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28721. 题目: Methylated naphthalenes as indicators for evaluating the source and source rock lithology of degraded oils
文章编号: N18063009
期刊: Organic Geochemistry
作者: Kenta Asahina, Noriyuki Suzuki
更新时间: 2018-06-30
摘要: Methylated naphthalenes in oils/condensates are relatively resistant to bio- and thermal degradation and can be useful compounds for evaluating the source organic matter and source rock lithology. Assuming that cadinene, abietic acid, and cholesterol are major precursors of methylated naphthalenes in oils and condensates, laboratory hydrous pyrolysis experiments for these possible precursors were performed to understand the precursor/products relationship. The major dimethylnaphthalenes (DMNs) and trimethylnaphthalenes (TMNs) in pyrolyzates of cadinene and abietic acid were 1,2,5-TMN and 1,6- and 1,5-DMNs, whereas those in pyrolyzates of cholesterol were 2,3,6-TMN and 1,3- and 1,7-DMNs. The experimental results suggested that the dimethylnaphthalene ratio (DMR) of [1,5- + 1,6-DMNs]/[1,3- + 1,7-DMNs], and the trimethylnaphthalene ratio (TMR) of 1,2,5-TMN/2,3,6-TMN, can be potential indicators of source organic matter. The relative abundance of TMNs in the pyrolyzates was controlled largely by the maturity level and presence or absence of montmorillonite catalyst. The relative abundance of total TMNs to total MNs (ΣTMNs/ΣMNs ratio) can be a novel indicator for evaluating the clay-catalytic effect in source rocks. A lower ΣTMNs/ΣMNs ratio is related to clay-poor source rocks, such as coal, carbonates, and siliceous rocks, whereas a higher ΣTMNs/ΣMNs ratio suggests shaly (clay-rich) source rocks. The DMR, TMR, and ΣTMNs/ΣMNs ratios of various oils and condensates are very consistent with their source organic matter and source rock lithology, indicating that these indicators are practically useful.

28722. 题目: The Structural and Dynamical Role of Water in Natural Organic Matter: a 2H NMR and XRD Study
文章编号: N18063008
期刊: Organic Geochemistry
作者: Raju Nanda, U. Venkateswara Reddy, Geoffrey M. Bowers, Mark Bowden, R. James Kirkpatrick
更新时间: 2018-06-30
摘要: Natural organic matter (NOM) is an important component in many near-surface geochemical environments, and its properties are greatly affected by the incorporation of water. Because of its importance, the macroscopic behavior and effects of water in NOM and soil organic matter (SOM) have been extensively studied using a wide range of experimental and computational methods. The molecular scale structural and dynamical behavior of water in these materials, however, is less well understood. This paper presents a variable temperature 2H NMR and XRD study of water in Suwannee River NOM and its fulvic acid (FA) and humic acid (HA) fractions that provides new insight into the dynamical behavior of structurally different types of water and exchangeable hydrogen environments in NOM. The results provide a basis for future studies of more complex natural organic materials and the interaction of organic materials with mineral surfaces. Room temperature 2H NMR spectra of samples hydrated in 2H2O and then dehydrated distinguish2H2O molecules that are in rapid reorientational motion (correlation times, νc, > 105 Hz), 2H exchanged onto carboxylic sites of the NOM that do not undergo rapid reorientation at frequencies > 103 Hz, and 2H exchanged onto phenolic and possibly other alcohol sites of the NOM that undergoes rapid but anisotropic dynamical reorientation. For samples exposed to water and not dried, the XRD results collected at temperatures from 173 to 298K show the formation of ice-1h in samples exposed to 100% relative humidity (R.H.) but not in samples exposed to 43% R.H. 2H NMR of those samples collected at temperatures from 313K to 173K show the presence of multiple sites. Near room temperature, the spectra contain a narrow resonance for mobile water undergoing rapid isotropic motion, and a broader symmetrical resonance probably due to a combination of more dynamically restricted water molecules and 2H exchanged onto phenolic and alcohol functional groups undergoing rapid anisotropic motion. The 43% R.H. samples also yield a broader quadrupole-dominated resonance for 2H exchanged onto functional groups of the NOM. With decreasing temperature, the resonances for dynamically restricted water molecules and 2H exchanged onto phenolic and alcohol functional groups become broader, reflecting a decreasing rate of exchange between the water molecules and functional groups and a decreasing rate of reorientation of the 2H2O molecules. The formation of ice-1h is directly reflected in the 2H spectra of the 100% R.H. samples as a resonance with a quadrupole coupling constant (QCC) of 180 kHz. For the 43% R.H. samples, there is also a broad, poorly resolved resonance with typical QCCs of 180 kHz for which the relative signal intensity increases with decreasing temperature. This signal represents 2H2O molecules that are not crystallized in ice-1h but have greatly reduced reorientation frequencies at low temperature and a hydrogen bonding network with hydrogen bond strengths similar to but somewhat weaker than ice-1h. Such molecules are also likely to be present in the 100% R.H. samples. At both R.H.s, some of the 2H2O molecules do not freeze and retain their isotropic motion down to 173K, the lowest temperature investigated.

