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所有论文

12581. 题目: The use of pedo-transfer functions for estimating soil organic carbon contents in maize cropland ecosystem in the Coastal Plains of Tanzania
文章编号: N18083107
期刊: CATENA
作者: S.B. Mwango, J. Wickama, B.M. Msanya, D.N. Kimaro, J.D. Mbogoni, J.L. Meliyo
更新时间: 2018-08-31
摘要: Soil organic carbon (OC) plays a vital role on physico-chemical and biological properties of soils and on climate change regulation. The use of pedo-transfer functions from easily available soil properties for estimating soil OC could be fast and cheap when considering field and laboratory work implications especially in Sub Saharan Africa including Tanzania. This paper attempts to develop a model for estimating soil OC contents under maize croplands ecosystem using pedo-transfer functions from soil texture. A total of 100 epipedon data entries were randomly collected from the previous soil sampling works that were conducted under maize croplands in coastal plains of Tanzania. Eighty percent of the collected data were used for training the model by using multiple regression analysis while the remained 20% were used to validate the model. The results indicated that, clay and silt had significant (p < 0.001) positive correlation with soil OC while sand contents in soils had negative (p < 0.001) correlation with soil OC. All together clay, sand and silt were revealed powerful predictors (p < 0.001, R2 = 0.82) of OC content in soils. On validation, the soil OC predicted agreed by 81.2% with the soil OC determined by laboratory test. These results imply that pedo-transfer functions for predicting soil OC based on soil texture is not only fast and cheap but also is an effective option for estimating OC content in soils.

12582. 题目: Impacts of soil stabilization treatments on reducing soil loss and runoff in cutslope of forest roads in Hyrcanian forests
文章编号: N18083106
期刊: CATENA
作者: Majid Lotfalian, Taleb Yousefi Babadi, Hasan Akbari
更新时间: 2018-08-31
摘要: Cutslopes are the most important source of sediment among other parts of forest roads network. A significant amount of runoff and sediment is observed in Hyrcanian forests because of the fine-textured soil. This study investigated the effectiveness of three treatments of jute cover (JC), mulch cover (MC) and bare cutslope as control plots (CP) under the natural rainfall condition. Two months investigation on two new and old roads with silty-clay cutslopes was done. Correlation between some of soil properties, soil loss and runoff showed that the sediment concentration was increased with increasing in soil bulk density. Runoff volume showed a significant negative correlation with the percentage of organic matter and a positive correlation with the plastic limit. With runoff volume increasing, sediment concentration and soil loss were significantly increased. Analysis of the results showed that in both new and old roads, the treatment of JC is superior. This treatment has reduced soil loss by 9.68 times compared to CP treatment. The treatment of JC compared to the MC on a new cutslope and an old one has reduced soil loss by 2.77 and 2.54 times. Also, JC have reduced soil loss by 2.67 times compared to the MC. The total cost per square meter of JC is US $ 0.21 and this amount is equivalent to $ 0.26 for the MC. According to the results, it is suggested that soil protection and bioengineering designs should be focused on the use of JC.

12583. 题目: Evaluating fluorescent dissolved organic matter released from wetland-plant derived biochar: Effects of extracting solutions
文章编号: N18083105
期刊: Chemosphere
作者: Haiming Wu, Xuyang Dong, Hai Liu
更新时间: 2018-08-31
摘要: This study investigated the quantity and quality of dissolved organic matter (DOM) released from wetland-plant derived biochar under various extracting conditions (deionized water, 0.1 mol/L HCl, 0.1 mol/L NaOH, and 0.1 mol/L NaCl) by using fluorescence excitation-emission matrix (EEM) spectrophotometry with parallel factor analysis (PARAFAC). Concentrations of dissolved organic carbon (DOC) released from biochar extracted in different extracting solutions ranged from 0.69 g/L to 1.22 g/L with the total contents of 13.7–23.5 g DOC/kg. The average DOC content was highest in the alkaline solution and lowest in the deionized water. Three humic acid-like substances, one fulvic acid-like substance and one tyrosine-like substance were identified. The distributions of the identified components in DOM were distinctively different among various extracts, and humic acid-like components were the dominant materials. The extraction conditions could affect significantly humic acid-like and fulvic acid-like fluorescence. The results would be beneficial to understand the biochar's effects and processes in possible environmental applications.
图文摘要:

12584. 题目: Desorption of atrazine in biochar-amended soils: Effects of root exudates and the aging interactions between biochar and soil
文章编号: N18083104
期刊: Chemosphere
作者: Xinhao Ren, Fei Wang, Fengmei Cao, Junkang Guo, Hongwen Sun
更新时间: 2018-08-31
摘要: The effects of wheat root exudates and the aging interactions between biochar and soil on atrazine desorption from biochar-amended soil were carefully examined. Compared with CaCl2 solution, wheat root exudates significantly increase the desorption of atrazine from biochar, mainly by promoting the desorption of atrazine adsorbed on biochar with specific forces. Wheat root exudates were effectively separated into three components with different electrical properties, namely, anionic, neutral, and cationic components. Mainly due to the carboxyl-containing compounds, the anionic component was the main active component in the wheat root exudates that enhances the desorption of atrazine from the biochar. Additionally, wheat root exudates can increase the desorption of atrazine from biochar-amended soil. The promotion of atrazine desorption by root exudates was more obvious in soils with low organic matter contents, where atrazine was mainly adsorbed by biochar. The aging interaction between the biochar and soil increased the total desorption rate and rapid desorbing fraction of the atrazine in the soil, most likely due to the reduction of the biochar sorption capacity in the aged biochar-amended soil.

12585. 题目: Iron sulfide formation in young and rapidly-deposited permeable sands at the land-sea transition zone
文章编号: N18083103
期刊: Science of The Total Environment
作者: Stephan L. Seibert, Michael E. Böttcher, Florian Schubert, Thomas Pollmann, Luise Giani, Sumiko Tsukamoto, Manfred Frechen, Holger Freund, Hannelore Waska, Heike Simon, Tobias Holt, Janek Greskowiak, Gudrun Massmann
更新时间: 2018-08-31
摘要: Organic-poor, permeable quartz sands are often present at land-sea transition zones in coastal regions. Yet, the biogeochemical cycles of carbon, sulfur, and iron are not well studied here. The aim of this work was, therefore, to improve our understanding regarding the chemical processes in these prominent coastal sediments. A 10 m core was collected at a dune base of the barrier island Spiekeroog, Germany, for this purpose. Additionally, groundwater was sampled from a multi-level well for one year to record seasonal hydrochemical variations. Methods included the analyses of geochemical (total carbon, total inorganic carbon, reactive iron, total sulfur, reduced inorganic sulfur) and hydrochemical parameters (field parameters, major ions, DOC, and molecular compositions of DOM), as well as stable sulfur isotopes (δ34S-sulfate, -sulfide, -total reduced inorganic sulfur). Moreover, optically stimulated luminescence (OSL) dating was applied. Results show that the core sediments are very young (<500 a) and were rapidly deposited. They are characterized by remarkably low contents of organic carbon (<0.1% dw.), reactive iron (~10 mmol/kg), and iron sulfides (<3 mmol/kg). Groundwater salinities were low in the top core sediments and increased at depth during most times of the year. However, the sampling site is subject to (seasonally) varying salinities, which could be linked to the biogeochemical cycles. For instance, the infiltration of seawater-derived labile DOM during inundation events drives microbial respiration besides sedimentary organic matter. Oxygen and nitrate were the dominant electron acceptors for the decomposition of organic matter in near-surface groundwater, while sulfate reduction was constrained to the lower brackish sediments. Here, authigenic pyrite formation was inferred based on the detection of dissolved sulfide, intact pyrite framboids, and matching stable sulfur isotope signatures of dissolved and solid sulfides. We concluded that the extremely low organic carbon contents limit pyrite formation in the organic-poor, permeable quartz sands.
图文摘要:

12586. 题目: Approach deliberation for source identification of sedimentary organic matters via comparing freshwater lakes with multi-ecotypes
文章编号: N18083102
期刊: Science of The Total Environment
作者: Xiaoguang Xu, Wei Li, Hui Deng, Megumu Fujibayashi, Munehiro Nomura, Osamu Nishimura, Guoxiang Wang
更新时间: 2018-08-31
摘要: Despite of the importance of understanding the sediment quality for lacustrine management, the source evaluation of sedimentary organic matter (SOM) in freshwater lakes is still insufficient. In this study, two shallow eutrophic lakes of Lake Taihu, China and Lake Izunuma, Japan were systematically investigated. Results of fatty acid profiles demonstrated that a wide range of organic matters, varying ecotypically, was inputted into the sediments of both lakes. Interestingly, there was a strong contribution from terrestrial plants to the sediments across ecotypes, with an approximate input from bacteria, and a relatively minor input from microalgae mainly included cyanobacteria, green algae, diatom and dinoflagellates. In addition, isotopic mixing model depicted a complementary picture that a significant, but spatially variable, amount of organic matter was derived from emergent and floating-leaf plants of Phragmites, Nelumbo, Nymphoides and Trapa L in Lake Izunuma. A general indicator selection procedure for the source assignments of SOM in freshwater ecosystems was therefore proposed: fatty acids could be a valid biomarker when the potential sources are unknown or unavailable; stable isotopes could be an effective supplement approach when assessing the special or defined organic sources.
图文摘要:

12587. 题目: Characterization and 2D structural model of corn straw and poplar leaf biochars
文章编号: N18083101
期刊: Environmental Science and Pollution Research
作者: Nan Zhao, YiZhong Lv, XiXiang Yang, Feng Huang, JianWen Yang
更新时间: 2018-08-31
摘要: The integrated experimental methods were used to analyze the physicochemical properties and structural characteristics and to build the 2D structural model of two kinds of biochars. Corn straw and poplar leaf biochars were gained by pyrolysing the raw materials slowly in a furnace at 300, 500, and 700 °C under oxygen-deficient conditions. Scanning electron microscope was applied to observe the surface morphology of the biochars. High temperatures destroyed the pore structures of the biochars, forming a particle mixture of varying sizes. The ash content, yield, pH, and surface area were also observed to describe the biochars’ properties. The yield decreases as the pyrolysis temperature increases. The biochars are neutral to alkaline. The biggest surface area is 251.11 m2/g for 700 °C corn straw biochar. Elemental analysis, infrared microspectroscopy, solid-state C-13 NMR spectroscopy, and pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) were also used to study the structural characteristics and build the 2D structural models of biochars. The C content in the corn straw and poplar leaf biochars increases with the increase of the pyrolysis temperature. A higher pyrolysis temperature makes the aryl carbon increase, and C=O, OH, and aliphatic hydrocarbon content decrease in the IR spectra. Solid-state C-13 NMR spectra show that a higher pyrolysis temperature makes the alkyl carbon and alkoxy carbon decrease and the aryl carbon increase. The results of IR microspectra and solid-state C-13 NMR spectra reveal that some noticeable differences exist in these two kinds of biochars and in the same type of biochar but under different pyrolysis temperatures. The conceptual elemental compositions of 500 °C corn straw and poplar leaf biochars are C61H33NO13 and C59H41N3O12, respectively. Significant differences exist in the SEM images, physicochemical properties, and structural characteristics of corn straw and poplar leaf biochars.

12588. 题目: Molecular Characterization of Cloud Water Samples Collected at the Puy de Dôme (France) by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
文章编号: N18083013
期刊: Environmental Science & Technology
作者: Angelica Bianco, Laurent Deguillaume, Mickaël Vaïtilingom, Edith Nicol, Jean-Luc Baray, Nadine Chaumerliac, Maxime Bridoux
更新时间: 2018-08-30
摘要: Cloud droplets contain dynamic and complex pools of highly heterogeneous organic matter, resulting from the dissolution of both water-soluble organic carbon in atmospheric aerosol particles and gas-phase soluble species, and are constantly impacted by chemical, photochemical, and biological transformations. Cloud samples from two summer events, characterized by different air masses and physicochemical properties, were collected at the Puy de Dôme station in France, concentrated on a strata-X solid-phase extraction cartridge and directly infused using electrospray ionization in the negative mode coupled with ultrahigh-resolution mass spectrometry. A significantly higher number (n = 5258) of monoisotopic molecular formulas, assigned to CHO, CHNO, CHSO, and CHNSO, were identified in the cloud sample whose air mass had passed over the highly urbanized Paris region (J1) compared to the cloud sample whose air mass had passed over remote areas (n = 2896; J2). Van Krevelen diagrams revealed that lignins/CRAM-like, aliphatics/proteins-like, and lipids-like compounds were the most abundant classes in both samples. Comparison of our results with previously published data sets on atmospheric aqueous media indicated that the average O/C ratios reported in this work (0.37) are similar to those reported for fog water and for biogenic aerosols but are lower than the values measured for aerosols sampled in the atmosphere and for aerosols produced artificially in environmental chambers.
图文摘要:

12589. 题目: Effects of underground mining on vegetation and environmental patterns in a semi-arid watershed with implications for resilience management
文章编号: N18083012
期刊: Environmental Earth Sciences
作者: Yongjun Yang, Peter D. Erskine, Shaoliang Zhang, Yunjia Wang, Zhengfu Bian, Shaogang Lei
更新时间: 2018-08-30
摘要: A rapid increase in underground mining in a semi-arid area of China has led to serious concerns about the health of vegetation overlying these coal seams. However, there have been no empirical studies to illustrate the response and persistence of surface vegetation in these underground mining areas. A combination of field assessments with remote sensing was used to examine vegetation patterns and responses to underground mining, while laying a foundation for environmental protection. The study area lies in a vulnerable watershed exposed to hazards caused by underground coal mining, located on the southern edge of Inner Mongolia in China. The results demonstrate that hydrological factors and soil attributes, including groundwater levels, soil organic matter, and soil moisture, control the structure of the local vegetation community. After mining begins, the vegetation community index based on plant density, coverage, and biomass in areas affected by subsidence fractures decreases by 0–21.5%. Nevertheless, the average Normalized Differential Vegetation Index at the entire watershed scale increased by 15% from 2001 to 2016, although this change appeared to be primarily related to rainfall. This study confirmed that underground coal mining in the watershed has not caused extensive vegetation degradation as feared. Positive climatic trends, the maintenance of important mudstone strata below a phreatic aquifer and the adaptation of vegetation to drought, contributed to the persistence of surface vegetation in underground mining areas. Considering that mining activities usually last for several years, resilience management, including approaches such as protection of important variables, long-term monitoring, and adaptive management, should be adopted in support of conservation and sustainable mining in this watershed and at similar mine sites.

12590. 题目: Soil texture and phosphorous under two contrasting land use types in the Loess Plateau
文章编号: N18083011
期刊: CATENA
作者: Nannan Ge, Xiaorong Wei, Xiang Wang, Xuetong Liu, Mingan Shao, Xiaoxu Jia, Xuezhang Li, Qingyin Zhang
更新时间: 2018-08-30
摘要: Organic carbon (OC) and nutrient dynamics are closely related to soil texture, but how texture influences the distribution of OC and nutrients in aggregates in various land use types has not been examined. This knowledge gap precludes our mechanistic understanding of soil biogeochemical cycles at large spatial scales. Herein we compared the contents and stoichiometric ratios of OC and nutrients in both bulk soils and aggregates in cropland and woodland across a clay content gradient (7–31%) in the Loess Plateau. The soil metrics that were measured included the proportions of water-stable aggregates, and the contents of OC, nitrogen (N) and phosphorous (P) in bulk soils and each aggregate fraction. The stoichiometric ratios of carbon (C), N and P were calculated. The relationships between soil metrics and clay content were analyzed. We hypothesize that OC, N and P in aggregates increase with clay content, and these relationships are independent of land use types. In partial support of these hypotheses, the proportion of macroaggregates and the contents of OC, N and P in bulk soils and most aggregate fractions linearly increased with clay content. The slopes of these linear relationships were not affected by land use type. The C/N ratio were minimally affected, while the C/P and N/P ratios in both bulk soils and aggregates increased with clay content, and these relationships changed with land use type. Proportion of macroaggregates, contents of OC and N, and ratios of C/N, C/P and N/P were significantly higher in woodland than in cropland across or within sites. Furthermore, the distribution patterns of OC, N and P contents, and C/P and N/P ratios among aggregates varied with site and land use type. These suggested that soil texture determines the distribution of OC, N and P and their stoichiometric ratios within soil aggregates in the Loess Plateau of China, and most of these determining relationships were independent from land use types.

12591. 题目: Agricultural soil characterization by FTIR spectroscopy at micrometer scales: Depth profiling by photoacoustic spectroscopy
文章编号: N18083010
期刊: Geoderma
作者: Zhe Xing, Kang Tian, Changwen Du, Chunyang Li, Jianmin Zhou, Zhikun Chen
更新时间: 2018-08-30
摘要: In a Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) mode, the scanning depths vary with the moving mirror velocity at specific wavenumbers, allowing depth profiling of materials. In this paper, we use FTIR-PAS spectroscopy to carry out a depth profiling of three types of agricultural soils (Fluvo-aquic soil, red soil and black soil) at micrometer scales by modulating the moving mirror velocity. The compositional and structural differences in soil organic matters were explored from the surface to a depth of about 4 μm. The results showed that the distribution of potential hydrophobic CH varied among different types of soils. The contribution of the soil organic matter (SOM) to the cation exchange capacity (CEC) also differed for each soil type. The results of the principal component analysis (PCA) indicated that most differences among the selected soil types occurred in the inner layer, and the discriminatory power of the soil spectra decreased with the reduction of scanning depths. Correlations between soil properties and spectral absorbance were carried out to determine the source of water extractable organic carbon (WEOC) of different soil types. For the black soil, WEOC were significantly and positively correlated to the absorbance at ~2920 cm−1, and this correlation increased with the probing depth at micrometer scales. However, the significant and negative correlation between the WEOC of the red soil, and the bond intensity of ~1650 cm−1 decreased with an increasing probing depth. This result demonstrates a selective retention of biotic components in the WEOC of the red soil. The WEOC of the black soil, with comparison to the red soil, has more contributions from the native organic matter. These results can be reasonably ascribed to different pedogenesis and cultivation systems that were practiced in the past.

12592. 题目: Soil microbial anaplerotic CO2 fixation in temperate soils
文章编号: N18083009
期刊: Geoderma
作者: Jacques A. Nel, Michael D. Cramer
更新时间: 2018-08-30
摘要: In soils both δ13C and δ15N values of soil organic matter (SOM) tend to increase with soil depth. This change in soil C and N isotopic composition is at least partially linked to soil microbial activity that has been suggested to drive fractionation during decomposition, preferential microbial decomposition of components of soil organic matter and mixing of diverse sources of C. Soil microbes are capable of fixing N2 and CO2 from the soil atmosphere. Apart from surface photosynthetic CO2 fixation and chemoautotrophic fixation, dark anaplerotic (i.e. non-photosynthetic) fixation of CO2 is especially important for provision of C-skeletons for amino acid synthesis. We hypothesized that these N2 and CO2 fixing processes may contribute to determining SOM δ13C and δ15N values. Soils from 10 sites across South Africa differing in soil properties were incubated in the dark for 3 d under continuous exposure to 13CO2- and 15N2-enriched atmospheres with varying soil moisture (10, 50 and 100% of field capacity) and temperature (4, 25, 40 °C). We did not detect significant N2 fixation in any treatment. Significant soil microbial anaplerotic CO2 fixation, however, occurred in all soils. Highest rates of anaplerotic CO2 fixation occurred in soils at 50% field capacity and 25 °C, suggesting a link with microbial biotic activity. Soils with low C and N concentrations and low C:N ratios exhibited the highest rates of CO2 fixation, indicating a possible link between anaplerotic CO2 fixation rates and soil nutrient status. The higher rates of CO2 fixation in soils with low nutrients may indicate that soil microbes rely increasingly on anaplerotic fixation as SOM-N declines, forcing greater reliance on de novo amino acid synthesis, and thus anaplerotic CO2 fixation. Diffusion of bulk atmospheric CO213C ca. −10‰) into the soil atmosphere (δ13C ≪ −10‰) drives soil atmospheric CO2 δ13C values up towards those of the bulk atmosphere. Anaplerotic CO2 fixation in this CO2 may contribute to determining soil δ13C values.

12593. 题目: Soil bacterial communities exhibit systematic spatial variation with landform across a commercial potato field
文章编号: N18083008
期刊: Geoderma
作者: Saraswoti Neupane, Claudia Goyer, Bernie J. Zebarth, Sheng Li, Sean Whitney
更新时间: 2018-08-30
摘要: Topography drives spatial variation of soil edaphic factors at the landscape scale however, it is unclear how it influences the spatial distribution of bacterial communities in distances relevant to agro-ecosystem management. This study examined the influence of soil physico-chemical properties and topographic features on bacterial communities and diversity in a commercial potato field with a rolling landform. Eighty-three soil samples were systematically collected across a transect 1100 m long. A significant negative correlation (r = −0.73) between soil pH (range 4.3–7.0) and slope gradient (range 1.8–11.9%) was observed. Regressions and/or a canonical correspondence analysis showed that pH, slope gradient and organic carbon were the major factors influencing bacterial α-diversity based on 16S rRNA gene sequences. Semivariogram analyses revealed that the bacterial α-diversity, the relative abundance of most phyla, pH and slope gradient showed strong to medium spatial autocorrelations with a range between 20.8 and 217.8 m. These results evidenced that soil pH and slope gradient were the major factors explaining variation in the spatial structure of the bacterial community. Our results showed that the soil bacterial communities varied in a systematic and predictable pattern in an agricultural field in response to variation in soil physico-chemical properties and topographic features.
图文摘要:

12594. 题目: Quantification and characterization of dissolved organic carbon from biochars
文章编号: N18083007
期刊: Geoderma
作者: Cheng-Hua Liu, Wenying Chu, Hui Li, Stephen A. Boyd, Brian J. Teppen, Jingdong Mao, Johannes Lehmann, Wei Zhang
更新时间: 2018-08-30
摘要: Dissolved organic carbon (DOC) in biochars is critical to carbon dynamics and contaminant transport in soils. This study aimed to develop a robust and easy method to characterize and quantify the biochar-DOC, using water-, acid-, and base-extractable DOC samples (WEOC, AEOC, and BEOC respectively) from 46 biochars produced from diverse feedstocks and pyrolysis conditions. BEOC concentrations were the highest (2.3–139 mg-C/g-biochar), followed by WEOC (0.5–40 mg-C/g-biochar) and AEOC (0.2–23 mg-C/g-biochar). Fast-pyrolysis biochars generally had higher DOC concentrations than slow-pyrolysis biochars. DOC concentrations in slow-pyrolysis biochars decreased exponentially with increasing pyrolysis temperature from 300 to 600 °C. The solid-state 13C NMR showed that biochar-DOC had abundant small fused-ring aromatics, aliphatic C, and carboxyl C. Biochar-DOC included an acid-precipitated (AP) fraction of higher molecular weight and aromaticity and an acid-soluble (AS) fraction of lower molecular weight and aromaticity. BEOC generally had a greater AP fraction than WEOC and AEOC. Molecular weight, aromaticity and composition of AEOC and BEOC differed from those of more environmentally-relevant WEOC, suggesting that the acid- and base-extraction may not produce the DOC released in real soils. Finally, a quick, easy and robust UV–vis spectrometric method was developed to measure the composition and concentrations of WEOC in diverse biochar samples (R2 = 0.96, n = 46).
图文摘要:

12595. 题目: Influence of clay clod size and number for organic carbon distribution in sandy soil with clay addition
文章编号: N18083006
期刊: Geoderma
作者: Amanda Schapel, Petra Marschner, Jock Churchman
更新时间: 2018-08-30
摘要: In agricultural soils, subsoil clay addition to sand has the potential to improve carbon sequestration by increasing soil organic carbon (OC) concentration through adsorption and occlusion. However, the factors influencing increased OC in these engineered soils are poorly understood. The addition of subsoil clay creates clods of different sizes, from a few mm up to 200 mm or more in diameter. This study assessed the i) size, number and vertical distribution of clods and OC at two clay-modified field sites and ii) effect of clod size and properties on OC in incubation experiments. The hypotheses were that smaller clods would increase and stabilise OC more than larger clods and that an even distribution of clods throughout the depth of modification will increase OC stock compared to patchy distribution. Two field sites with differing clay modification method, delved and spaded, were studied. Soil was excavated from a 30 cm quadrat in 10 cm increments down the profile, sieved into clod sizes and mass with clod number and OC concentration determined. Delving elevated clay from 40 to 60 cm depth and created few clods, which were poorly distributed in the depth of modification. Spading mixed clay from 20 to 30 cm below the soil surface and created many, smaller sized clods, which were more evenly distributed within the 0–30 cm modification depth. OC concentration was highest in the smallest clods, particularly at the soil surface. OC stock increased with clod number. Clods collected from the two field sites were further used in incubation experiments to determine the effect of clod size and properties (clay and iron concentration) on the accumulation and protection of OC. Clods (2–6 and 6–20 mm) were added to sand at 80 mg clay g−1 sand and incubated 300 or 420 days at optimal moisture conditions with monthly wheat residue addition in the accumulation experiment. Smaller clods (2–6 mm) accumulated OC at a higher rate and offered greater protection from decomposition by microbes than larger clods (6–20 mm). These results support our hypotheses that smaller clods and even vertical distribution is important to increase OC. Furthermore, clod number was a critical factor in increasing OC content. We conclude that in clay-modified soils the addition of many, smaller sized clods distributed throughout the depth of modification can improve OC content.

12596. 题目: Material cycling in coastal waters and the role of the Kiritappu Wetland in Hamanaka, Hokkaido: An analysis using the surf clam (Pseudocardium sachalinense) as an environmental indicator
文章编号: N18083005
期刊: Marine Chemistry
作者: X. Ba, N. Kouchi, K. Watanabe, M. Nakaoka, M. Fujii
更新时间: 2018-08-30
摘要: The suspension feeding benthic bivalve surf clam, Pseudocardium sachalinense, which feeds on phytoplankton, benthic microalgae, and detritus in coastal waters, is one of the most important marine resources in Hamanaka, Hokkaido Prefecture, Japan. We measured stable carbon and nitrogen isotope ratios (δ13C and δ15N) and carbon‑nitrogen (C/N) ratios of surf clam adductor muscle and stomach contents, oceanic particulate organic matter (POM), oceanic sediments, riverine POM, and soil, as well as physical and chemical parameters such as temperature, salinity, chlorophyll-a, and nutrients in Hamanaka from April through September 2015. We also examined the food sources that support the surf clam, the possible connection between wetlands and coastal waters, and the spatial and seasonal variation. Our results showed that the isotope and C/N values of surf clams and oceanic organic matter were significantly different from those of riverine organic matter, and that there were no significant differences among different sites of coastal areas. This means that land-derived organic matter is not a direct food source for the surf clam and does not affect the coastal environment. In addition, benthic microalgae and epiphytes are considered to be the major food sources for the surf clam in all sampling seasons, since they have isotope and C/N values similar to those of the surf clam. The overall results, also with reference to previous relevant studies, imply the importance of conservation of wetlands which buffer excessive inflow of land-derived organic matter that may harm surf clams and the coastal environment.

12597. 题目: Production of bio-oil from agricultural waste by using a continuous fast microwave pyrolysis system
文章编号: N18083004
期刊: Bioresource Technology
作者: Yunpu Wang, Zihong Zeng, Xiaojie Tian, Leilei Dai, Ling Jiang, Shumei Zhang, Qiuhao Wu, Pingwei Wen, Guiming Fu, Yuhuan Liu, Roger Ruan
更新时间: 2018-08-30
摘要: In this study, a continuous fast microwave-assisted pyrolysis system was developed to produce bio-oil, gas, and biochar from rice straw and Camellia oleifera shell. The effects of different pyrolysis temperatures (400 °C, 500 °C, and 600 °C) and feed rates (rice straw: 25, 45, and 66 g/min; C. oleifera shell: 100, 200, and 400 g/min) on bio-oil production were investigated. Experimental results showed that the yields of bio-oil (31.86 wt%) and gas (54.49 wt%) produced by the microwave-assisted pyrolysis of rice straw increased with increasing temperature. By contrast, the yields of bio-oil (27.45 wt%) and biochar (35.47 wt%) produced by the pyrolysis of C. oleifera shell decreased with increasing temperature. The contents of phenols, aldehydes, and alcohols in bio-oil produced from the shell were higher than those in bio-oil derived from rice straw.

