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25301. 题目: Measuring total dissolved Fe concentrations in phytoplankton cultures in the presence of synthetic and organic ligands using a modified ferrozine method
文章编号: N18063019
期刊: Marine Chemistry
作者: Hanieh Tohidi Farid, Kai G. Schulz, Andrew L. Rose
更新时间: 2018-06-30
摘要: Low concentrations and complex speciation can present major challenges for measuring Fe in natural waters easily and accurately. This study describes an optimized ferrozine method for measuring total dissolved Fe in the nanomolar range in seawater samples containing various concentrations of organic matter, as well as the commercially available Fe ligands ethylenediaminetetraacetic acid (EDTA) and desferrioxamine B (DFB), which are widely used in phytoplankton cultures. The method involves sample acidification to liberate Fe from strong complexes and/or colloids, followed by reduction of Fe(III) to Fe(II) using sulfite, and finally the measurement of Fe(II)-ferrozine complexes using long optical path spectrophotometry. The performance of each step was improved in such a way as to achieve the most efficient dissociation rate of Fe from the given ligands in the least possible time, regardless of their type or concentration. Storage of samples at pH 1 for 15 days enabled full recovery of Fe in the presence of 50 μmol/L DFB, while the duration required for full Fe recovery in the presence of the same concentration of EDTA was only about 1 h. Addition of ferrozine after a brief (about 15 min) reduction step with subsequent incubation for 24 h resulted in stable color development in the samples over time. The approach was successfully applied to determine total dissolved Fe in samples from coastal waters containing 10.5 μmol/L of particulate organic carbon (POC), and also in samples containing 2 μmol/L EDTA and 800 μmol/L of POC collected from laboratory cultures of the marine cyanobacterium, Trichodesmium erythraeum.

25302. 题目: Effect of photo-biodegradation and biodegradation on the biogeochemical cycling of dissolved organic matter across diverse surface water bodies
文章编号: N18063018
期刊: Journal of Environmental Sciences
作者: M.S. Sankar, Padmanava Dash, Shatrughan Singh, YueHan Lu, Andrew E. Mercer, Shuo Chen
更新时间: 2018-06-30
摘要: The objective of this research was to quantify the temporal variation of dissolved organic matter (DOM) in five distinct waterbodies in watersheds with diverse types of land use and land cover in the presence and absence of sunlight. The water bodies were an agricultural pond, a lake in a forested watershed, a man-made reservoir, an estuary, and a bay. Two sets of samples were prepared by dispensing unfiltered samples into filtered samples in 1:10 ratio (v/v). The first set was exposed to sunlight (10 hr per day for 30 days) for examining the combined effect of photo-biodegradation, while the second set was stored in dark for examining biodegradation alone. Spectroscopic measurements in tandem with multivariate statistics were used to interpret DOM lability and composition. The results suggest that the agricultural pond behaved differently compared to other study locations during degradation experiments due to the presence of higher amount of microbial humic-like and protein-like components derived from microbial/anthropogenic sources. For all samples, a larger decrease in dissolved organic carbon (DOC) concentration (10.12% ± 9.81% for photo-biodegradation and 6.65% ± 2.83% for biodegradation) and rapid transformation of DOM components (i.e., terrestrial humic-like components into microbial humic and protein-like components) were observed during photo-biodegradation experiments. Results suggest that sunlight facilitated DOM biodegradation, resulting in simpler recalcitrant molecules regardless of original composition. Overall, it was found that combined effects of light and bacteria are more efficient than bacterial effects alone in remineralizing and altering DOM, which highlights the crucial importance of sunlight in transforming aquatic DOM.

