive carbonization cycles. The biochar produced contained a high energy content of 24.6 ± 0.7 MJ kg−1, which was suitable to be used as a coal substitute.

22739. 题目: Nutrient addition reduces carbon sequestration in a Tibetan grassland soil: Disentangling microbial and physical controls
文章编号: N20022616
期刊: Soil Biology and Biochemistry
作者: Ruyi Luo, Yakov Kuzyakov, Deyan Liu, Jianling Fan, Jiafa Luo, Stuart Lindsey, Jin-Sheng He, Weixin Ding
更新时间: 2020-02-26
摘要: Nitrogen (N) and phosphorus (P) availability strongly affects carbon (C) cycling and storage in terrestrial ecosystems. Nutrient addition can increase C inputs into soil via increased above- and belowground plant productivity, but at the same time can accelerate organic matter decomposition in the soil. The mechanisms underlying these effects on soil organic C (SOC) dynamics remain unclear, especially in nutrient-limited alpine ecosystems that have been subjected to increasing N and P availability in recent decades. The aim of this study was to clarify the mechanisms underlying SOC decomposition and stabilization in an alpine grassland soil after four years of N and P additions. The soil aggregate size distribution, microbial community structure (lipid biomarkers), microbial C use efficiency (CUE) and microbial necromass composition (amino sugar biomarkers) were analyzed. Nutrient addition increased dominance of fast-growing bacteria (copiotrophs), while P addition alone intensified the competitive interactions between arbuscular mycorrhizal and saprotrophic fungi. These changes led to decreases in the microbial CUE of glucose by 1.6–3.5% and of vanillin by 8.5%, and therefore, reduced SOC content in the topsoil. The total microbial necromass remained unaffected by nutrient addition, but the contribution of fungal necromass to SOC increased. The increased abundance of arbuscular mycorrhizal fungi and fungal necromass under elevated N availability raised the mass proportion of soil macroaggregates (>250 μm) by 16.5–20.3%. Therefore, fungi were highly involved in macroaggregation following N addition, and so, moderated the SOC losses through enhanced physical protection. Overall, the complex interactions between microbial physiology (CUE), necromass composition (amino sugars) and physical protection (macroaggregation) in mediating SOC dynamics in response to nutrient enrichment were disentangled to better predict the capability of alpine grassland soils to act as a C sink or source under global change.

22740. 题目: Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition
文章编号: N20022615
期刊: Proceedings of the National Academy of Sciences
作者: Laura Fierce, Timothy B. Onasch, Christopher D. Cappa, Claudio Mazzoleni, Swarup China, Janarjan Bhandari, Paul Davidovits, D. Al Fischer, Taylor Helgestad, Andrew T. Lambe, Arthur J. Sedlacek, Geoffrey D. Smith, Lindsay Wolff
更新时间: 2020-02-26
摘要: Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC’s radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model–measurement differences. We show that accounting for these two effects—variability in per-particle composition and deviations from the core-shell approximation—reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC’s radiative effect on climate.