论文检索

总访问量：2568006次

总访客量：120693人

所有论文

23561. 题目: Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw
文章编号: N19012619
期刊: Global Change Biology
作者: Carolina Voigt, Maija E. Marushchak, Mikhail Mastepanov, Richard E. Lamprecht, Torben R. Christensen, Maxim Dorodnikov, Marcin Jackowicz‐Korczyński, Amelie Lindgren, Annalea Lohila, Hannu Nykänen, Markku Oinonen, Timo Oksanen, Vesa Palonen, Claire C. Treat, Pertti J. Martikainen, Christina Biasi
更新时间: 2019-01-26
摘要: Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long‐term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO₂) and methane (CH₄) to the atmosphere, but how much, at which time‐span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland. A novel experimental approach using intact plant–soil systems (mesocosms) allowed us to simulate permafrost thaw under near‐natural conditions. We monitored GHG flux dynamics via high‐resolution flow‐through gas measurements, combined with detailed monitoring of soil GHG concentration dynamics, yielding insights into GHG production and consumption potential of individual soil layers. Thawing the upper 10–15cm of permafrost under dry conditions increased CO₂ emissions to the atmosphere (without vegetation: 0.74±0.49 vs. 0.84±0.60g CO₂–C m⁻²d⁻¹; with vegetation: 1.20±0.50 vs. 1.32±0.60g CO₂–C m⁻²d⁻¹, mean±SD, pre‐ and post‐thaw, respectively). Radiocarbon dating (¹⁴C) of respired CO₂, supported by an independent curve fitting approach, showed a clear contribution (9–27%) of old carbon to this enhanced post‐thaw CO₂ flux. Elevated concentrations of CO₂, CH₄, and dissolved organic carbon at depth indicated not just pulse emissions during the thawing process, but sustained decomposition and GHG production from thawed permafrost. Oxidation of CH₄ in the peat column, however, prevented CH₄ release to the atmosphere. Importantly, we show here that, under dry conditions, peatlands strengthen the permafrost–carbon feedback by adding to the atmospheric CO₂ burden post‐thaw. However, as long as the water table remains low, our results reveal a strong CH₄ sink capacity in these types of Arctic ecosystems pre‐ and post‐thaw, with the potential to compensate part of the permafrost CO₂ losses over longer timescales.

23562. 题目: Factors controlling the variation in organic carbon stocks in agricultural soils of Germany
文章编号: N19012618
期刊: European Journal of Soil Science
作者: C. Vos, A. Don, E.U. Hobley, R. Prietz, A. Heidkamp, A. Freibauer
更新时间: 2019-01-26
摘要: This study gives an overview of soil organic carbon (SOC) stocks in Germany's agricultural soils, and quantifies and explains the influence of explanatory variables such as land use and management, soil type and climate. Over 2500 agricultural sites were sampled and their SOC stocks determined, together with other soil properties. Machine‐learning algorithms were used to identify the most important variables. Land use, land‐use history, clay content and electrical conductivity were the main predictors in the topsoil, whereas bedrock material, relief and electrical conductivity governed the variation in subsoil carbon stocks. We found that 32% of all soil profiles were anthropogenically transformed. Influence of climate variables was surprisingly small, whereas site variables, in particular in the subsoil, explained a large proportion of the variation in soil carbon. The understanding of SOC dynamics at the regional scale requires a thorough description of the spatial variation in soil properties. The effect of agronomic management on SOC stocks was important near the soil surface, but was mainly attributable to land use (grassland or arable and not to other management factors.

23563. 题目: Shifting cultivation maintains but its conversion to mono-cropping decreases soil carbon and nitrogen stocks compared to natural forest in Western Ethiopia
文章编号: N19012617
期刊: Water, Air, & Soil Pollution
作者: Berhanu Terefe, Dong-Gill Kim
更新时间: 2019-01-26
摘要: Aims: This study was conducted to assess the effects of shifting cultivation and its conversion to mono-cropping on soil organic carbon (SOC) and total nitrogen (STN). Methods: We compared soil pH, texture, bulk density and SOC and STN contents and stocks (0–100 cm) in natural forest (NF), adjacent shifting cultivation (SC) areas (> 100 years old) having three (SC-3Y), five (SC-5Y) and seven (SC-7Y)-year-old fallowing, and 10 year-old mono-cropping field (MCF) converted from shifting cultivation in Western Ethiopia. Results: There was no significant difference in soil pH in NF and all shifting cultivation areas. However, MCF had lower soil pH compared to SC-3Y and SC-5Y. There was no or very little difference in soil texture and bulk density across the study sites. Shifting cultivation did not affect SOC and STN stocks. However, conversion of shifting cultivation to mono-cropping decreased SOC (45–50% over 10 years; loss of 11.6 ± 0.2 Mg C ha⁻¹ yr.⁻¹) and STN stocks (18–45% over 10 years; loss of 0.6 ± 0.1 Mg N ha⁻¹ yr.⁻¹). Conclusions: While shifting cultivation maintained SOC and STN, its conversion to mono-cropping decreased them, potentially contributing to global warming and decreasing soil fertility.