25303. 题目: Ground-truthing the planktic foraminifer-bound nitrogen isotope paleo-proxy in the Sargasso Sea
文章编号: N18063014
期刊: Geochimica et Cosmochimica Acta
作者: Sandi M. Smart, Haojia Ren, Sarah E. Fawcett, Ralf Schiebel, Maureen Conte, Patrick A. Rafter, Karen K. Ellis, Mira A. Weigand, Sergey Oleynik, Gerald H. Haug, Daniel M. Sigman
更新时间: 2018-06-30
摘要: We report the nitrogen (N) isotope ratios (δ15N) of planktic foraminifera collected from upper-ocean net tows (surface to 200 m), moored sediment traps, and core-top sediments at the Bermuda Time-series Site in the northern Sargasso Sea between 2009 and 2013. Consistent with previous measurements from low-latitude core-top sediments, the annually-averaged δ15N of organic matter bound within the shells of euphotic zone-dwelling, dinoflagellate symbiont-bearing foraminifera collected in net tows (2.3‰ on average) approximates that of shallow thermocline ( 200 m) nitrate (2.6‰), the dominant source of new N to Sargasso Sea surface waters. Deeper-dwelling foraminifer species without dinoflagellate symbionts tend to have a higher δ15N (3.6‰ on average). We observe no systematic difference between the bulk tissue and shell-bound δ15N in net tow-collected foraminifera. A decline in shell N content is observed from net tows (6.8 nmol/mg) to sediment traps (5.4 nmol/mg) and surface sediment (3.0 nmol/mg). On average, shell-bound δ15N rises from net tows (3.1‰) to sediment traps (3.7‰) but does not change further upon incorporation into the sediments (3.7‰). Together, these observations are consistent with preferential loss of shells or shell portions with lower δ15N and higher N content during sinking through the upper 500 m, followed by a non-isotope fractionating decrease in N content between sinking and burial. Time-series data from sediment traps (and to a lesser extent, surface net tows) exhibit seasonal δ15N variations, with a minimum in early spring, a maximum in late spring and a decline from summer to fall. These variations appear to arise from seasonal changes in the δ15N of total upper-ocean biomass, which are, in turn, driven by early springtime nitrate supply, subsequent nitrate drawdown, and an increase in the relative importance of ammonium recycling into the late summer and early fall. The δ15N connection between total upper ocean biomass and foraminifera indicates that foraminifer-bound δ15N records the δ15N of the annual nitrate supply in oligotrophic (e.g., subtropical) environments but will also be sensitive to the degree of nitrate consumption in high-nutrient regions and possibly to changes in upper-ocean ammonium recycling under some conditions.

25304. 题目: Controls of climate, catchment erosion and biological production on long-term community and functional changes of chironomids in High Arctic lakes (Svalbard)
文章编号: N18063013
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Tomi P. Luoto, Antti E.K. Ojala
更新时间: 2018-06-30
摘要: Arctic freshwater basins are diversity hotspots and sentinels of climate change, but their long-term variability and the environmental variables controlling them are not well defined. We examined four available lake sediment sequences from High Arctic Svalbard for their subfossil Chironomidae communities, biodiversity and functional traits and assessed the influence of climatic and limnological variability on the long-term ecological dynamics. Our results indicated that collector-filterers had an important role in the oligotrophic sites, whereas collector-gatherers dominated the nutrient-enriched sites with significant bird guano inputs. In the oligotrophic sites, benthic production, taxon richness and taxonomic and functional diversity were highest during the early Holocene, when temperatures showed a rapid increase. An increase in subfossil abundance and diversity metrics was also found in recent samples of the oligotrophic sites, but not in the bird-impacted sites, where the trends were decreasing. When partitioning out the environmental forcing on chironomid communities, the influence of climate was significant in all the sites, whereas in-lake production (organic matter) was significant in two of the sites and catchment erosion (magnetic susceptibility) had only minor influence. The findings suggest that major changes in Arctic chironomid assemblages were driven by climate warming with increasing diversity in oligotrophic sites, but deteriorating ecological functions in environmentally stressed sites. We found that although taxonomic and functional diversity were always coupled, taxonomical and functional turnovers were coupled only in the oligotrophic sites suggesting that the ecological functions operated by chironomids in these low-productivity sites may not be as resilient to future environmental change.

25305. 题目: Maastrichtian oil shale deposition on the southern Tethys margin, Egypt: Insights into greenhouse climate and paleoceanography
文章编号: N18063012
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Douaa Fathy, Michael Wagreich, Susanne Gier, Ramadan S.A. Mohamed, Rafat Zaki, Mohamed M. El Nady
更新时间: 2018-06-30
摘要: A comprehensive set of organic and inorganic geochemical proxies, clay mineralogy, and molecular fossils are presented from two biostratigraphically well-dated oil shale horizons of Egypt, within the Upper Cretaceous Duwi and Dakhla formations. The studied oil shales were deposited within intracratonic sedimentary basins in a broad northern African epeiric sea. Calcareous nannofossil biostratigraphy indicates that the oil shales range from early to late Maastrichtian in age, covering nannofossil zones UC18, UC19, and UC20. The oil shales contain smectite and kaolinite as the main clay minerals that formed by weathering of precursor basement rocks. The relative abundances of clay minerals and several geochemical proxies (e.g. C-value, CIA, Ga/Rb, Rb/Sr and Sr/Cu), along with the occurrence of warm-water nannofossil taxa, demonstrate that the Maastrichtian oil shales accumulated under a warm, arid to humid greenhouse climate during a general Maastrichtian cooling trend. This episode of oil shale deposition in Egypt coincided with the first potential imprint of the global warming, that has been recorded during early-to-late Maastrichtian times (~70.6–67.7 Ma). Elevated eolian terrigenous input was recorded within the Duwi Formation oil shales, shown by high Ti/Al, Si/Al, Zr/Al and low La/Lu ratios. The Duwi Formation environment was characterized by enhanced salinity and a stratified water column, compared to that of the Dakhla Formation, shown by elevated values of the gammacerane index, tetracyclic terpane, β carotene and Sr/Ba ratio. The CaCO3 content and carbonate/siliciclastic ratio indicate that the Dakhla Formation oil shales were deposited during a relative sea-level rise in a deeper marine setting than the Duwi Formation oil shales. The data further imply a wind-driven upwelling scenario of nutrient inputs that simulated primary production and increased organic matter fluxes. Thus, paleoclimate and paleoceanography had a considerable impact on organic matter enrichment.

