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22721. 题目: Linking heterotrophic bacterioplankton community composition to the optical dynamics of dissolved organic matter in a large eutrophic Chinese lake
文章编号: N19050811
期刊: Science of The Total Environment
作者: Wei Zhang, Yongqiang Zhou, Erik Jeppesen, Liqing Wang, Hongxin Tan, Junyi Zhang
更新时间: 2019-05-08
摘要: Elucidation of the linkages between the bacterial community composition and chromophoric dissolved organic matter (CDOM) in lake ecosystems is critical for the understanding of the inland water carbon cycling. Despite substantial research into the relationship between the bacteria community and the bulk DOM pool, knowledge of the specific relationship between the optical dynamics of DOM and the bacterioplankton community in lake ecosystems is still poor. We investigated the linkages between the optical dynamics of DOM and bacteria composition in shallow eutrophic Lake Taihu, China. Redundancy Analysis (RDA) indicated that besides water temperature and phytoplankton biomass, also CDOM was an important factor determining the composition of the bacterial community. Generalized Additive Models (GAM) showed that terrestrial humic-like C1 and tyrosine-like C4 were the key factors explaining the abundance of the main bacterial clades. C1 was closely correlated with Verrucomicrobia, Actinobacteria, Alphaproteobacteria, Betaproteobacteria and Planctomycetes, and C4 was closely related to the latter two and to Bacteroidetes. At family level, the dominant families – Pelagibacteraceae (Alphaproteobacteria) and Gemmataceae (Planctomycetes) – were related to both allochthonous and autochthonous CDOM fluorophores but responded differently to the various CDOM components. Tryptophan-like C2 was significantly and positively correlated with Gemmataceae and Ellin6075 (Acidobacteria). Additionally, we found that the biomasses of Cyanophyta, terrestrial humic-like C1, tryptophan-like C4 and C5 were significantly related to the richness of heterotrophic bacterioplankton. Our results provide new insight into the relationship between bacteria and DOM optical dynamics although the mechanisms leading to these relationships need further experimental investigations.
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22722. 题目: Influence of different redox conditions and dissolved organic matter on pesticide biodegradation in simulated groundwater systems
文章编号: N19050810
期刊: Science of The Total Environment
作者: Yujia Luo, Siavash Atashgahi, Huub H.M. Rijnaarts, Rob N.J. Comans, Nora B. Sutton
更新时间: 2019-05-08
摘要: Insights into the influence of redox conditions, that is the availability of electron acceptors, and dissolved organic matter (DOM) on pesticide biodegradation in groundwater are key to understanding the environmental fate of pesticides in natural groundwater systems. Here, the influence of redox conditions and supplemental DOM addition on biodegradation of pesticides, 2,4-dichlorophenoxyacetic acid (2,4-D), 2,6-dichlorobenzamide (BAM), mecoprop-p (MCPP) and bentazone, was tested in microcosm and subsequent column experiments. Pesticide degradation, functional genes and changes in specific fractions and quantity of DOM were systematically quantified. In aerobic microcosm experiments, the highest 2,4-D degradation rate was obtained with the presence of more assimilable DOM. In column experiments, minimal pesticide degradation (≤33.77%) in any anaerobic redox conditions was observed in the absence of DOM. However, in the presence of DOM, 2,4-D biodegradation was considerably enhanced under nitrate-reducing conditions (from 23.5 ± 10.2% to 82.3 ± 11.6%) and in a column without external electron acceptor amendment (from −6.3 ± 12.6% to 31.1 ± 36.3%). Observed preferential depletion of the fulvic acid fraction of DOM provides indications for specific functional DOM properties. The qPCR results show an increase in microbial biomass and functional genes (tfdA) in liquid phase after DOM addition. The results of this work provide insights into the interplays among DOM, redox geochemistry, and pesticide biodegradation, and show the potential of a novel approach – DOM addition to groundwater systems – for in situ biostimulation technology to remove pesticides from groundwater systems.
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22723. 题目: Characterization of coastal wetland soil organic matter: Implications for wetland submergence
文章编号: N19050809
期刊: Science of The Total Environment
作者: Havalend E. Steinmuller, Lisa G. Chambers
更新时间: 2019-05-08
