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24601. 题目: Framework for Cost-Effective Prediction of Unregulated Disinfection By-Products in Drinking Water Distribution Using Differential Free Chlorine
文章编号: N18080106
期刊: Environmental Science: Water Research & Technology
作者: Gyan Chhipi Shrestha, Manuel J. Rodriguez, Rehan Sadiq
更新时间: 2018-08-01
摘要: Unregulated disinfection by-products (U-DBPs) in drinking water are formed primarily by the reaction of disinfectants (e.g., chlorine) and natural organic matter (NOM). The formation can be dictated by basic water quality and operational parameters. This purpose of this study was to develop a cost-effective framework for predicting U-DBP concentration in water distribution networks (WDNs) based on changes in free chlorine in the WDN with respect to that at the water treatment plant (WTP) outlet (called differential free chlorine, i.e., Cl2). Under the framework, mixed-effects models were developed to predict U-DBP families: haloacetonitriles (HANs) and haloketones (HKs) and individual compounds: chloropicrin (CPK), dichloroacetonitrile (DCAN), borochloroacetonitrile (BCAN), and 1,1,1 trichloropropanone (TCP). Common water quality parameters at the WTP outlet were also included to increase the effectiveness of the models. The models developed were applied successfully to two applications: a single large-sized and combined medium-sized water systems with the R2 of predictive models up to 0.95 and a 95% confidence interval of percent difference in the predictions of -27% to 32%. These applications show that Cl2 only or with basic water quality parameters at WTP are effective parameters for estimating U-DBP concentration in WDNs. The proposed framework can be used by water utilities as a low-cost method to develop models for their water systems to identify potential locations to monitor U-DBPs. Moreover, the frameworks can be used by public health organizations to assess population exposure to U-DBPs in drinking water.
24602. 题目: No difference in ectomycorrhizal morphotype composition between abandoned and inhabited nests of wood ants (Formica polyctena) in a central European spruce forest
文章编号: N18080105
期刊: Geoderma
作者: Veronika Jílková, Martin Vohník, Ondřej Mudrák, Hana Šimáčková, Jan Frouz
更新时间: 2018-08-01
摘要: In temperate forest ecosystems, ectomycorrhizal (EcM) fungi substantially support coniferous trees by nutrients, but importance of EcM for tree nutrition might be lower in nutrient-rich hotspots, such as in wood ant nests. In this study, we focused on differences in EcM morphotype composition between natural nutrient-rich hot spots of various quality (inhabited vs. abandoned wood ant nests) and the surrounding forest floor. In a secondary Norway spruce forest typical for central Europe, we took samples from different belowground parts of five inhabited and five abandoned nests (centre and rim) as well as from the forest floor 20 cm from the nests (run-off zone) and >3 m from the nests (forest soil). The substrates were subjected to analyses of the EcM morphotype composition, moisture and nutrient contents. Wood ant nest substrates had several times increased nutrient contents compared to the forest soil, but there were no significant differences in moisture. Available nutrient contents were higher in inhabited nests than in abandoned nests. The EcM morphotype composition differed between the nest samples and the forest floor samples but not between the inhabited and abandoned nests suggesting that, apart from the level of nutrient enrichment and their availability, moisture is another important factor affecting EcM community composition.
24603. 题目: Biochars mediated degradation, leaching and bioavailability of pyrazosulfuron-ethyl in a sandy loam soil
文章编号: N18080104
期刊: Geoderma
作者: Suman Manna, Neera Singh
更新时间: 2018-08-01
摘要: Burning of crop residues after harvest is a quick, cheap and an easy way to manage the large quantities of agricultural biomass for timely preparation of the field for next crop. Conversion of the crop harvest residues into biochars and incorporating them back in the same field can address the issue of land clearing, waste utilization and nutrient conservation but, any amendment to the soil changes its physico-chemical characteristics and can affect the fate of soil applied herbicides. The present study reports the effect of low (400 °C) and high (600 °C) temperature wheat (WBC) and rice (RBC) straw biochar's amendment on leaching, degradation and bioavailability of pyrazosulfuron-ethyl (PYRAZO) in a sandy loam soil. The PYRAZO was poorly retained in the control soil column where 78% of the soil-applied herbicide leached out of the control soil column. Biochars addition (0.02 and 0.05 g kg−1) significantly reduced the PYRAZO leaching by affecting herbicide's breakthrough time and its maximum concentration in leachate.