25306. 题目: Mercury anomalies, volcanic pulses, and drowning episodes along the northern Tethyan margin during the latest Hauterivian-earliest Aptian
文章编号: N18063011
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Guillaume Charbonnier, Alexis Godet, Stéphane Bodin, Thierry Adatte, Karl B. F?llmi
更新时间: 2018-06-30
摘要: The latest Hauterivian-earliest Aptian time interval includes three episodes of significant environmental change (Faraoni, late early-Barremian, and Taxy Episodes). This time interval appears to partially overlap with large-scale volcanic activity related to the Tristan da Cunha plume along the Rio Grande Rise, High Arctic large igneous province volcanism, and the early phase in the formation of the greater Ontong Java LIP in the Pacific. The establishment of exact temporal relationships between volcanic activity and environmental change remains, however, a major challenge, due to the scarcity of numerical ages for the Early Cretaceous. We report mercury (Hg) contents in uppermost Hauterivian-lowermost Aptian marl/limestone alternations from seven sections along a NS transect in the Western Tethys. The Hg contents in marl samples display rather scattered records, which are generally well correlated with the total organic carbon (TOC) records. In associated limestone beds, five distinct spikes in Hg concentrations occur in three intervals (latest Hauterivian, early Barremian, and latest Barremian). The small amounts of organic matter (<0.2 wt%) in the limestones suggest that organic matter only played a limited role in Hg sequestration. Three Hg peaks in the middle of the Balearites balearis Zone, in the Faraoni level, and in the early Barremian occur only in one of the seven studied sections, which indicate a regionally variable distribution of Hg during these episodes. However, two distinct enrichments in Hg concentrations at the top of the B. balearis Zone (below the Faraoni level) and the M. sarasini Zone (below the Taxy level) appear comparable and correlatable between the sections. These data indicate that important volcanic activity antedating the Faraoni and the Taxy episodes may have contributed to the onset of associated environmental and ecological perturbations during the latest Hauterivian and latest Barremian, such as carbonate platform drowning phases.

25307. 题目: Volcanic and hydrothermal activities recorded in phosphate nodules from the Lower Cambrian Niutitang Formation black shales in South China
文章编号: N18063010
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Ping Gao, Zhiliang He, Shuangjian Li, Gary G. Lash, Boyuan Li, Boyu Huang, Detian Yan
更新时间: 2018-06-30
摘要: Deposition of black shale of the Lower Cambrian Niutitang Formation (NTT) of the Yangtze Block, South China, in association with the Ediacaran-Cambrian (E-C) transition was accompanied by widespread formation of phosphate nodules. Petrological and geochemical studies of the nodules and host sedimentary rocks were carried out to elucidate hydrographic conditions of the Early Cambrian ocean. Our results reveal that NTT phosphate nodules are composed principally of concentrically banded carbonate fluorapatite (CFA) that likely reflects changing Eh and pH conditions contemporaneous with diagenetic nodule growth. Accumulation of organic-rich sediment and nodule growth may have been induced and sustained by contemporaneous volcanic and hydrothermal activities on the Yangtze Block. The introduction of voluminous nutrients with volcanic ash, including phosphate and aqueous Fe and Si, promoted the bloom of plankton, including sponges and lower algae leading to organic matter enrichment. Productivity may have been further enhanced by upwelling of phosphate-rich bottom water that resulted in widespread phosphogenesis and formation of phosphate nodules. The hyalophane-quartz association documented from phosphate nodules suggests the possible interaction of K-feldspar-rich volcanic ash and Ba-rich hydrothermal fluids at lower pH levels in association with nodule growth. The formation of phosphate nodules of the Niutitang Formation, then, reflects the complex interaction among primary productivity, volcanic and hydrothermal activity, and the accumulation of organic matter at a critical period of Earth history.

25308. 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.

25309. 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.

25310. 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.

25311. 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.

25312. 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.

25313. 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).

25314. 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.

25315. 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.

25316. 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.

25317. 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.

25318. 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.

25319. 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.

25320. 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.