摘要: High rates of relative sea level rise can cause coastal wetland submergence, jeopardizing the stability of soil organic matter (SOM) sequestered within wetlands. Following submergence, SOM can be lost through mineralization, exported into the coastal ocean, or reburied within adjacent subtidal sediments. By combining measures of soil physicochemical properties, microbial community abundance, organic carbon fractionation, and stable isotope signatures, this study characterized subsurface SOM within a coastal wetland to inform its potential fate under altered environmental conditions. Nine soil cores were collected to a depth of 150 cm from a wetland currently experiencing rapid erosion and submergence within Barataria Bay, LA (USA), and were sectioned into 10 cm intervals. Each soil segment was analyzed to determine total carbon (C), nitrogen (N), phosphorus (P), and stable isotope (δ¹³C and δ¹⁵N) content, as well as extractable ammonium (NH₄⁺), nitrate (NO₃⁻), and soluble reactive phosphorus (SRP). Extractable NH₄⁺ and SRP concentrations increased 7× and 11×, respectively, between 0–10 cm and 130–140 cm. Through quantitative PCR, number of gene copies of bacteria and sulfate reduction genes were found to decrease with depth while there was no change in number of gene copies of archaea. This study also demonstrated only small decreases in labile: refractory C ratios with depth; by combining δ¹⁵N data with labile:refractory C ratios and no observed change in C:N ratios with depth, we inferred the presence of minimally processed organic material within deep soils and high nutrient availability, challenging the applicability of the traditional theory of selective preservation and decreased soil quality with depth. As wetland submergence progresses and soils are exposed to oxygenated seawater, this relatively labile SOM and bioavailable N and P stored at depth has the potential for rapid mineralization and/or export into the coastal zone.
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22724. 题目: Controlling factors of organic carbon stocks in agricultural topsoils and subsoils of Bavaria
文章编号: N19050808
期刊: Soil and Tillage Research
作者: Stefanie Mayer, Anna Kühnel, Johannes Burmeister, Ingrid Kögel-Knabner, Martin Wiesmeier
更新时间: 2019-05-08
摘要: Agricultural soils are highly important organic carbon (OC) reservoirs in Central Europe. Their OC stocks are crucial for a wide range of ecosystem services such as food security or climate regulation through atmospheric CO₂ storage. There is increasing evidence that the controlling factors of OC stocks may differ between topsoil and subsoil, but distinct knowledge about the factors at a regional scale for temperate soils is scarce. In order to identify the controlling factors of OC storage in agricultural soils we implemented a random forest model on a data set of 692 soil profiles located in Bavaria, Southeast Germany. We differentiated between topsoil (0–30 cm profile depth) and subsoil (30–100 cm) and predicted OC stocks (kg OC m⁻²) using 13 predictor variables including soil type, topographical factors, climatic factors and information on land use. The explained variance of the topsoil random forest was higher than that of the subsoil (51 and 23%, respectively). The fact that major proportions of the variance in the modelling of subsoil OC remained unexplained, revealed high uncertainties that persist about subsoil OC storage. OC storage of both, topsoils and subsoils, was to a large extend determined by four factors: land use history, soil type, major landform and topographic wetness index (TWI). Climatic factors as well as clay content had surprisingly low impact on the model. Topsoil OC was mainly controlled by the legacy of the land use resulting in highest stocks under permanent grassland use. In contrast, soil type and topographical factors, i.e. major landform and TWI, largely determined subsoil OC stocks. The topography indicates the lateral transport of OC due to soil erosion and its subsequent deposition in low lying landform positions. There, high soil moisture as indicated by the TWI, hampers the decomposition of the OC. Human activities such as tillage amplify the lateral OC transport and therefore the amount of buried OC. As a result of these processes, highest subsoil stocks were found in alluvial, colluvial and groundwater affected soils. The findings demonstrate the close link between the generic soil type, topography, land use and OC stocks. We further conclude that the legacy of human activities affect both, topsoil and subsoil OC storage.