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24604. 题目: Characterizing dissolved organic matter in eroded sediments from a loess hilly catchment using fluorescence EEM-PARAFAC and UV–Visible absorption: Insights from source identification and carbon cycling
文章编号: N18080103
期刊: Geoderma
作者: Chun Liu, Zhongwu Li, Asmeret Asefaw Berhe, Haibing Xiao, Lin Liu, Danyang Wang, Hao Peng, Guangming Zeng
更新时间: 2018-08-01
摘要: The chemical characteristics of dissolved organic matter (DOM) in soils that experience erosion and deposition are key to the biogeochemical cycle of carbon on the earth's surface. However, data related to the transport and fate of DOM from soils that experience erosion and different management practices are scarce, particularly at catchment scales. In this study, soil samples (uppermost 10 cm) were collected from uplands representing four land use types (cropland, fallow, grassland, and forests) as well as gullies, and sediment samples (100 cm sampled at 10 depths) were collected from sediments retained by a check dam. Chemical characteristics of DOM in soils and sediments, as well as subsequent source identification, were inferred from UV–Visible absorption and fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC) as well as principal component analysis (PCA). The results indicated higher aromaticity, hydrophobic fraction, and molecular size in DOM from forest soils than those from other land use types and gullies. These factors were also higher in soils at the eroding sites than in sediments. EEM-PARAFAC analysis demonstrated that more protein-like components (tyrosine-like and tryptophan-like combined, accounting for >42.77%) were present in sediments compared to soils with terrestrial humic-like substances. PCA results revealed that approximately 72% of the variance in the DOM characteristics was explained by the first two principal components and that the DOM in upland and gully soils had a negligible contribution to DOM in sediments. Combined our results indicate that, despite the large amount of sediment-associated carbon that is transported by erosion and trapped in check dams, DOM is likely mineralized during soil transport. Furthermore, biological production of new organic compounds (autochthonous sources) are likely the major source of sediment DOM in depositional settings.
24605. 题目: Anaerobic organic carbon mineralization in tidal wetlands along a low-level salinity gradient of a subtropical estuary: Rates, pathways, and controls
文章编号: N18080102
期刊: Geoderma
作者: Min Luo, Wenfeng Zhu, Jiafang Huang, Yuxiu Liu, Xun Duan, Jie Wu, Chuan Tong
更新时间: 2018-08-01
摘要: To examine how the rates and pathways of anaerobic organic carbon mineralization (AOCM) of tidal freshwater wetlands change with low-level increases in salinity, we investigated the rates and controls of microbial iron and sulfate reduction, methane production, and total AOCM in tidal wetlands along a freshwater to oligohaline (0.1–3.3 ppt) gradient in the Min River Estuary in southeastern China. Porewater chloride was found to be strongly correlated with total organic carbon (TOC), carbon to nitrogen (C:N) ratios, and porewater geochemistry (sulfate, pH, ammonium, and dissolved methane levels). Furthermore, a higher plant biomass, larger iron oxides pool, and lower sulfide levels were observed in the oligohaline wetlands. The contribution of microbial sulfate reduction to AOCM increased from 16% to 67%. In contrast, the contribution of microbial iron reduction and methane production declined from 52% to 22% and 12% to 2%, respectively, along the increasing salinity gradient. No consistent changes were found in the total AOCM rates. The rates of methane production were primarily controlled by the C:N ratios and concentrations of porewater ammonium and amorphous iron oxides, while the microbial sulfate and iron reduction rates were mainly controlled by belowground biomass, water content, and concentrations of porewater chloride and sulfate. Our findings provide insight into the potential consequences of modest saltwater intrusion; these may not alter the rates of AOCM in the Min River Estuary, but could change the dominant AOCM pathway from microbial iron reduction to sulfate reduction and accelerate sulfidic effects in this historically freshwater wetland ecosystem.