12598. 题目: The effects of humic acid on the toxicity of graphene oxide to Scenedesmus obliquus and Daphnia magna
文章编号: N18083003
期刊: Science of The Total Environment
作者: Ying Zhang, Tiantian Meng, Liu Shi, Xi Guo, Xiaohui Si, Ruixin Yang, Xie Quan
更新时间: 2018-08-30
摘要: The wide production and application of graphene oxide (GO) has inevitably caused its release to the aquatic ecosystem. However, the influence of natural organic matter (NOM) on the toxicity of GO to aquatic organisms needs further investigation. In this study, we conducted several toxicity tests (i.e., acute toxicity and oxidative damage) with Scenedesmus obliquus (S. obliquus) and Daphnia magna (D. magna), as well as a chronic toxicity test with D. magna, to investigate the toxicity of GO with or without the presence of humic acid (HA). Our results showed that GO induced significant toxicity to S. obliquus and D. magna, and the median lethal concentrations (72 h-LC50 and 48 h-LC50) for acute toxicity were 20.6 and 84.2 mg L−1, respectively, while the 21 d-LC50 for chronic toxicity to D. magna was 3.3 mg L−1. Additionally, HA mitigated the acute toxicity of GO to S. obliquus and D. magna by 28.6% and 32.3%, respectively, and mitigated the chronic toxicity of GO to D. magna. In the presence of HA, the decreased toxicity of GO was attributed to the alleviation of oxidative damage by HA to both S. obliquus and D. magna, the mitigation of surface envelopment to S. obliquus and the body accumulation in D. magna. Our study provides useful and basic biotoxicity data of GO with a consideration of its interaction with NOM which could aid in preventing an overestimation of the risks of GO to the natural aquatic environment.
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12599. 题目: Selective antibiotic resistance genes in multiphase samples during biofilm growth in a simulated drinking water distribution system: Occurrence, correlation and low-pressure ultraviolet removal
文章编号: N18083002
期刊: Science of The Total Environment
作者: Minglu Zhang, Li Wang, Mengyao Xu, He Zhou, Shuangling Wang, YongJing Wang, Miao Bai, Can Zhang
更新时间: 2018-08-30
摘要: The aim of this study was to gain comprehensive insights into the characteristics of antibiotic resistance genes (ARGs) in multiphase samples from drinking water distribution pipelines using a simulated biofilm reactor. During 120 d of continuous operation, common parameters and six ARGs (ermA, ermB, aphA2, ampC, sulII, and tetO) in samples of three phases (water, particle, and biofilm) from the reactor were investigated, which demonstrated secondary contamination by ARGs. Abundances of the six ARGs in the reactor effluent increased gradually, and in the 120 d effluent, the relative abundances of aphA2 and sulII were the highest, at 9.9 × 10−4 and 1.3 × 10−3, respectively, with a 1.5-fold and 2.8-fold increase, compared with those in the influent. The relative abundances of the six ARGs in the biofilm phase increased significantly (P < 0.05) at 120 d, which was caused by robust bacteria in biofilm that was newly exposed following the detachment of a large piece of aging biofilm. In the particle phase, four of the ARGs did not change significantly during the 120 d period. The six ARGs in the samples of three phases showed a negative correlation with residual chlorine in the pipe water, which demonstrated that low abundance of ARGs in the samples of three phases was related to the improvement of residual chlorine. The proportion of cultivable bacteria illustrated that the robust and active bacteria were negatively correlated with the six ARGs in the biofilm. Total organic carbon (TOC) in the pipeline showed a positive correlation with the proportion of cultivable bacteria in both the water and biofilm phases, which indicated that a TOC reduction in the pipeline contributed to low abundance of ARGs. With low-pressure ultraviolet (LP-UV) irradiation of 20 mJ/cm2, ARGs in the samples of three phases were efficiently controlled, which showed that LP-UV can be used for ARG removal in terminal water for supplemental bactericidal treatment of pipeline effluent.
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12600. 题目: One step co-sintering process for low-cost fly ash based ceramic microfiltration membrane in oil-in-water emulsion treatment
文章编号: N18083001
期刊: Separation and Purification Technology
作者: Dong Zou, Minghui Qiu, Xianfu Chen, Enrico Drioli, Yiqun Fan
更新时间: 2018-08-30
摘要: Ceramic membranes with higher chemical stabilities and organic solvent resistances are indispensable for water purification. The fabrication of low-cost ceramic membranes (lower sintering consumption and cheaper membrane materials) facilitates practical water treatment applications. In this study, a novel process for the fabrication of a low-cost fly ash based microfiltration (MF) membrane via a co-sintering process was proposed. In the novel process, the MF layer was sprayed on a “green” fly ash support and co-sintered. The mullite fibers with excellent heat resistance and stability were proposed to alleviate the shrinkage difference in the co-sintering process, and improve the porosity and bending strength of the support. The raw material cost, energy consumption, and preparation period of the ceramic membrane could be significantly reduced. The prepared ceramic MF membrane had an average pore size of 100 nm with a high permeability of 450 Lm−2 h−1 bar−1. Moreover, it exhibited a high total organic carbon (TOC) removal efficiency (>99%) for oil-in-water (O/W) emulsion, and a high stable permeability of 165 Lm−2 h−1 bar−1 was maintained. This technique, combining low-cost materials and the co-sintering process, can serve as a cost-effective method for the production of high-performance ceramic membranes for water purification.

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