28723. 题目: Assessment of revegetation of an acidic metal(loid)-polluted soils six years after the incorporation of lime with and without compost
文章编号: N18063007
期刊: Geoderma
作者: Javier Pardo, Pedro Mondaca, Juan L. Celis-Diez, Rosanna Ginocchio, Claudia Navarro-Villarroel, Alexander Neaman
更新时间: 2018-06-30
摘要: The process of passive revegetation of chemically degraded soils through assisted remediation was assessed under field conditions 6 years after amendment application. In 2009, three treatments were applied: unamended soil (untreated), soil amended with lime, and soil amended with lime + compost. For each field plot, main soil physico-chemical characteristics were determined (pH, organic matter, moisture content at field capacity and exchangeable Cu), while plant colonist development was assessed (plant cover and aboveground biomass). The same evaluation was carried out in 2015. A single application of amendments maintains a neutral pH after 6 years. Thus, neutralization of the soil acidity was stable over time. In 2009, lime + compost was the best treatment for increasing the plant cover. Although the soil organic matter content decreases in year 6, plant cover remained stable over time in this treatment. Incorporation of both organic matter and lime was pivotal at the beginning of the revegetation process, allowing the creation of a potentially self-sustaining ecosystem. No maintenance and/or additional application of amendments was required. Aboveground biomass showed differences between years, possibly explained by changes in climate conditions between 2009 and 2015, and/or changes in nutritional conditions (soil fertility) and plant competition. Plant biodiversity in year 6 was similar for all treatments. The long-term results of plant cover show lime and specially lime + compost as promising amendments to revegetate polluted soils of the Puchuncaví Valley.

28724. 题目: Cascading effects of elevated ozone on wheat rhizosphere microbial communities depend on temperature and cultivar sensitivity
文章编号: N18063005
期刊: Environmental Pollution
作者: F. Changey, M. Bagard, M. Souleymane, T.Z. Lerch
更新时间: 2018-06-30
摘要: Tropospheric ozone (O3) concentrations have now reached levels that can potentially affect crop production in several regions of the world. The interacting effects of the elevated O3 and temperature on plants are still unclear and their consequences on the rhizosphere microbial communities never studied yet. Here, we conducted a 3-week fumigation experiment on two cultivars of wheat with different tolerance to O3 (Premio and Soissons) at two temperatures (20 °C and 30 °C). The impacts of O3 were measured on plants physiology, rhizosphere chemical environment and microbial communities. Globally, most of the results showed that elevated O3 effects were more pronounced at 20 °C than 30 °C, especially on the most O3-sensitive cultivar (Soissons). Elevated O3 reduced significantly plant root biomass (up to 37% for Soissons) compared to non-fumigated plants. A decrease in the dissolved organic matter with a relative increase of aromatic compounds concentration was also observed under elevated O3, suggesting quantitative and qualitative impacts on roots exudation. While bacterial abundance was negatively affected by O3 plant stress, fungal abundance was found to be stimulated (up to 12 fold compared to non-fumigated plants for Soissons at 20 °C). These changes were accompanied by modifications of the genetic structures and metabolic profiles, with a relative increase of amino acids catabolism. This fully controlled laboratory experiment showed that the effects of elevated O3 on soil microbial communities i) are plant-mediated and depend on the cultivar sensitivity, ii) decrease in warming condition, iii) increase the fungi to bacteria ratio and iv) alter both the genetic structure and the metabolic activities. This study highlights the importance of considering interactive effects between pollutants and climate changes on plant-microbe relationship to better inform models and improve predictions of future states of agroecosystems.

28725. 题目: Heavy metal concentrations and chemical fractions in sediment from Swan Lagoon, China: Their relation to the physiochemical properties of sediment
文章编号: N18063004
期刊: Chemosphere
作者: Chengye Hu, Xiaolong Yang, Jianyu Dong, Xiumei Zhang
更新时间: 2018-06-30
摘要: This study was performed to determine the distribution and chemical fractions of five heavy metals (Cd, Cr, Cu, Pb, and Zn) in sediment from three sampling areas in Swan Lagoon, and their relation to the physiochemical properties of sediment were explored. The results revealed that Cd in sediment from the sand part (SP), muddy sand part (MSP) and sand muddy part (SMP) were potentially highly susceptible and bioavailable since the exchangeable fractions were 21.0%, 27.4%, and 32.1%, respectively, of the total concentrations. A portion of Pb and Zn were observed as reducible fractions owing to their affinity to Fe-Mn; they were able to complex with Fe-Mn oxides and oxyhydroxides in the sediment. A large amount of Cu in the oxidizable fraction may be due to the fact that Cu can easily form stable complexes with organic matter. Cr was overwhelmingly found in the residual fraction, suggesting that Cr was strongly bound in mineral lattices. Enrichment factors (EF) indicated that Cd in three sampling areas suffered severe enrichment, whereas other metals were present in only minor amounts. In addition, Cd may pose a medium to high risk in the MSP and SMP based on risk assessment codes. According to the mean probable effects level quotient, the samples from the MSP and SMP had a 21% probability of toxicity. The multivariate statistical analysis suggested that sediment texture (d0.5, sand and silt), Fe-Mn, and the total organic carbon (TOC) influenced the distribution of the studied metals and their chemical fractions.

28726. 题目: Mussel-inspired functionalization of biological calcium carbonate for improving Eu(III) adsorption and the related mechanisms
文章编号: N18063003
期刊: Chemical Engineering Journal
作者: Xueli Zhou, Weizhen Liu, Chen Tian, Siqi Mo, Xueming Liu, Hong Deng, Zhang Lin
更新时间: 2018-06-30
摘要: The high value rare earth elements (REEs) recycling from wastewater remains a great challenge. In the present work, biological calcium carbonate (bio-CaCO3) was functionalized by mussel-inspired polydopamine (PDA) chemistry to improve its Eu(III) adsorption in aqueous solutions. The functional groups of the organic matters in bio-CaCO3 that served as both reductant and coupling agent were found to be able to effectively inhibit the auto-oxidation of PDA in alkaline environments, rendering a uniform and tight PDA coating on bio-CaCO3. The batch experiments indicated that the mussel-inspired PDA functionalized bio-CaCO3 (bio-PDA) exhibited superior Eu(III) adsorption capacity in aqueous solutions. The adsorption isotherm was fitted well with the Langmuir model, and the maximum adsorption capacity was determined to be 151.52 mg/g. The adsorption kinetics followed pseudo-second-order model, suggesting that the adsorption was chemisorption. Based on the scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and X-ray photoelectron spectroscopic (XPS) analyses, the possible Eu(III) adsorption mechanism of bio-PDA was proposed as the coordination of Eu(III) with the abundant catechol and amine/imine groups on the PDA coating. Our work has demonstrated great application potentials of bio-PDA as an efficient Eu(III) adsorbent and provided new insights into the interaction mechanism between PDA and Eu(III).

28727. 题目: Temperature adaptability of soil respiration in short-term incubation experiments
文章编号: N18063002
期刊: Journal of Soils and Sediments
作者: Guiying You, Zhiyuan Zhang, Renduo Zhang
更新时间: 2018-06-30
摘要: Purpose: The soil is the largest carbon pool in the terrestrial ecosystem. Changes of soil respiration with the climate warming are essential for the carbon cycling between the terrestrial ecosystem and the atmosphere. The aim of this study was to investigate the temperature adaptability of soil respiration and the possible mechanisms. Materials and methods: Experiments with a meadow soil were conducted through pre-incubation for 3 days at 22 °C, then incubation under temperatures of 22 ± 1, 30 ± 1, and 38 ± 1 °C, respectively, for 35 days. For the different incubation temperatures, gas samples were collected on days 3, 9, 13, 16, 20, 23, 30, and 35, respectively. The gas samples were used for measurements of CO2 concentrations and calculation of soil respiration rates. The temperature sensibility of soil respiration was characterized with the index Q10 (i.e., the increasing multiple of respiration rate with temperature increase of 10 °C). Soil properties related to respiration rates were measured, including total carbon (TC), dissolved organic carbon (DOC), soil organic matter (SOM), microbial biomass carbon (MBC), enzyme activities, and microbial community structure. Results and discussion: After 35 days of incubation, the temperature sensibility of soil respiration decreased with the incubation temperatures, i.e., Q10 (22 °C) > Q10 (30 °C) > Q10 (38 °C). The result showed that soil respiration exhibited temperature adaptability. The TC and SOM contents were not significantly different among the different temperatures, indicating sufficient substrate availability during the short incubation period. The warming scenarios led to lower activities of enzymes relative to C and N cycles and MBC and significantly changed the microbial community, especially decreased abundance of gram-negative bacteria. The elevated temperatures also reduced the comparability of bacteria and fungi and increased the diversity of microbial community structure. Conclusions: Mechanisms of the temperature adaptability of soil respiration included reduction of the carbon-use efficiency and temperature adaptation of microorganisms. Among them, the microbial adaptation was the dominant mechanism for the temperature adaptability of soil respiration during the short-term incubation experiments.