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24606. 题目: The occurrence, distribution and degradation of antibiotics by ionizing radiation: An overview
文章编号: N18080101
期刊: Science of The Total Environment
作者: Jianlong Wang, Run Zhuan, Libing Chu
更新时间: 2018-08-01
摘要: Antibiotics have been extensively applied, making them ubiquitous in aquatic environment. As emerging contaminants, the occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystem. However, antibiotics cannot be effectively removed in conventional biological treatment processes, and their natural biodegradation is also ineffective. In this review, the occurrence and distribution of antibiotics in aquatic environments, including surface water, wastewater and effluent of wastewater treatment plants, were analyzed and summarized. Recent progress of antibiotics degradation by ionizing radiation was reviewed. The various influencing factors, such as absorbed dose, initial concentration, inorganic anions and organic matters, on the removal efficiency of antibiotics were introduced and discussed. To improve their removal efficiency, several advanced oxidation processes (AOPs) such as H2O2, Fe2+, Fe2+/H2O2, as well as biological treatment processes, are combined with ionizing radiation. Some suggestions for future studies of antibiotics degradation by ionizing radiation were proposed. Ionizing radiation may be a promising technology for removal of antibiotics from water and wastewater.
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24607. 题目: Climate and plant controls on soil organic matter in coastal wetlands
文章编号: N18073118
期刊: Global Change Biology
作者: Michael J. Osland, Christopher A. Gabler, James B. Grace, Richard H. Day, Meagan L. McCoy, Jennie L. McLeod, Andrew S. From, Nicholas M. Enwright, Laura C. Feher, Camille L. Stagg, Stephen B. Hartley
更新时间: 2018-07-31
摘要: Coastal wetlands are among the most productive and carbon‐rich ecosystems on Earth. Long‐term carbon storage in coastal wetlands occurs primarily belowground as soil organic matter (SOM). In addition to serving as a carbon sink, SOM influences wetland ecosystem structure, function, and stability. To anticipate and mitigate the effects of climate change, there is a need to advance understanding of environmental controls on wetland SOM. Here, we investigated the influence of four soil formation factors: climate, biota, parent materials, and topography. Along the northern Gulf of Mexico, we collected wetland plant and soil data across elevation and zonation gradients within 10 estuaries that span broad temperature and precipitation gradients. Our results highlight the importance of climate–plant controls and indicate that the influence of elevation is scale and location dependent. Coastal wetland plants are sensitive to climate change; small changes in temperature or precipitation can transform coastal wetland plant communities. Across the region, SOM was greatest in mangrove forests and in salt marshes dominated by graminoid plants. SOM was lower in salt flats that lacked vascular plants and in salt marshes dominated by succulent plants. We quantified strong relationships between precipitation, salinity, plant productivity, and SOM. Low precipitation leads to high salinity, which limits plant productivity and appears to constrain SOM accumulation. Our analyses use data from the Gulf of Mexico, but our results can be related to coastal wetlands across the globe and provide a foundation for predicting the ecological effects of future reductions in precipitation and freshwater availability. Coastal wetlands provide many ecosystem services that are SOM dependent and highly vulnerable to climate change. Collectively, our results indicate that future changes in SOM and plant productivity, regulated by cascading effects of precipitation on freshwater availability and salinity, could impact wetland stability and affect the supply of some wetland ecosystem services.
24608. 题目: Performances and mechanisms of efficient degradation of atrazine using peroxymonosulfate and ferrate as oxidants
文章编号: N18073117
期刊: Chemical Engineering Journal
作者: Shaohua Wu, Huiru Li, Xiang Li, Huijun He, Chunping Yang
更新时间: 2018-07-31
摘要: In this study, the degradation efficiencies and mechanisms of atrazine, a recalcitrant herbicide, were thoroughly investigated using ferrate (Fe(VI))/peroxymonosulfate (PMS) process. In comparison with Fe(VI) or PMS alone, Fe(VI)/PMS process significantly enhanced the degradation of atrazine, and its degradation efficiency was higher than that of Fe(VI)/persulfate or Fe(VI)/H2O2 process at pH 6.0. Complete degradation of atrazine at an initial concentration of 46.5 µM could be achieved within 20 min at initial concentrations of 6.0 mM Fe(VI), 5.0 mM PMS, pH 6.0, and 25 °C. Fe(VI)/PMS could efficiently degrade atrazine within a wide range of pH values (5–9). NOM concentration lower than 4.0 mg/L was favorable for atrazine degradation. Results of electron spin resonance and quenching studies indicated that both hydroxyl radical and sulfate radical were generated in the Fe(VI)/PMS process, while sulfate radical was the dominant reactive radical responsible for atrazine degradation. The mechanisms of PMS activation were elucidated on the basis of the results of XRD and XPS. In addition, fourteen intermediates from atrazine degradation were identified by LC/MS/MS, and consequently pathways for the degradation were proposed.