23564. 题目: Linear and nonlinear partition of nonionic organic compounds into resin ADS-21 from water
文章编号: N19012616
期刊: Environmental Pollution
作者: Chenkai Zhou, Long Qi, Daohui Lin, Kun Yang
更新时间: 2019-01-26
摘要: The predominance of natural organic matter (NOM) in nonlinear sorption of nonionic organic compounds (NOCs) is a fundamental behavior that controlling the fate, transfer and bioavailability of NOCs in natural environment. There is a debate, i.e., whether the nonlinear sorption is captured by nonlinear partition mechanism or adsorption mechanism. The debate has been going on for decades because characteristics of nonlinear partition are still unknown due to the lack of an adsorbent that can partition NOCs nonlinearly. We find a resin ADS-21, with specific surface area undetectable (<0.5 m² g⁻¹) but high sorption capacity for NOCs (up to 1000 mg g⁻¹ for phenol as an example), is an ideal adsorbent for examining characteristics of nonlinear partitioning. This resin has nonlinear isotherms for phenols and anilines but linear isotherms for polycyclic aromatic hydrocarbons and nitrobenzenes. The observed positively linear relationship of sorption capacities of NOCs with NOCs solubility in water or octanol, could be one of the characteristics of nonlinear partition. Moreover, competitive sorption and no desorption hysteresis could be observed for the nonlinear partition. Hydrogen-bonding of phenols and anilines with ADS-21 is responsible for nonlinear partition, competitive sorption and isotherm nonlinearity. These evidences would be supportive for understanding nonlinear partition and the nonlinear sorption of NOCs by NOM.
图文摘要:

23565. 题目: Microbial decomposition of biomass residues mitigated hydrogeochemical dynamics in strongly alkaline bauxite residues
文章编号: N19012615
期刊: Science of The Total Environment
作者: Fang You, Liping Zhang, Jun Ye, Longbin Huang
更新时间: 2019-01-26
摘要: Effective neutralization of strongly alkaline conditions in bauxite residues (BR) is the fundamental step to initiate the process of eco-engineering BR into growth substrate (or soil-like medium) for direct phytostabilization with pioneer plant species. The present study aimed to evaluate the effectiveness of microbial decomposition of organic matter (OM) (i.e., biomass residues) in neutralizing the strong alkalinity of residues under saturated conditions, together with the regulatory role of calcium sulfate (CaSO₄) addition. Admixing OM (i.e., sugarcane mulch, Lucerne hay) alone in the BR significantly lowered the porewater pH from 11.4 to around 9.0 by Day 7, which persisted until the end of incubation (Day 28). The pH reduction in the porewater of OM-amended BR coincided with the production of acidic organic compounds (mainly acetic acid). Diverse species of organotrophic bacteria (e.g., Enterobacteriales, Pasteurellales, Lactobacillales, and Streptophyta) were found to have colonized in the OM-amended BR, but which were dominated by haloalkaliphilic bacteria (e.g., Halomonas and Bacillaceae). The CaSO₄ addition in the OM-amended BR further lowered pH to 8.3 in the porewater. Besides, the bioneutralization effects resulted in dramatic reduction (>90%) of soluble Al in the porewater, which is a prerequisite to lowering Al toxicity in plants. At the same time, the levels of major cations (i.e., K, Ca, Mg) in the porewater were elevated by the OM + CaSO₄ amendment, which would facilitate subsequent leaching of these soluble salts to lower the salinity in the BR, and improve the diversity of organotrophic bacterial communities in the amended BR.
图文摘要:

23566. 题目: Enrofloxacin and copper plant uptake by Phragmites australis from a liquid digestate: Single versus combined application
文章编号: N19012614
期刊: Science of The Total Environment
作者: Stéphanie Sayen, Cristina Rocha, Cristiana Silva, Emmanuelle Vulliet, Emmanuel Guillon, C. Marisa R. Almeida
更新时间: 2019-01-26
摘要: Application of anaerobically digested sludges and manure (digestates) to agricultural fields reduces the need for fertilizer application, but might also pose environmental risks due to the introduction of various pollutants –including metal trace elements and pharmaceuticals– to amended soils. The simultaneous presence of different contaminants can affect plant uptake, altering the performance of phytoremediation. This work aims to investigate and compare the single and combined effects of Enrofloxacin (Enro) and Cu on their plant uptake from digestate solutions. Plant uptake experiments were carried out by exposing, for 5 days, Phragmites australis to three different concentrations of a liquid digestate doped with Cu and/or Enro. Contaminant concentrations were afterward determined in both plant tissues and digestate solutions. Contaminant speciation in solution and Cu speciation in plant roots were also assessed. Cu plant uptake (mostly in plant roots, Cu concentration varied between 55 and 254 μg·g⁻¹) was observed, especially at low concentration of digestate. At high digestate concentration, Cu uptake decreased due to the formation of Cu-DOC complexes rendering Cu less bioavailable. The presence of the antibiotic slightly further reduced Cu plant uptake due to the formation of Cu-Enro complexes. Plant roots also accumulated Enro, an accumulation also higher for the lowest concentration of digestate (an increase of 40%), and that slightly increased in the presence of Cu (up to 226 μg·g⁻¹). However, proportion of free Enro in solution decreased (up to 70%) in the presence of Cu due to complexation. Cu speciation in plant roots confirmed the implication of the complexation in the uptake of Cu and Enro when they are simultaneously present in solution. Thus, the presence of amendments (such as digestates) increasing the DOC content, in addition to the interactions between contaminants, should be taken into account for field crop soils as well as for phytoremediation technologies.
图文摘要:

23567. 题目: Effect of cotton straw-derived materials on native soil organic carbon
文章编号: N19012613
期刊: Science of The Total Environment
作者: Xiangyun Song, Yan Li, Xin Yue, Qaiser Hussain, Jinjing Zhang, Qinghua Liu, Shengai Jin, Dejie Cui
更新时间: 2019-01-26
摘要: Different types of crop straw and their derived biochars and compost treatments have huge potential for carbon sequestration to sustain crop productivity. In this study, cotton straw (straw), cotton straw-derived compost (compost) and cotton straw-derived biochar (biochar) with equivalent carbon (C) content were added to soil and incubated for 30 and 180 days. The C sequestration potential of these organic materials was determined by ¹³C isotope trace method. The structural characteristic of soil organic carbon (SOC) was analyzed by solid-state ¹³C NMR spectroscopy. The SOC concentration was measured by wet oxidation and dry combustion methods. The results showed that 50.84%, 41.03% and 38.55% of native SOC were replaced by biochar, compost, and straw, respectively. The carbohydrate C and methoxyl C contents were significantly higher in straw and biochar amendments respectively, while phenolic C and alkyl C were high in compost amendment and a higher proportion of aryl C occurred in biochar treatment. These findings revealed that straw material was easier to be decomposed, but compost and biochar showing better stability.
图文摘要:

23568. 题目: To burn or retain crop residues on croplands? An integrated analysis of crop residue management in China
文章编号: N19012612
期刊: Science of The Total Environment
作者: Jinghua Chen, Yazhen Gong, Shaoqiang Wang, Baozhu Guan, Juraj Balkovic, Florian Kraxner
更新时间: 2019-01-26
摘要: Crop residue burning influences human health and global climate change. In China—the world's largest crop residue producer—farmers burn almost one quarter of their crop residues in the field after harvest, despite the government providing financial incentives such as subsidies to retain crop residues. This study combined economic analyses with simulations of soil carbon accumulation and carbon emission reduction associated with different residue management practices to determine the minimum level of incentives needed for Chinese farmers to shift from burning to retaining crop residues for generating carbon benefits. Simulation results showed that [1] the density of topsoil organic carbon in China's croplands would have increased from about 21.8 t ha⁻¹ in 2000 to 23.9 t ha⁻¹ in 2010, and soil organic carbon sequestration would have reached 24.4 Tg C yr⁻¹ if farmers had shifted from burning to retaining crop residues on croplands during this period; and [2] retaining crop residues would have avoided about 149.9 Tg of CO₂ emission per year. Economic analyses showed that [1] existing subsidies in all regions of China, except Northeast China, only accounted for 18–82% of the incentives required for farmers to shift from burning to crop residue retention; [2] Northeast China required the lowest incentive (287 CNY ha⁻¹), while eastern China required the highest (837 CNY ha⁻¹); and [3] the prevailing market prices (1.4–60.2 CNY tCO₂e⁻¹) in China's seven pilot carbon markets seem to be below the required incentives (39.6–189.1 CNY tCO₂e⁻¹⁾. Our study suggests that the Chinese government should increase subsidies or seek innovative incentive schemes to encourage farmers to change their crop residue management practices for global climate change mitigation and health benefits.
图文摘要:

23569. 题目: Applying aluminum-organic matter precipitates to reduce soil permeability in-situ: A field and modeling study
文章编号: N19012611
期刊: Science of The Total Environment
作者: J. Zhou, S. Laumann, T.J. Heimovaara
更新时间: 2019-01-26
摘要: Using naturally occurring processes to modify the engineering properties of the subsurface has received increasing attention from industry and research communities as they aid in the development of cost-effective, robust and sustainable engineering technologies. In line with this trend, we propose to use precipitates of aluminum (Al) and organic matter (OM) to reduce soil permeability in-situ. This process is inspired by podzolization: a soil stratification process where a layer with low permeability is developed at depth via the precipitation of metal-OM complexes.In this study, the concept of applying Al-OM precipitates for in-situ soil permeability reduction was for the first time applied in the field. The aim of the field experiment was to create a cylindrical flow barrier in a sand layer at depth. In order to design and engineer the field application, we performed a series of scenario analyses with a site-specific 3D reactive transport model. This led to an in-situ engineering approach where a flow barrier was created by separate injection of Al and OM using a combined injection/extraction strategy. During the field application, the local variation of soil conditions required significant modifications to the design. Further scenario analyses with the model were conducted to adapt the original design and to understand the consequences of these modifications.The results show that a cylindrical flow barrier was created after an injection period of 8 days. The precipitation of Al-OM is a highly localized process, where large amount of precipitates is formed in the close vicinity of the injection filter screens. Evaluation of pumping tests that were performed after the injection activities revealed that the permeability of the treated sand was reduced to 2% of its original value. This first full-scale field test demonstrates that applying Al-OM precipitates is a suitable bio-based engineering tool to reduce soil permeability in-situ.
图文摘要:

23570. 题目: Spatial distribution of metal(loid) depletion and accumulation zones around a natural carbon dioxide degassing site
文章编号: N19012610
期刊: Chemical Geology
作者: Judith Mehlhorn, Lukas A. Gerber, Britta Planer-Friedrich
更新时间: 2019-01-26
摘要: Long-term influence of geogenic CO₂ affects soil conditions and pedogenesis. Mobilization of metals and metalloids from soil to solution has been reported to occur in natural CO₂ degassing sites, so-called mofettes. We determined metal(loid)-specific spatial distribution patterns in soil around a mofette as well as metal(loid) pore water concentrations along a CO₂ gradient (0–98% CO₂ in soil air). Depletion of Mn, Co, and Ni in soil in the mofette center was caused by leaching due to the long-term soil acidification leading to correspondingly low pore water concentrations and thus indicating no recent influence of CO₂ on metal(loid) mobility. Iron and As were also depleted in soil within the mofette center where pedogenic Fe (oxyhydr)oxides could not form due to absence of oxygen. Small-scale variations in redox conditions lead to ongoing Fe cycling and the repeated reduction of Fe (oxyhydr)oxides resulted in increased Fe and As pore water concentrations at high CO₂. Precipitation in form of sulfide minerals caused immobilization and accumulation of Cd, Cu, and Zn directly in the degassing center. The highest mobilization risk occurred within 2–4 m distance from the degassing center, where complexation with dissolved organic matter (DOM) increased the mobility of Al, As, Cr, Cu, Fe, and Zn. Our results show that CO₂ as soil-forming factor influences the spatial distribution of metal(loid)s. The highest metal(loid) mobilization risk after long-term CO₂ influence arises from accumulation of scarcely degraded organic matter, which can easily dissolve and form mobile metal(loid)-DOM complexes.
图文摘要:

23571. 题目: A critical reevaluation of palaeoclimate proxy records from loess in the Carpathian Basin
文章编号: N19012609
期刊: Earth-Science Reviews
作者: Igor Obreht, Christian Zeeden, Ulrich Hambach, Daniel Veres, Slobodan B. Marković, Frank Lehmkuhl
更新时间: 2019-01-26
摘要: In the Carpathian Basin, loess is the most important archive of Quaternary palaeoclimate evolution, but only in the past two decades systematic and high-resolution investigations were conducted. Those studies remarkably improved our knowledge of the regional past environmental change; palaeoclimate inferences based on the magnetic susceptibility and grain-size distribution, as the most commonly used palaeoenvironmental proxies for the Carpathian Basin loess, indicate colder and drier climatic conditions during glacials when compared to interglacials. With an increasing number of studies using novel proxies in loess research, such a traditional understanding of dry and cold glacials and humid and warm interglacials in the Carpathian Basin has been questioned. As an illustrative example, mollusc-based climate reconstructions suggest generally warm and very dry summer conditions with mean July temperatures up to 21 °C for the southern Carpathian Basin during the last glacial. Results based on stable carbon isotopes strongly oppose such high summer temperatures, but studies based on n-alkanes are in general agreement with the mollusc data when it comes to the vegetation reconstruction indicating mostly steppic conditions. However, n-alkanes studies contradict warm and dry glacial conditions as indicated by mollusc-based reconstructions, pointing instead to cold and relatively humid glacials. In addition, there is an ongoing debate whether or not millennial-scale climatic oscillations can be observed in the Carpathian Basin loess, as well as whether this area was an important Northern Hemisphere dust source or rather a sink of far distance dust transport. Consequently, the current state of the art of the palaeoclimate reconstructions from loess in the Carpathian Basin is rather inconsistent.In order to “make sense” of the existing palaeoclimate data from the Carpathian Basin loess, we have reevaluated and reinterpreted the available data. We discuss and propose a coherent interpretation of rock magnetic, grain-size, malacological, stable carbon and nitrogen isotope, n-alkane and bacterial membrane lipid data for the last glacial cycle loess archives from the Carpathian Basin. We show that glacial conditions in the Carpathian Basin led to a notable increasing North-South gradient in temperature and an even stronger expressed decreasing trend in humidity, and that most of the biomarker proxy data conducted in loess for the very dry southern part of the Carpathian Basin show a strong bias towards arid conditions. In particular, palaeotemperature reconstructions seem to be misleading. Glacial conditions were drier and colder than previously proposed (summer temperatures likely under 15 °C during glacials), but notably warmer than in other parts of Western, Central, and Eastern Europe. The vegetation consisted mostly of steppic environments during both, glacials and interglacials. We indicate that the Carpathian Basin has a potential to be a major dust source of the Northern Hemisphere during glacials, although it was at the same time exposed to the deposition of fine far distance travelled dust. Moreover, the main issues in the regional and continental correlation of loess are highlighted, as well as the sensitivity of the Carpathian Basin loess to the millennial-scale climate variability recorded in other Northern Hemisphere records. Finally, we suggest that the onset of loess formation in the investigated area occurred during the Middle Pleistocene Transition, and it was probably related to intensive silt production related to glacier dynamics in the Alpine ice cap.

23572. 题目: Concurrent adsorption and micro-electrolysis of Cr(VI) by nanoscale zerovalent iron/biochar/Ca-alginate composite
文章编号: N19012608
期刊: Environmental Pollution
作者: Zhonghao Wan, Dong-Wan Cho, Daniel C.W. Tsang, Meng Li, Tan Sun, Francis Verpoort
更新时间: 2019-01-26
摘要: This study introduced a new approach for simultaneously enhancing Cr(VI) removal performance and mitigating release of dissolved Fe during nanoscale zero-valent iron (nZVI)-mediated reactions. After entrapping nZVI-impregnated biochar (BC) in the matrix of calcium-alginate (CA) bead, the physicochemical characterization of nZVI/BC/CA composites revealed that nZVI/BC particles were embedded inside CA having a spherical shape and several cracks on its outer layer. The multi-functionality of nZVI/BC/CA composites consisting of reductant (nZVI), porous adsorbent (BC), and external screening layer (CA) enhanced the removal of Cr(VI) with the maximum adsorption capacity of 86.4 mg/g (based on the Langmuir isotherm) and little release of dissolved Fe. With the XPS analysis and fitting results of kinetics (pseudo second order) and isotherms (Redlich-Peterson model), plausible removal mechanisms of Cr(VI) were simultaneous adsorption and micro-electrolysis reactions by nZVI/BC/CA composites. The practical applicability of nZVI/BC/CA composites was further demonstrated through the fixed-bed column experiments. These results provide new insights into the design of high-performance engineered biochar for wastewater treatment.
图文摘要:

23573. 题目: Aged biochar alters nitrogen pathways in bauxite-processing residue sand: Environmental impact and biogeochemical mechanisms
文章编号: N19012607
期刊: Environmental Pollution
作者: M. Rezaei Rashti, M. Esfandbod, I.R. Phillips, C.R. Chen
更新时间: 2019-01-26
摘要: Low nitrogen (N) content and retention in bauxite-processing residue sand (BRS) disposal areas pose a great challenge to the establishment of sustainable vegetation cover in this highly alkaline environment. The budget and fate of applied N in BRS and its potential environmental impacts are largely unknown. We investigated the effect of combined application of biochars [aged acidic (AC) vs alkaline pine (PC)] and di-ammonium phosphate (DAP) fertiliser on ammonia (NH₃) volatilisation, nitrous oxide (N₂O) emission and N retention in a 116-day glasshouse study. The application of AC to BRS decreased pH (≈0.5 units) in BRS, while PC biochar increased pH (≈0.3 units). The application of AC reduced NH₃ volatilisation by ca. 80%, while PC by ca. 25%. On the other hand, the AC treatment increased N₂O emission by 5 folds. However, the N loss via N₂O emission in the AC treatment only accounted for ca. 0.4% of applied N. The reduction in BRS pH and increased retention of mineral N due to the presence of oxygen-containing (phenolic and carboxylic) functional groups in AC may be responsible for reduced NH₃ volatilisation and increased N₂O emission. This study has highlighted the potential of biochar (particularly aged biochar) in improving N retention and minimising environmental impacts in highly alkaline environments.
图文摘要:

23574. 题目: Iron uptake by bloom-forming freshwater cyanobacterium Microcystis aeruginosa in natural and effluent waters
文章编号: N19012606
期刊: Environmental Pollution
作者: Qing-Long Fu, Manabu Fujii, Masafumi Natsuike, T. David Waite
更新时间: 2019-01-26
摘要: Studies on Fe uptake by phytoplankton have been often conducted using artificial culture media. However, Fe chemistry in freshwater can be influenced by riverine anthropogenic impacts and other factors causing water quality changes. In this study, therefore, Fe uptake in natural (river and reservoir) and effluent waters was investigated for the notorious bloom-forming freshwater cyanobacterium Microcystis aeruginosa. To investigate the Fe uptake mechanism, a short-term incubational assay was conducted in the presence of light, Fe(II) ligand and Fe(III) reductant, with results consistently indicating that unchelated Fe(III) is the major substrate for Fe uptake by M. aeruginosa. Further assays using various freshwater samples indicated that Fe uptake is lower in natural waters compared to that of effluent waters and, interestingly, Fe uptake was found to be limited in natural waters. These results suggest that Fe limitation can be alleviated by the inflow of effluent waters. Statistical analysis with various water quality variables indicated that Fe availability is significantly influenced by concentrations of dissolved Fe and organic matter as well as specific UV absorbance (an index of aromaticity). Overall, findings of this study highlight that watershed anthropogenic activities exert important roles in Fe uptake by freshwater cyanobacteria via alteration of Fe speciation.
图文摘要:

23575. 题目: When drought meets forest management: Effects on the soil microbial community of a Holm oak forest ecosystem
文章编号: N19012605
期刊: Science of The Total Environment
作者: F. Bastida, R. López-Mondéjar, P. Baldrian, M. Andrés-Abellán, N. Jehmlich, I.F. Torres, C. García, F.R. López-Serrano
更新时间: 2019-01-26
摘要: The growth and survival of plants in semiarid Mediterranean forests can be improved through the benefits conferred by thinning, a forest management practice that removes trees and reduces the competition between the remaining ones. Here, we evaluate the impacts of induced drought (the exclusion of 25% of the natural rainfall for 5 years) and thinning, and their interaction, with the objective of determining whether the thinning of Holm oak (Quercus ilex L.) modulates the resistance of the soil microbial community to drought. Sequencing of 16S rRNA and ITS amplicons revealed that drought, thinning, and their interaction influenced the composition of the bacterial community, while the fungal community was exclusively affected by thinning. Thinning consisted of the removal of the aboveground parts of the Holm oak trees, which were thereafter left in forest stand. Thinning contributed to the C and N contents, with parallel increases in microbial biomass, particularly in summer. Drought increased the amounts of total organic C and total N, likely due to the reduced enzyme activities. Indeed, the composition of the bacterial community was modulated primarily by the indirect and long-term effects of drought - the accumulation of soil organic matter - rather than by the direct effect of the lower water content imposed by the drought treatments. Thinning under drought conditions did not increase soil organic C (SOC) content. However, the resistance of the soil microbial community to drought was fostered by thinning, particularly at the functional level, as indicated by the enzyme activities related to C, N and P cycles. These responses were associated to variations in the composition of the microbial communities in thinned, drought-exposed plots, in comparison to unthinned, drought-exposed plots. In conclusion, the interaction between forest management and drought influenced the soil microbial community of a Holm oak-dominated Mediterranean ecosystem.
图文摘要:

23576. 题目: Depolymerization of lignocellulose of oil palm empty fruit bunch by thermophilic microorganisms from tropical climate
文章编号: N19012604
期刊: Bioresource Technology
作者: Nadia Farhana Azman, Megat Johari Megat Mohd Noor, Fazrena Nadia MD Akhir, Ang May Yen, Hazni Hashim, Nor'Azizi Othman, Zuriati Zakaria, Hirofumi Hara
更新时间: 2019-01-26
摘要: Previous studies on screening of lignin-degrading bacteria mainly focused on the ligninolytic ability of the isolated bacteria for the utilization of lignin monomers. In this study, we focused on the depolymerization of alkali lignin to prove the ability of the isolated thermophilic bacterial strains to utilize and depolymerize more than a monomer of alkali lignin within 7 days of incubation. Indigenous thermophilic bacterial isolates from the palm oil plantation were used to evaluate the depolymerization and utilization of alkali lignin. The confirmation of the bacterium-mediated depolymerization of oil palm empty fruit bunch was achieved through the removal of silica bodies, as observed with scanning electron microscopy. Stenotrophomonas sp. S2 and Bacillus subtilis S11Y were able to reduce approximately 50% and 20% of alkali lignin at 7 days of incubation without the requirement for additional carbon sources.

23577. 题目: A green and robust method to measure nanomolar dissolved organic nitrogen (DON) by vacuum ultraviolet
文章编号: N19012603
期刊: Chemical Engineering Journal
作者: Yi Chen, Junli Wang, Baiyang Chen, Lei Wang
更新时间: 2019-01-26
摘要: Quantifying trace dissolved organic nitrogen (DON) in water is currently challenging for conventional methods not only because of the presence of dissolved inorganic nitrogen (DIN) species, which usually dominate in total nitrogen (TN), but also because of the high method detection limits (MDLs) of current TN methods, which are ≥100 μg/L. In order to overcome these barriers, an earlier study has applied electrodialysis to eliminate DINs from water, thereby reducing the interference of DIN. However, it remains difficult to analyze DON at nanomolar level. To address this issue, this study proposes to convert DON completely into DIN by vacuum ultraviolet irradiation (VUV) and then to measure DON by the sum of DINs (i.e., ammonia, nitrite, and nitrate). A number of verification tests show that the proposed method had comparable results with conventional methods for selected model compounds and real samples. The average nitrogen recovery for sixteen model DON compounds (each at 2.0 mg-N/L) with varying structures and molecular weights was 89 ± 16%, similar to those obtained by thermal-activated persulfate oxidation (87 ± 18%) and high temperature catalytic oxidation (86 ± 20%) methods. Moreover, this method features an advantage that it reached a MDL of 1.5 μg-N/L, much lower than conventional TN methods. With a prolonged 12-h irradiation, this approach was able to convert ammonia completely into nitrate, thus enabling detection of DON by using ion chromatography only.
图文摘要:

23578. 题目: Prescribed fire affects the concentration and aromaticity of soluble soil organic matter in forest soils
文章编号: N19012602
期刊: Geoderma
作者: Eleanor U. Hobley, Lena C. Zoor, Hari R. Shrestha, Lauren T. Bennett, Christopher J. Weston, Thomas G. Baker
更新时间: 2019-01-26
摘要: Prescribed burning is used widely across Australia to reduce fuel load and associated wildfire hazard. However, prescribed burning can influence carbon (C) storage in affected ecosystems, potentially influencing C cycling. One important component of the C cycle is soluble C, which is available to microorganisms and therefore a key driver of nutrient cycling. However, studies of the effects of fire on soluble C in natural ecosystems are few. In this study, UV–Vis spectra of water extracts of soils from an Australian Eucalyptus forest were used to investigate soluble soil C characteristics to 30 cm depth after autumn burning every three or ten years for three decades contrasted with long non-burnt controls. A random forest prediction model was fit to the UV–VIS spectra and the wavelengths important to predicting soluble C investigated using conditional inference trees. The main absorbance of the UV–Vis spectra was in the aromatic region (~280 nm) indicating chemically complex soluble organic matter in both burnt and non-burnt soils. Water extractable organic carbon decreased significantly with depth and was reduced by 3-yearly burning in surface soils. Furthermore, burning, irrespective of treatment, led to significant shifts in the locations of soil spectra peaks, which were consistent with both lower quantities of non-aromatic substances and less substituted aromatic substances in the burnt than non-burnt sites. These results indicate that repeated prescribed fire over decades reduced the quantity of soluble C, and enhanced its aromaticity, potentially reducing biological availability and therefore nutrient cycling in the soils.

