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19881. 题目: Chemical cleaning of ceramic ultrafiltration membranes – Ozone versus conventional cleaning chemicals
文章编号: N19040710
期刊: Chemosphere
作者: Mohammad T. Alresheedi, Onita D. Basu, Benoit Barbeau
更新时间: 2019-04-07
摘要: This study investigates chemical cleaning mechanisms of a tubular ceramic UF membrane. The effect of cleaner type (ozone (O3), sodium hypochlorite (NaOCl) and sodium hydroxide (NaOH)), clean in place (CIP) pH (11 vs. 12), and cleaning sequence on the removal of irreversible fouling of hydrophobic (humic acids) and hydrophilic (alginate with and without calcium (alginate + Ca+2 and alginate - Ca+2, respectively)) NOM fractions were investigated. Results showed that different NOM types responded differently to chemical cleaning. Alginate-Ca+2 and humic acids were equivalently removed by NaOCl or NaOH whereas a lower cleaning efficiency of alginate + Ca+2 was observed. Increasing the pH of NaOCl and NaOH CIP increased the removal of the chemically reversible fouling index (UMFIcr). The efficiency of NaOCl was always lower than that of NaOH at the same pH, which was attributed to surface tension (λ) differences in the CIP water and potential differences in cleaning mechanism. The ceramic UF CIP cleaning using O3 (0.50 mg O3/mgC) for 1 h demonstrated higher cleaning efficiency for humic acids and alginate ± Ca+2, (%UMFIcr > 98%), than NaOCl or NaOH alone (%UMFIcr>80%). The O3 CIP was as effective as 4 h cleaning using a sequential NaOH/NaOCl or combined NaOCl + NaOH CIP.