24609. 题目: Bioavailability and preservation of organic phosphorus in lake sediments: Insights from enzymatic hydrolysis and 31P nuclear magnetic resonance
文章编号: N18073116
期刊: Chemosphere
作者: Yuanrong Zhu, Weiying Feng, Shasha Liu, Zhongqi He, Xiaoli Zhao, Yong Liu, Jianyang Guo, John P. Giesy, Fengchang Wu
更新时间: 2018-07-31
摘要: Bioavailability and preservation of organic P (Po) in the sediment profiles (DC-1 and DC-2) from Lake Dianchi, a eutrophic lake in China, were investigated by a combination of enzymatic hydrolysis and solution 31P nuclear magnetic resonance (NMR) spectroscopy. Results showed that large of Po could be extracted by NaOH-EDTA (NaOH-EDTA Po), with little Po in residues after extraction with NaOH-EDTA. Bioavailability and preservation of NaOH-EDTA Po provide key information for biogeochemical cycling of Po in sediments. The details of P species and their bioavailability in NaOH-EDTA Po showed that 54.8–70.4% in DC-1 and 54.6–100% in DC-2, measured by 31P NMR, could be hydrolyzed by the phosphatase. Whereas, some proportion of NaOH-EDTA Po could not be hydrolyzed by the phosphatase, and decreased with sediment depth. Interaction between Po and other organic matter (e.g., humic acids) is likely an important factor for preservation of these Po in the sediment profiles. Simulation experiments of hydrolysis of model Po compounds adsorbed by minerals, such as goethite and montmorillonite, further indicated that adsorption to minerals protected some Po, especially phytate-like P, from enzymatic hydrolysis, thus preserving these forms of Po in sediments. Interactions of Po with organic matter and minerals in the sediments are two important factors determining biogeochemical cycling of Po in lakes. Intervention to break the cycle of FeP and bioavailable Po (e.g., labile monoester P) in the history of eutrophication is important way to control algal blooming.
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24610. 题目: Redistribution of methane emission hot spots under drawdown conditions
文章编号: N18073115
期刊: Science of The Total Environment
作者: Stephan Hilgert, Cristovão Vicente Scapulatempo Fernandes, Stephan Fuchs
更新时间: 2018-07-31
摘要: In the context of reservoirs, sediment trapping, and aquatic greenhouse gas (GHG) production, knowledge about the distribution of hot and low spots is essential for improved measurement strategies. It is also a key to a precise assessment of the GHG emissions of each reservoir. Large numbers of reservoirs are used mainly for hydroelectric power generation and, hence, affected by strong changes in water level. Drawdown events may lead to significant changes in spatial sediment and organic carbon distribution and, consequently, strongly alter the GHG emission patterns of the water body. We combined hydroacoustic sediment classification, sediment magnitude detection, and ebullition flux assessment with in-situ pore water investigations and sediment coring to detect ebullition distribution patterns after strong reservoir drawdown. The research was conducted in the Capivari Reservoir in the southeast of Brazil, which was affected by up to 15 m of drawdown within the last 10 years.
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24611. 题目: Iron-organic matter complexes accelerate microbial iron cycling in an iron-rich fen
文章编号: N18073114
期刊: Science of The Total Environment
作者: Stefan Kügler, Rebecca E. Cooper, Carl-Eric Wegner, Jan Frieder Mohr, Thomas Wichard, Kirsten Küsel
更新时间: 2018-07-31
摘要: The accessibility of iron (Fe) species for microbial processes is dependent on solubility and redox state, which are influenced by complexation with dissolved organic matter (DOM) and water-extractable organic matter (WEOM). We evaluated the complexation of these pools of organic matter to soluble Fe(II) and Fe(III) in the slightly acidic Schlöppnerbrunnen fen and subsequent effects on Fe(II) oxidation and Fe(III) reduction. We found the majority of soluble Fe(II) and Fe(III) is complexed to DOM. High-resolution mass spectrometry identified potential complexing partners in peat-derived water extracts (PWE), including compound classes known to function as ligands or electron shuttles, like tannins and sulfur-containing compounds. Furthermore, we observed clear differences in the stability of Fe(II)- and Fe(III)-DOM, with more labile complexes dominating the upper, oxic layers (0–10 cm) and more stable complexes in lower, anoxic layers (15–30 cm). Metal isotope-coded profiling identified a single potential chemical formula (C42H57O13N9Fe2) associated with a stable Fe-DOM complex. Fe(III) reduction and Fe(II) oxidation incubations with Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1 or Sideroxydans CL-21, respectively, were used to determine the influence of Fe-DOM complexes on Fe cycling rates. The addition of PWE led to a 2.3-fold increase in Fe(III) reduction rates and 0.5-fold increase in Fe(II) oxidation rates, indicating Fe-DOM complexes greatly influence microbial Fe cycling by potentially serving as electron shuttles. Molecular analyses revealed Fe(III)-reducing and Fe(II)-oxidizing bacteria co-exist across all depths, in approximately equal proportions (representing 0.1–1.0% of the total microbial community), despite observed changes in redox potential. The activity of Fe(III)-reducing bacteria might explain the presence of the detected Fe(II) stabilized via complexation with DOM even under oxic conditions in upper peat layers. Therefore, these Fe(II)-DOM complexes can be recycled by microaerophilic Fe(II)-oxidizers. Taken together, these results suggest Fe-DOM complexation in the fen accelerates microbial-mediated redox processes across the entire redox continuum.
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24612. 题目: Enhanced nitrate removal and high selectivity towards dinitrogen for groundwater remediation using biochar-supported nano zero-valent iron
文章编号: N18073113
期刊: Chemical Engineering Journal
作者: Anlei Wei, Jing Ma, Jingjing Chen, Yan Zhang, Jinxi Song, Xiangyang Yu
更新时间: 2018-07-31
摘要: We prepared nano zero-valent iron/biochar composites (nZVI/BC) to remove nitrate from groundwater with harmless products. Results show nZVI/BCs derived from different mass ratios of Fe(0) to biochar exhibited different nitrate removal efficiencies, and the mass ratio of 1:2 developed the nZVI/BC with optimum nitrate removal. The nZVI/BC maintained preferable nitrate removal (75.0%–97.0%) over a wide pH range 2–12. Nitrate removal amount declined due to serious corrosion and clogging of nZVI/BC’s surface when initial nitrate concentration exceeded 40 mg/L. The nitrate removal process followed a first-order kinetic reaction. As regards real groundwater, the nZVI/BC removed more nitrate than both pure Fe(0) nanoparticles and biochar. Reaction product analysis revealed 60.1% of removed nitrate selectively became dinitrogen. X-ray photoelectron spectroscopy measurements suggested that nitrate-oxidized Fe(0) resulted in significant increase of magnetite on the surface of nZVI/BC. The redox potential and pH of long duration in reaction changed around −210 mV and 8–9, respectively. These changes facilitated the selective reduction of nitrate to dinitrogen. We also proposed that biochar may provide favorable circumstances for nitrate reduction by directly mediating redox potential, pH and electron transfer, which establishes a possible mechanism for the enhanced removal and selective reduction of nitrate. Our study suggests that nZVI/BC would be a promising alternative for the remediation of nitrate-contaminated groundwater.
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24613. 题目: Sodium hypochlorite assisted membrane cleaning: Alterations in the characteristics of organic foulants and membrane permeability
文章编号: N18073112
期刊: Chemosphere
作者: Shu Zhai, Weiming Zhang, Ting Li, Wenbin Zhang, Lu Lv, Bingcai Pan
更新时间: 2018-07-31
摘要: Chemical cleaning is an important approach for alleviating severe fouling in membrane separation processes. In this study, lysozyme (LYS) was exposed to sodium hypochlorite (NaClO) with varied concentrations (0–2000 ppm) to understand the changes in the physicochemical properties and functional groups as well as the variations in membrane permeabilities. The results showed that membrane filterability exhibited an obvious ‘U-shaped’ trend, and the valley existed when the ratio of Cl/C (the ratio of NaClO and TOC concentrations in feed water) is among 1.35–3.09. Upon exposure to low dose NaClO, three-dimensional fluorescence excitation-emission matrix (3D-EEM) spectra showed that tryptophan protein substances were transformed to more hydrophobic humic-like substances. Fourier transform infrared (FTIR) analysis further confirmed that exposure to low dose NaClO promoted the breakage of aromatic substituents, leading to the formation of hydrophobic condensed aromatic substances. On the contrary, at high NaClO loads, protein structures were destroyed completely and almost no obvious fluorescent intensities could be detected, which promoted the recovery of membrane filterabilities. Notably, the chemical cleaning mechanisms of fouled membranes with NaClO were understood in depth in this study. These results provide new information about the oxidation products of LYS and the cleaning efficiency upon exposure to NaClO.
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24614. 题目: Dynamic changes of polychlorinated biphenyls (PCBs) degradation and adsorption to biochar as affected by soil organic carbon content
文章编号: N18073111
期刊: Chemosphere
作者: Shengyan Huang, Jianping Bao, Mingjuan Shan, Hua Qin, Hailong Wang, Xuejun Yu, Junhui Chen, Qiufang Xu
更新时间: 2018-07-31
摘要: Biochar amendment constitutes an effective soil remediation strategy for organic contaminants, but how the soil organic carbon (SOC) content affects polychlorinated biphenyls (PCBs) degradation and adsorption to biochar remains unclear. A 120-day biochar amendment experiment was conducted to investigate the dynamic effects of SOC on PCBs degradation in soil and adsorption to biochar. Biochar in low-SOC (LSOC) soils adsorbed a significantly higher amount of PCBs than did that in high-SOC (HSOC) soils. PCBs degradation was also greatly enhanced in LSOC soils when compared with that in HSOC soils after 30 days of biochar amendment. Degradation of di- and tri-chlorobiphenyls (CBs) were significantly enhanced in the LSOC soils than in the HSOC soils, while the biochar in the LSOC soil tended to adsorb significantly higher amount of tetra- and penta-CBs. Compared to biochar adsorption, microbial degradation contributed significantly to soil PCBs removal. Soil bacterial 16S rDNA abundance increased concomitantly with soil PCBs degradation. Regardless of SOC, soil bacterial communities and PCB congener compositions changed significantly after 30 days of biochar amendment. The abundance of Actinobacteria and Firmicutes were negatively correlated with the soil PCBs removal, while Gemmatimonadetes and Proteobacteria were positively correlated. The results of this study revealed that, compared with that to HSOC soils, biochar amendment to LSOC soils may have a greater positive effect on both soil PCB degradation and biochar adsorption. Therefore, the application of bamboo biochar to LSOC soils could be more effective than that to HSOC soils with respect to the remediation of PCBs contamination.
24615. 题目: Effects of freeze-thaw cycles on aggregate-associated organic carbon and glomalin-related soil protein in natural-succession grassland and Chinese pine forest on the Loess Plateau
文章编号: N18073110
期刊: Geoderma
作者: Lie Xiao, Yang Zhang, Peng Li, Guoce Xu, Peng Shi, Yi Zhang
更新时间: 2018-07-31
摘要: Glomalin-related soil protein (GRSP) is a hydrophobic glycoprotein that can protect soil organic carbon (SOC) from decomposition by promoting the formation of soil aggregates. Few studies, however, have evaluated the response of aggregate-associated SOC and GRSP to freeze-thaw cycles (FTs) under different patterns of vegetation restoration. Soil samples were collected from three typical natural-succession grasslands (dominated by Artemisia capillaris, A. sacrorum, and Bothriochloa ischaemum) and a Chinese pine (Pinus tabuliformis) forest before and after natural FTs during a winter-spring season on the Loess Plateau in China. The soil aggregate stability and concentrations of SOC, easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) in different aggregate fractions were measured. The FTs decreased the proportion of >5.0 mm wet-sieved fractions, increased the proportion of <0.25 mm wet-sieved fractions, and decreased the mean weight diameters by 8.7, 9.5, 2.9, and 9.4% in the soils of A. capillaris, A. sacrorum, B. ischaemum, and P. tabuliformis, respectively. The SOC, T-GRSP, and EE-GRSP concentrations in each aggregate fraction generally decreased after FTs in the four vegetation types. The SOC, T-GRSP, and EE-GRSP concentrations did not differ significantly in the larger aggregate fractions before the FTs in the soils for B. ischaemum and P. tabuliformis, but their concentrations were significantly higher for B. ischaemum than P. tabuliformis after FTs. The SOC and GRSP concentrations were significantly and linearly correlated in most aggregate fractions both before and after the FTs. These results indicated that the FTs decreased SOC by decreasing the GRSP concentration in each aggregate fraction and that SOC was more sensitive to FTs in forest than in natural-succession grassland.
24616. 题目: Universal Biomarker Analysis: Aromatic hydrocarbons
文章编号: N18073109
期刊: Organic Geochemistry
作者: Clifford C. Walters, Frank C Wang, Meytal B. Higgins, Marlene E. Madincea
更新时间: 2018-07-31
摘要: Universal Biomarker Analysis is a GC×GC-ToFMS method that provides absolute quantification and non-targeted pseudo MS-MS for all resolved hydrocarbon components in petroleum and rock extracts. This is achieved by merging two chromatographic datasets obtained under field ionization (FI), which provides molecular ions, and electron impact (EI), which provides diagnostic fragment ions. We recently demonstrated this technique for the analysis of saturated biomarkers (Walters et al., 2018. Org. Geochem. 115, 57). Here, we show its application to aromatic biomarkers. Universal Biomarker Analysis is compared to conventional GC-MS for frequently analyzed aromatic hydrocarbons, such as the alkylated naphthalenes and biphenyls, mono- and tri-aromatic steroidal hydrocarbons to illustrate where this new method provides demonstrated advantages. The technique is well suited for the analysis of rare species not commonly analyzed in targeted GC-MS/MS analyses. This is illustrated by the tentative identification of A/B-ring C26-C29 diaromatic steroidal hydrocarbons in a crude oil, compounds that have been previously identified as minor components of immature rock extracts, and indications of previously unknown C26 methyl-triaromatic steroidal hydrocarbons.
24617. 题目: Comparisons of NOM fouling and cleaning of ceramic and polymeric membranes during water treatment
文章编号: N18073108
期刊: Separation and Purification Technology
作者: Mohammad T. Alresheedi, Benoit Barbeau, Onita D. Basu
更新时间: 2018-07-31
摘要: This research examines the effect of various NOM fractions on ceramic and polymeric UF membranes performance in terms of fouling and cleaning. Fouling experiments were performed using five model solutions, humic acid, protein as bovine serum albumin (BSA), alginate with and without calcium, and a combined NOM mixture. Two chemical agents were selected: an oxidant (NaOCl) and caustic (NaOH). Fouling and cleaning behavior were assessed using the resistance in series (RIS) model, membrane permeability, carbon mass balance, and fluorescence excitation and emission matrix (FEEM) analysis. The results demonstrated that NOM fouling order of the ceramic UF was similar to polymeric UF with the following trend: NOM mixture ≈BSA > alginate ±Ca+2 > humic acid. However, the backwash efficiency was 1.5×–2× higher for the ceramic UF in comparison to the polymeric UF, indicating a much higher hydraulic reversibility for the ceramic UF. A carbon mass balance in compliment with FEEM plots determined that NOM removal by the ceramic UF was ≈ 10% higher than the polymeric UF. Chemical cleaning was found to be effective for both membrane types. Thus, it was not possible to conclude, that the ceramic membrane demonstrated an advantage for chemical cleaning under the conditions studied.
