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25641. 题目: Low operating pressure nanofiltration membrane with functionalized natural nanoclay as antifouling and flux promoting agent
文章编号: N18101307
期刊: Chemical Engineering Journal
作者: R. Nidhi Maalige, Kanakaraj Aruchamy, Ashesh Mahto, Vibha Sharma, D. Deepika, Dibyendu Mondal, Sanna Kotrappanavar Nataraj
更新时间: 2018-10-13
摘要: Exceptionally successful conventional bilayer system of thin film composite (TFC) polyamide nanofiltration and reverse osmosis (NF/RO) membranes are gradually facing several challenges, including trade-off relationship between flux and rejection due to high tendency to fouling. Herein, we demonstrate preparation of nanocomposite membranes comprising functionalized natural clay Bentonite in polyamide selective layer as flux promoting and antifouling agent for NF applications. Herein, the sulfonated clay was induced in polyamide selective layer via modified interfacial polymerization method. Polyamide (PA) thin selective layer on polysulfone (PSf) ultrafiltration membrane was used as support for both facial coating on fabric support as well as free standing membranes. Morphology of modified PA layer was considerably altered by introduction of functionalized nanoclay. Further, membranes were characterized for their functionality, and morphologies using ATR-IR and field emission scanning electron microscopy (FESEM), respectively. Membrane performance in NF processes was evaluated in terms of pure water flux, commercial standard MgSO₄ salt (>20%) and malachite green oxalate dye (>98%) rejections. The anti-fouling studies were performed using humic acid feed. At low operating pressure modified membrane showed exceptional flux reclamation potential (3–4 fold) making it economical for NF process operations. Hydrophilicity characteristics of pristine and modified membranes were recorded using contact angle measurements.

25642. 题目: A recyclable nanosheet of Mo/N-doped TiO₂ nanorods decorated on carbon nanofibers for organic pollutants degradation under simulated sunlight irradiation
文章编号: N18101306
期刊: Chemosphere
作者: Jinli Qiu, Fuqiang Liu, Cailiang Yue, Chen Ling, Aimin Li
更新时间: 2018-10-13
摘要: A novel nanosheet of Mo/N-codoped TiO₂ nanorods immobilized on carbon nanofibers (MNTC nanosheet) was self-synthesized through two facile steps. The Mo/N-doped TiO₂ nanorods dispersed through in situ growth on the network constructed by long and vertical carbon nanofibers (CNFs). The fabricated MNTC nanosheet displayed superb photocatalytic activity of methylene blue (MB), and the degradation ratio by the MNTC nanosheet was nearly twice than that of pure nanoparticles. The photocatalytic activities during the degradation process in the presence of environmental media such as inorganic salts and natural organic matter (NOM) were also determined. Intermediates were analyzed by ion chromatography and electrospray ionization-mass spectrometry to unravel the potential degradation pathways, and the excellent mineralization ratio for MB over MNTC nanosheet was 79.8%. The trapping active species experiments verified that h⁺ was the main active species in the degradation process. Notably, the recycling experiment proved that the MNTC nanosheet was more stable, and it was successfully applied in purifying practical wastewater. Lastly, the fabricated MNTC nanosheet also displayed remarkable degradation performance towards sulfamethoxazole and bisphenol A.
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25643. 题目: Enzymatic pretreatment of lignocellulosic biomass for enhanced biomethane production-A review
文章编号: N18101305
期刊: Journal of Environmental Management
作者: E. Hosseini Koupaie, S. Dahadha, A.A. Bazyar Lakeh, A. Azizi, E. Elbeshbishy
更新时间: 2018-10-13
摘要: The rapid depletion of natural resources and the environmental concerns associated with the use of fossil fuels as the main source of global energy is leading to an increased interest in alternative and renewable energy sources. Particular interest has been given to the lignocellulosic biomass as the most abundant source of organic matter with a potential of being utilized for energy recovery. Different approaches have been applied to convert the lignocellulosic biomass to energy products including anaerobic digestion (AD), fermentation, combustion, pyrolysis, and gasification. The AD process has been proven as an effective technology for converting organic material into energy in the form of methane-rich biogas. However, the complex structure of the lignocellulosic biomass comprised of cellulose, hemicelluloses, and lignin hinders the ability of microorganisms in an AD process to degrade and convert these compounds to biogas. Therefore, a pretreatment step is essential to improve the degradability of the lignocellulosic biomass to achieve higher biogas rate and yield. A system that uses pretreatment and AD is known as advanced AD. Several pretreatment methods have been studied over the past few years including physical, thermal, chemical and biological pretreatment. This paper reviews the enzymatic pretreatment as one of the biological pretreatment methods which has received less attention in the literature than the other pretreatment methods. This paper includes a review of lignocellulosic biomass composition, AD process, challenges in degrading lignocellulosic materials, the current status of research to improve the biogas rate and yield from the AD of lignocellulosic biomass via enzymatic pretreatment, and the future trend in research for the reduction of enzymatic pretreatment cost.