19882. 题目: Biostimulation of in situ microbial degradation processes in organically-enriched sediments mitigates the impact of aquaculture
文章编号: N19040709
期刊: Chemosphere
作者: Francesca Ape, Elena Manini, Grazia Marina Quero, Gian Marco Luna, Gianluca Sarà, Paolo Vecchio, Pierlorenzo Brignoli, Sante Ansferri, Simone Mirto
更新时间: 2019-04-07
摘要: Fish farm deposition, resulting in organic matter accumulation on bottom sediments, has been identified as among the main phenomena causing negative environmental impacts in aquaculture. An in situ bioremediation treatment was carried out in order to reduce the organic matter accumulation in the fish farm sediments by promoting the natural microbial biodegradation processes. To assess the effect of the treatment, the concentration of organic matter in the sediment and its microbial degradation, as well as the response of the benthic prokaryotic community, were investigated. The results showed a significant effect of the treatment in stimulating microbial degradation rates, and the consequent decrease in the concentration of biochemical components beneath the cages during the treatment. During the bioremediation process, the prokaryotic community in the fish farm sediment responded to the overall improvement of the sediment conditions by showing the decrease of certain anaerobic taxa (e.g. Clostridiales, Acidaminobacteraceae and Caldilinaceae). This suggested that the bioactivator was effective in promoting a shift from an anaerobic to an aerobic metabolism in the prokaryotic community. However, the larger importance of Lachnospiraceae (members of the gut and faecal microbiota of the farmed fishes) in treated compared to non-treated sediments suggested that the bioactivator was not efficient in reducing the accumulation of faecal bacteria from the farmed fishes. Our results indicate that bioremediation is a promising tool to mitigate the aquaculture impact in fish farm sediments, and that further research needs to be oriented to identifying more successful interventions able to specifically target also fish-faeces related microbes.
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19883. 题目: Enhanced Pb immobilization via the combination of biochar and phosphate solubilizing bacteria
文章编号: N19040708
期刊: Environment International
作者: Haoming Chen, Jiawen Zhang, Lingyi Tang, Mu Su, Da Tian, Lin Zhang, Zhen Li, Shuijin Hu
更新时间: 2019-04-07
摘要: Application of biochar in heavy metal remediation suffers from lack of long-term stability. Phosphate-solubilizing bacteria (PSB) are able to elevate P release and the subsequent reaction with Pb to form stable pyromorphite. This study investigated the feasibility of applying PSB modified biochar to enhance immobilization of Pb2+. An alkaline biochar produced from rice husk (RB) and a slightly acidic biochar produced from sludge (SB) were selected. It showed that the biochars can effectively remove Pb2+ via adsorption, i.e., aqueous Pb concentrations after RB and SB addition were reduced by 18.61 and 53.89% respectively. The addition of PSB increased the Pb2+ removal for both biochars (to 24.11 and 60.85%, respectively). In particular, PSB significantly enhanced the formation of stable pyromorphite on surface of SB. This is due to that the evenly distributed PSB enhanced P release and regulated pH on the biochar surface. Moreover, small particles (<0.074 mm) showed their higher ability to induce the formation of pyromorphite, for both RB and SB. Nevertheless, SB demonstrated higher capability of sorption, together with its more abundant P content, which provided a more suitable platform to attract PSB to immobilize heavy metals. Therefore, the combination of biochar and PSB is a promising candidate material for heavy metal remediation. However, the types and particle size distribution of biochar should be addressed.
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19884. 题目: Natural biochar effect on sorption–desorption and mobility of diclosulam and pendimethalin in soil
文章编号: N19040707
期刊: Geoderma
作者: Kassio Ferreira Mendes, Glaucia Peregrina Olivatto, Rodrigo Nogueira de Sousa, Leonardo Vilela Junqueira, Valdemar Luiz Tornisielo
更新时间: 2019-04-07
摘要: The amendment of anthropogenic soils with natural biochar (without pyrolysis process) presents several environmental and agronomic benefits. However, there is little information available on the interaction of natural biochar with the herbicides applied directly into the soil. To address this knowledge gap, the influence of natural biochar on the sorption–desorption and mobility of diclosulam and pendimethalin herbicides in an agricultural soil was evaluated. The biochar was extracted from the profile of an Oxisol and post-dates the Holocene. The Ultisol-Typic Hapludalf used in this study was amended with natural biochar at rates of 0 (control), 0.1, 0.5 and 1.0% (m m−1). The 14C-diclosulam and 14C-pendimethalin showed specific activities of 0.002587 and 5.55 MBq mg−1, respectively. The sorption–desorption process was assessed by batch–equilibrium experiments. Liquid scintillation counting and soil thin-layer chromatography were used to determine herbicides adsorption and mobility. Application of natural biochar slightly increased the linear sorption coefficient (Kd) of each herbicide (from 0.22 to 0.50 L kg−1 for diclosulam, and from 25.55 and 37.81 L kg−1 for pendimethalin) in the soil, and the corresponding sorption percentages were 18.53–34.14% and 96.22–97.42%, respectively. However, the soil amendment did not alter the mobility of either herbicide, with retention factor (Rf) values of ~0.99 and 0.20 for diclosulam and pendimethalin, respectively, regardless of the natural biochar amount. Therefore, the presence of biochar in soil may not interfere with the bioavailability of diclosulam and pendimethalin in weed control under field conditions.
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19885. 题目: The effect of biochar mild air oxidation on the optimization of lead(II) adsorption from wastewater
文章编号: N19040706
期刊: Journal of Environmental Management
作者: Raoof Bardestani, Christian Roy, Serge Kaliaguine
更新时间: 2019-04-07
摘要: In the present study, the effects of mild air oxidation of a biochar produced by the Pyrovac Inc. pyrolysis process, on the adsorption of lead(II) from synthetic wastewater under batch experimental conditions have been investigated. The adsorption experiments were performed under several conditions suggested by the response surface methodology, which allowed finding the optimal conditions, in order to maximize the adsorption capacity Qmgg1, as well as the extraction efficiency (E (%)). The optimal conditions of lead ions adsorption were as follows: pH = 5, agitation time = 300 min, adsorbent mass = 0.5 g (per 50 cm3 of solution), and lead initial concentration = 100gm3, resulted in an adsorption capacity of 7.9 mg g−1. Equilibrium adsorption was then obtained by keeping pH and adsorbent mass at the optimal values and changing the lead initial concentration for a sufficient agitation time.Results showed that mild air oxidation increased the equilibrium adsorption capacity of biochar from 2.5 to 44 mg g−1. Oxidized biochar after equilibrium adsorption was submitted to SEM/EDX and XPS analysis. From SEM it was found that lead particles were distributed heterogeneously after adsorption. From XPS analysis, it was revealed that the external surface of oxidized biochar particles becomes saturated for the initial point of equilibrium diagram, obtained at lead initial concentration of 100gm3, suggesting that for a higher concentration, the internal surfaces of particles participate in the cations adsorption. The participation of surface functional groups in the adsorption process showed that carbonyl, carboxylic, and aromatic rings of oxidized biochar were involved in the adsorption.This work suggests that the very simple process of mild air oxidation can be used instead of the usual costly chemical activation, in order to improve biochar cation exchange capacity.
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19886. 题目: Upgrading volatile fatty acids production through anaerobic co-fermentation of mushroom residue and sewage sludge: Performance evaluation and kinetic analysis
文章编号: N19040705
期刊: Journal of Environmental Management
作者: Wei Fang, Panyue Zhang, Tao Zhang, David Carmona Requeson, Morgane Poser
更新时间: 2019-04-07
摘要: Due to complex inherent structure of lignocellulosic biomass, inefficient hydrolysis and acidification limits fermentative volatile fatty acids (VFA) production of mushroom residues. Meanwhile, the mushroom residues present insufficient nutrient with a high C/N ratio. To solve this issue, anaerobic co-fermentation of cellulose-rich Oyster champost and sewage sludge was tested to enhance the VFA production, and the effect of proportion of mixed substrate was investigated in this study. The results indicated that the sewage sludge yielded higher VFAs than the Oyster champost in single-substrate fermentative system. The maximal VFA yield of 595 mgCOD/gVSadded was achieved when the proportion of sewage sludge increased to 50% in the mixed substrate. In the co-fermentation system, the optimal C/N ratio and features of mixed substrate contributed to the enhancement in hydrolysis and acidification in terms of organic solubilization and VFA production, respectively. But the co-fermentation could not increase VFA/SCOD ratio, probably due to the existence of refractory products such as humic-like and protein-like materials. Besides, this co-fermentation system had strong buffer capacity and it was not necessary to dose chemicals to control the system pH for stable VFA production. Acetate was the dominant VFA product in co-fermentation systems. A modified-Logistic model fitted co-fermentation of sludge and Oyster champost well, and presented a faster rate and higher efficiency of VFA production.