22725. 题目: Lead and Antimony in Basal Ice From Col du Dome (French Alps) Dated With Radiocarbon: A Record of Pollution During Antiquity
文章编号: N19050807
期刊: Geophysical Research Letters
作者: Susanne Preunkert, Joseph R. McConnell, Helene Hoffmann, Michel Legrand, Andrew I. Wilson, Sabine Eckhardt, Andreas Stohl, Nathan J. Chellman, Monica M. Arienzo, Ronny Friedrich
更新时间: 2019-05-08
摘要: Lead and antimony measurements in basal ice from the Col du Dome glacier document heavy metal pollution in western Europe associated with emissions from mining and smelting operations during European antiquity. Radiocarbon dating of the particulate organic carbon fraction in the ice suggests that the basal ice dates to ~5,000 ± 600 cal years BP. In agreement with a precisely dated Greenland lead record, the Col du Dome record indicates two periods of significant lead pollution during the Roman period, that is, the last centuries before the Common Era to the second century of the Common Era. Atmospheric modeling and the Col du Dome record consistently show an overall magnitude of the lead perturbation 100 times larger than in the Greenland record. Antimony closely tracked lead, with antimony pollution about 2 orders of magnitude lower, consistent with European peat records.

22726. 题目: SOIL ORGANIC CARBON STOCKS UNDER RECOMMENDED MANAGEMENT PRACTICES IN DIFFERENT SOILS OF SEMI‐ARID VINEYARDS
文章编号: N19050806
期刊: Land Degradation & Development
作者: Luciano Gristina, Riccardo Scalenghe, Andrés García‐Díaz, Maria Gabriella Matranga, Vito Ferraro, Fabio Guaitoli, Agata Novara
更新时间: 2019-05-08
摘要: Intergovernmental Panel On Climate Change (IPCC) approach is widely used to estimate C account through the use of standardized coefficients which are not site specific. For these reasons, the aim of the work was to define specific IPCC coefficient taking into account differences in pedological characteristics which affect soil C steady state.

22727. 题目: Vermicompost can suppress Fusarium oxysporum f. sp. lycopersici via generation of beneficial bacteria in a long-term tomato monoculture soil
文章编号: N19050805
期刊: Plant and Soil
作者: Fengyan Zhao, Yongyong Zhang, Wenge Dong, Yueqi Zhang, Guoxian Zhang, Zhouping Sun, Lijuan Yang
更新时间: 2019-05-08
摘要: Background and aims: Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) has severely decreased global tomato production. Organic amendments are widely applied to suppress Fol all over the world. However, the ways in which different amendments alter soil bulk microflora and thereby induce the suppression of Fol remain unclear. Methods: In this study, the effects of three organic amendments on the suppression of Fol in soil and the underlying mechanisms of those effects were studied. The organic amendments included in this study are rice straw, chicken manure compost, and vermicompost. High-throughput HiSeq sequencing and Real-Time PCR were used to determine the effect of the soil microbiota on the abundance of Fol. Results: The abundance of Fol increased significantly with the duration of tomato cultivation. Vermicompost was the most effective organic fertilizer to suppress Fol in long-term continuous tomato cropping soil. Partial Least Squares Path Modeling revealed a strong positive relationship between the relative abundance of bacterial groups (including the genera Nocardioides, Ilumatobacter and Gaiella) and Fol inhibition. Soil chemical properties (pH, NH₄⁺-N, soil organic matter and dissolved organic carbon) were positively associated with the genera Nocardioides, Ilumatobacter and Gaiella. Compared with chemical fertilizer and rice straw, vermicompost addition significantly increased soil pH, NH₄⁺-N, soil organic matter and dissolved organic carbon concentrations in the soil with 20 years of tomato cultivation. Most importantly, the genera Nocardioides, Ilumatobacter and Gaiella were enriched in vermicompost, which may contribute to the propagation of these bacteria in the soil when vermicompost is added. Conclusions: This study provides a mechanistic framework that permits the exploration of specific functions at lower taxonomic levels. This may represent a novel approach in the management of crop pathogens via promotion of beneficial organisms.

22728. 题目: Rhizosphere carbon supply accelerates soil organic matter decomposition in the presence of fresh organic substrates
文章编号: N19050804
期刊: Plant and Soil
作者: Oyindamola Jackson, Richard S. Quilliam, Andy Stott, Helen Grant, Jens-Arne Subke
更新时间: 2019-05-08
摘要: Background and aims: Belowground C supply from plant roots may accelerate the decomposition of SOM through the rhizosphere priming effect, but the detailed interaction between substrate quality and rhizosphere C supply is poorly understood. We hypothesize that decomposition of organic matter is enhanced by the combined effect of assimilate C supply to the rhizosphere and substrate amendments. Methods: Birch trees (Betula pendula) planted in experimental mesocosms; half of these trees were shaded to reduce the supply of assimilate C to roots and ECM fungi. Either ¹³C-enriched glucose, straw, fungal necromass or C₄ biochar were subsequently added to each mesocosm. CO₂ efflux derived from substrates were separated from that derived from native SOM and roots based on the isotopic composition of total respired CO₂. Results: The addition of all substrates increased fluxes in both un-shaded and shaded treatments, with greatest total CO₂ efflux observed in soils amended with straw. Increases in un-labelled CO₂ were observed to be greater in the presence of belowground C supply than in mesocosms with shaded trees. Conclusions: Turnover of SOM is closely linked to belowground C allocation. The biochemical quality and recalcitrance of litter entering the soil C pool is of critical importance to this priming, as is the interaction with rhizosphere-associated decomposition activity.

22729. 题目: Priming effect of litter mineralization: the role of root exudate depends on its interactions with litter quality and soil condition
文章编号: N19050803
期刊: Plant and Soil
作者: Kai Tian, Xiangshi Kong, Liuhuan Yuan, Hong Lin, Zaihua He, Bei Yao, Yanli Ji, Junbo Yang, Shucun Sun, Xingjun Tian
更新时间: 2019-05-08
摘要: Background and aims: Root exudation can prime microbial synthesis of additional exoenzymes and consequently accelerate organic carbon (C) and nitrogen (N) mineralization. Such exudate induced priming effect (EPE) has been hypothesized to depend on exudate rate and stoichiometry. Little is known about how EPE would affect litter decomposition. We employed a microcosm experiment to evaluate the influence of root exudate on litter nutrient release and microbial enzyme functions. Methods: Leaf litters of Pinus massoniana, Quercus variabilis and Robinia pseudoacacia were incubated under two soil conditions (fertile versus barren). Solutions of chemicals often found in root exudates with contrasting C:N ratios were inoculated frequently into the microcosms to simulate exudation. By comparing with a water control, exudate effect was determined. Results: In barren soils, exudates with C:N ratio of 10 significantly decelerated C loss of R. pseudoacacia, all N-containing exudates significantly enhanced the N-cycling related enzymes in decomposing Q. variabilis, while C-only exudate accelerated N loss of P. massoniana. In fertile soils, C-only exudate promoted the N-cycling related enzymes in decomposing R. pseudoacacia. Conclusions: A stoichiometric C:N constraint on microbial utilization of exudates arose in decomposing recalcitrant litters in barren soil. EPE and its stoichiometric constraint depend on interactions with litter quality and soil condition. The findings arouse the consequences of exudate rate and stoichiometry changes in determining soil nutrient balance.

22730. 题目: Potential of Cedrella fissilis bark as an adsorbent for the removal of red 97 dye from aqueous effluents
文章编号: N19050802
期刊: Environmental Science and Pollution Research
作者: Jordana Georgin, Dison S. P. Franco, Patricia Grassi, Denise Tonato, Daniel G. A. Piccilli, Lucas Meili, Guilherme L. Dotto
更新时间: 2019-05-08
摘要: Cedar bark (Cedrella fissilis), a waste from wood processing, was evaluated as an adsorbent for the removal of red 97 dye from effluents. The material exhibited an amorphous structure, irregular surface, and was mainly composed of lignin and holocellulose. The adsorption was favored at pH 2.0. The general order model was most suitable for describing the experimental kinetic data, being the equilibrium reached in around 30 min. The isotherm experiments were better described by the Langmuir model. The maximum adsorption capacity was 422.87 mg g⁻¹ at 328 K. The values of standard Gibbs free energy change (ΔG⁰) were from − 21 to − 26 kJ mol⁻¹, indicating a spontaneous and favorable process. The enthalpy change (ΔH⁰) was 18.98 kJ mol⁻¹, indicating an endothermic process. From the fixed bed adsorption experiment, an inclined breakthrough curve was found, with a mass transfer zone of 5.36 cm and a breakthrough time of 329 min. Cedar bark was able to treat a simulated effluent attaining color removal of 86.6%. These findings indicated that cedar bark has the potential to be applied as a low-cost adsorbent for the treatment of colored effluents in batch and continuous adsorption systems.