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25644. 题目: Algal fouling control in a hollow fiber module during ultrafiltration by angular vibrations
文章编号: N18101304
期刊: Journal of Membrane Science
作者: Yan Zhang, Xiaolei Li, Rongwei Xu, Chengwu Ma, Xinyi Wang, Qiang Fu
更新时间: 2018-10-13
摘要: In this work, a lab-scale membrane system was developed to accommodate angular vibrations with a hollow fiber module. A series of filtration experiments were designed and implemented to investigate the effects of angular vibrations on fouling by various algae-derived foulants, including algal cells, debris, extracellular organic matter (EOM), and intracellular organic matter (IOM). The experimental results indicated the effects of angular vibrations on fouling mitigation at the frequency of 2 Hz in the following order: algal cells (~97.4%) > debris (~93.6%) > IOM (~81.8%) > EOM (~52.3%). The vibrations mainly targeted the cake layer formed by these foulants, but was ineffective for pore blocking which constituted a large portion of EOM fouling. Although the fouling rates were accelerated during the normal ultrafiltration of the combined foulants, the effects of angular vibrations continued to be impressive (67.8–92.6%). This was because the cake layer formation was the dominant fouling mechanism. Furthermore, the vibrations were found to improve the organic removal by alleviating concentration polarization. In this paper, quantitative analysis is presented to demonstrate the potential of angular vibrations to control algal fouling with the relatively low energy consumption of 0.034 mW.
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25645. 题目: Biochar increased field soil inorganic carbon content five years after application
文章编号: N18101303
期刊: Soil and Tillage Research
作者: Xinliang Dong, Bhupinder Pal Singh, Guitong Li, Qimei Lin, Xiaorong Zhao
更新时间: 2018-10-13
摘要: Soil inorganic carbon (SIC) plays an important role in terrestrial ecosystem carbon cycling, especially in arid and semi-arid areas. Biochar has becoming a great of interest as a mean for carbon sequestration, resulting from its high content of carbon and long-term persistence in soil. Moreover, there is abundance of information about the effect of biochar on the turnover of soil organic carbon; however, up to date, no study has been done on the impact of biochar on soil inorganic carbon pool despite biochar contains inorganic carbon. This study was conducted in a long-term field condition to investigate the effect of different biochar application rates (0, 30, 60 and 90 t ha⁻¹) on soil inorganic carbon content and composition in the soil profile (0–100 cm). Using stable δ¹³C isotope signatures, the SIC was distinguished into lithogenic and pedogenic inorganic carbon. The results showed that long-term biochar application, at 30, 60 and 90 t ha⁻¹, increased soil total inorganic carbon by 18.8, 42.4 and 62.3% and native soil inorganic carbon by 7.8, 20.2 and 28.3%, respectively, in the 0–20 cm soil layer. Biochar application at these rates also increased total inorganic carbon in the 20–40 cm soil layer by 13.4, 22.8 and 30.5%, respectively, but did not influence the total inorganic carbon content below the 40 cm soil depth. Moreover, as biochar application rate increased, δ¹³C of native soil inorganic carbon decreased, which indicated that pedogenic inorganic carbon was formed. Biochar application rates were positively related to the pedogenic inorganic carbon contents, however, it did not influence the lithogenic inorganic carbon contents. This is the first study about the effect of biochar application on native inorganic carbon content and its composition, which strengthens the understanding about the role of biochar in soil C sequestration.