19887. 题目: Temperature sensitivity of soil organic matter decomposition after forest fire in Canadian permafrost region
文章编号: N19040704
期刊: Journal of Environmental Management
作者: Heidi Aaltonen, Marjo Palviainen, Xuan Zhou, Egle Köster, Frank Berninger, Jukka Pumpanen, Kajar Köster
更新时间: 2019-04-07
摘要: Climate warming in arctic/subarctic ecosystems will result in increased frequency of forest fires, elevated soil temperatures and thawing of permafrost, which have implications for soil organic matter (SOM) decomposition rates, the CO2 emissions and globally significant soil C stocks in this region. It is still unclear how decomposability and temperature sensitivity of SOM varies in different depths and different stages of succession following forest fire in permafrost regions and studies on long term effects of forest fires in these areas are lacking. To study this question, we took soil samples from 5, 10 and 30 cm depths from forest stands in Northwest Canada, underlain by permafrost, that were burnt by wildfire 3, 25 and over 100 years ago. We measured heterotrophic soil respiration at 1, 7, 13 and 19 °C. Fire had a significant effect on the active layer depth, and it increased the temperature sensitivity (Q10) of respiration in the surface (5 cm) and in the deepest soil layer (30 cm) in the 3-year-old area compared to the 25- and more than 100-year-old areas. Also the metabolic quotient (qCO2) of soil microbes was increased after fire. Though fires may facilitate the SOM decomposition by increasing active layer depth, they also decreased SOM quality, which may limit the rate of decomposition. After fire all of these changes reverted back to original levels with forest succession.

19888. 题目: Early diagenetic sequestration of microbial mat lipid biomarkers through covalent binding into insoluble macromolecular organic matter (IMOM) as revealed by sequential chemolysis and catalytic hydropyrolysis
文章编号: N19040703
期刊: Organic Geochemistry
作者: Carina Lee, Gordon D. Love, Linda L. Jahnke, Michael D. Kubo, David J. Des Marais
更新时间: 2019-04-07
摘要: Analyses of lipids in modern microbial mat ecosystems provide valuable insights into the taxonomic affinities of the dominant biological producers and consumers as well as carbon flow within the mat community. Such microbial mat biomarker assemblages also provide a window into the ancient biomarker record, facilitating paleobiological and paleoenvironmental reconstructions of analogous ecosystems on early Earth. Our focus was to investigate the covalent binding of lipid biomarkers into insoluble macromolecular organic matter (IMOM) during diagenesis in the well-studied hypersaline microbial mat ecosystems and underlying sediments at Guerrero Negro, Baja California Sur, Mexico. Following exhaustive solvent extraction, three different chemical degradation reagents of varying reactivity (acid methanolysis, trichloroacetic acid extraction, and periodate oxidation) were applied to two shallow sedimentary layers prior to fragmentation of the recalcitrant insoluble residues using catalytic hydropyrolysis (HyPy). The hydrocarbons released by HyPy included a complex variety of linear, branched and polycyclic alkane structures, including hopanes, methylhopanes and steranes. Our findings indicate that a significant fraction of the bound biomarker pool was strongly linked by covalent binding through functional groups into IMOM but that a portion of this bound pool was not recoverable by chemolysis treatment. These results provide new insights about the mode and timing of chemical binding of steroids and hopanoids, and their early diagenetic transformation products, into IMOM. The formation of sedimentary IMOM from the earliest stages of organic matter diagenesis, commencing on a timescale of only years, aids the long-term preservation of biomarker lipids in the geological record.