28728. 题目: Impact of waste-derived organic and inorganic amendments on the mobility and bioavailability of arsenic and cadmium in alkaline and acid soils
文章编号: N18063001
期刊: Environmental Science and Pollution Research
作者: Claudia Rocco, Balaji Seshadri, Paola Adamo, Nanthi S. Bolan, Kenneth Mbene, Ravi Naidu
更新时间: 2018-06-30
摘要: In agriculture, more and more frequently waste-derived amendments are applied to soil to improve physical and chemical properties. Nevertheless, in soils polluted by potentially toxic metal(loid)s, this agricultural practice may significantly affect the mobility and bioavailability of pollutants modifying the risks for biota and human health. This work was aimed to assess the influence of poultry manure, biochar and coal fly ash on the mobility and bioavailability of As and Cd spiked in two Australian soils with different pH and texture: Mount Gambier (MGB)-alkaline sandy clay loam and Kapuda (KPD)-acid loamy sand. After 4 weeks of incubation from spiking and another 4 weeks from amendment addition, the soils were analysed for pH and amounts of As and Cd in pore-water and following 1 M NH4NO3 extraction. Bioavailable amounts were assessed by plant uptake, using Zea mays L. as test crop. In the alkaline MGB soil, the availability of Cd was reduced, while that of As increased. An opposite behaviour was observed in the acid KPD soil. All amendments, when added to KPD soil, increased pH and consequently reduced the mobility of Cd and increased the mobility of As. In MGB, the amendment addition had an effect only on As mobility and bioavailability, which increased likely as a result of the increased competition for adsorption with DOC released by organic compounds. These trends were confirmed by the amounts of Cd and As uptaken by maize plants.

28729. 题目: Effects of biochar on the dynamics of aggregate stability in clay and sandy loam soils
文章编号: N18062903
期刊: European Journal of Soil Science
作者: C. Pituello , N. Dal Ferro , O. Francioso , G. Simonetti , A. Berti , I. Piccoli , A. Pisi , F. Morari
更新时间: 2018-06-29
摘要: Recent advances suggest that organic substances of different origins might have different aggregate stability dynamics. We investigated the extent to which contrasting soil types affect the dynamics of aggregation after the addition of crop residues (R) and of biochar at two doses (BC20, 20 Mg ha 1; BC40, 40 Mg ha 1) in a 2‐year experiment. To evaluate disaggregation, we measured a set of physical–chemical and structure‐related properties of clay and sandy loam aggregates sieved to 1–2 mm, including wet aggregate stability after different pretreatments combined with laser diffraction analysis. The electrochemical properties of the colloidal suspension were also analysed to identify changes in soil chemistry affected by organic inputs. Different amounts of added biochar and soil types produced contrasting effects on wet aggregate stability. In sandy loam, the increased soil surface area from added biochar (at either dose) offset the initial small soil organic carbon (SOC) content and subsequently promoted SOC‐controlled aggregation. Conversely in clay soil, the larger biochar dose (BC40) strengthened the repulsive forces between particles with the same charge and monovalent cations, which led to chemical perturbation and some aggregate breakdown not found with BC20. Pore structure also changed in clay aggregates. A shift towards more micropores (30–5 μm, + 29% more than in the control) and ultramicropores (5–0.1 μm, + 22% more than in the control), which contributed to aggregate stabilization, resulted when biochar was added, but not for residue. Our results suggest that biochar promotes aggregate stability, which, in turn, improves the physical fertility of soil, especially if it has a coarse texture and small organic carbon content. Further study is needed of the physical–chemical interactions between added biochar and surface‐charged clay‐rich soils.

28730. 题目: Effects of sheet and rill erosion on soil aggregates and organic carbon losses for a Mollisol hillslope under rainfall simulation
文章编号: N18062902
期刊: Journal of Soils and Sediments
作者: Yiliang Jiang, Fenli Zheng, Leilei Wen, Hai-ou Shen
更新时间: 2018-06-29
摘要: Purpose: Characterizations of soil aggregates and soil organic carbon (SOC) losses affected by different water erosion patterns at the hillslope scale are poorly understood. Therefore, the objective of this study was to quantify how sheet and rill erosion affect soil aggregates and soil organic carbon losses for a Mollisol hillslope in Northeast China under indoor simulated rainfall. Materials and methods: The soil used in this study was a Mollisol (USDA Taxonomy), collected from a maize field (0–20 cm depth) in Northeast China. A soil pan with dimensions 8 m long, 1.5 m wide and 0.6 m deep was subjected to rainfall intensities of 50 and 100 mm h 1. The experimental treatments included sheet erosion dominated (SED) and rill erosion dominated (RED) treatments. Runoff with sediment samples was collected during each experimental run, and then the samples were separated into six aggregate fractions (0–0.25, 0.25–0.5, 0.5–1, 1–2, 2–5, > 5 mm) to determine the soil aggregate and SOC losses. Results and discussion: At rainfall intensities of 50 and 100 mm h 1, soil losses from the RED treatment were 1.4 and 3.5 times higher than those from the SED treatment, and SOC losses were 1.7 and 3.8 times greater than those from the SED treatment, respectively. However, the SOC enrichment ratio in sediment from the SED treatment was 1.15 on average and higher than that from the RED treatment. Furthermore, the loss of < 0.25 mm aggregates occupied 41.1 to 73.1% of the total sediment aggregates for the SED treatment, whereas the loss of > 0.25 mm aggregates occupied 53.2 to 67.3% of the total sediment aggregates for the RED treatment. For the organic carbon loss among the six aggregate fractions, the loss of 0–0.25 mm aggregate organic carbon dominated for both treatments. When rainfall intensity increased from 50 to 100 mm h 1, aggregate organic carbon loss increased from 1.04 to 5.87 times for six aggregate fractions under the SED treatment, whereas the loss increased from 3.82 to 27.84 times for six aggregate fractions under the RED treatment. Conclusions: This study highlights the effects of sheet and rill erosion on soil and carbon losses at the hillslope scale, and further study should quantify the effects of erosion patterns on SOC loss at a larger scale to accurately estimate agricultural ecosystem carbon flux.

28731. 题目: Removal of aromatic and hydrophobic fractions of natural organic matter (NOM) using surfactant modified magnetic nanoadsorbents (MNPs)
文章编号: N18062901
期刊: Environmental Science and Pollution Research
作者: Minashree Kumari, Sunil Kumar Gupta
更新时间: 2018-06-29
摘要: The present study investigated the potential of surfactant modified magnetic nanoadsorbents (MNPs) for the removal of aromatic and hydrophobic fractions of natural organic matter (NOM), leading to the formation of trihalomethanes (THMs) in chlorinated drinking water. Co-precipitation method was used for the synthesis of MNPs. However, MNPs have a tendency to form an agglomeration. Therefore, polyethylene glycol (PEG) was used as a surface modifier to reduce the agglomeration. The PEG-coated MNPs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), BET surface area, X-ray diffraction (XRD), Fourier transform spectrometer (FTIR), and zeta (ζ) potential. FESEM observation indicates that PEG-coated MNPs were spherical in shape and 25 nm in size. Zeta potential values ( 58.35 to 74.9 mV) indicated excellent stability of PEG-MNPs. FTIR spectra indicated the presence of a CH2 group, responsible for the chemical interaction between aromatic and humic content. Batch experiments were conducted by studying the effect of pH, contact time, and adsorbent dosage on NOM removal. Excellent removal of DOC (94.49%) and UV254 (89.32%) was observed at the optimum dose of adsorbent (0.75 g/L) and at pH 7.0. Adsorption kinetics followed pseudo-second-order reaction (R2, 0.973) and occurs by multilayer chemisorption which is due to the chemical interaction between aromatic and humic compounds of NOM with MNPs. Thus, MNPs showed great potential as a novel adsorbent for the removal of aromatic and hydrophobic compounds of NOM and can significantly be used to curtail the problem of THMs in drinking water supplies.

28732. 题目: Quantitative analysis of how different checkerboard sand barrier materials influence soil properties: a study from the eastern edge of the Tengger Desert, China
文章编号: N18062801
期刊: Environmental Earth Sciences
作者: Xiaojia Li, Ruiping Zhou, Hongtao Jiang, Dandan Zhou, Xiwei Zhang, Yunhu Xie, Wenbang Gao, Jing Shi, Yuhao Wang, Jing Wang, Rui Dong, Ganbat Byambaa, Ji Wang, Zhibo Wu, Chunxing Hai
更新时间: 2018-06-28
摘要: Sand encroachment is a serious problem in arid regions. Checkerboard barriers are commonly used as wind buffers and to stabilize soils at risk of desertification. These interventions can also improve soil nutrients. Checkboard sand barriers are widely used in arid regions, but different barrier types are seldom optimized for specific areas or land management objectives. This research studied how checkerboard barriers made of different types of materials influenced soil properties (soil organic carbon, available nitrogen, available phosphorus, available potassium, pH and soil moisture). These parameters were measured at various soil depths within test plots protected by eleven different types of checkerboard barrier material. Data were then analyzed by constructing a soil quality index (SQI) model based on coefficients identified by principal component analysis of soils at depths of 0–20, 20–40, 40–60 cm and for the complete 0–60 cm profile. The results generally found that barriers improve soil quality. They also showed significant variation in soil properties at different depths for different types of barrier material. For the 0–60 cm soil profile, barriers increased soil available nitrogen, available potassium, soil organic carbon and soil moisture but decreased soil available phosphorus and pH. The SQI values indicated that rice straw barriers optimized soil nutrients at soil depths of 0–20 cm, low vertical corn straw checkerboard barriers at soil depth of 20–40 cm, while 30 cm wide gravel checkerboard barriers optimized nutrients at 40–60 cm soil depth. Plots protected by low vertical branch barriers showed the greatest overall soil quality improvement for the complete 0–60 cm profile. This study found that corn straw, clay, 30 cm wide gravel and low vertical branch barriers can significantly protect and restore soils on the eastern edge of the Tengger Desert.

28733. 题目: The interactions between tree-herb layer diversity and soil properties in the oriental beech ( Fagus orientalis Lipsky) stands in Hyrcanian forest
文章编号: N18062611
期刊: Environmental Monitoring and Assessment
作者: Behzad Bakhshandeh-Navroud, Kambiz Abrari Vajari, Babak Pilehvar, Yahya Kooch
更新时间: 2018-06-26
摘要: This study investigated the interactions between tree-herb layer diversity and some physico-chemical and eco-physiological characteristics of soil in natural oriental beech stand in western Guilan, Iran. The data were collected from nine research sites (50 m × 50 m) which were described as a gradient from pure oriental beech (Fagus orientalis Lipsky) stands to mixed stands with up to nine deciduous tree species (n = 27) in Hyrcanian forest. Herbaceous plants were sampled within ten 1 m × 1 m sub-plots in two plots of 400 m2 which were installed randomly in each research site. Composite soil samples were taken at five positions in each research site. We found that the increase in tree diversity in mature oriental beech stands brought about an increase in microbial biomass carbon, soil carbon content, and the ratio of microbial biomass carbon to the organic carbon (Cmic/Corg). Increased soil organic carbon raised microbial biomass carbon through creating suitable environment for microorganisms. The findings also indicated that the ratio of microbial biomass carbon to the organic carbon (Cmic/Corg) increased as a quantitative indicator of soil carbon dynamics that finally benefits soil fertility of mixed oriental beech stands compared to pure oriental beech stands. The results showed that humus layer and litter thickness were negatively correlated with tree layer richness. Generally, it can be stated that maintaining a mixture of tree layer species in natural oriental beech stands results in an increase in richness and diversity values of herb plants as well as carbon content and microbial biomass carbon of soil.

28734. 题目: Promoting revegetation and soil carbon sequestration on decommissioned forest roads in Colorado, USA: A comparative assessment of organic soil amendments
文章编号: N18062608
期刊: Forest Ecology and Management
作者: M. Ramlow, C.C. Rhoades, M.F. Cotrufo
更新时间: 2018-06-26
摘要: Forest roads are commonly decommissioned and revegetated to decrease erosion, prevent weed encroachment, manage recreation and improve overall watershed condition on federal lands, but may also provide a complementary opportunity to sequester carbon (C) in soils. Soils on decommissioned roads are typically compacted with limited capacity for water retention, decreased mineral nitrogen (N) availability and low organic matter content, impairing revegetation and soil C sequestration efforts. We evaluated the effects of an organic fertilizer, wood strand mulch and a woody biochar on soil physical, chemical and biological processes to improve revegetation and C sequestration on decompacted forest roads. We monitored plant and soil responses to the treatments and their combinations over three growing seasons on four decommissioned road segments in northern Colorado. The organic fertilizer increased plant available mineral N for the first year of the study and resulted in a 21% increase in total plant cover and 67% increase in root biomass. The wood strand mulch increased total plant cover and root biomass to a similar extent, but had no effect on soil water content or mineral N availability. Instead, mulch stimulated soil microbial respiration and increased soil C content, two of the best predictors of plant cover and biomass. The woody biochar increased soil water content by 26% and elevated mineral N availability throughout the study, but did not improve plant cover, above- or belowground biomass. Mulch, biochar and their combined treatments sequestered C, but through distinct pathways. Microbial processing of wood strand mulch added C to the mineral soil fraction, whereas biochar added C directly to the coarse particulate fraction with no effect on mineral soil C or soil respiration. Restoration practitioners can utilize these results to inform management decisions and guide further research on different rates and combinations of organic amendments to revegetate and sequester C on decommissioned forest roads.

28735. 题目: How do logging residues of different tree species affect soil N cycling after final felling?
文章编号: N18062607
期刊: Forest Ecology and Management
作者: Tiina T?rm?nen, Veikko Kitunen, Antti-Jussi Lindroos, Juha Heikkinen, Aino Smolander
更新时间: 2018-06-26
摘要: The aim of this study was to compare how logging residues of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth.) affect the dynamics of N and C cycling processes in forest soil after final felling. The study site was located in southeastern Finland. After clear-cutting, piles consisting of 40 kg m 2 of fresh logging residues of each tree species were established, together with a control plot as an additional treatment. Samples were taken from the organic layer and uppermost mineral soil at the beginning of the experiment and each spring and autumn in the two following years. Logging residues stimulated net N mineralization and net nitrification and increased both NH4- and NO3-N concentrations in the organic layer. Logging residues increased the soil pH, organic matter content (%) and C mineralization, whereas microbial biomass C and N decreased. No major, consistent differences were observed between the effects of the separate tree species, although there were tree-species-specific differences on the dynamics of soil processes. Logging residues of spruce, pine and birch all strongly accelerated the processes of soil N cycling soon after clear-cutting. This study provides new information for the discussion on the sustainability of logging residue distribution and harvesting in boreal forests.

28736. 题目: Effects of tree species and soil properties on the composition and diversity of the soil bacterial community following afforestation
文章编号: N18062606
期刊: Forest Ecology and Management
作者: Jinliang Liu, Peng Dang, Yang Gao, Hailan Zhu, Huinan Zhu, Fei Zhao, Zhong Zhao
更新时间: 2018-06-26
摘要: Afforestation with single and mixed tree species on cropland alters soil properties and the composition and diversity of soil bacterial community. We investigated changes in soil properties and the soil bacterial community composition in the topsoil (0–20 cm) following afforestation on cropland on the Loess Plateau. Forests of six types ranging from 23 to 25 years in age were chosen in this study: Robinia pseudoacacia (RP), Platycladus orientalis (PO), Pinus tabuliformis (PT), Robinia pseudoacacia + Platycladus orientalis (RPPO), Robinia pseudoacacia + Pinus tabuliformis (RPPT), and Platycladus orientalis + Pinus tabuliformis (POPT). Afforestation with different tree species altered the soil nutrient contents, with total nitrogen (TN) and ammonium nitrogen (NH4 +) contents increased by 18.28–87.10% and 13.97–141.34%, respectively, and available phosphorus (AP) content decreased by 56.09–82.13% compared to cropland sites. Cropland afforestation reduced the soil bacterial richness and core bacterial genera abundance (relative abundance ≥ 0.1%), and significantly altered the bacterial diversity. Soil properties explained 73.41% of the total variation in the core soil bacterial community composition at the genus level, and soil organic carbon (SOC), TN, nitrate nitrogen (NO3 ), NH4 +, AP, pH and the carbon:phosphorus (C:P) ratio were significantly correlated with first two RDA (redundancy analysis) axes. The results of hierarchical clustering indicated that the soil bacterial community composition in the RPPO, RPPT and POPT sites was largely affected by Platycladus, Pinus tabuliformis and Platycladus, respectively. Our observations suggest that soil bacterial community composition and diversity following afforestation were mainly affected by tree species, followed by soil parameters. The effect of afforestation on the soil bacterial diversity was larger than its effect on bacterial richness.

28737. 题目: C and N cycle monitoring under Quercus castaneifolia plantation
文章编号: N18062605
期刊: Forest Ecology and Management
作者: Mohammad Kazem Parsapour, Yahya Kooch, Seyed Mohsen Hosseini, Seyed Jalil Alavi
更新时间: 2018-06-26
摘要: In temperate forests, oak (Quercus castaneifolia) is an important species that grows along an elevation gradient from the flood prone plains to high topographical positions of the landscape. This study was aimed to monitor the effect of oak plantation on the soil C and N cycles and dynamics in the north of Iran. We tested the following hypotheses: (i) reclamation of deforested areas, planting of oak can improve topsoil fertility via forest floor inputs in the long-term, (ii) soil C and N microbial indices can be enhanced under oak plantation, 25 years after planting. For this purpose, three afforested oak stands with 15, 20, and 25 years old, besides a site without plantation, were selected and thirty samples per each site were taken from forest floor and soil (20 × 20 × 10 cm) layers and their physicochemical, biological, and enzymatic properties were assessed. The acquired data demonstrated that forest floor quality, physicochemical and biological properties and enzymatic activities (i.e. urease, acid phosphatase, arylsulfatase and invertase) have been changed over time of oak plantation. Moreover, the microbial activity of soil C and N include basal respiration (BR), substrate inducted respiration (SIR), microbial biomass carbon (MBC), Metabolic quotient (qCO2), microbial entropy (MBC/C), carbon availability index (CAI), carbon management index (CMI), particle organic carbon (POC) and dissolved organic carbon (DOC) were significantly higher in the plantation areas than without plantation site. Oak plantation significantly improved the N microbial characteristics [NH4 +, NO3 , N mineralization, microbial biomass nitrogen (MBN), particle organic nitrogen (PON) and dissolved organic nitrogen (DON)]. Under different land covers, soil microbial activities were more affected by variations in forest floor and soil chemical properties with higher ratio of C, N and available nutrients. Taken together, plantation with suitable native broadleaved species could be considered to rehabilitate degraded natural forests through improving soil quality. Findings also highlighted the importance of understanding C and N cycles in the plantation areas which could involve in global warming phenomena.

28738. 题目: Preparation, characterizations and performance evaluations of alumina hollow fiber membrane incorporated with UiO-66 particles for humic acid removal
文章编号: N18062604
期刊: Journal of Membrane Science
作者: Norfazliana Abdullah, Mukhlis A. Rahman, Mohd Hafiz Dzarfan Othman, Juhana Jaafar, Azian Abd Aziz
更新时间: 2018-06-26
摘要: Humic acid removal requires ceramic membranes incorporated with metal organic framework (MOF) to display remarkable stability over water. Recent work has shown UiO-66, a Zr-based MOF, as an emerging material with the potential to fulfill this requirement. This work investigated the preparation, characterization and performance of UiO-66 particles deposited on alumina hollow fiber membranes. Concentrations of Zr precursors and synthesis period were varied in the preparation of UiO-66 using solvothermal synthesis. The presence of UiO-66 particles was characterized using the field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) mapping, x-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis. Pure water flux and humic acid rejection tests were carried out on both pristine alumina hollow fiber membranes and alumina hollow fiber membranes deposited with UiO-66 particles. In the former, a high pure water flux value of 231.24 L m 2 h 1 was recorded, while in the latter the recorded value dropped to 9.36 L m 2 h 1. Pristine ceramic hollow fiber membranes used to separate humic acid (1 g L 1) from an aqueous solution showed a rejection rate of 98%. When UiO-66 particles were deposited on the ceramic membranes, the solute flux of the membranes increased to 68.36 L m 2 h 1. Surprisingly, it was found that 99% humic acid was rejected from a feed solution using the membranes incorporated with UiO-66 particles. Findings showed that the weight loading of the UiO-66 particles on the alumina hollow fiber membranes was very low, showing a reading of only approximately ~ 0.01 g. Based on the adsorption-desorption analysis, at high pH values (≥ 9), UiO-66 particles and humic acid displayed a similar surface charge, creating a repulsion effect during the filtration process. UiO-66 particles on alumina hollow fiber membranes showed excellent stability, making it viable for water purification applications.

28739. 题目: Rapid immobilisation of U(VI) by Eucalyptus bark: Adsorption without reduction
文章编号: N18062603
期刊: Applied Geochemistry
作者: Susan A. Cumberland, Siobhan A. Wilson, Barbara Etschmann, Peter Kappen, Daryl Howard, David Paterson, Jo?l Brugger
更新时间: 2018-06-26
摘要: Organic matter is increasingly shown to influence the mobility of uranium (U) in the environment. The mobility of U likely depends on whether the organic matter is in dissolved or solid form, with the latter able to retard U mobility. In this work, column experiments were used to reveal that solid organic matter, in the form of well characterized tree bark from Eucalyptus globulus, dramatically reduced the mobility of aqueous U(VI) which was introduced as uranyl nitrate [UO2(NO3)2]. Eucalyptus globulus bark contains high levels of carboxylic and phenolic acid groups which are known to bind to U. Admixtures containing 20 wt. % tree bark and sand were compared to columns containing sand only. We show that soluble U is adsorbed onto the tree bark, likely via a cation exchange with calcium, with no change in U oxidation state as confirmed by X-ray Absorption Near Edge Structure (XANES) analyses. Cation concentrations in column outflow solutions indicated that U was retained in the columns containing tree bark but was released from the sand-only columns. These results demonstrate that solid organic matter such as tree bark has potential applications in trapping U, possibly within permeable reactive barriers, without necessitating further engineering to reduce U(VI) to U(IV). Building on previous work on organic sedimentary U-deposits, this study also helps understand processes of U enrichment from groundwater as observed in environments high in organic matter including wetlands and sediment-hosted ore deposits.

28740. 题目: Iron reductive dissolution in vadose zone soils: Implication for groundwater pollution in landfill impacted sites
文章编号: N18062602
期刊: Applied Geochemistry
作者: Akua B. Oppong-Anane, Katherine Y. Deliz Qui?ones, Willie Harris, Timothy Townsend, Jean-Claude J. Bonzongo
更新时间: 2018-06-26
摘要: Iron (Fe) contamination of groundwater has become a problem of concern at a number of landfill impacted locations, and long-term monitoring studies suggest that the reductive dissolution of iron (hydr)oxide minerals present in soils and aquifer sediments could be one the sources of dissolved Fe measured in impacted aquifers. In this study, vadose zone soil samples were collected along a gradient emphasizing differences in both soil water saturation levels and degrees of crystallization of Fe-minerals. Collected soil samples were analyzed for pH, organic matter content, particle size distribution, and Fe speciation into amorphous and crystalline fractions. Batch experiments were conducted under anaerobic conditions using soil slurries with (treatments) or without (controls) landfill leachate addition to the liquid phase. Under the experimental conditions used in this study, tested soils released Fe primarily via reductive dissolution pathways, with rates ranging from 0.3 to 12 mg Fe/kg.day. However, no clear trend was evident between the amount of Fe released and the crystallinity degrees of the iron minerals present in the tested soils. The addition of organic carbon sources to prepared vadose soils slurries fueled the microbial driven Fe-reductive dissolution, suggesting that organic-rich landfill leachate would play a significant role in the dissolution of iron (hydr)oxide minerals, and potentially in the mobilization of toxic metals co-precipitated with or adsorbed onto iron (hydr)oxide minerals.