25646. 题目: Different efficiencies of grain legumes in crop rotations to improve soil aggregation and organic carbon in the short-term in a sandy Cambisol
文章编号: N18101302
期刊: Soil and Tillage Research
作者: Miguel Oliveira, Pierre Barré, Henrique Trindade, Iñigo Virto
更新时间: 2018-10-13
摘要: Legume plants can promote C storage by enhancing the formation and stabilization of soil aggregates that protect soil organic C (SOC) from mineralization. However, this effect can vary with soil biochemical properties, environmental conditions and legume species. This work aimed to test if including grain legumes in rotation with cereals in a sandy acid soil in a Mediterranean climate can enhance aggregation and SOC storage. Triticale (× Triticosecale ‘Alter’ cv.) fodder was monocultivated with and without synthetic-N fertilizer and in rotation either with irrigated cowpeas (Vigna unguiculata’ Fradel’ cv.), rainfed faba beans (Vicia faba ‘Favel’ cv.) or peas (Pisum sativum ‘Grisel’ cv.) in a sandy loam Cambisol for three years. Legume residues were incorporated into the soil after grain harvest. Crop yields and respective organic C inputs were determined. Topsoil (0–20 cm) samples were analyzed for clay-size minerals mineralogy and mass and C distribution in aggregate-size fractions obtained by wet-sieving. SOC stocks were calculated before and after the trial and in non-cultivated controls. Despite differences in C inputs to the soil, SOC storage was not enhanced with legume cultivation. This may be due to the short duration of the experiment or to the low clay content (10%) and very low reactivity of the clay-size minerals (kaolinite-dominated) of the soil, which seem to have weakened SOC protection. However, non-cultivated controls had up to three times higher SOC stocks, indicating that organic C can be stored in this soil under adequate conditions. Nonetheless, a legume-effect on soil aggregation was observed. Introducing irrigated cowpea in the rotation maintained soil structure, as evidenced by a similar macroaggregate (>250 μm, Magg) content to the baseline, which was deteriorated in the fertilized cereal monoculture in the respective site (less Magg than the baseline). Furthermore, including rainfed faba bean in the rotation improved the soil structure (more Magg than the baseline), which was similar to the baseline when pea was used instead or when cereal was monocropped with synthetic N fertilizer. We conclude that including legumes in rotation with cereal can benefit soil structure in the short-term in the studied edaphoclimatic conditions, but these benefits depend on legume species and agricultural management. However, beneficial effects in SOC stock seem not to be attainable in these conditions in such a short period.

25647. 题目: Trophic relationships of deep-sea benthic invertebrates on a continental margin in the NW Atlantic inferred by stable isotope, elemental, and fatty acid composition
文章编号: N18101301
期刊: Progress in Oceanography
作者: Camilla Parzanini, Christopher C. Parrish, Jean-François Hamel, Annie Mercier
更新时间: 2018-10-13
摘要: As deep-sea benthic ecosystems of continental margins provide numerous functions and services to humans, a better understanding of these key habitats and their communities is needed to help predict climate-driven shifts and support conservation efforts. Here stable isotope (δ¹³C and δ¹⁵N), elemental (%C, %N, and molar C:N), and fatty acid (FA) composition of 50 different deep-sea species, belonging to 7 major taxa, were analyzed in order to characterize their diet and trophic position, and to study the fate of energy and essential nutrients in the food web. In addition, relationships between depth and biochemical signatures (δ¹³C, δ¹⁵N, %C, %N, C:N_m, and FAs) were also investigated, and %C, oleic acid (18:1ω9), and arachidonic acid (ARA, 20:4ω6) were found to increase with depth. While the increase of %C was likely due to the preferential assimilation of the more nutritious N along the gradient, that of 18:1ω9 was presumed to reflect the need for longer-term energy reserves in deeper organisms, and that of ARA to indicate a higher reliance on the benthic trophic pathway at greater depth. Analyses also revealed that the focal deep-sea invertebrates occupied three trophic levels, whereas the weak correlation between δ¹³C and δ¹⁵N indicated that two or more trophic pathways were represented. Several feeding modes were also recognized within the assemblage. The lowest trophic positions were occupied by sponges selectively feeding on bacteria. Intermediate positions were mainly occupied by suspension feeders (e.g. sea anemones, corals), detritivores (e.g. the sea urchin Phormosoma placenta), and predators on small infaunal animals (e.g. the sea star Leptychaser arcticus). Conversely, predator/scavengers (e.g. various sea stars, gastropods, polychaete worms) occupied the highest trophic positions, together with sponges that were determined to be either carnivorous (e.g. Iophon piceum), or to feed on ¹⁵N- and ¹³C-enriched organic matter. Energetic compounds (i.e. 20:1ω11(13), 20:1ω9, and 22:1ω7) and essential nutrients (i.e. ARA) were found to increase in proportion across trophic levels throughout this food web, emphasizing the importance of certain dietary FAs for optimal organism health, and the key role of benthic communities in carbon cycling.