19889. 题目: Carbon and phosphorus addition effects on microbial carbon use efficiency, soil organic matter priming, gross nitrogen mineralization and nitrous oxide emission from soil
文章编号: N19040702
期刊: Soil Biology and Biochemistry
作者: Kazi R. Mehnaz, Paola E. Corneo, Claudia Keitel, Feike A. Dijkstra
更新时间: 2019-04-07
摘要: The quantity and chemical composition of soil organic carbon (C) are primary factors controlling the growth and activity of soil microorganisms. However, availability of phosphorus (P) can also limit microbial activity as it is required for the synthesis of genetic and cellular components, metabolism and energy transfer. Little is known about how P availability influences microbial activity in response to C of varying chemical composition and recalcitrance. A laboratory incubation experiment was conducted to examine the effect of 13C-labeled glucose, oxalic acid and phenol, with and without P, on microbial C use efficiency (CUE), soil organic matter (SOM) priming, gross nitrogen (N) mineralization and nitrous oxide (N2O) emission from a grassland soil. Our results showed that microbes used glucose more efficiently but oxalic acid less efficiently compared to more recalcitrant phenol, and did not rely on P nutrition to partition C into growth and respiration. All three C substrates caused real SOM priming independent of their energy content or chemical structure, while addition of P increased the priming effect. Variability in chemical structures of C substrates affected gross N mineralization and hence N2O emission, while P application directly influenced N2O emission, especially when C substrates were added. In conclusion, our findings emphasize that the coupling of C and P fertilization in soils can have strong effects on terrestrial C stocks by favoring native soil organic C loss, as well as on N2O emission.

19890. 题目: Dung beetles and nutrient cycling in a dryland environment
文章编号: N19040701
期刊: CATENA
作者: M. Belén Maldonado, Julieta N. Aranibar, Alejandro M. Serrano, Natacha P. Chacoff, Diego P. Vázquez
更新时间: 2019-04-07
摘要: Insects are involved in the biogeochemical cycles of multiple elements and influence soil fertility. In particular, soil insects and the functions that they support can affect the response of terrestrial ecosystems to environmental changes. We experimentally studied the role of dung beetles as recyclers of cow dung in drylands of the Central Monte in mid-western Argentina; and we extrapolated these results to ecosystem impact in a grazing field, considering the dung beetle's abundance in summer. We conducted experiments with four species of dung beetles (Sulcophanaeus imperator, Eucranium arachnoides, Digitonthophagus gazella and Malagoniella puncticollis), and quantified their abundance on the field. Dung beetles incorporated nitrogen, ammonium, and phosphorous to the soil, but this activity varied substantially among species. The highest quantity of organic matter, nitrogen and phosphate was incorporated to the soil by S. imperator, one of the larger beetle studied. While the per capita effect of S. imperator is superior to other species studied, the impact on the ecosystem of the invasive D. gazella might be superior due to their major abundance in grazing fields. Our results highlight the importance of considering both components, per capita effect and abundance, to estimate with more reliability the relative importance of dung beetle species. Given that the effect of dung beetles on nutrient cycling is variable among species, and their abundance is variable in space, it is important to conserve beetle diversity in order to maximize their beneficial impacts on soils. Therefore, dung beetle effect on soil might be crucial in drylands to mitigate the nitrogen losses caused by grazing.

19891. 题目: Heterotrophic carbon metabolism and energy acquisition in Candidatus Thioglobus singularis strain PS1, a member of the SUP05 clade of marine Gammaproteobacteria
文章编号: N19040613
期刊: Environmental Microbiology
作者: Rachel L. Spietz, Rachel A. Lundeen, Xiaowei Zhao, Daniela Nicastro, Anitra E. Ingalls, Robert M. Morris
更新时间: 2019-04-06
摘要: A hallmark of the SUP05 clade of marine Gammaproteobacteria is the ability to use energy obtained from reduced inorganic sulfur to fuel autotrophic fixation of carbon using RuBisCo. However, some SUP05 also have the genetic potential for heterotrophic growth, raising questions about the roles of SUP05 in the marine carbon cycle. We used genomic reconstructions, physiological growth experiments, and proteomics to characterize central carbon and energy metabolism in Candidatus Thioglobus singularis strain PS1, a representative from the SUP05 clade that has the genetic potential for autotrophy and heterotrophy. Here we show that the addition of individual organic compounds and 0.2 μm filtered diatom lysate significantly enhanced the growth of this bacterium. This positive growth response to organic substrates, combined with expression of a complete TCA cycle, heterotrophic pathways for carbon assimilation, and methylotrophic pathways for energy conversion demonstrate strain PS1's capacity for heterotrophic growth. Further, our inability to verify expression of RuBisCO suggests that carbon fixation was not critical for growth. These results highlight the metabolic diversity of the SUP05 clade that harbors both primary producers and consumers of organic carbon in the oceans and expand our understanding of specific pathways of organic matter oxidation by the heterotrophic SUP05.

19892. 题目: Elevated CO2 alters the structure of the bacterial community assimilating plant‐derived carbon in the rhizosphere of soya bean
文章编号: N19040612
期刊: European Journal of Soil Science
作者: Y. H. Wang, Z. H. Yu, Y. S. Li, G. H. Wang, C. Tang, X. B. Liu, J. J. Liu, Z. H. Xie, J. Jin
更新时间: 2019-04-06
摘要: Elevated CO2 (eCO2) increases rhizodeposits, which in turn alters the soil microbial community. However, it is relatively unknown how the microbial community metabolizes plant‐derived carbon (C) in the rhizosphere under eCO2, especially in agricultural soils. This study used a 13CO2 labelling technique combined with DNA‐stable isotope probing (SIP) to fractionate the 13C‐DNA and 12C‐DNA from the rhizosphere of soya bean plants (Glycine max (L.) Merr. cv. Suinong 14) grown for 54 days under ambient CO2 (aCO2) (390 ppm or eCO2 (550 ppm). The DNA fractions were then subjected to Illumina Miseq sequencing. The results showed that eCO2 decreased the richness and diversity of the 13C‐assimilating bacterial community compared to aCO2 (p < 0.05). Elevated CO2 decreased the abundances of genera including Pseudarthrobacter, Gaiellales_uncultured, Microlunatus, Gemmatimonas, Gemmatimonadaceae_uncultured, Ramlibacter, Massilia, Luteimonas, Acidobacteriaceae_uncultured, Bryobacter and Candidatus_Solibacter. These genera were probably fast‐growing bacteria and sensitive to labile C. In contrast, eCO2 stimulated the growth of genera Novosphingobium, Acidimicrobiales_uncultured, Bacillus, Flavisolibacter and Schlesneria which were able to assimilate complex C compounds. Moreover, the increased population of Novosphingobium under eCO2 might have accelerated electron flow from the oxidation of organic C. Correspondingly, eCO2 did not affect the concentration of the dissolved organic C but increased the plant‐derived 13C in the rhizosphere. These results indicated that an eCO2‐induced increase in non‐labile C in rhizodeposits contributed to the increase in population size of a number of the plant‐C metabolizing genera that might become the mechanism for the turnover of fresh C in the rhizosphere, modifying the soil C cycle under eCO2 environments.

19893. 题目: Effect of reduction of aggregate size on the priming effect in a Mollisol under different soil managements
文章编号: N19040611
期刊: European Journal of Soil Science
作者: M. You, X. Han, X. Chen, J. Yan, N. Li, W. Zou, X. Lu, Y. Li, W. R. Horwath
更新时间: 2019-04-06
摘要: The priming effect (PE) is influenced by the amount and quality of soil organic carbon (SOC) held in different soil aggregates sizes. We examined the PE in Mollisols managed for > 30 years as a grassland, farmland and bare fallow with 51, 32 and 27 g of SOC kg‐1 soil, respectively, in a 60‐day incubation. Grassland soil contained 75% of aggregates in the macro size fractions > 0.25‐mm compared to < 32% in farmland and bare fallow. Farmland and bare fallow soils contained proportionately more micro size fractions. The effect of aggregate size on the PE was assessed by comparing soils with intact aggregates to those where macroaggregates were reduced to microaggregate size fractions. In the grassland soil, cumulative CO2 mineralization increased 20% in the reduced aggregate‐size treatment with no effect on farmland or bare fallow soils. Substrate additions to examine the PE included 13C‐glucose and 13C‐alanine (0.4 g C kg‐1 dry soil), and inorganic N (2 mg N kg‐1 dry soil). The PE was in the order glucose > alanine > (NH4)2SO4 and was most intense at day 3 of the incubation. Aggregate‐size reduction did not affect the PE within soil management treatments regardless of substrate addition. Most of the CO2 produced was derived from SOC rather than substrate addition and peaked at day 3. There was an interaction between microbial biomass C and dissolved organic C on the PE in the grassland soil only. The results suggested that the PE is an intrinsic characteristic of soils that are more affected by available C than the SOC in different aggregate fractions.

19894. 题目: Understanding the relations between soil organic matter fractions and N2O emissions in a long‐term integrated crop–livestock system
文章编号: N19040610
期刊: European Journal of Soil Science
作者: Juliana Hiromi Sato, Cícero Célio de Figueiredo, Robélio Leandro Marchão, Alexsandra Duarte de Oliveira, Lourival Vilela, Francisco Marcos Delvico, Bruno José Rodrigues Alves, Arminda Moreira de Carvalho
更新时间: 2019-04-06
摘要: The nitrous oxide (N2O) emissions in agricultural systems are influenced by edaphoclimatic conditions, and the availability of soil organic matter (SOM) is a key factor. The objective of this study was to evaluate the accumulation of labile and stable SOM fractions and possible relations with N2O emissions using a multivariate approach in a 24‐year integrated crop–livestock experiment in the Cerrado region. The management systems consisted of: continuous cropping under no tillage (CC‐NT), continuous cropping under annual heavy disc harrow (CC‐CT), an integrated crop–livestock system under no tillage (CLS‐NT) and an adjacent area of native Cerrado as reference. The cumulative N2O emissions were quantified over a period of 146 days, throughout the cultivation of sorghum (Sorghum bicolor (L.) Moench). Labile and stable soil carbon (C) fractions and C contents in classes of aggregates (macroagreggates > 0.250 mm and microagreggates < 0.250 mm) were determined. The cumulative N2O emissions were larger in the CC‐CT system, intermediate in the CC‐NT and CLS‐NT systems, and smaller in the Cerrado. The decomposition of crop residues during the crop succession (first and second crop seasons) and the presence of a grass forage (with grazing and not grazed) in both systems (CLS‐NT and CC‐NT, respectively) explain the differences in N2O fluxes between the land uses. Smaller cumulative N2O emissions were observed in the integrated system (CLS‐NT), which could be attributed to the greatest increase in soil C in its most stable SOM fractions (fulvic acid) and occluded in microaggregates. This confirms the hypothesis that the accumulation of C in the most stable SOM fractions of the soil, unavailable to the microbiota, results in smaller N2O emissions. Principal component analysis also revealed that aggregation is a key attribute that correlates with soil N2O emissions. Thus, conservation systems such as CLS‐NT had larger average diameter of aggregates and the smallest N2O emissions among the agroecosystems.