24618. 题目: Structure and activity of soil microbial communities in three Mediterranean forests
文章编号: N18073107
期刊: Applied Soil Ecology
作者: Felicia Grosso, Paola Iovieno, Anna Alfani, Flavia De Nicola
更新时间: 2018-07-31
摘要: The effect of plant cover on soil microbial community structure and activity was investigated in forest ecosystems dominated by holm oak (Quercus ilex), Turkey oak (Quercus cerris) and beech (Fagus sylvatica), in two seasons (autumn and early summer). Microbial community structure was investigated by phospholipid fatty acid (PLFA) profile and ergosterol determination. Microbial community activity was assessed by fluorescein diacetate hydrolisys, β-glucosidase and cellulase activities. The Turkey oak forest showed the lowest soil microbial biomass, both as total and specific PLFA markers. PLFA profile showed a different microbial community structure among forest soils, mainly between the two oak systems. Enzyme activities were affected by soil organic carbon content, with the lowest values measured in Turkey oak. A seasonal effect both on microbial biomass and on enzyme activity was generally observed. Among the investigated forest systems, the beech forest appeared to store more carbon both in aboveground biomass and in soil.
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24619. 题目: Short- and long-term warming alters soil microbial community and relates to soil traits
文章编号: N18073106
期刊: Applied Soil Ecology
作者: Hongying Yu, Quanhui Ma, Xiaodi Liu, Zhenzhu Xu, Guangsheng Zhou, Yaohui Shi
更新时间: 2018-07-31
摘要: Climatic warming abnormally alters the structure and function of terrestrial ecosystems. It is vital to understand the response of belowground biota such as soil microbial communities to warming regimes, especially in native arid areas. The present in situ experiment was established to determine the effects of climatic warming regimes on soil microbe communities and the relationships between soil microbial groups and soil physicochemical features in a desert grassland ecosystem. Two warming regimes—long-term moderate warming (T1) and short-term acute warming (T2)—were established to simulate different climatic change scenarios. Soil from each plot was collected in 2014 at the late stage of the experiment, and phospholipid fatty acid (PLFA) profiling analysis was performed to assess the composition of the soil microbial communities. It was found that warming induced a severe water deficit stress. The T2 warming regime significantly increased the ratio of bacteria to fungi (B/F), and the ratio of Gram-positive to Gram-negative bacteria (GP/GN) in August. Belowground biomass (BGB) and soil organic carbon (SOC) were significantly correlated with all of the soil microbial groups in August. The changes in B/F and GP/GN ratios might indirectly induce changes in microbial structure. It was concluded that alterations in the structure of soil microbial communities may strongly depend on growing seasons and that soil nutrient status might have a profound impact on soil microbial communities’ responses to climatic warming.
24620. 题目: The response of metal leaching from soils to climate change and land management in a temperate lowland catchment
文章编号: N18073105
期刊: CATENA
作者: Marcel van der Perk, Maria Stergiadi, Ton C.M. de Nijs, Rob N.J. Comans, Marc F.P. Bierkens
更新时间: 2018-07-31
摘要: Changes in soil hydrology as a result of climate change or changes in land management may affect metal release and leaching from soils. The aim of this study is to assess the cascading response of SOM and DOC levels and metal leaching to climate change in the medium-sized lowland Dommel catchment in the southern part of the Netherlands. We implemented the CENTURY model in a spatial setting to simulate SOM, DOC, and water dynamics in topsoils of the Dutch portion of the Dommel catchment under various climate and land management scenarios. These CENTURY model outputs were subsequently used to calculate changes in the topsoil concentrations, solubility, and leaching of cadmium (Cd) and zinc (Zn) for current (1991–2010) and future (2081–2100) conditions using empirical partition-relations. Since the metal leaching model could not be evaluated quantitatively against measured values, we focus mainly on the trends in the projected metal concentrations and leaching rates for the different scenarios. Our results show that under all climate and land management scenarios, the SOM contents in the topsoil of the Dommel catchment are projected to increase by about 10% and the DOC concentrations to decrease by about 20% in the period from present to 2100. These changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates under the climate change scenarios. Our scenario calculations show a considerable decrease in topsoil Cd concentrations in the next century as a result of increased percolation rates. Zinc, however, shows an increase due to agricultural inputs to soil via manure application. These trends are primarily controlled by the balance between atmospheric and agricultural inputs and output via leaching. While SOM and DOC are important controls on the spatial variation in metal mobility and leaching rates, climate-induced changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates. The climate-induced changes in metal concentrations in both the topsoil and the soil leachate are primarily driven by changes in precipitation and associated water percolation rates.