25648. 题目: Multiple models and experiments underscore large uncertainty in soil carbon dynamics
文章编号: N18101219
期刊: Biogeochemistry
作者: Benjamin N. Sulman, Jessica A. M. Moore, Rose Abramoff, Colin Averill, Stephanie Kivlin, Katerina Georgiou, Bhavya Sridhar, Melannie D. Hartman, Gangsheng Wang, William R. Wieder, Mark A. Bradford, Yiqi Luo, Melanie A. Mayes, Eric Morrison, William J. Riley, Alejandro Salazar, Joshua P. Schimel, Jinyun Tang, Aimée T. Classen
更新时间: 2018-10-12
摘要: Soils contain more carbon than plants or the atmosphere, and sensitivities of soil organic carbon (SOC) stocks to changing climate and plant productivity are a major uncertainty in global carbon cycle projections. Despite a consensus that microbial degradation and mineral stabilization processes control SOC cycling, no systematic synthesis of long-term warming and litter addition experiments has been used to test process-based microbe-mineral SOC models. We explored SOC responses to warming and increased carbon inputs using a synthesis of 147 field manipulation experiments and five SOC models with different representations of microbial and mineral processes. Model projections diverged but encompassed a similar range of variability as the experimental results. Experimental measurements were insufficient to eliminate or validate individual model outcomes. While all models projected that CO₂ efflux would increase and SOC stocks would decline under warming, nearly one-third of experiments observed decreases in CO₂ flux and nearly half of experiments observed increases in SOC stocks under warming. Long-term measurements of C inputs to soil and their changes under warming are needed to reconcile modeled and observed patterns. Measurements separating the responses of mineral-protected and unprotected SOC fractions in manipulation experiments are needed to address key uncertainties in microbial degradation and mineral stabilization mechanisms. Integrating models with experimental design will allow targeting of these uncertainties and help to reconcile divergence among models to produce more confident projections of SOC responses to global changes.

25649. 题目: Effects of termite foraging activity on topsoil physical properties and water infiltration in Vertisol
文章编号: N18101218
期刊: Applied Soil Ecology
作者: Sougueh Cheik, Nicolas Bottinelli, Benoit Soudan, Ajay Harit, Ekta Chaudhary, Raman Sukumar, Pascal Jouquet
更新时间: 2018-10-12
摘要: In the tropics, termites are key litter decomposers and soil bioturbators. Termite foraging activity involves the production of sheetings and galleries that influence the physical, chemical and hydraulic properties of soils. The functional impacts of these biogenic structures and biopores have been acknowledged for a long time in soils dominated by 1:1 minerals. Less is known, however, on their functional impacts in soils dominated by 2:1 minerals, such as vertisol which represent 22% of the land surface in India. Therefore, an experiment was carried out in a vertisol in southern India where elephant (Elephas maximus) dung pats (ED) and Lantana camara twigs (LT) were applied on the ground and protected (+) or not (−) from termite activity. Termite activity was only measured below ED−, showing a clear preference for organic matter derived from elephant dung. Soil sheetings had similar properties to the surrounding topsoil, with the exception of their C content that was reduced. This result raised the question of the origin of the soil used by termites for covering ED. ED− was also associated with the presence of effective macropores up to 5 cm depth and a significant increase in water hydraulic conductivity (12-fold). However, the utilization of the coefficient of linear extensibility showed that these galleries were unstable and most likely short-lived. In conclusion, this study confirmed that the structure of soils dominated by 2:1 minerals is mainly controlled by physical processes (i.e., the shrinking and swelling of soils). This study also stresses the need to better understand the dynamic of termite galleries in soil and to quantify the origin and fate of organic matter in soil sheetings.

25650. 题目: Appraising the effect of in-situ remediation of heavy metal contaminated sediment by biochar and activated carbon on Cu immobilization and microbial community
文章编号: N18101217
期刊: Ecological Engineering
作者: Wei Que, Ya-hui Zhou, Yun-guo Liu, Jun Wen, Xiao-fei Tan, Si-jia Liu, Lu-hua Jiang
更新时间: 2018-10-12
摘要: The immobilization of heavy metal Cu with rice husk biochar (RHB) and activated carbon (AC) addition were compared by in-situ remediation of sediment in this research. The RHB and AC were characterized using SEM, FTIR, XRD, XPS, Raman and BET surface area measurements. Heavy-metal contaminated sediments were immobilized by RHB and AC with the addition amount of 2%, 5% and 10% (w/w). The sequential extraction experiment demonstrated that the acid-soluble fractions of Cu were reduced by 48%–93% and 18%–31% with the treatment of AC and RHB, respectively. With the decrease of acid-soluble fractions of Cu, the results showed that the surface water concentration of Cu decreased by 32%–68% and 8%–60% with the treatment by AC and RHB, respectively. The Cu concentration of interstitial water decreased by 14.8%–63% and 11.1%–48.1% with the treatment by AC and RHB, respectively. Meanwhile, hierarchical cluster analysis which was used for the detection of microbial community was conducted. The results showed that the microbial community was destroyed in the sediment treatment with high amount of AC. However, new microbial community appeared in the sediment treatment with three addition amount of RHB. Based on the data analysis, AC was more effective than RHB on Cu immobilization in the sediment. Unfortunately, AC was more expensive than RHB and had potential negative effect on microbial community. By comparing these aspects comprehensively, our results suggest that the RHB would be a low-cost and environmentally friendly material for heavy-metal contaminated site remediation.

25651. 题目: Biochar vs. clay: Comparison of their effects on nutrient retention of a tropical Arenosol
文章编号: N18101216
期刊: Geoderma
作者: Christine Beusch, Arne Cierjacks, Johannes Böhm, Jan Mertens, Wolf-Anno Bischoff, José Coelho de Araújo Filho, Martin Kaupenjohann
更新时间: 2018-10-12
摘要: The use of biochar as a soil amendment is being widely studied, whereas clay addition to meliorate soils has only been considered in a few studies. However, there is a limited understanding of the impact of biochar and clay on nutrient retention under field conditions, especially in seasonally dry tropical forests in semi-arid regions. In this study, biochar and clay were added to a tropical Arenosol to quantify nutrient leaching as a measure of nutrient retention to test the potential of both amendments for soil amelioration.In a field experiment, planting holes were prepared with 5 vol% medium-temperature biochar made of Prosopis juliflora (SW) DC, produced locally in the traditional manner in a kiln, or 10 vol% clayey sediment from a temporarily dry lake. Both amendments and control were tested as fertilised and unfertilised treatments. Then seedlings of the endemic tree Spondias tuberosa Arr. were planted. Self-integrating accumulators (SIAs) were used to quantify nutrient leaching at a depth of 0.7 m for ammonium-N (NH₄⁺ − N), nitrate-N (NO₃⁻ − N), and potassium (K⁺). Leaching was assessed for two consecutive periods of eight months each.In the fertilised treatments, biochar addition significantly reduced NO₃⁻ − N leaching by 46% in the first period; leaching of all other nutrients was reduced but remained non-significant. In contrast, clay addition significantly reduced NH₄⁺ − N leaching by 79% in the second period, K⁺ leaching by 51% in the first period, and by 45% in the second period, but significantly increased NO₃⁻ − N leaching by 57% in the second period. Both treatments showed pronouncedly different leaching patterns over time. Between the first and second period, the ability of biochar to reduce leaching relative to the control decreased by about half for the nutrients tested, whereas the ability of the clay treatment remained rather stable over 1.5 years for NH₄⁺ − N and K⁺. The reason for the distinct decrease in nutrient retention of biochar in the second period may be the rapid decomposition of biochar carbon by 51% within 16 months.Under the given conditions, only clay can be recommended as a sustainable land management strategy to enhance NH₄⁺ − N and K⁺ retention capacity of Arenosols in seasonally dry tropical forests.

25652. 题目: Microbialites in Last Glacial Maximum and deglacial reefs of the Great Barrier Reef (IODP Expedition 325, NE Australia)
文章编号: N18101215
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Juan C. Braga, Ángel Puga-Bernabéu, Katrin Heindel, Madhavi A. Patterson, Daniel Birgel, Jörn Peckmann, Isabel M. Sánchez-Almazo, Jody M. Webster, Yusuke Yokoyama, Robert Riding
更新时间: 2018-10-12
摘要: Microbialites are volumetrically abundant components in Last Glacial Maximum and deglacial reefs in the Australian Great Barrier Reef sampled by IODP Expedition 325 in 34 holes from 17 sites (M0030–M0058), along four transects on the shelf edge. Detailed radiometric datings show that four distinct reef phases developed between 28and 10 ka, displaying offlapping and then backstepping patterns. The reef boundstone facies include coralgal, coralgal-microbialite and microbialite boundstone. The microbialite consists of combinations of micrite/microspar, bioclasts, siliciclastic grains (up to 14.5%), fenestrae and encrusting epibionts. The micrite/microspar is high-magnesian calcite commonly irregularly clotted, fenestral and peloidal. Mesoscale microbialite fabrics include laminated, structureless, digitate, intraskeletal and boring-filling, and coatings on debris. Intraskeletal and boring-filling is the first fabric to develop in skeletal voids and borings. It is usually followed by structureless and laminated microbialite, locally overlain by digitate fabric. Microbialite-coated debris can occur at any stage in this succession, including in bioclastic accumulations where the scarce in situ framework builders are mainly encrusting corals. Lipid biomarkers of intermediate to high specificity for sulfate-reducing bacteria, together with δ¹³C values of these lipids, indicate that microbialite formation was favored by sulfate-reducing bacteria in anoxic microenvironments, probably under high nutrient levels. The microbialite in fore-reef deposits accumulated in the photic zone in water depths of a few to several tens of meters, within small spaces generated by large bioclasts and encrusting corals in the topmost centimeters of the sediment. These crusts that formed on the illuminated surface constitute a previously unrecognized style of microbialite formation in Quaternary reefs. As with the cryptic crusts described from other reef locations, its greatest development occurred during the Last Glacial Maximum and early deglaciation. Microbial carbonate formation during this interval may reflect elevated seawater carbonate saturation corresponding with relatively low levels of atmospheric CO₂.

25653. 题目: Biochemical modeling of microbial memory effects and catabolite repression on soil organic carbon compounds
文章编号: N18101214
期刊: Soil Biology and Biochemistry
作者: Daniele la Cecilia, William J. Riley, Federico Maggi
更新时间: 2018-10-12
摘要: Microbial decomposition of Soil Organic Matter (SOM) is largely controlled by environmental and edaphic factors such as temperature, pH, and moisture. However, microbial metabolism is controlled by catabolite repression, which leads microbes to grow on preferred nutrient and energy sources first. In particular, Catabolite Repression for Carbon (CR-C) defines the hierarchical preference of bacteria for particular C sources. This control depends on the presence of signal molecules conferring bacteria a memory for recent growth conditions on less preferred C sources. The combined effect of catabolite repression and microbial memory (called here Memory-Associated Catabolite Repression for Carbon, MACR-C) has not yet been investigated in detail. First, we use observations and a numerical model to test the hypothesis that MACR-C explains substrate preferential consumption in a simple, 2-C substrate system, whereas Michaelis-Menten-Monod kinetics of competitive substrate consumption, non-competitive inhibition, or their combination, do not. Next, we carry out numerical analyses to explore the sensitivity of (1) estimated parameters to experimental observations and (2) model structure to steady-state substrate concentration under pulse or continuous substrate application. Our results show that MACR-C substantially affected substrate consumption and microbial readiness to switch between C sources.

25654. 题目: Soil microbial response following wildfires in thermic oak-pine forests
文章编号: N18101213
期刊: Biology and Fertility of Soils
作者: Michael S. Huffman, Michael D. Madritch
更新时间: 2018-10-12
摘要: The ecosystem response to wildfire is often linked to fire severity, with potentially large consequences for belowground biogeochemistry and microbial processes. While the impacts of wildfire on belowground processes are generally well documented, it remains unclear how fire affects the fine-scale composition of microbial communities. Here, we investigate the composition of soil bacterial and fungal communities in burned and unburned forests in an attempt to better understand how these diverse communities respond to wildfire. We explored the belowground responses to three wildfires in Linville Gorge, NC, USA. Wildfires generally increased soil carbon content while simultaneously reducing soil respiration. We employed amplicon sequencing to describe soil microbial communities and found that fires decreased both bacterial and fungal diversity. In addition, wildfires resulted in significant shifts in both bacterial and fungal community composition. Bacterial phylum-level distributions in response to fire were mixed without clear patterns, with members of Acidobacteria being representative of both burned and unburned sites. Fungal communities showed consistent increases in Ascomycota dominance and concurrent decreases in Basidiomycota and Zygomycota dominance in response to burning. Indicator species analysis confirmed shift to Ascomycota in burned sites. These shifts in microbial communities may reflect differences in the quality and quantity of soil organic matter following wildfires.

25655. 题目: Chemical nature of soil organic carbon under different long-term fertilization regimes is coupled with changes in the bacterial community composition in a Calcaric Fluvisol
文章编号: N18101212
期刊: Biology and Fertility of Soils
作者: Dandan Li, Lin Chen, Jisheng Xu, Lei Ma, Dan C. Olk, Bingzi Zhao, Jiabao Zhang, Xiuli Xin
更新时间: 2018-10-12
摘要: Fertilization is an important factor influencing the chemical structure of soil organic carbon (SOC) and soil microbial communities; however, whether any connection exists between the two under different fertilization regimes remains unclear. Soils from a 27-year field experiment were used to explore potential associations between SOC functional groups and specific bacterial taxa, using quantitative multiple cross-polarization magic-angle spinning ¹³C nuclear magnetic resonance and 16S rRNA gene sequencing. Treatments included balanced fertilization with organic materials (OM) and with nitrogen (N), phosphorus (P), and potassium (K) mineral fertilizers (NPK); unbalanced fertilization without one of the major elements (NP, PK, or NK); and an unamended control. These treatments were divided into four distinct groups, namely OM, NPK, NP plus PK, and NK plus control, according to their bacterial community composition and SOC chemical structure. Soil total P, available P, and SOC contents were the major determinants of bacterial community composition after long-term fertilization. Compared to NPK, the OM treatment generated a higher aromatic C–O and OCH₃ and lower alkyl C and OCH abundance, which were associated with the enhanced abundance of members of the Acidobacteria subgroups 6 and 5, Cytophagaceae, Chitinophagaceae, and Bacillus sp.; NP plus PK treatments resulted in a higher OCH and lower aromatic C–C abundance, which showed a close association with the enrichment of unclassified Chloracidobacteria, Syntrophobacteraceae, and Anaerolineae and depletion of Bacillales; and NK plus control treatments resulted in a higher abundance of aromatic C–C, which was associated with the enhanced abundance of Bacillales. Our results indicate that different fertilization regimes changed the SOC chemical structure and bacterial community composition in different patterns. The results also suggest that fertilization-induced variations in SOC chemical structure were strongly associated with shifts in specific microbial taxa which, in turn, may be affected by changes in soil properties.

25656. 题目: Effects of Fe-Mn modified biochar composite treatment on the properties of As-polluted paddy soil
文章编号: N18101211
期刊: Environmental Pollution
作者: Lina Lin, Zhongyang Li, Xuewei Liu, Weiwen Qiu, Zhengguo Song
更新时间: 2018-10-12
摘要: This study aimed to determine the effects of Fe-Mn modified biochar composite (FMBC) treatment on the pH, redox properties, enzyme activities, and bacterial communities of As-polluted paddy soil. The two utilized FMBCs (FMBC₁ and FMBC₂) exhibited markedly different effects on soil pH, and treatment with biochar (BC) or FMBCs increased the soil redox potential and reduced the content of available As, facilitating the conversion of originally present non-specifically sorbed and specifically bound As forms to residual, amorphous hydrous oxide–bound, and crystalline hydrous oxide–bound ones. In general, the activities of soil enzymes increased after the above treatment, with the exception of that of alkaline phosphatase, which decreased upon supplementation with FMBC₂. Supplementation with BC or FMBCs increased the abundance of Proteobacteria and Firmicutes, decreasing that of Bacteroidetes. Notably, FMBC₁ and FMBC₂ affected soil properties in different ways, although the mechanisms of the corresponding influence were similar. Thus, treatment with BC-based materials changed the distribution of As and the activities of soil enzymes, additionally affecting a variety of other physicochemical soil properties to make it suitable for microbial growth.
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25657. 题目: Formation of disinfection by-products during chlorination of organic matter from phoenix tree leaves and Chlorella vulgaris
文章编号: N18101210
期刊: Environmental Pollution
作者: Hongjie Sun, Xuhui Song, Ting Ye, Junbiao Hu, Huachang Hong, Jianrong Chen, Hongjun Lin, Haiying Yu
更新时间: 2018-10-12
摘要: To better understand the precursor of disinfection by-products (DBPs) and provide useful information for water utilities to manage the drinking water, a study of DBP formation was conducted through chlorination of leaf organic matter (OM) from phoenix tree and algal OM from Chlorella vulgaris. DBPs investigated include trichloromethane (TCM), trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), chloroacetic acid (CAA), dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCNM). Results show that the specific yields (μg/mg C) of C-DBPs (TCM, CAA, DCAA and TCAA) from leaf OM were higher but the specific yields of N-DBPs (DCAN and TCNM) were lower than those from algal OM. Correlation analysis revealed that C-DBPs yields (μg/L) were significantly (p < 0.01) interrelated with each other (r = 0.937–0.996), and for each C-DBP, the hydrophobic OM contributed more to their formation (61–90% of total yields) as compared with hydrophilic OM. In spite of these characteristics, an in-depth examination was conducted revealing that the hydrophobicity and aromaticity of C-DBPs precursors were in the order of TCAA > DCAA & TCM > CAA. DCAN precursors were highly variable: they were dominated by hydrophobic OM (leaf OM: 86%) or hydrophilic OM (algal OM: 61%). Hydrophilic OM was the most important precursor for TCNM (76–79% of total yields), followed by hydrophobic neutral and base substances (29–45% of total yields), but the hydrophobic acids exhibited an inhibition role in TCNM formation.
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25658. 题目: Enzyme activity indicates soil functionality affectation with low levels of trace elements
文章编号: N18101209
期刊: Environmental Pollution
作者: Juan Pedro Martín-Sanz, Inmaculada Valverde-Asenjo, Ana de Santiago-Martín, José Ramón Quintana-Nieto, Concepción González-Huecas, Antonio L. López-Lafuente, Ana Dieguéz-Antón
更新时间: 2018-10-12
摘要: The use of the soil can alter its functionality and influence the (bio)availability of any contaminants present. Our study considers two types of agricultural soils, rainfed and olive soils, managed according to conventional practices that apply contaminants directly to the soil (fertilizers, pesticides, fungicides, etc.) and receive contaminants from the atmosphere (traffic, industry, etc.); and a forest soil that is not subject to these agricultural practices. In this scenario, we consider a mixture of 16 trace elements (As, Ba, Be, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sb, Sn, V and Zn), since their interactions with the soil can produce synergistic and/or antagonistic effects that are not considered in most studies. We studied whether the content and (bio)availability of low concentrations of a mixture of trace elements affect the soil functionality in terms of the activity of some key enzymes We analysed the total, potentially and immediately available fractions, the soil parameters and soil enzyme activity. The results show that the functionality of the soils studied was affected despite the low concentrations of trace elements. The highest concentrations of total trace elements and available fractions were found in forest soils compared to the other two uses. Soil enzyme activity is best explained by the potentially available fraction of a mixture of trace elements and physico-chemical soil variables. In our study, pH, total nitrogen, organic carbon and fine mineral particles (silt and clay) had an influence on soil enzyme activity and the (bio)available fractions of trace elements.
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25659. 题目: Light absorption of organic carbon and its sources at a southeastern U.S. location in summer
文章编号: N18101208
期刊: Environmental Pollution
作者: Mingjie Xie, Xi Chen, Amara L. Holder, Michael D. Hays, Michael Lewandowski, John H. Offenberg, Tadeusz E. Kleindienst, Mohammed Jaoui, Michael P. Hannigan
更新时间: 2018-10-12
摘要: Light-absorbing organic carbon (OC), also referred to as “brown carbon” (BrC), has been intensively investigated in atmospheres impacted by biomass burning. However, other BrC sources (e.g., secondary formation in the atmosphere) are rarely studied in ambient aerosols. In the current work, forty-five PM_2.5 filter samples were collected in Research Triangle Park (RTP), NC, USA from June 1st to July 15th, 2013. The bulk carbonaceous components, including OC, elemental carbon (EC), water soluble OC (WSOC), and an array of organic molecular markers were measured; an ultraviolet/visible spectrometer was used to measure the light absorption of methanol extractable OC and WSOC. The average light absorption per OC and WSOC mass of PM_2.5 samples in summer RTP are 0.36 ± 0.16 m² gC⁻¹ and 0.29 ± 0.13 m² gC⁻¹, respectively, lower than the ambient aerosol samples impacted by biomass burning and/or fossil fuel combustion (0.7–1.6 m² gC⁻¹) from other places. Less than 1% of the aqueous extracts absorption is attributed to the light-absorbing chromophores (nitroaromatic compounds) identified in this work. To identify the major sources of BrC absorption in RTP in the summer, Positive Matrix Factorization (PMF) was applied to a dataset containing optical properties and chemical compositions of carbonaceous components in PM_2.5. The results suggest that the formation of biogenic secondary organic aerosol (SOA) containing organosulfates is an important BrC source, contributing up to half of the BrC absorption in RTP during the summertime.
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25660. 题目: Decreased atmospheric nitrogen deposition in eastern North America: Predicted responses of forest ecosystems
文章编号: N18101207
期刊: Environmental Pollution
作者: Frank S. Gilliam, Douglas A. Burns, Charles T. Driscoll, Serita D. Frey, Gary M. Lovett, Shaun A. Watmough
更新时间: 2018-10-12
摘要: Historical increases in emissions and atmospheric deposition of oxidized and reduced nitrogen (N) provided the impetus for extensive, global-scale research investigating the effects of excess N in terrestrial and aquatic ecosystems, with several regions within the Eastern Deciduous Forest of the United States found to be susceptible to negative effects of excess N. The Clean Air Act and associated rules have led to decreases in emissions and deposition of oxidized N, especially in eastern U.S., representing a research challenge and opportunity for ecosystem ecologists and biogeochemists. The purpose of this paper is to predict changes in the structure and function of North American forest ecosystems in a future of decreased N deposition. Hysteresis is a property of a system wherein output is not a strict function of corresponding input, incorporating lag, delay, or history dependence, particularly when the response to decreasing input is different from the response to increasing input. We suggest a conceptual hysteretic model predicting varying lag times in recovery of soil acidification, plant biodiversity, soil microbial communities, forest carbon (C) and N cycling, and surface water chemistry toward pre-N impact conditions. Nearly all of these can potentially respond strongly to reductions in N deposition. Most responses are expected to show some degree of hysteresis, with the greatest delays in response occurring in processes most tightly linked to “slow pools” of N in wood and soil organic matter. Because experimental studies of declines in N loads in forests of North America are lacking and because of the expected hysteresis, it is difficult to generalize from experimental results to patterns expected from declining N deposition. These will likely be long-term phenomena, difficult to distinguish from other, concurrent environmental changes, including elevated atmospheric CO₂, climate change, reductions in acidity, invasions of new species, and long-term vegetation responses to past disturbance.
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