19895. 题目: Aquatic biomarkers record Pleistocene environmental changes at Paleolake Olduvai, Tanzania
文章编号: N19040609
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Devon E. Colcord, Andrea M. Shilling, Katherine H. Freeman, Jackson K. Njau, Ian G. Stanistreet, Harald Stollhofen, Kathy D. Schick, Nicholas Toth, Simon C. Brassell
更新时间: 2019-04-06
摘要: Several hypotheses invoke climatic variability as a driving force for hominin evolution. Thus, high-resolution records of climate and environmental variability from anthropologically significant locations can help test these hypotheses. Sedimentary sequences recovered by the Olduvai Gorge Coring Project (OGCP) help evaluate climatic and environmental changes at Olduvai Gorge, Tanzania through the analyses of various biogeochemical proxies. The stratigraphic sequence of OGCP Core 2A can be correlated with horizons associated with hominins and is chronologically constrained by distinctive dated horizons, such as the Bed I Basalt and Tuff IB. The lacustrine interval from 76.6 to 86.9 m depth is ideally suited for high-resolution analyses of biogeochemical proxies as it is rich in organic carbon (>1%TOC). The hydrogen isotopic composition of nC31 in this interval of OGCP Core 2A records the effects of precession-driven wet-dry cycles on the terrestrial environment that led to alternations between woodland and grassland ecosystems, comparable to those documented by previous investigations of outcrop analogues at Olduvai. Here, we examine stratigraphic variations in the abundance of biomarkers (C28 steradienes, C17 and C23 n-alkanes, C27 and C28 A-norsteranes, fern-8-ene, and chromans) derived from aquatic organisms (algae, cyanobacteria, sponges, macrophytes, etc.) to determine the response of Paleolake Olduvai to climate variability. In general, these aquatic biomarkers reflect the productivity of the lake environment and exhibit the same precession-driven wet-dry cycles recorded by terrestrial biogeochemical signatures. However, they also provide evidence of abrupt (<~300 yr) changes in lake level and corresponding aquatic communities superimposed on the longer-term Milankovitch cycles. Thus, evidence for climatic variability is manifested through the pacing and intensity of changes in both terrestrial and aquatic ecosystems, but the different rates of the responses on land and in the aquatic environment potentially had a complex influence on water and food resources that were important factors for hominin habitation and evolution.

19896. 题目: Impact of hydrotechnical works on outflow of mercury from the riparian zone to a river and input to the sea
文章编号: N19040608
期刊: Marine Pollution Bulletin
作者: Dominika Saniewska, Karolina Gębka, Magdalena Bełdowska, Grzegorz Siedlewicz, Jacek Bełdowski, Bartłomiej Wilman
更新时间: 2019-04-06
摘要: The aim of this research was to assess the impact of hydrotechnical works within the riverbed and riparian zone on the mobility of mercury in soil and its outflow to the river and the sea. Deepening and reconstruction of the riverbed or the cutting of reeds, influenced the fate of mercury in the river system. However, only activitis that disturbed the riperian zone increased mobilization of Hg in soils. Hg transformations in these places were controled by inflow of fresh organic matter in soil and sediments as well as by oxidation-reduction potential. In areas where reducing conditions occurred, mercury released from the soil was incorporated into the sediment. However, in areas where oxidizing conditions prevailed in the sediment, mercury flowing out of the soil occurred mainly in dissolved form and most of it was transported downstream from where it could reach the sea.
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19897. 题目: The behaviour of organic matter in hybrid water treatment system
文章编号: N19040607
期刊: Separation and Purification Technology
作者: Kazuhisa Mimura, Youichiro Takahashi, Shinichi Takanashi, Hiroshi Deguchi
更新时间: 2019-04-06
摘要: The removal of organic matter is a fundamental process in sewage treatment. Small scale sewage treatment plants, in particular, demand low cost and easy operation and maintenance. It is said that a hybrid water treatment system incorporating more physicochemical than biological processes for the removal of organic matter can be more convenient and incur less cost compared with a conventional activated sludge systems. Therefore, in this study, we propose a hybrid water treatment system equipped with a jet mixed separator (JMS), which is a type of pre-coagulation-sedimentation tank, and an aerobic moving bed biofilter (MBB). We then investigate the behaviour of particulate and soluble organic matter and the oxygen consumption by the biofilm in this hybrid system. The results indicate that the addition of the poly silicate iron coagulant in JMS increases the quantity of removed organic matter by approximately 30% compared with the process without coagulant, and that the majority of the removed organic matter is soluble. That is, the JMS effectively reduced the organic matter that can be eliminated only by biological treatment, and not by mechanical treatment. The residual organic matter of JMS was removed from the liquid phase within an hour, which is the hydraulic retention time (HRT) of MBB, and the removed soluble organic matter was almost perfectly biodegraded in the biofilm within a day. That is, MBB could continuously operate without excess growth of microorganisms as long as the filtering was working properly. Thus, the hybrid system is expected to maximize the performance of MBB.

19898. 题目: Carbon uptake in surface water food webs fed by palaeo‐groundwater.
文章编号: N19040606
期刊: Journal of Geophysical Research: Biogeosciences
作者: Debashish Mazumder, Neil Saintilan, Suzanne Hollins, Karina Meredith, Geraldine Jacobsen, Tsuyoshi Kobayashi, Li Wen
更新时间: 2019-04-06
摘要: The use of 14C to elucidate sources of carbon within freshwater aquatic ecosystems is challenging the assumption that modern autochthonous carbon dominates energy flows. We measured the uptake of old carbon through several trophic levels of a wetland fed by groundwater of the Great Artesian Basin (GAB), Australia, the largest artesian basin in the world. Stable isotopes (δ13C and δ15N) and radiocarbon (14C) were used to quantify food chain links and connection between groundwater and surface water food webs. Our results suggest that old groundwater was the dominant carbon source even at the highest trophic levels, with predatory fish returning apparent carbon ages of up to 11 ka. Stable isotope analysis (δ13C and δ15N) identified trophic links between fish, aquatic insects and algae with smaller contributions from particulate organic matter (POM) to the food webs. As natural mound springs and associated wetlands are the only source of reliable water during dry periods over vast areas of the western GAB, the result has potential implications for the interpretation of archaeological artefacts associated with indigenous passage within the interior.

19899. 题目: Postfire Soil Carbon Accumulation Does Not Recover Boreal Peatland Combustion Loss in Some Hydrogeological Settings
文章编号: N19040605
期刊: Journal of Geophysical Research: Biogeosciences
作者: R. C. Ingram, P. A. Moore, S. Wilkinson, R. M. Petrone, J. M. Waddington
更新时间: 2019-04-06
摘要: Deep peat burning at the interface between subhumid Boreal Plains (BP) peatlands and forestlands (margin ecotones) in some hydrogeological settings has brought into question the long‐term stability of these peatlands under current and future predicted climate. Small peatlands located at midtopographic positions on coarse sediments have been identified as hot spots for severe burning, as these peatland margins are not regularly connected to regional groundwater flow. The ability of these peatland systems to recover carbon lost from both the interior and margin within the fire return interval, however, has not yet been investigated. Here we examine peatland soil carbon accumulation along a chronosequence of time since fire for 26 BP ombrotrophic bogs located across a range of hydrogeological settings. Soil organic carbon accumulation following wildfire does not appear to be influenced by hydrogeological setting; however, the ability of a peatland to recover the quantity of carbon lost within the fire return interval is dependent on the amount of carbon that was released through smoldering, which is influenced by hydrogeological setting for peatland margins. Based on published measurements of organic soil carbon loss during wildfire and our soil carbon accumulation rates, we suggest that peatlands located at topographic lows on coarse‐grained glaciofluvial outwash sediments or on low‐relief, fine‐grained sediment deposits from glaciolacustrine or subglacial paleoenvironments are currently resilient to wildfire on the BP landscape. Peatlands that experience severe smoldering at the margins, such as ephemerally perched systems on glaciofluvial outwash sediments, will likely undergo permanent loss of legacy carbon stores.

19900. 题目: Grazing and enclosure alter the vertical distribution of organic nitrogen pools and bacterial communities in semiarid grassland soils
文章编号: N19040604
期刊: Plant and Soil
作者: Huanhe Wang, Jiangye Li, Qichun Zhang, Jun Liu, Bo Yi, Yong Li, Jingwen Wang, Hongjie Di
更新时间: 2019-04-06
摘要: Background and aims: Different grazing management practices have a significant impact on the sustainability of grassland ecosystems. This study invested the vertical distribution of soil nitrogen (N) forms and soil microbial community structures in a semiarid grassland ecosystem under different grazing management practices in Inner Mongolia. Methods: Soil samples were collected from three semiarid grassland plots subjected to different long-term management practices namely, free grazing (FG) and two different periods of enclosure (E83, enclosed since 1983 and E97, enclosed since 1997). The soil organic nitrogen (N) pools were analyzed by classical methods, and the bacterial community was assessed by PCR-DGGE and high-throughput sequencing. Results: The surface soil N-supplying capacity was in the order of E97 ≥ E83 ≥ FG. The soil ammonium N, amino N, and N-supplying capacity were greater in the enclosed plots than in the FG plot. Additionally, the 0–40-cm soil layer showed the influence of different management practices on the soil properties. The structure and diversity of the soil microbial community also varied with the management type. The soil organic N composition was significantly related to the soil bacterial community structure and microbial categories. Conclusions: An appropriate number of years of fencing helps to improve the soil surface nutrient status, whereas overgrazing and prolonged enclosure are not conducive to the restoration of soil nutrients. Different grazing management practices can affect the microbial community structure and turnover of soil N in grasslands.

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