23579. 题目: Riverine mixing at the molecular scale – An ultrahigh-resolution mass spectrometry study on dissolved organic matter and selected metals in the Amazon confluence zone (Manaus, Brazil)
文章编号: N19012601
期刊: Organic Geochemistry
作者: C. Simon, H. Osterholz, A. Koschinsky, T. Dittmar
更新时间: 2019-01-26
摘要: The Amazon delivers a fifth of the global continental runoff and riverine dissolved organic carbon (DOC) to the ocean. Intensified biogeochemical processes are expected at the junction of the Amazon’s major blackwater tributary, the Rio Negro, and its parent, the Rio Solimões, due to large gradients in pH, conductivity, DOC and particle load. Dissolved organic matter (DOM) plays a major role in aquatic biogeochemical processes which are poorly understood on the molecular level. To gain insights into the potential role of DOM in non-conservative processes, we assessed dynamics of Cu, Fe and DOM by ultrahigh resolution mass spectrometry in: (1) endmembers, (2) regional samples and (3) laboratory mixing experiments under presence/absence of natural particles (> 0.2 μm). The relative abundances of 3,600 DOM molecular formulae were interpreted via multivariate statistics which revealed major dynamics in the DOM molecular composition. More than 40% of molecular formulae displayed conservative behavior even in the presence of natural particles, agreeing with bulk DOC behavior, but opposing the often-presumed non-conservative behavior of DOM. Another 16–27% of formulae fluctuated in FT-ICRMS signal intensity during mixing, but did not show consistent non-conservative behavior. Both rivers left a clear molecular imprint within the DOM of the Amazon, each being linked to > 800 molecular formulae. Characteristic for the Rio Negro was a dominance of phenolics with a wide molecular mass range (centered at ∼ 400 Da), and for the Rio Solimões more saturated but lower-molecular mass compounds (centered at ∼ 300 Da). Both Fe and Cu showed distinct non-conservative mixing patterns under particle presence. In the controlled mixing experiments including original particles at natural concentration, up to 0.5 μg L^-1 Cu was released from the particles into solution at 20–40% blackwater contribution. Our molecular analysis revealed distinct DOM compositional changes in polyphenol- and nitrogen-containing formulae paralleling this release, suggesting links to desorption of potential ligands and charge-induced effects at particle surfaces caused by pH and conductivity changes in the course of mixing.
图文摘要:

23580. 题目: Effect of low intensity sonic mediated fragmentation of anaerobic granules on biosurfactant secreting bacterial pretreatment: Energy and mass balance analysis
文章编号: N19012513
期刊: Bioresource Technology
作者: S. Kavitha, R. Yukesh Kannah, M. Gunasekaran, Dinh Duc Nguyen, Ala'a Hamed Al-Muhtaseb, Jeong-Hoon Park, J. Rajesh Banu
更新时间: 2019-01-25
摘要: In this study, fragmentation of anaerobic granules (AG) was carried out by low intensity sonification (LIS) to release its extracellular polymeric substance (EPS). The experimental outcome of the study shows that 30 sec treatment time and 60 W sonic power was effective for fragmentation of AG. The fragmented anaerobic granules were further subjected to pretreatment by biosurfactant secreting bacteria. Bacterial pretreatment achieves a maximum biogranules lysis of 20.3 % and biosolids reduction of 17.1 % for fragmented anaerobic granules bacterial pretreatment (FAG-BP). Whereas for bacterial pretreatment (BP) alone, it achieves 10.9 % and 8.6% of biogranules lysis and biosolids reduction respectively. Exponential first order kinetic model of biomethane production data revealed greater biomethane production for FAG-BP (0.247 g COD/ g COD) than BP (0.131 g COD/ g COD). Cost analysis of FAG mediated bacterial pretreatment results in a net profit of 48.606 USD/Ton.
图文摘要: