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25401. 题目: The composition difference of macrophyte litter-derived dissolved organic matter by photodegradation and biodegradation: Role of reactive oxygen species on refractory component
文章编号: N19102703
期刊: Chemosphere
作者: Na Song, Leilei Bai, Huacheng Xu, He-Long Jiang
更新时间: 2019-10-27
摘要: The overgrowth of macrophytes has become serious due to increasing eutrophication in shallow lakes. The primary degradation processes of macrophytes litter, including photodegradation and biodegradation, induce considerable patchiness in the concentration and bioavailability of dissolved organic matter (DOM). In this study we investigated the composition evolution of DOM derived from emergent aquatic plant litter, Phragmites australis, in microbial degradation, photodegradation, and the combination of bio- and photo-degradation. Results revealed that the effects of photo- and biodegradation on the composition difference of macrophyte litter-derived DOM during short- and long-term degradation phase were different. Although large changes in DOM were observed after five days of incubation, the abundance and chemical composition were similar in the three treatments. However, more concentration of DOM was produced by combined photo- and biodegradation at the long-term degradation phase, and the composition of DOM showed less lignin-like formulae, as well as less condensed aromatic and aromatic compounds when compared to sole treatments. More reactive oxygen species (ROS) were found under the combined treatments, thus the contents of refractory components (condensed aromatic- and aromatic compound groups) were reduced. This study provide deeper insight into the fate of DOM and relevant biogeochemical processes in eutrophic lakes.
25402. 题目: Climatic and environmental changes across the Early Eocene Climatic Optimum at mid-Waipara River, Canterbury Basin, New Zealand
文章编号: N19102702
期刊: Earth-Science Reviews
作者: E.M. Crouch, C.L. Shepherd, H.E.G. Morgans, B.D.A. Naafs, E. Dallanave, A. Phillips, C.J. Hollis, R.D. Pancost
更新时间: 2019-10-27
摘要: The Cretaceous–Paleogene marine sedimentary succession exposed in the banks of the middle reaches of the Waipara River (referred to as mid-Waipara), north Canterbury, New Zealand, has been the subject of several high-profile studies of Paleogene paleoclimate over the past decade. It is one of relatively few sections globally where a multi-proxy approach is possible due to the good preservation of microfossils and organic biomarkers. The Eocene section is also well dated by magnetostratigraphy and biostratigraphy based on planktic foraminifera, calcareous nannofossils and dinoflagellate cysts (dinocysts). Here, we build on this previous work and undertake a comprehensive analysis of paleontological and geochemical indicators of climatic and environmental changes through the early–middle Eocene part of the section, with particular focus on the Early Eocene Climatic Optimum (EECO; 53.26–49.14 Ma). We correlate a 33.5 m-thick interval with the EECO, based on biostratigraphy, magnetostratigraphy, TEX86-paleothermometry and bulk carbonate δ13C. Our new sea-surface temperature (SST) record based on TEX86 agrees with a previous lower resolution record based on TEX86 and planktic foraminiferal δ18O and Mg/Ca ratios. The EECO interval in this section extends from the upper part of the New Zealand Waipawan Stage to the Mangaorapan/Heretaungan Stage boundary at 49.27 Ma. The EECO onset is not exposed, but the termination is well constrained by a fall in SST and shift to more positive δ13C values. Six negative carbon isotope excursions (CIEs) are recognised within the EECO and are tentatively correlated with CIEs J/K, M, O, Q, T and C22nH4 in the global δ13C compilation. The CIEs are associated with warmer SSTs, indicating that they represent hyperthermals. The BAYSPAR TEX86 calibration indicates SST increased by as much as 12 °C from the early Eocene (∼55 Ma) to the EECO, where SST peaked at 35 °C. SST gradually declined from mid EECO (∼51 Ma) into the middle Eocene. The marked warming in the early EECO is associated with the highest abundance of warm-water taxa in calcareous nannofossil and dinocyst assemblages, the highest proportion of planktic foraminifera, and a coeval long-term shift to abundant angiosperm vegetation, primarily driven by a rise in Casuarinaceae. There is good agreement between TEX86 and marine microfossil-based proxies for temperature, providing confidence that both approaches are useful guides to past water temperature. Warm-water marine taxa are most abundant in the EECO but are not dominant. Comparison of the abundance of nannofossil warm-water taxa between mid-Waipara and a low-latitude site on Shatsky Rise suggests the latitudinal temperature gradient between mid- and low-latitudes in the EECO was greater than the TEX86 proxy implies. There is no clear evidence for enhanced sedimentation rates associated with the EECO, in contrast to evidence from the nearby Mead Stream section. Superabundant Homotryblium, a euryhaline dinocyst, in the early and middle EECO suggests elevated salinity and/or stratified surface waters, and there is no clear evidence of increased surface productivity associated with the EECO. Declining SST in the late EECO, ∼50 Ma, corresponds with an increase in cool-water taxa and terrigenous material. This article highlights the importance of combining well-calibrated paleontological and geochemical records to better constrain and understand past warm climate states.
25403. 题目: Plant source and soil interact to determine characteristics of dissolved organic matter leached into waterways from riparian leaf litter
文章编号: N19102701
期刊: Science of The Total Environment
作者: Hannah M. Franklin, Anthony R. Carroll, Chenrong Chen, Paul Maxwell, Michele A. Burford
更新时间: 2019-10-27
摘要: Wetting of leaf litter accumulated in riparian zones during rainfall events provides pulses of dissolved organic matter (DOM) to rivers. Restoring riparian vegetation aims to reduce sediment and nutrient transport into rivers, however DOM from leaf litter can stimulate phytoplankton growth and interfere with water treatment processes. Improved understanding of the loads and chemical composition of DOM leached from leaf litter of different plant species, and how subsequent leaching through soils affects DOM retention or transformation, is needed to predict the outcomes of riparian revegetation. To investigate this, we simulated rapid leaching of rainfall through the leaf litter of two riparian tree species with and without subsequent leaching through soil, comparing dissolved organic carbon (DOC) and nitrogen (DON) loads, and DOM chemical composition (via spectroscopic and novel NMR-fingerprinting techniques). Plant source affected the load and composition of DOM leaching, with Eucalyptus tereticornis leaching more DOC than Casuarina cunninghamiana. Additionally, E. tereticornis DOM had a higher sugar, myo-inositol, benzoic acid, flavonoid and oxygenated aromatic content. More than 90% of leaf litter DOM was retained in the soil under simulated repeated heavy rainfall. The DOM chemistry of these species determined the total loads and changes in DOM composition leaching through soil. Less E. tereticornis DOM was retained by the soil than C. cunninghamiana DOM, with sugars, myo-inositol and amino acids being poorly retained compared to fatty acids and aromatic compounds. It also appears that DOM from E. tereticornis litter primed the soil, resulting in more DON being leached compared with bare soil. In comparison, C. cunninghamiana litter resulted in greater retention of DON, oxygenated aromatic compounds and the amino acid tryptophan. This study provides new information on how a range of DOM sources and transformations affect the DOM ultimately leached into waterways, key to developing improved models of DOM transformations in catchments.
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25404. 题目: Competitive sorption and availability of coexisting heavy metals in mining-contaminated soil: Contrasting effects of mesquite and fishbone biochars
文章编号: N19102611
期刊: Environmental Research
作者: Yassir Abdin, Adel Usman, Yong Sik Ok, Yiu Fai Tsang, Mohammad Al-Wabel
更新时间: 2019-10-26
摘要: Mesquite and fishbone were pyrolyzed to produce biochar (MBC and FBC, respectively) at different temperatures. The effects of the MBC and FBC on the removal of single and competitive metals (Cd, Pb, Zn, and Cu) from aqueous solutions were evaluated. A greenhouse pot experiment was also conducted using wheat plants with the mining-contaminated soils. In the presence of MBC or FBC (dosages of 15 and 30 g kg−1), the bioavailability of co-existing Cd, Pb, Zn, Cu, Mn, and Fe were assessed. The results clearly indicated competitive adsorption among metals with the highest adsorption preference toward Pb. The removal efficiency and partition coefficient (PC) values of heavy metals for FBCs were higher than those for MBCs. These two values increased with MBC pyrolysis temperature under both single- and multi-metals adsorption conditions. Applying FBC to mining soil resulted in the highest reduction in most NH4NO3-extractable heavy metals, reducing their availability to wheat plants. At the highest application dosage of 30 g kg−1, the highest metal immobilization, which accounted for 40.0% and 43.0% for Pb, 61.7% and 66.2% for Cu, 48.3% and 55.6% for Zn, and 32.7% and 33.8% for Cd, was achieved following the application of FBC400 and FBC600, respectively. However, applying MBC lead to a significant reduction in the availability of Cu and Pb but not that of Zn and Cd. FBC is thus more effective in removing heavy metal from aqueous solutions, as well as in immobilizing co-existing heavy metals in contaminated mining soil. It could, therefore, be an effective sorbent and immobilizing agent.
25405. 题目: Treatment of horizontal silage bunker runoff using biochar amended vegetative filter strips
文章编号: N19102610
期刊: Journal of Environmental Management
作者: J.R. Sanford, R.A. Larson
更新时间: 2019-10-26
摘要: Horizontal silage bunkers produce leachate that contains contaminants that can be detrimental to the environment if released untreated. Vegetated filter strips are used to treat silage bunker runoff to prevent contamination of surface waters via infiltration, however increased infiltration poses risks to groundwater, particularly for nitrate (NO3−). Vegetated filter strip plots with a sandy loam soil, half of which are amended with biochar, were investigated to assess the treatment of silage bunker runoff over 20 application events. The subsurface effluent biological oxygen demand (BOD5), chemical oxygen demand (COD), and total phosphorus (TP) were reduced on average by 40%, 46%, and 75%, respectively, and there was no statistical difference between treatments. The total nitrogen (TN) was reduced by 49 and 64% for control and biochar plots, respectively, which was significantly different between treatments. Biochar significantly reduced nitrate nitrogen (NO3−-N) leaching by 40% compared to the control, however, the NO3−-N concentration in leachate was still high ranging from 0.19 to 191.04 mg NO3−-N L−1 and 0.18–108.89 mg NO3−-N L−1 for control and biochar plots, respectively. A mass balance suggests the primary mechanism for a decrease in TN and NO3−-N leaching from biochar amended plots was greater retention of NO3−-N and organic N (ORG-N) within the soil/biochar matrix. The development of oxygenated functional groups and/or formation of organomineral layer on the biochar surface likely enhanced N retention.
25406. 题目: Probing the efficiency of magnetically modified biomass-derived biochar for effective phosphate removal
文章编号: N19102609
期刊: Journal of Environmental Management
作者: Zeeshan Ajmal, Atif Muhmood, Renjie Dong, Shubiao Wu
更新时间: 2019-10-26
摘要: Characterization of the driving forces for effective and economical phosphate (PO43−) removal from wastewater by using magnetically modified biochar was performed in this study. The biochar produced from slow pyrolysis of local agricultural biomass (wood and rice husks) were magnetically modified by co-precipitation of Fe(II) and Fe(III) ions in their presence. The surface characteristics before and after modification and their efficacy for PO43− sorption, and desorption were compared. Results show that, even though magnetic biochar surface modification slightly decreased their surface area, PO43− adsorption to the modified biochars was almost double (25–28 mg g−1) than that to the raw biochar (12–15 mg g−1). The adsorption isotherm of raw biochars was better simulated via the Langmuir model, while that of modified biochars was better fitted to the Freundlich model. Moreover, the integrated analysis by XRD, EDX, and FTIR show that PO43− sorption to modified biochars could be attributed to the simultaneously-occurring electrostatic attraction, surface precipitation, and ligand exchange. While the electrostatic attraction was dominant in the presence of unmodified biochars. The regenerated modified biochars retained substantial PO43− adsorption capacity up to several regeneration cycles. Their high reusability potential leads to the effective and economical phosphate recovery and thus modified biochars could offer a viable strategy for PO43− removal.
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25407. 题目: Analyzing vegetation cover-induced organic matter mineralization dynamics in sandy soils from tropical dry coastal ecosystems
文章编号: N19102608
期刊: CATENA
作者: Adolfo Campos C., Gabriela Suárez M., Javier Laborde
更新时间: 2019-10-26
摘要: To gain knowledge about carbon and nitrogen mineralization potentials and their interaction with sandy soil environment in tropical dry coastal ecosystems, we carried out a short-term laboratory incubation experiment. For this, soil surface (0–10 cm) samples were collected from tropical semi-deciduous forest (TSdF), secondary forest (SecF), coastal dune scrub_crest (DS_C), and coastal dune scrub_slack (DS_S). Soil samples were incubated at 25 °C with constant soil moisture (at field capacity) for 97 days, and over this time 10 and 11 sampling occasions were analyzed to determine carbon (CO2-C) and nitrogen (NH4, NO3) dynamics, respectively. We used a simple exponential model to estimate soil carbon and nitrogen mineralization pools. On average, soil organic carbon mineralization rates ranged between 0.017 and 0.053 mg CO2-C g−1 soil d−1 and varied in the following order: DS_S > SecF > TSdF > DS_C. Average net mineralization rates (mg N kg−1 soil d−1) ranged between 16.9 and 18.8 and varied in the following order: SecF > DS_S > TSdF, whereas in DS_C it was −0.44, indicating N immobilization. Co and No represented, on average, 1.08% and 5% of soil organic carbon and total organic nitrogen, respectively. On average, mineralization constants (k) for Co and No were 0.29 d−1 and 0.23 d−1, respectively, showing that SOM is easily mineralized. The proportion of NO3Nm was very high in SecF (89%) and TSdF (75%), while DS_C showed nitrate immobilization. The increase in NO3Nm ratio in SecF could be associated with legume species that have established in the nature restoration (SecF) on ex-grassland. Across all study sites, linear regression analyses suggested that soil physical and chemical properties may regulate SOM mineralization (p < 0.05).
25408. 题目: Effects of conversion from boreal natural wetlands to rice paddy fields on the dynamics of total dissolved iron during extreme precipitation events
文章编号: N19102607
期刊: Chemosphere
作者: Jiunian Guan, Kun Qi, Junyang Wang, Jiahui Zhuang, Xing Yuan, Baixing Yan, Nan Lu, Jiao Qu
更新时间: 2019-10-26
摘要: Natural wetlands play a critical role in increasing the total dissolved Fe (TDFe) concentration in boreal fluvial systems. In the Sanjiang Plain, which is the largest concentrated distribution area of natural wetlands in China, over 80% of the natural wetlands have been converted to rice paddy fields (RPFs) during the last six decades; the altered hydrological processes are hypothesized to influence the dynamics of TDFe, particularly during extreme precipitation events (EPEs). In the current study, the TDFe dynamics in typical natural freshwater wetlands in the Sanjiang Plain were elucidated. The TDFe species including Fe(II), Fe(III) and colloidal Fe, were monitored in a Deyeucia angustifolia wetland (DAW), Carex lasiocarpa wetland (CLW), and RPF during the rainy season from 2012 to 2014. Compared to normal precipitation days, the average TDFe concentration increased significantlys in all wetlands during the EPEs, among which the fluctuation of TDFe during the EPEs was more largely in the RPF than in the natural wetlands. The dynamics of the TDFe speciation in the different wetlands also showed different patterns; moreover, TDFe and its species showed a significantly positive relationship with dissolved organic matter. With an increasing frequency of EPEs anticipated by climate change models, our results suggest higher levels of TDFe will be transported to the Amur River and Okhotsk Sea, which may potentially affect TDFe cycling, water quality and ecosystem dynamics.
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25409. 题目: Influence of phyllosilicates on the hydrothermal alteration of organic matter in asteroids: experimental perspectives
文章编号: N19102606
期刊: Geochimica et Cosmochimica Acta
作者: V. Vinogradoff, C. Le Guillou, S. Bernard, J.C. Viennet, M. Jaber, L. Remusat
更新时间: 2019-10-26
摘要: The origin of the diverse organic compounds present in carbonaceous chondrites (CC) remains uncertain. We aim at investigating the role that hydrothermal alteration may have had on the molecular evolution of organic matter (OM). In particular, within CC matrices, OM is intimately embedded within phyllosilicates down to the nanometer scale, which raises the question of the influence of phyllosilicates on OM transformation during hydrothermal alteration on parent bodies. We conducted hydrothermal experiments at 150°C and alkaline pH, using a well-known molecule present in processed interstellar ice analogues, the hexamethylenetetramine (HMT), in the presence of Al- and Fe-rich smectites. Experimental products were characterized by gas chromatography mass spectrometry, infrared spectroscopy, X-ray diffraction and synchrotron-based X-ray absorption near edge structure spectroscopy. Within 31 days, the HMT+smectites+H2O system leads to (1) the formation of a diverse suite of soluble organic compounds, yet less abundant and less complex than in the absence of smectite, (2) carbon-rich smectite residues (3.8 wt.% and 2.6 wt.% of carbon for the Al- and Fe-rich smectite residues, respectively). In addition, the abundance and molecular composition of the final organic compounds depend on the nature of the phyllosilicate (Al vs. Fe-smectite). Various and complex interaction mechanisms could occur between OM and smectite. Physisorption, chemisorption and intercalation processes have likely entrapped a significant portion of the organic compounds, thereby altering their chemical evolution. The present work demonstrates that the presence and the nature of phyllosilicates influences the reaction pathways of organic compounds during hydrothermal alteration and that the presence of organic compounds may impact the mineral assemblage. This could have had significant importance for the co-evolution of OM and mineral phases in primitive bodies during hydrothermal alteration.
25410. 题目: Bismuth impregnated biochar for efficient estrone degradation: The synergistic effect between biochar and Bi/Bi2O3 for a high photocatalytic performance
文章编号: N19102605
期刊: Journal of Hazardous Materials
作者: Ningyuan Zhu, Chunquan Li, Lingjun Bu, Cilai Tang, Sichu Wang, Pengfei Duan, Lunguang Yao, Jun Tang, Dionysios D. Dionysiou, Yonghong Wu
更新时间: 2019-10-26
摘要: An innovative advanced oxidation process was successfully developed to photocatalytic-degradation of estrone through the synergistic effect of biochar and Bi/Bi2O3 in bismuth-containing photocatalytic biochar (BiPB). The highest reaction rate constant (kobs) of estrone degradation by BiPB was 0.045 min−1 under the conditions of initial concentration of estrone =10.4 μmol L−1, [BiPB] =1 g L−1, pH = 7.0. The kobs was almost tenfold and more than 20 times than that of biochar without bismuth impregnation and pristine Bi/Bi2O3, respectively. The best photocatalytic performance of BiPB composites for the degradation of estrone was primarily attributed to generation of OH radicals. Impregnation of bismuth helped control the concentration of persistent free radicals (PFRs) and develop a hierarchical porous structure of biochar. The presence of biochar facilitated pre-concentration estrone on BiPB and improved the separation and transfer efficiency of charge carriers. The synergistic effect between biochar and Bi/Bi2O3 contributed to the generation of OH radicals for estrone degradation under neutral pH conditions. The transformation pathway of estrone was also proposed based on the measured transformation products in the presence of BiPB. The high efficiency of BiPB composites indicated that this easily-obtained material was promising for estrone-wastewater treatment applications as a low-cost composite photocatalyst.
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25411. 题目: Removal of chemical oxygen demand and ammonia nitrogen from lead smelting wastewater with high salts content using electrochemical oxidation combined with coagulation–flocculation treatment
文章编号: N19102604
期刊: Separation and Purification Technology
作者: Xiangsong Meng, Sultan Ahmed Khoso, Feng Jiang, Ye Zhang, Tong Yue, Jiande Gao, Shangyong Lin, Runqing Liu, Zhiyong Gao, Pan Chen, Li Wang, Haisheng Han, Honghu Tang, Wei Sun, Yuehua Hu
更新时间: 2019-10-26
摘要: Electrochemical oxidation (EO) is a versatile treatment method; however, it has not been used yet for the removal of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) wastewater produced from the lead smelting or other smelting operations. In current research work, an attempt was made to apply EO combined with coagulation–flocculation (CF) mechanism for the removal of COD and NH4+-N from lead smelting wastewater containing high salts by using low-cost graphite anode. Systematic studies based on laboratory experiments were conducted to evaluate COD and NH4+-N removal, and the removal mechanism was discussed. Results showed that, current density was the most influential factor among the three factors studied including current density, initial pH and Cl− concentration. Both the COD and NH4+-N were removed completely from the wastewater with increasing current density and electrolysis time. The morphology of graphene stripped out after electrolysis was also studied. Total organic carbon and excitation–emission matrix fluorescence analysis proved that the reduction of COD was mainly due to the degradation of most of the organic matter in wastewater to carbon dioxide. The total nitrogen analysis means that the reduction of NH4+-N was mainly due to the degradation of NH4+-N to nitrogen. From overall results, it was concluded that COD reduction was the result of the synergistic effect of the direct oxidation of organic matter on the anode plate and the indirect oxidation of active chlorine in solution, while the reduction of NH4+-N was the indirect oxidation of the active chlorine in solution. As the low-cost graphite electrode was used as anode, thus the current technology avoided the use of costly boron-doped diamond and metal oxide (eg. RuO2, IrO2 and PbO2) electrodes and achieved the fixed investment cost of electrode plates lower and more advantageous in industrial applications. Laboratory-scale test treatment cost was 9.28 US$/m3.
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25412. 题目: Land-use alters the temperature response of microbial carbon-use efficiency in soils – a consumption-based approach
文章编号: N19102603
期刊: Soil Biology and Biochemistry
作者: Tobias Bölscher, Göran I. Ågren, Anke M. Herrmann
更新时间: 2019-10-26
摘要: Soil organic carbon (SOC) is a substantial source of atmospheric CO2, but also a large cause of uncertainties in Earth-system models. A principal control on soil CO2 release is the carbon-use efficiency (CUE) of microbial communities, which partitions the carbon (C) allocation between biosynthetic stabilization and CO2 respiration during SOC decomposition. In Earth-system models, CUE is commonly considered as a constant, although it should be susceptible to environmental factors such as temperature. We explored CUE across a set of land-uses and temperatures, and we show the hitherto neglected phenomenon that land-use can alter the temperature response of CUE. In arable soils, CUE was constant over a temperature range between 5 and 20 °C, but it decreased with temperature in ley farming, grassland, and forest soils at temperatures above 12.5 °C. The decrease in CUE was strongest for forest soils. Implementing our findings into a soil-C model revealed substantial differences in projected SOC losses: Assuming an increase of mean annual temperature of 2 or 4 °C, soils were projected to lose up to 6 or 15% of their current SOC, respectively, until they reach a new steady-state. These projections varied among land-uses. Our findings confront the current representation of CUE in global C models and challenges C sequestration strategies based on land-use changes, because land-uses such as e.g. forest ecosystems with current high C storage may lose substantially more C than agricultural soils due to strong declines of CUE.
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25413. 题目: Arbuscular mycorrhiza enhances rhizodeposition and reduces the rhizosphere priming effect on the decomposition of soil organic matter
文章编号: N19102602
期刊: Soil Biology and Biochemistry
作者: Jie Zhou, Huadong Zang, Sebastian Loeppmann, Matthias Gube, Yakov Kuzyakov, Johanna Pausch
更新时间: 2019-10-26
摘要: Arbuscular mycorrhizal fungi (AMF) represent an important route for plant carbon (C) inputs into the soil. Nonetheless, the C input via AMF as well as its impact on soil organic matter (SOM) stabilization and C sequestration remains largely unknown. A mycorrhizal wild type progenitor (MYC) and its mycorrhiza defective mutant (reduced mycorrhizal colonization: rmc) of tomato were continuously labeled with 13CO2 to trace root C inputs into the soil and quantify rhizosphere priming effects (RPE) as affected by AMF symbiosis and N fertilization. Mycorrhizal abundance and 13C incorporation into shoots, roots, soil and CO2 were measured at 8, 12 and 16 weeks after transplanting.AMF symbiosis decreased the relative C allocation (% of total assimilated C) to roots, in turn increased the net rhizodeposition. Positive RPE was recorded for both MYC and rmc plants, ranging from 16 to 71% and 25–101% of the unplanted control, respectively. Although net rhizodeposition was higher for MYC than rmc plants 16 weeks after transplanting, the RPE was comparatively lower. This indicated a higher potential for C sequestration by plants colonized with AMF (MYC) because the reduced nutrient availability restricts the activity of free-living decomposers. Although N fertilization decreased the relative C allocation to roots, rhizosphere and bulk soil, it had no effect on the absolute amount of rhizodeposition to the soil. The RPE and N-cycling enzyme activities decreased by N fertilization 8 and 12 weeks after transplanting, suggesting a lower microbial N demand from SOM mining. The positive relationship between enzyme activities involved in C cycling, microbial biomass C and SOM decomposition underlines the microbial activation hypothesis, which explains the RPE. We therefore concluded that AMF symbiosis and N fertilization increase C sequestration in soil not only by increasing root C inputs, but also by lowering native SOM decomposition and RPE.
25414. 题目: Characterization of stratified EPS and their role in the initial adhesion of anammox consortia
文章编号: N19102601
期刊: Water Research
作者: Weigang Wang, Yuan Yan, Yuhao Zhao, Qin Shi, Yayi Wang
更新时间: 2019-10-26
摘要: Anammox bacteria tend to self-aggregate, and biofilm-based anammox processes are widely used as sustainable alternative methods for nitrogen removal from wastewater. However, the mechanism for the initial adhesion of anammox bacteria remains unclear. In this work, extracellular polymeric substances (EPS) were extracted separately from anammox granules and then characterized by multi-methods. The adhesion properties of anammox consortia to biotic and abiotic surfaces were examined separately before and after the extraction of three stratified EPS, using aggregation assays and a quartz crystal microbalance technique with dissipation monitoring, respectively. The extraction of each of the three stratified EPS gradually increased the initial aggregation of anammox consortia from 77.6 ± 3.0% to 85.2 ± 2.6%. Fourier transform infrared spectrometry confirmed that the aggregation of anammox consortia depended largely on the interactions between functional groups on the cell surfaces. All three stratified EPS had positive effects on the initial adhesion rate and mass of anammox consortia to abiotic surfaces. More importantly, the structure of the adhered layer was more compact before the extraction of each of the three stratified EPS. We therefore hypothesized that the initial adhesion among anammox consortia was due to the ability of the anammox bacteria to express adhesion molecules on the bacterial surfaces and that the three stratified EPS were excreted to adhere inert particulates and form a compact biofilm structure. This study clarifies the role of stratified EPS on the initial formation of anammox biofilms and provides a theoretical basis for accelerating the formation of anammox biofilms.
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25415. 题目: Using functional traits to assess the influence of burrowing bivalves on nitrogen-removal in streams
文章编号: N19102508
期刊: Biogeochemistry
作者: Zachary L. Nickerson, Behzad Mortazavi, Carla L. Atkinson
更新时间: 2019-10-25
摘要: Functional traits define an organism in terms of how the organism interacts with its environment and determine the influence the organism has on dynamic ecosystem processes, such as biogeochemical nutrient cycling. Freshwater mussels (Bivalvia: Unionidae) form hotspots of biogeochemical activity in benthic environments by alleviating nutrient limitation at the sediment–water interface; however, little is known about the influence of mussel functional traits on sediment biogeochemical cycles, particularly nitrogen (N)-removal via denitrification and anammox. Our aim was to model the influence of two mussel functional traits: ammonium (NH4+) excretion and organic matter (OM) biodeposition, on N-removal in stream sediments. We quantified mussel excretion and biodeposition and incubated mussels in microcosms containing river sediment using flow-through methods. We measured nutrient and gas fluxes to quantify real-time ambient N-removal (denitrification + anammox), and conducted isotope pairing techniques to determine the maximum N-removal potential for denitrification and anammox pathways. NH4+ excretion was shown to be a significant predictor of ambient N-removal, whereas OM biodeposition significantly increased the maximum N-removal potential in the sediment. Our study is the first of its kind to link mussel functional traits specifically to N-removal and contributes to the growing knowledge of the role these highly imperiled organisms play by directly and indirectly influencing ecosystem-scale processes in lotic systems.
25416. 题目: Dissolved black carbon enhanced the aquatic photo-transformation of chlortetracycline via triplet excited-state species: The role of chemical composition
文章编号: N19102507
期刊: Environmental Research
作者: Yajun Tian, Li Feng, Chun Wang, Yongze Liu, Jinru Zou, Renna Li, Ziwen Du, Liqiu Zhang
更新时间: 2019-10-25
摘要: Dissolved black carbon (DBC), widely distributed in the aquatic environments, can accelerate sunlight-driven photo-transformation of micropollutants, however the photosensitization mechanisms are not clear. Herein, the DBC was extracted from bamboo biochar and fractionated by molecular weight (i.e. <10 k, <3 k, and <1 k Da). The effects of DBC on chlortetracycline (CTC) photolysis behaviors, and the role of chemical composition (i.e., molecular weight and chemical structure) in DBC-mediated photo-transformation were investigated. The results showed that DBC could accelerate CTC photodegradation significantly. At low DBC concentrations (<6.0 mg C/L), the photodegradation rate constant of CTC increased from 0.0299 to 0.0416 min−1 with the increasing DBC concentration. Via quenching experiment, the triplet excited-state of DBC was identified as the dominant reactive intermediate with >90% contribution to total CTC photodegradation. In addition, it was found that the photosensitive efficiency of DBC increased as the molecular weight decreased, and the stronger photosensitization ability exhibited in DBC with low-molecular weight was potentially attributed to its higher content of carbonyl compounds. The observed photosensitive efficiency of DBC sharply decreased after reduction by NaBH4, further confirming the key role of carbonyl compounds in the photosensitization process. Moreover, based on the result of photoproducts, the amidogen in CTC was verified to be susceptible to react with 3DBC*.
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25417. 题目: Llandovery (Lower Silurian) nodular barite from the northern margin of Yangtze Block, South China, and its paleoceanographic implications
文章编号: N19102506
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Bowen Zan, Jiaxin Yan, Shugen Liu, Chuanlong Mou, Bo Ran
更新时间: 2019-10-25
摘要: The Llandovery epoch (Early Silurian) was marked by the interruption of widespread oceanic anoxia and associated oxygenation of seawater. The first oxygenation event appears to occurred near the Rhuddanian–Aeronian stages boundary. However, ventilation of the marine environments is a dynamic process, differing in timing and magnitude from place to place, basic variations in the nature of marine circulation; e.g., open shelf versus restricted shelf. The correlation of oxygenation events from open to restricted shelf environments is of significance to enhancing our understanding of marine ventilation processes. This paper describes nodular barite that accumulated in the open marine environment near the boundary at the northern margin of the Yangtze Block, South China, emphasizing its origin and environmental implications. Petrographic evidence suggests that the nodular barite is early diagenetic. Barium was likely derived from the dissolution of biogenic barite as suggested by the 87Sr/86Sr values of the diagenetic barite. The REE+Y pattern, low Y/Ho and high Ce*/Ce values of the barite nodules demonstrate that microbial degradation of organic matter in association with Ce oxidation controlled REE composition of the nodules. PAAS-normalized positive Eu anomalies of the studied barite, however, suggest an anoxic porewater environment perhaps related to bacterial sulfate reduction or the anaerobic oxidation of methane focused within the sulfate-methane transition zone (SMTZ) as also indicated by the minor contribution of radiogenic terrigenous Sr isotopes. We infer that high marine productivity and the associated transport of barite to the sea floor may critical to the formation of the studied barite nodules. Formation and preservation of barite in Aeronian stage deposits may indicate that circulation of open marine water masses has been much ameliorated. Our results are consistent with earlier suggestions that the restricted shelf experienced a transition from anoxic or even euxinic conditions to a more oxygenated (probably suboxic) condition during the early Aeronian. The approximately contemporaneous nature of this transition and global cooling associated with the glacial pulses indicate the critical role that global climate change near the Rhuddanian–Aeronian (R-A) boundary played in the redox evolution of the Yangtze Block, South China.
25418. 题目: Molecular properties are a primary control on the microbial utilization of dissolved organic matter in the ocean
文章编号: N19102505
期刊: Limnology and Oceanography
作者: Yuan Shen, Ronald Benner
更新时间: 2019-10-25
摘要: The global ocean sequesters a large amount of reduced carbon in dissolved organic molecules that can persist for centuries to millennia. The persistence of dissolved organic carbon (DOC) in the deep ocean has been attributed to inherently refractory molecules and to low concentrations of molecules, but the relative roles of molecular properties and molecular concentrations remain uncertain. We investigate both of these possibilities using bioassay experiments with unfiltered seawater collected from five depths (50–1500 m) at the Bermuda Atlantic Time‐Series Study site. The microbial utilization of compositionally distinct forms of seawater DOC at in situ and elevated concentrations was determined. Microbial utilization of in situ organic carbon ranged from 6% to 7% in surface waters to 0% in deep water after 180 d. Additions of surface plankton‐derived DOC (~18 μmol L−1), which was enriched in amino acids and carbohydrates, revealed substantial (50–75%) removal of the added DOC at all depths within 7 d. In sharp contrast, additions of C‐18 isolated deep‐sea DOC (~20 μmol L−1) showed insignificant or minimal utilization at all depths after 7 or 180 d, even when primed with labile substrates. These experiments demonstrate microbial communities from varying depths and environments in the ocean could rapidly utilize elevated concentrations of plankton‐derived DOC, whereas these same microbes failed to utilize elevated concentrations of C‐18 DOC. These results indicate molecular properties are the primary control on the microbial utilization of DOC in the ocean. Our findings imply a dynamic DOC reservoir with a flexible capacity for carbon sequestration in the global ocean.
25419. 题目: Organic N deposition favours soil C sequestration by decreasing priming effect
文章编号: N19102504
期刊: Plant and Soil
作者: Peng Tian, Shengen Liu, Qingkui Wang, Tao Sun, Evgenia Blagodatskaya
更新时间: 2019-10-25
摘要: Background and aims: Atmospheric nitrogen (N) deposition alters the priming effect (PE), which is defined as the change in native soil organic carbon (SOC) decomposition by exogenous C inputs. However, how the priming intensity varies under chemically heterogeneous N deposition, particularly with increasing labile C input, remains unclear. Methods: We collected soils from a temperate forest in northeastern China that had received simulated organic and/or inorganic N deposition for 6 years. The soils were incubated with or without three levels of 13C-labelled glucose solution for 152 days. CO2 emission and its 13C value were continuously measured to calculate the PE. Results: Enhanced SOC decomposition (i.e., a positive PE) was observed after glucose addition, regardless of the N deposition form. The PE intensity increased with the increase in the glucose addition level. However, organic N decreased the PE by 12.3-23.2%. The SOC-derived microbial biomass was 16.2-34.3% lower in organic N-treated soil, indicating that preferential utilization of exogenous labile C by microorganisms was responsible for the decrease in PE. The PE inhibition by organic N increased nonlinearly as a function of glucose level. Furthermore, the net annual change in SOC as a balance between the replenishment of added glucose-C and primed C was larger in organic N-treated soil due to a decrease in soil microbial metabolic quotient. Conclusions: In this study, we found that organic N deposition inhibited the PE, and the inhibition effect was intensified with increasing C inputs, favouring SOC sequestration.
25420. 题目: Multivariate analysis and multiple linear regression as a tool to estimate the behavior of hexazinone in Brazilian soils
文章编号: N19102503
期刊: Environmental Monitoring and Assessment
作者: Luiz Odonil Gomes dos Santos, Matheus de Freitas Souza, Paulo Sergio Fernandes das Chagas, Taliane Maria Silva da Teófilo, Maria Alice Porto Formiga, Rita Cássia Araújo de Medeiros, Daniel Valadão Silva
更新时间: 2019-10-25
摘要: Weed control efficiency and the environmental contamination potential of herbicides depend on soil sorption and desorption. Among the indexes that evaluate the soil adsorption processes, the coefficients sorption (Kfs) and desorption (Kfd) obtained by Freundlich isotherms can provide accurate information about the behavior of an herbicide in the soil. The values of Kfs and Kfd of an herbicide vary according to the physicochemical characteristics of the soil, so it is possible to estimate these coefficients with high precision if good predictive mathematical models are constructed. Therefore, our objective aimed to evaluate the use of multiple regression models (MLR) associated with multivariate techniques to estimate the coefficient Kfs and Kfd for the hexazinone based on the chemical and physical attributes of soils. The correlation analyses, principal components, and clustering analysis allowed the multiple linear regression technique to generate models with higher adjustment coefficient (R2) for Kfs (0.73 to 0.99) and Kfd (0.94 to 0.99), and lower root mean squared error (RMSE) for Kfs (0.003 to 0.065) and Kfd (0.018 to 0.120). Regression models created from groups of soils showed greater prediction performance for Kfs and Kfd. The organic matter followed by the cation exchange capacity was the most important attributes of soils in sorption and desorption processes of hexazinone.