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14601. 题目: Effects of shrub encroachment on vertical changes in soil organic carbon in Mongolian grasslands: using a multi-biomarker approach
文章编号: N18092502
期刊: Plant and Soil
作者: Luhong Zhou, He Li, Haihua Shen, Yunping Xu, Yinghui Wang, Aijun Xing, Yankun Zhu, Shangzhe Zhou, Jingyun Fang
更新时间: 2018-09-25
摘要: Aims: In recent decades, ecologists have investigated the effects of shrub encroachment on regional carbon cycling in semi-arid and arid regions. Although differences in carbon sequestration and stocks have been recognized in different soil layers, the vertical changes in soil organic carbon (SOC) at the molecular level following shrub encroachment remain unexplored. In this study, we used biomarkers to assess the impacts of shrub encroachment on SOC composition. Methods: We collected soil samples along the 1-m profile within shrub patches and grassy matrix in three typical shrub-encroached grassland (SEG) sites in Inner Mongolia, and quantified the vertical distribution of the biomarkers, including free lipids, bound lipids and lignin-derived phenols. Results: The principal component analysis (PCA) of the biomarker data showed that samples in the grassy matrix had strong positive loadings along the first two components (PCs); in contrast, samples in the upper 50 cm of the shrub patches had negative loadings along the first component (PC1) as well as a narrower range. The acid to aldehyde ratios of the vanillyl and syringyl type monomers increased simultaneously along the 1-m profile in the grassy matrix; however, this trend was not observed in the shrub patches. In addition, the vanillyls to syringyls to cinnamyls ratio was approximately 3:2:1 in the shrub patches and 3:2:1 or 2:2:1 in the grassy matrix. Conclusions: Shrub encroachment altered the vertical patterns in SOC composition, especially in the upper 50 cm, as well as the oxidation status of lignin-derived phenols along the entire 1-m profile. Further, shrub encroachment influenced the soil carbon composition under the shrub canopy as well as in the grassy matrix due to the sprawling canopies and the horizontal extension of the root systems of the encroaching shrubs. These results provided new insights into the vertical patterns of SOC changes after shrub encroachment at the molecular level and have important implications for understanding the mechanisms of soil carbon dynamics with changes in vegetation structure and composition.

14602. 题目: Effect of different biochars on phosphorus (P) dynamics in the rhizosphere of Zea mays L. (maize)
文章编号: N18092501
期刊: Plant and Soil
作者: Marie Louise Bornø, Joseph Osafo Eduah, Dorette Sophie Müller-Stöver, Fulai Liu
更新时间: 2018-09-25
摘要: Aim: To investigate the effects of biochar on biological and chemical phosphorus (P) processes and identify potential interactive effects between P fertilizer and biochar on P bioavailability in the rhizosphere of maize. Methods: We conducted a pot-experiment with maize in a sandy loam soil with two fertilizer levels (0 and 100 mg P kg −1) and three biochars produced from soft wood (SW), rice husk (RH) and oil seed rape (OSR). Sequential P fractionation was performed on biochar, bulk soil, and rhizosphere soil samples. Acid and alkaline phosphatase activity and root exudates of citrate, glucose, fructose, and sucrose in the rhizosphere were determined. Results: RH and OSR increased readily available soil P, whereas SW had no effect. However, over time available P from the biochars moved to less available P pools (Al-P and Fe-P). There were no interactive effects between P fertilizer and biochar on P bioavailability. Exudates of glucose and fructose were strongly affected by especially RH, whereas sucrose was mostly affected by P fertilizer. Alkaline phosphatase activity was positively correlated with pH, and citrate was positively correlated with readily available P. Conclusion: Biochar effects on biological and chemical P processes in the rhizosphere are driven by biochar properties.

14603. 题目: Integrated treatment of reverse osmosis brines coupling electrocoagulation with advanced oxidation processes
文章编号: N18092415
期刊: Chemical Engineering Journal
作者: Sara P. Azerrad, Mor Isaacs, Carlos G. Dosoretz
更新时间: 2018-09-24
摘要: The potential of integrating electrocoagulation (EleC) with two-stage reverse osmosis (RO) to enhance desalination of secondary/tertiary effluents through removal of dissolved organic matter (DOM) and scaling salts from brines was studied. EleC appears advantageous due to the high electrical conductivity of RO brines and low residual ions concentration. EleC was performed in batch mode in a flow-through cell with recirculation through a stirred reservoir at 9.4 mA/cm2 current density. Anode was made of Fe or Al as indicated, and cathode of stainless steel. Chemical coagulation (CC) with FeCl3 was tested as reference. EleC resulted in effective removal of phosphate (>99%), carbonate (88–98%) and DOM (40–50%) at a high Faradaic efficiency (>90%). Fe-EleC resulted less suitable than Al-EleC due to partial Fe(II) oxidation at pH 5.5 required for optimal DOM removal, leaving high Fe content and consequently turbidity in the supernatant, whereas residual Al was negligible. At optimal conditions Al release was 75 mg/L for 1st-stage brines-RO1 (2-fold concentrated) and 300 mg/L for 2nd-stage brines-RO2 (∼8.3-fold concentrated), corresponding to a specific energy consumption of 0.30 and 0.23 kWh/dm/(3mS/cm), respectively. Similar results were obtained with CC, however, its main disadvantage was the considerable increase of chlorides in the supernatant. Since coagulation removes quenching components from brines, coupling EleC with advanced oxidation processes (AOP), either UVA/TiO2 or UVC/H2O2, was also evaluated for oxidation of model micropollutants from brines prior to discharge. Either EleC or CC in tandem with AOP increased micropollutants oxidation by 3–4 fold compared to raw brines, achieving practically complete transformation.

14604. 题目: Degradation of three nonsteroidal anti-inflammatory drugs by UV/persulfate: Degradation mechanisms, efficiency in effluents disposal
文章编号: N18092414
期刊: Chemical Engineering Journal
作者: Yingying Fu, Xingsheng Gao, Jinju Geng, Shaoli Li, Gang Wu, Hongqiang Ren
更新时间: 2018-09-24
摘要: This study investigated the degradation of three nonsteroidal anti-inflammatory drugs (NSAIDs) (diclofenac (DCF), ibuprofen (IBP) and naproxen (NPX)) by UV/persulfate (UV/PS) in pure water and the influence of wastewater on UV/PS performance. Three NSAIDs have no obvious removal in the PS system, while they all showed a decrease in the UV system, and DCF showed the most significant decrease among the three NSAIDs in the UV system. The degradation of NSAIDs in UV/PS system followed the pseudo first-order degradation kinetics, and the kinetic constants orders are: kDCF > kNPX > kIBP. SO4 contributes more than ·OH in NSAIDs degradation according to tertiary butanol and methanol inhibition tests. According to the degradation products detected by LC-MS, hydroxylation and decarboxylation are main pathways in NSAIDs degradation, and dechlorination is also a main path in DCF degradation. When UV/PS was used to dispose effluents spiked with NSAIDs solution (DCF, NPX, IBP, 0.1 μM each), 10 times of PS dosage and 6 times treatment time were needed to get the same removal in pure water. The water quality parameters (i.e., natural organic matter (NOM), HCO3, Cl and NO3) affects the degradation of NSAIDs by UV/PS. The degradation efficiency of NSAIDs was inhibited in the presence of humic acid and HCO3. Meanwhile, Cl and NO3 barely influenced the degradation efficiency.
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14605. 题目: Stable and efficient partial nitritation granular sludge reactor treating domestic sewage at low temperature
文章编号: N18092413
期刊: Bioresource Technology
作者: Jianhua Zhang, Qiong Zhang, Yuanyuan Miao, Yawen Sun, Jianfei Chen, Yongzhen Peng
更新时间: 2018-09-24
摘要: The success of combined partial nitritation (PN) and anammox process treating low-strength domestic wastewater depends on achieving a stable and efficient PN. In this study, desirable PN for domestic sewage with low temperature of 11.8-16.9 °C was achieved in a granular sludge reactor operated in anaerobic/aerobic (A/O) mode. Average nitrite accumulation ratio of 97.3% was obtained with an effluent nitrite/ammonium ratio of 1.2 for influent ammonium of 39.3-78.7 mg·L-1. Quantitative microbial analysis and activity batch test showed that nitrite oxidizing bacteria (NOB) were effectively suppressed, while ammonium oxidizing bacteria (AOB) were dominant. For the efficient suppression of NOB, A/O mode, aerobic phosphorus uptake and granular sludge could play important roles. Furthermore, high AOB activity was obtained with an average ammonium oxidation rate of 11.6 mg N·L-1·h-1, which could be due to the abundant psychrotolerant microorganisms, increased content of extracellular polymeric substances and relatively high dissolved oxygen condition of the reactor.
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14606. 题目: Hydrodynamic shear force shaped the microbial community and function in the aerobic granular sequencing batch reactors for low carbon to nitrogen (C/N) municipal wastewater treatment
文章编号: N18092412
期刊: Bioresource Technology
作者: Qiulai He, Li Chen, Shujia Zhang, Rongfan Chen, Hongyu Wang
更新时间: 2018-09-24
摘要: The lab-scale aerobic granules process was applied for low carbon to nitrogen (C/N < 4) wastewater treatment under different hydrodynamic shear forces. Results revealed that aerobic granules exhibited strong adaptability and stability. The aerobic granules might adopt an extracellular polymeric substances (EPS) regulating mechanism to address the changes in operational conditions, especially through growing secretion of fluorescence protein. The hydrodynamic shear force determinedly shaped and regulated the diversity and structure of dominant microbial community, briefly, reduced aeration intensity with increased time led to higher microbial richness, lower diversity and evenness, and shifts of predominant microorganisms. Phylogenetic classification of the key functional groups including bacteria related to carbon and nutrients removal, EPS production and quorum sensing (QS) presented much more differences among the reactors subject to different conditions. Therefore, the present work adds insight into the comprehensive understanding of the effect of aeration induced hydrodynamic shear force on aerobic granules.
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14607. 题目: Effects of biochar size and type on gaseous emissions during pig manure/wheat straw aerobic composting: Insights into multivariate-microscale characterization and microbial mechanism
文章编号: N18092411
期刊: Bioresource Technology
作者: Xueqin He, Hongjie Yin, Lujia Han, Ruxiu Cui, Chen Fang, Guangqun Huang
更新时间: 2018-09-24
摘要: Greenhouse gas and ammonia emissions during composting with different biochar types and particle sizes were investigated. Compared with powder-biochar, granular-biochar improved pore connectivity and was benefit to methanotrophs activities, like Methylococcaceae, reducing CH4 emissions. At the same particle size, bamboo biochar (BB) had a higher pore volume and more aerobic microenvironment within the compost than rice straw biochar (RSB), reducing GHG emissions. Bamboo biochar had high aromatic compound and NO3 concentrations and therefore surface π–π electron donor/acceptor interactions, causing low N2O emissions and inhibiting denitrifying bacteria (e.g., Bacteroidales). More C–O and C=O bonds in rice straw biochar than bamboo biochar caused lower NH3 emissions using rice straw than bamboo biochar. Powdered biochar had more exposed reactive functional groups and decreased NH3 production better than granular biochar. Powdered bamboo biochar controls gaseous emissions better than other biochars during aerobic pig manure/wheat straw composting.
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14608. 题目: High-efficient nitrogen removal from municipal wastewater via two-stage nitritation/anammox process: long-term stability assessment and mechanism analysis
文章编号: N18092410
期刊: Bioresource Technology
作者: Pengfei Jin, Baikun Li, Dongyang Mu, Xiyao Li, Yongzhen Peng
更新时间: 2018-09-24
摘要: This study focused on the long-term stability of a novel two-stage partial-nitritation/anammox (PN/A) process treating municipal wastewater with fluctuated water quality. Specifically, two parallel sequencing batch reactors (SBRs) were used for removing organic matters and achieving complete nitritation, while the expanded granular sludge bed (ANA-EGSB) was used for anammox. With the influent ammonium concentration varying from 32 to 79 mg/L and the average hydraulic retention time of 3.39 h in this system, more than 93% of ammonium was removed and the effluent TIN was 4.8-11.8 mg/L. The partial denitrifying occurring in the anammox reactor could reduce nitrate to nitrite that was reused by anammox bacterium, enhancing the TIN removal efficiency. Further, the “overconsumption of ammonium” under anaerobic conditions was observed in ANA-EGSB. Microbial community analysis showed that Nitrosomonas (AOB) were the dominant nitrifying bacteria in the nitritation SBR and Candidatus_Brocadia with the relative abundance of 6-13% dominated in ANA-EGSB.
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14609. 题目: Concentration and mineralization of organic carbon in forest soils along a climatic gradient
文章编号: N18092409
期刊: Forest Ecology and Management
作者: Zhongna Zhao, Xiaorong Wei, Xiang Wang, Tiane Ma, Linqi Huang, Hailong Gao, Jun Fan, Xuezhang Li, Xiaoxu Jia
更新时间: 2018-09-24
摘要: Forty-four percent of the organic carbon (OC) in the world's forests is stored in soils. However, the distribution and stability of OC in forest soils along a climatic gradient remain largely unclear, hindering our understanding and the accurate prediction of biogeochemical cycles in forest ecosystems in a changing world. To address these uncertainties, we measured OC and nitrogen (N) concentrations and mineralization of OC in soils from broadleaved and coniferous forests along a wide-ranging climatic gradient in China and related these to experimental N addition and climatic conditions. An 85-day incubation was conducted under 25 °C and 60% of soil moisture at field capacity to determine the mineralization of soil OC. We hypothesized that the concentrations of OC and N would be higher but the mineralization of OC would be lower in soils from colder and drier forests and that the mineralization would be positively responsive to N addition. In support of these hypotheses, the concentrations of OC and N decreased, while the mineralization of OC measured under standard laboratory condition increased, with mean annual precipitation (MAP) and temperature (MAT). These metrics were not affected by forest type or the interaction between forest type and site. Nitrogen addition increased the cumulative mineralized OC (Cm, g kg−1) by 6–67%, and the effects varied with site and soil depth, but were similar between the broadleaved and coniferous forests. The Cm decreased with increasing soil OC concentration, C/N ratio and mineral N, while the rate constant of OC mineralization (k, day−1) showed opposite relationships with these metrics. The addition of N did not change the slopes of the relationships of Cm and k with the C/N ratio, MAP, and MAT; however, it strengthened the negative relationship of Cm with OC and mineral N concentrations. The results from this study suggested that the mineralization of OC was limited by N availability in the studied forested soils, and the response of OC mineralization to N addition was independent of climatic conditions.

14610. 题目: Reconstruction of palaeo-depositional environment in North-Eastern Arabian Sea
文章编号: N18092408
期刊: Environmental Earth Sciences
作者: Joel E. Diniz, G. N. Nayak, Cheryl A. Noronha-D’Mello, Ravi Mishra
更新时间: 2018-09-24
摘要: A sediment gravity core recovered from the North-Eastern Arabian Sea was investigated for sediment grain size, total organic carbon (TOC) and selected trace metals to understand the changes in the depositional environment over time. The core exhibited three distinct zones of sediment, the lower zone I, middle zone II and upper zone III, representing the varying conditions of sediment deposition. The lower zone is dominated by the silt-sized fraction with low organic carbon that revealed a shallow depositional environment and led to oxidation of organic matter, while the low metal concentration in this zone was either due to the low intensity of monsoon or the dilution by biogenic components and aeolian sediment influx. On other hand, the middle zone represented a transition phase where metal along with clay and organic carbon concentration started increasing due to strengthening monsoon intensity. Further, the upper zone that represented the Holocene sediments pointed to the increase in concentration of metals Al, Fe, Co and Cu that indicated an increase in the intensity of the South-West Monsoon and led to large fluvial inputs. TOC also increased towards the surface, indicating an increase in productivity that was controlled by South-West Monsoon.

14611. 题目: Soil aggregate-associated distribution of DDTs and HCHs in farmland and bareland soils in the Danjiangkou Reservoir Area of China
文章编号: N18092407
期刊: Environmental Pollution
作者: Li Wang, Cheng Xue, Yushu Zhang, Zhiguo Li, Chuang Liu, Xia Pan, Fang Chen, Yi Liu
更新时间: 2018-09-24
摘要: Soil organic matter (SOM) is the principal aggregating agent for soil aggregation and also the main adsorbent for organochlorine pesticides (OCPs) such as dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH), which may thereby affect OCP distribution in soils subjected to different land use types. However, the potential effects of land use on SOM and OCP distribution patterns in soil aggregates are not well understood. In this study, soils from farmlands and barelands in the Danjiangkou Reservoir area were analyzed to determine the influence of land use on OCP distribution and composition in different aggregate fractions (>3, 1–3, 0.25–1, and <0.25 mm). The results showed that the levels of ∑DDTs ranged from 9.01 to 27.48 with a mean of 14.40 ng g−1, and ∑HCHs ranged from 2.06 to 4.66 with a mean of 3.19 ng g−1 in farmland soils. In comparison, bareland soils were less contaminated, with total DDTs and HCHs fell in the range of 0.75–5.01 ng g−1 and not detected (n.d.)-1.40 ng g−1 respectively. In regard to the distribution patterns in soil aggregates, the residual levels of ∑DDTs and ∑HCHs tended to a certain degree to enrich in microaggregates (<0.25 mm) relative to bulk soils. A further analysis revealed that the enrichment of ∑DDTs and ∑HCHs in microaggregates were mainly attributed to the accumulation of p,p'-DDE and β-HCH. Moreover, SOM was found also enriched in microaggregates. The enrichment of SOM was significantly and positively correlated with these of ∑DDTs, ∑HCHs, and the dominant metabolites (i.e., DDE and β-HCH) in both land use types. Such results indicated that the variations in behavior of OCPs could be linked to the processes of soil aggregate turnover. These findings may help to enrich the theory of soil OCPs sequestration and establish targeted strategies to mitigate their health risks in the environment.
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14612. 题目: Rapidly probing the interaction between sulfamethazine antibiotics and fulvic acids
文章编号: N18092406
期刊: Environmental Pollution
作者: Juan Xu, Yan-Yun Hu, Xiu-Yan Li, Jie-Jie Chen, Guo-Ping Sheng
更新时间: 2018-09-24
摘要: Antibiotics residuals in the environments receive wide concerns due to the high risk of generating antibiotic resistance. Natural organic matters (NOM) existed in the environments are considered to have the capacity of binding with organic contaminants, consequently influencing their speciation and transformation in the natural environments. To assess the migration of antibiotics in the environments, it is crucial to understand the binding mechanisms between NOM and antibiotics, which is still unclear due to the limit of available research methods. In this study, the interaction between fulvic acids (FA), one of the main components of NOM, and sulfamethazine (SMZ) was characterized by nuclear magnetic resonance (NMR) combined with surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) technology. The parameters related to kinetics and thermodynamics of the interaction were determined, and the possible mechanisms driving the interaction were also proposed. In addition, density functional theory (DFT) was used to predict the binding mode between FA and SMZ to reveal the interaction mechanism. Results indicate that FA can effectively bound with SMZ to form a stable complex with a binding constant at the level of 103 L/mol. The kinetic parameters including association and dissociation constants were 29.4 L/mol/s and 6.64 × 10−3 1/s, respectively. Hydrophobic interaction might play significant roles in the binding interaction with ancillary contribution of π-π conjunction arising from the aromatic rings stacking of FA and SMZ.
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14613. 题目: Microbially mediated nitrate-reducing Fe(II) oxidation: Quantification of chemodenitrification and biological reactions
文章编号: N18092405
期刊: Geochimica et Cosmochimica Acta
作者: Tongxu Liu, Dandan Chen, Xiaobo Luo, Xiaomin Li, Fangbai Li
更新时间: 2018-09-24
摘要: Redox reactions between iron and nitrogen drive the global biogeochemical cycles of these two elements and, concomitantly, change the fate of nutrients in and the mineralogy of the cycles. The microbially mediated NO3-reducing Fe(II) oxidation process (NRFO) plays a key role in Fe/N interactions under neutral-anoxic conditions. Microbially mediated NRFO was considered a biological process, yet recently it has been documented that chemical mechanisms are also at play. However, the relative contributions of biological processes and chemical processes to Fe(II) oxidation remain largely unquantified owing to the co-occurrence of the reactions. Herein, the kinetics and secondary minerals of microbially mediated NRFO by Pseudogulbenkiania sp. strain 2002 and Acidovorax sp. strain BoFeN1 were investigated with acetate as electron donor unless otherwise stated. The results of Cells + NO3 suggested the two strains could biologically reduce NO3 to NO3/NOx/N2O/N2 and concomitantly oxidize acetate and result in cell growth. Fe(II) oxidation and NO3 reduction occurred simultaneously in the presence of Fe(II) (Cells + Fe(II) + NO3). For strain BoFeN1, the presence of Fe(II) slightly enhanced the NO3 reduction, acetate consumption, and cell growth, all of which were substantially retarded by Fe(II) for strain 2002. When compared with the microbial nitrite reduction, the relatively higher rate of chemical reaction between NO2 and dissolved Fe(II) confirmed the occurrence of chemodenitrification in the microbially mediated NRFO processes. After 5 days’ incubation, no green rust was observed, and lepidocrocite, goethite, and magnetite were observed with the Cells + Fe(II) + NO3 treatment, but only goethite was found with the Fe(II) + NO2. The spectra for the EPSs + Fe(II) treatment suggested that the oxidized c-Cyts in the EPSs could oxidize Fe(II), which show the theoretical capability of taking electrons from Fe(II) into the cells via c-Cyts. A brief model was established by combining the verified reactions of (1) biological reduction of NO3 to NO2/NOx/N2O/N2, (2) Fe(II) oxidation by NO2, and (3) Fe(II) oxidation by c-Cyts in EPSs. Based on the model, the rate constant of Fe(II) oxidation by c-Cyts in EPSs was derived. For nitrite reduction, the relative contribution of biological processes to the nitrite reduction was higher than that of chemodenitrification. For Fe(II) oxidation, the relative contribution of the chemical process via nitrite to Fe(II) oxidation was higher than that of biological processes. These findings provide a quantitative interpretation of the chemodenitrification and biological reactions in the microbially mediated NRFO processes, which could assist the mechanistic understanding of the global biogeochemical cycles of iron and nitrogen in subsurface environments.

14614. 题目: Long-term effect of biochar amendment on the biodegradation of petroleum hydrocarbons in soil microbial fuel cells
文章编号: N18092404
期刊: Science of The Total Environment
作者: Xiaojing Li, Yue Li, Xiaolin Zhang, Xiaodong Zhao, Yang Sun, Liping Weng, Yongtao Li
更新时间: 2018-09-24
摘要: Biochar is extensively applied in amendment of contaminated soils. However, the effect of biochar on the biodegradation of petroleum hydrocarbons and electricity generation in soil microbial fuel cells (MFCs) remains unclear. Here, three biochars respectively derived from poultry (chicken manure, CB), agriculture (wheat straw, SB) and forestry industries (wood sawdust, WB) were investigated after 223 days of amendment. Consequently, high removal for alkanes was in CB with the mineral nutrition and phosphorus while aromatics were in SB with the most N content and the highest molecular polarity. The lowest removal efficiency of total petroleum hydrocarbons was observed in WB with the highest surface area, whereas the most charge was obtained. The different performance of soil MFCs was due to physicochemical properties of biochar and colonized microbial communities of bacteria and archaea. The abundance of Actinotalea increased by 144–263% in SB and CB while that of Desulfatitalea distinctly increased in WB. Meanwhile, species from Methanosarcina, Methanoculleus, Halovivax and Natronorubrum exerted probably a methanogenic degrading role. This study revealed that the degrader, azotobacter and electricigens exhibited a close relationship in order to degrade hydrocarbons and generate electricity in soil bioelectrochemical remediation systems.
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14615. 题目: Succession and diversity of microbial communities in landfills with depths and ages and its association with dissolved organic matter and heavy metals
文章编号: N18092403
期刊: Science of The Total Environment
作者: Si-jia Liu, Bei-Dou Xi, Zhong-Ping Qiu, Xiao-Song He, Hui Zhang, Qiu-Ling Dang, Xin-Yu Zhao, Dan Li
更新时间: 2018-09-24
摘要: Landfill is an important method for the treatment of municipal solid wastes. Microbes play a central role in the biodegradation and stabilization of organic matter during landfill; however, the succession of microbial communities in landfills and their association with organic matter still remain unclear. This study investigated the succession and diversity of microorganisms in landfill depending on different depths and ages as well as its association with dissolved organic matter (DOM) and heavy metals. The results showed that the actinobacterial diversity and richness were high compared to bacteria in young landfill cells. The diversity and richness of bacteria and actinobacterial were the highest in the middle layer in the intermediate and old landfill cells. Firmicutes, Proteobacteria, and Actinobacteria were the most dominant phyla. Firmicutes were mainly affected by the humification degree, and the aromatic and protein-like substance content of the landfill-derived DOM. The phylum Proteobacteria was greatly affected by the lipid and humic-like substances content of the landfill-derived DOM, while the distribution of Actinobacteria was regulated by both aromatic and humic-like substances. The effect of dissolved heavy metals on the microbial distribution in landfill differed for the metals Cr, Ni, Pb, Mn, Cu, Zn, and Cd. Siderophile elements (Cr, Ni, and Pb) were necessary trace elements for Proteobacteria and Actinobacteria, and promoted their growth. Oxyphilic element (Mn) was an important factor promoting the growth of Actinobacteria. However, no apparent relationship was found between sulfurophile elements (Cu, Zn, and Cd) and microorganisms.
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14616. 题目: Human-induced and natural carbon storage in floodplains of the Central Valley of California
文章编号: N18092402
期刊: Science of The Total Environment
作者: Kristin Steger, Peter Fiener, Mark Marvin-DiPasquale, Joshua H. Viers, David R. Smart
更新时间: 2018-09-24
摘要: Active floodplains can putatively store large amounts of organic carbon (SOC) in subsoils originating from catchment erosion processes with subsequent floodplain deposition. Our study focussed on the assessment of SOC pools associated with alluvial floodplain soils that are affected by human-induced changes in floodplain deposition and in situ SOC mineralisation due to land use change and drainage. We evaluated depth-dependent SOC contents based on 23 soil cores down to 3 m and 10 drillings down to 7 m in a floodplain area of the lower Cosumnes River. An estimate of 266 Mg C ha−1 or about 59% of the entire SOC stored within the 7 m profiles was found in the upper 2 m. Most profiles (n = 25) contained discrete buried A horizons at depths of approximately 0.8 m. These profiles had up to 130% higher SOC stocks. The mean δ13C of all deep soil profiles clearly indicated that arable land use has already altered the stable isotopic signature in the first meter of the profile. Radiocarbon dating showed that the 14C age in the buried horizon was younger than in overlaying soils indicating a substantial sedimentation phase for the overlaying soils. An additional analysis of total mercury contents in the soil profiles indicated that this sedimentation was associated with upstream hydraulic gold mining after the 1850s. In summary, deep alluvial soils in floodplains store large amounts of SOC not yet accounted for in global carbon models. Historic data give evidence that large amounts of sediment were transported into the floodplains of most rivers of the Central Valley and deposited over organically rich topsoil, which promoted the stabilization of SOC, and needs to be considered to improve our understanding of the human-induced interference with C cycling.
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14617. 题目: Effect of anaerobic/aerobic duration on nitrogen removal and microbial community in a simultaneous partial nitrification and denitrification system under low salinity
文章编号: N18092401
期刊: Science of The Total Environment
作者: Wuyi Huang, Zonglian She, Mengchun Gao, Qun Wang, Chunji Jin, Yangguo Zhao, Liang Guo
更新时间: 2018-09-24
摘要: In this study, the simultaneous partial nitrification and denitrification (SPND) process was investigated in a hybrid sequencing batch biofilm reactor (HSBBR) fed with synthetic wastewater with 1.2% salinity. Different anaerobic/aerobic (An/Ae) durations were selected for evaluating the removal performance of contaminants and the succession of the microbial community in the reactor. The highest organic matter removal efficiency was obtained at An/Ae hour ratio of 0/6.5, with an average chemical oxygen demand (COD) removal of 89.6% at the steady state. Similarly high nitrogen removal efficiencies were achieved at An/Ae hour ratios of 1/5.5, 1.5/5 and 2/4.5,with over 92% of average total nitrogen removed. This represents an increase of more than 10% compared to the mode with An/Ae hour ratio of 0/6.5. High-throughput sequencing analysis revealed that the increase of the An/Ae hour ratio changed the characteristics of the community structures in the HSBBR. Azoarcus was the most dominant genus when the An/Ae hour ratio was 0/6.5 in both suspended sludge (S-sludge) and biofilm, while Candidatus_Competibacter was the most abundant genus at An/Ae hour ratios of 2/4.5 and 3/3.5. Nitrosomonas was the only ammonia oxidizing bacteria (AOB) detected in this study. Nitrospira, a kind of nitrite oxidizing bacteria (NOB), was sensitive to salinity and altering the An/Ae mode; this was detected only in S-sludge samples in a fully aerobic mode with a low percentage of 0.1%. S-sludge and biofilm samples shared a similar bacterial composition. This research demonstrated that efficient nitrogen and carbon removal could be achieved via the SPND process by the symbiotic functional groups in a hybrid S-sludge and biofilm reactor.
图文摘要:

14618. 题目: Decoupling of Macromolecular Compositions of Particulate Organic Matters between the Water Columns and the Sediment in Geoje-Hansan Bay, South Korea
文章编号: N18092317
期刊: Ocean Science Journal
作者: Hyung Chul Kim, Jae Hyung Lee, Won-Chan Lee, Sokjin Hong, Jae Joong Kang, Dabin Lee, Naeun Jo, P. S. Bhavya
更新时间: 2018-09-23
摘要: The biochemical composition of particulate organic matter (POM) is very important to understand in relation to the trophic conditions of marine ecosystems since it forms the primary trophic base. The present study investigated the biochemical compositions (i.e., carbohydrates, proteins, and lipids) of POM monthly from January to December 2015 in Geoje-Hansan Bay to determine if the macromolecular composition of POM is coupled between the water columns and sediment. A spatial difference in the macromolecular compositions was observed in the water columns between the inner and outer bays, which may be caused by the different physiological conditions of phytoplankton growth that are due to the water circulation pattern in the bay. In contrast, no distinctive spatial difference in the macromolecular compositions was found in the sedimentary organic matter. Overall, while carbohydrates were the dominant (45.7%) macromolecules of the POM in the water columns, proteins were dominant (47.9%) in the sedimentary organic matter during our observation period. Decoupling of the macromolecular compositions between the water columns and underneath the sediment in Geoje-Hansan Bay appears to be a result of the various effects of selective filter feeding by oysters and protein-dominant benthic microalgae and fouling organisms.

14619. 题目: Influence of hydrodynamic processes on the fate of sedimentary organic matter on continental margins
文章编号: N18092316
期刊: Global Biogeochemical Cycles
作者: Rui Bao, Tessa S. van der Voort, Meixun Zhao, Xinyu Guo, Daniel B. Montluçon, Cameron McIntyre, Timothy I. Eglinton
更新时间: 2018-09-23
摘要: Understanding the effects of hydrodynamic forcing on organic matter (OM) composition is important for assessment of organic carbon (OC) burial in marginal seas on regional and global scales. Here, we examine the relationships between regional oceanographic conditions (bottom shear stress), and the physical characteristics (mineral surface area [SA], grain size) and geochemical properties (OC content [OC%], carbon isotope compositions [13C, 14C]) of a large suite of surface sediments from the Chinese marginal seas to assess the influence of hydrodynamic processes on the fate of OM on shallow continental shelves. Our results suggest that 14C content is primarily controlled by organo‐mineral interactions and hydrodynamically‐driven resuspension processes, highlighted by i) positive correlations between 14C content and OC% (and SA), and ii) negative correlations between 14C content and grain size (and bottom shear stress). Hydrodynamic processes influence 14C content due to both OC aging during lateral transport and accompanying selective degradation of OM associated with sediment (re) mobilization, these effects being superimposed on the original 14C characteristics of carbon source. Our observations support the hypotheses of Blair and Aller (2012) and Leithold et al. (2016) that hydrodynamically‐driven sediment translocation results in greater OC 14C depletion in broad, shallow marginal seas common to passive margin settings than on active margins. On a global scale, this may influence the extent to which continental margins act as net carbon sources and sinks. Our findings thus suggest that hydrodynamic processes are important in shaping the nature, dynamics, and magnitude of OC export and burial in passive marginal seas.

14620. 题目: Drivers of oxygen consumption in the northern Gulf of Mexico hypoxic waters - A stable carbon isotope perspective
文章编号: N18092315
期刊: Geophysical Research Letters
作者: Hongjie Wang, Xinping Hu, Nancy N. Rabalais, Jay Brandes
更新时间: 2018-09-23
摘要: We examined the stable carbon isotopic composition of remineralized organic carbon (δ13COCx) in the northern Gulf of Mexico (nGoM) using incubations (sediment and water) and a three end‐member mixing model. δ13COCx in incubating sediments was ‐18.1±1.3‰, and δ13COCx in incubating near‐surface and near‐bottom waters varied with salinity, ranging from ‐30.4‰ to ‐16.2‰ from brackish water to full strength Gulf water. The average δ13COCx was ‐18.6 ±1.8‰ at salinity >23. A three end‐member mixing model based on a multi‐year dataset collected in previous summer hypoxia cruises (2011, 2012, 2014, 2015 and 2016) suggested that δ13COCx in near‐bottom waters across the nGoM (5‐50 m) was ‐18.1±0.6‰. The close agreement of δ13COCx obtained from the three independent approaches, i.e., incubations of water column, surface sediments, and mixing model, suggests that 13C‐enriched organic matter of marine origin played the dominant role in near‐bottom water and benthic oxygen consumption in the nGoM shelf in summer.

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