22731. 题目: Effects of crop residue retention on soil carbon pools after 6 years of rice–wheat cropping system
文章编号: N19050801
期刊: Environmental Earth Sciences
作者: Sandeep Sharma, H. S. Thind, Yadvinder-Singh, H. S. Sidhu, M. L. Jat, C. M. Parihar
更新时间: 2019-05-08
摘要: Enhancing soil organic carbon (SOC) is an important strategy to sustain and improve the soil quality, mitigate climate change and increase crop productivity under intensive tillage-based rice–wheat (RW) system in the Indo-Gangetic Plains (IGP) of South Asia. Therefore, the effects of tillage, crop establishment, and residue management practices on total as well as different pools of SOC in a sandy loam after 6 years of RW system were studied. The imposed three main plot treatments to the rice plots were: (1) ZTDSR, zero till dry seeded rice; (2) CTDSR, conventional till dry seeded rice; and (3) PTR, conventional puddled transplanted rice, and the three sub-plot treatments in succeeding wheat were (i) CTW − R, conventional tillage (CT) wheat with both rice and wheat residues removed; (ii) ZTW − R, zero tillage (ZT) wheat with both the residues removed and (iii) ZTW + R, ZT wheat with rice residue. Total soil organic content increased by 6.5–12.5% and 3.1–12.9% in different soil layers up to 0–60 cm depth in ZTDSR followed by ZTW + R over PTR followed by CTW − R practices, respectively. The corresponding increase of the oxidizable C was 4.2–28.2% and 8.2–8.5%, respectively. Significant enhancement in all the carbon pools (non-labile, less labile, labile, very labile pools, water soluble and microbial biomass carbon) and glomalin content were also recorded in ZTW + R treatment. The carbon management index was significantly higher in ZTW + R than ZTW − R and CTW − R treatments. In conservation-based agriculture systems, the principal component analysis revealed that passive pools of SOC and microbial biomass carbon were the most promising and reliable indicators for assessing soil quality. This study showed that adoption of ZTDSR followed by ZTW + R was the better crop production strategy for increasing C-sequestration, improving and sustaining the soil quality and crop productivity in the RW system. This practice also provides an opportunity to retain crop residues as an alternative to burning, which causes severe air pollution in the RW system in the IGP of South Asia.

22732. 题目: Degradation of internal organic matter is the main control on pteropod shell dissolution after death
文章编号: N19050703
期刊: Global Biogeochemical Cycles
作者: R.L. Oakes, V.L. Peck, C. Manno, T.J. Bralower
更新时间: 2019-05-07
摘要: The potential for preservation of thecosome pteropods is thought to be largely governed by the chemical stability of their delicate aragonitic shells in seawater. However, sediment trap studies have found that significant carbonate dissolution can occur above the carbonate saturation horizon. Here we present the results from experiments conducted on two cruises to the Scotia Sea to directly test whether the breakdown of the organic pteropod body influences shell dissolution. We find that, on the timescales of three to thirteen days, the oxidation of organic matter within the shells of dead pteropods is a stronger driver of shell dissolution than the saturation state of seawater. Three to four days after death, shells became milky white and nano‐SEM images reveal smoothing of internal surface features and increased shell porosity, both indicative of aragonite dissolution. These findings have implications for the interpretation of the condition of pteropod shells from sediment traps and the fossil record, as well as for understanding the processes controlling particulate carbonate export from the surface ocean.

22733. 题目: Variation in dissolved organic matter (DOM) stoichiometry in U.K. freshwaters: Assessing the influence of land cover and soil C:N ratio on DOM composition
文章编号: N19050702
期刊: Limnology and Oceanography
作者: Christopher A. Yates, Penny J. Johnes, Alun T. Owen, Francesca L. Brailsford, Helen C. Glanville, Christopher D. Evans, Miles R. Marshall, David L. Jones, Charlotte E. M. Lloyd, Tim Jickells, Richard P. Evershed
更新时间: 2019-05-07
摘要: Dissolved organic matter (DOM) plays an important role in freshwater biogeochemistry. To investigate the influence of catchment character on the quality and quantity of DOM in freshwaters, 45 sampling sites draining subcatchments of contrasting soil type, hydrology, and land cover within one large upland‐dominated and one large lowland‐dominated catchment were sampled over a 1‐yr period. Dominant land cover in each subcatchment included: arable and horticultural, blanket peatland, coniferous woodland, and improved, unimproved, acid, and calcareous grasslands. The composition of the C, N, and P pool was determined as a function of the inorganic nutrient species (NO₃⁻, NO₂⁻, NH₄⁺, and PO₄³⁻) and dissolved organic nutrient (dissolved organic carbon [DOC], dissolved organic nitrogen [DON], and dissolved organic phosphorus [DOP]) concentrations. DOM quality was assessed by calculation of the molar DOC : DON and DOC : DOP ratios and specific ultraviolet absorbance (SUVA₂₅₄). In catchments with little anthropogenic nutrient inputs, DON and DOP typically composed > 80% of the total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) concentrations. By contrast, in heavily impacted agricultural catchments DON and DOP typically comprised 5–15% of TDN and 10–25% of TDP concentrations. Significant differences in DOC : DON and DOC : DOP ratios were observed between land cover class with significant correlations observed between both the DOC : DON and DOC : DOP molar ratios and SUVA₂₅₄ (r_s = 0.88 and 0.84, respectively). Analysis also demonstrated a significant correlation between soil C : N ratio and instream DOC : DON/DOP (r_s = 0.79 and 0.71, respectively). We infer from this that soil properties, specifically the C : N ratio of the soil organic matter pool, has a significant influence on the composition of DOM in streams draining through these landscapes.

22734. 题目: Natural organic matter fractions and their removal in full-scale drinking water treatment under cold climate conditions in Nordic capitals
文章编号: N19050701
期刊: Journal of Environmental Management
作者: P. Krzeminski, C. Vogelsang, T. Meyn, S.J. Köhler, H. Poutanen, H.A. de Wit, W. Uhl
更新时间: 2019-05-07
摘要: Drinking water treatment plants (DWTPs) designed to remove natural organic matter (NOM) are challenged as concentrations of NOM in raw waters are increasing. Here, we assess seasonal differences in NOM quality and quantity, from raw waters to the distribution network, at three large DWTPs in Oslo, Stockholm and Helsinki. Samples, collected during stable stratification in both winter and summer and during the autumnal turnover, were analysed for NOM concentrations and composition. The NOM was characterized by common routine parameters, size and content (TFF, LC-OCD, fluorescence) and biodegradability. The NOM concentration decreased to 2.5 mg/L (55%), 4.0 mg/L (48%) and 5.7 mg/L (76%) at the respective DWTPs in Oslo, Stockholm and Helsinki. The NOM in raw waters were predominantly in the largest size fraction (>50 kDa), in particular from Oslo. High MW fractions >50 kDa and humics remained the largest fractions with minimum 30% and maximum 80% of the total NOM. The BDOC in treated water <0.3 mg/L and the conditions in the distribution network imply low probability for bacteria regrowth.The multi-step treatment consisting of coagulation/flocculation, sedimentation, rapid sand filtration, ozonation and biological activated carbon filtration (BAC) was most effective in removing NOM. Coagulation/flocculation followed by sedimentation and sand filtration were critical, especially for the removal of biopolymers and humics, and somewhat for building blocks. The sand filtration provided up to 25% additional removal of biopolymers and below 7% removal of other fractions. The ozonation and BAC was more effective and removed 11% of biopolymers, and about 35% of building blocks and LMW neutrals.
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22735. 题目: Soil biota, carbon cycling and crop plant biomass responses to biochar in a temperate mesocosm experiment
文章编号: N19050603
期刊: Plant and Soil
作者: Sarah A. McCormack, Nick Ostle, Richard D. Bardgett, David W. Hopkins, M. Glória Pereira, Adam J. Vanbergen
更新时间: 2019-05-06
摘要: Background and aims: Biochar addition to soil is a carbon capture and storage option with potential to mitigate rising atmospheric CO₂ concentrations, yet the consequences for soil organisms and linked ecosystem processes are inconsistent or unknown. We tested biochar impact on soil biodiversity, ecosystem functions, and their interactions, in temperate agricultural soils. Methods: We performed a 27-month factorial experiment to determine effects of biochar, soil texture, and crop species treatments on microbial biomass (PFLA), soil invertebrate density, crop biomass and ecosystem CO₂ flux in plant-soil mesocosms. Results: Overall soil microbial biomass, microarthropod abundance and crop biomass were unaffected by biochar, although there was an increase in fungal-bacterial ratio and a positive relationship between the 16:1ω5 fatty acid marker of AMF mass and collembolan density in the biochar-treated mesocosms. Ecosystem CO₂ fluxes were unaffected by biochar, but soil carbon content of biochar-treated mesocosms was significantly lower, signifying a possible movement/loss of biochar or priming effect. Conclusions: Compared to soil texture and crop type, biochar had minimal impact on soil biota, crop production and carbon cycling. Future research should examine subtler effects of biochar on biotic regulation of ecosystem production and if the apparent robustness to biochar weakens over greater time spans or in combination with other ecological perturbations.

22736. 题目: Realgar (As 4 S 4 ) bioprecipitation in microcosm fed by a natural groundwater and organic matter
文章编号: N19050602
期刊: Environmental Science and Pollution Research
作者: Lukáš Falteisek, Vojtěch Duchoslav, Petr Drahota
更新时间: 2019-05-06
摘要: Sequestration of arsenic to biogenic sulfide minerals is known from As-contaminated anoxic environments. Despite numerous successful laboratory experiments, the process remains difficult to predict in moderate arsenic conditions. We performed microcosm experiments using naturally contaminated groundwater (containing ca. 6 mg/L As) and natural organic matter (NOM) particles both collected from wetland soil. Macroscopic realgar precipitates, occasionally accompanied by bonazziite, a FeS phase, elementary S, calcite, and whewellite, appeared after 4 to 18 months. Realgar only precipitated in microcosms moderately poisoned by azide or antibiotics and those in which oxidation of hydrogen sulfide to sulfur took place. The biomineralization process was not affected by the presence of additional carbon sources or the diversity, community structure, and functional composition of the microbial community. Hydrogen sulfide concentration was greater in the realgar-free microcosms, suggesting that arsenic thiolation prevented precipitation of realgar. We compared our data to available microbial community data from soils with different rates of realgar precipitation, and found that the communities from realgar-encrusted NOM particles usually showed limited sulfate reduction and the presence of fermentative metabolisms, whereas communities from realgar-free NOM particles were strongly dominated by sulfate reducers. We argue that the limited sulfate supply and intensive fermentation amplify reducing conditions, which make arsenic sulfide precipitation plausible in high-sulfate, low-arsenic groundwaters.

22737. 题目: Soil organic matter temperature sensitivity cannot be directly inferred from spatial gradients
文章编号: N19050601
期刊: Global Biogeochemical Cycles
作者: Rose Z. Abramoff, Margaret S. Torn, Katerina Georgiou, Jinyun Tang, William J. Riley
更新时间: 2019-05-06
摘要: Developing and testing decadal‐scale predictions of soil response to climate change is difficult because there are few long‐term warming experiments or other direct observations of temperature response. As a result, spatial variation in temperature is often used to characterize the influence of temperature on soil organic carbon (SOC) stocks under current and warmer temperatures. This approach assumes that the decadal‐scale response of SOC to warming is similar to the relationship between temperature and SOC stocks across sites that are at quasi‐steady‐state; however, this assumption is poorly tested. We developed four variants of a Reaction‐network‐based model of Soil Organic Matter and microbes (ReSOM) using measured SOC stocks from a 4000 km latitudinal transect. Each variant reflects different assumptions about the temperature sensitivities of microbial activity and mineral sorption. All four model variants predicted the same response of SOC to temperature at steady state, but different projections of transient warming responses. The relative importance of Q_max, MAT, and NPP, assessed using a machine‐learning algorithm, changed depending on warming duration. When mineral sorption was temperature sensitive, the predicted average change in SOC after 100 years of 5°C warming was ‐18% if warming decreased sorption or +9%, if warming increased sorption. When microbial activity was temperature sensitive but mineral sorption was not, average site‐level SOC loss was 5%. We conclude that spatial climate gradients of SOC stocks are insufficient to constrain the transient response; measurements that distinguish process controls and/or observations from long‐term warming experiments, especially mineral fractions, are needed.

22738. 题目: Tree water use strategies and soil type determine growth responses to biochar and compost organic amendments
文章编号: N19050510
期刊: Soil and Tillage Research
作者: Peter D Somerville, Claire Farrell, Peter B May, Stephen J Livesley
更新时间: 2019-05-05
摘要: Background and aims Organic matter is often used as an amendment to attempt restoration of degraded soils to improve tree establishment and growth. One key aim is to increase plant available water in the soil profile. The texture of the soil, the type of organic amendment (e.g. compost or biochar), and the native environment of the tree (mesic or xeric) will impact how successful restoration efforts are. We aimed to determine whether compost and biochar amendments, either individually or in combination, would improve plant available water (PAW) in both clay and sand soils. We then aimed to measure whether changes in PAW would translate into increased water use and plant growth of both mesic (Corymbia maculata) or xeric (Eucalyptus torquata) tree species under well-watered (WW) or water deficit (WD) conditions. Methods Clay and sand soils were amended with compost, biochar or a compost and biochar mix, whilst unamended soils acted as controls. Soil moisture characteristics of the soil mixes were determined with samples in the laboratory. Fifteen replicate pots (6 l) of each soil treatment were then planted with either mesic and xeric tree species. All pots and trees were subjected to either a WW or WD irrigation regime for 7 weeks. WD irrigation was a set percentage of the daily WW evapotranspiration (ET). ET was calculated as total pot mass one hour after irrigation (to allow for drainage) minus the total pre-dawn pot mass of the subsequent day. The tree biomass, biomass partitioning, ET, and tree water status were measured throughout the experiment to understand growth and stress responses. Key results The xeric tree species (E. torquata) grown in sand soil had a significant increase in growth with all three OM amendments but did not when grown in clay soil. In contrast, we found no significant growth response for the mesic tree species (C. maculata) when grown in either clay or sand amended with any OM treatment. The ET of the xeric tree species was greater for all the OM amended soils for both WW and WD plants in the sand soil. Conclusions This study shows that OM amendments may improve the soil water properties of sand-based soils which in turn can increase the growth of xeric tree species. However, more expensive organic amendments may not be necessary, nor mixing of OM types, as we found no tree growth differences amongst the three different OM treatments.

22739. 题目: Enzymatic esterification of oleic acid by Candida rugosa lipase immobilized onto biochar
文章编号: N19050509
期刊: Journal of Environmental Management
作者: Mara Cea, María Eugenia González, Macarena Abarzúa, Rodrigo Navia
更新时间: 2019-05-05
摘要: The immobilization of Candida rugosa lipase (CRL) onto biochar was studied in a series of batch experiments. CRL sorption behavior was evaluated as a function of pH, enzyme concentration, temperature and ionic strength. As the immobilized lipase was used for the catalytic esterification of oleic acid, its resistance to solvents and thermal stability were evaluated. CRL adsorption increased by increasing temperature, and with higher pH, reaching a maximum at pH 7.0. Immobilization increased lipase stability at 40 °C by more than 80% when compared to the free enzyme. Moreover, immobilized CRL showed high stability in the presence of tert-butanol, which prevents premature deactivation of the enzyme caused by alcohols during the reaction. Immobilization of CRL increased the oleic acid conversion rate. Our results suggest that biochar is a highly promising material for the immobilization of CRL lipase for the catalytic production of esters.

22740. 题目: Enhanced adsorption of Zn²⁺ by salinity-aided aerobic granular sludge: Performance and binding mechanism
文章编号: N19050508
期刊: Journal of Environmental Management
作者: Xiao Wu, Wei Li, Dong Ou, Cheng Li, Meng Hou, Hui Li, Yongdi Liu
更新时间: 2019-05-05
摘要: Aerobic granular sludge (AGS), which is formed by closely associating microorganisms through the production of extracellular polymeric substances (EPS), has proved to be an excellent and promising biosorbent. The reutilization of excess AGS as a kind of biosorbent would be an environmental-friendly means for heavy metal removal and reutilization of excess AGS. In this study, short-term exposure experiments were conducted to determine whether salinity (NaCl concentration ranged from 0 to 50 g/L) caused positive effects on Zn²⁺ adsorption performance by AGS. The results showed that the AGS formed in response to a 30 g/L saline treatment exhibited the best adsorption performance. Compared with the control (salinity of 0 g/L), the adsorptive capacity at equilibrium increased by 19.90% and reached 29.76 mg/g. The calculated maximum adsorption capacity in 30 g/L saline treatment group was 73.94 mg/g which was higher than described in previous studies using biochar, clarified sludge and aerobic granules. Analysis of EPS components suggested the enhanced adsorption of AGS might be ascribed to increasing polysaccharides content in the EPS after saline treatments. Additionally, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results indicated hydroxyl groups of EPS played an important role in Zn²⁺ binding. These findings provide further insight into the application of AGS for heavy metal adsorption.