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29041. 题目: Pentachlorophenol dissipation and ferrous iron accumulation in flooded paddy soils with contrasting organic matter contents and incorporation of legume green manures
文章编号: N18070103
期刊: Journal of Soils and Sediments
作者: Yong Liu, Sifan Wang, Lian Zhu, Yunsheng Xia, Huihua Zhang, Shan Wang,Xiongsheng Yu, Jun Lou, Fangbai Li, Jianming Xu
更新时间: 2018-07-01
摘要: Purpose: The effects of different amendment rates (1 and 3%) of Chinese milk vetch (Astragalus sinicus L.) and bird vetch (Vicia cracca L.) on the dissipation of extractable pentachlorophenol (PCP) residues were investigated in two flooded paddy soils with contrasting soil organic matter (SOM) contents. Following incorporation of the legume green manures, whether acetate-extractable ferrous iron [Fe(II)NaOAc] is useful for revealing the reductive dechlorination mechanism of PCP in flooded paddy soils was verified. Materials and methods: The kinetic parameters of PCP dissipation and Fe(II)NaOAc accumulation were estimated using logistic curve fitting. Correlation and regression analyses were performed on PCP, Fe(II)NaOAc, water-soluble organic carbon (WSOC), pH, and oxidation-reduction potential data. Results and discussion: The kinetic parameters of PCP dissipation and Fe(II)NaOAc accumulation varied significantly with the amendment rate of legume green manure. The changes in pH value and WSOC content varied significantly with the level of SOM and with the amendment rate of legume green manure. At a low amendment rate of green manure, the pH increase and WSOC consumption greatly enhanced Fe(II)NaOAc accumulation and contributed to PCP dissipation. The rate of PCP dissipation decreased with decreasing pH and WSOC accumulation, especially in the high-SOM soil amended with the higher rate of green manure. Legume green manure species had no effect on PCP dissipation. Conclusions: In terms of soil chemistry, Fe(II)NaOAc was found to be the key variable that could explain the mechanisms involved in the reductive dissipation of PCP in flooded paddy soils with contrasting SOM contents and incorporation of legume green manures.

29042. 题目: Retention of silver nanoparticles and silver ion to natural soils: effects of soil physicochemical properties
文章编号: N18070102
期刊: Journal of Soils and Sediments
作者: Rui Wang, Huan Du, Yujun Wang, Dengjun Wang, Qian Sun, Dongmei Zhou
更新时间: 2018-07-01
摘要: Purpose: The mass production and widespread use of silver nanoparticles (AgNPs) have led to their wide dissimilation in the subsurface environments (e.g., natural soils). The retention propensities of AgNPs in soils dictate their fate, transport, and transformation in the subsurface environments. The aim of this study was to explore the retention behaviors of AgNPs and Ag+ ion (as a comparison) in ten natural soils with different physicochemical properties, identifying which properties dominate their mobility in soils. Materials and methods: Ten surface (0–20 cm) soils sampled across five geographical regions of China and AgNPs coated by polyvinylpyrrolidone (PVP) with an average transmission electron microscopy (TEM) diameter of ~ 10 nm were used in this study. Batch retention experiments of AgNPs and AgNO3 in ten soils (pass through 60-mesh sieve) were conducted in triplicate at 25 °C for 24 h. Multiple regression analyses of maximum retention capacity (Qmax for AgNPs or Ag+ ion) simulated by Langmuir retention models were performed to identify which soil physicochemical properties dominate the retention behavior of AgNPs and Ag+ ion. TEM combined with energy dispersive X-ray spectroscopy (EDS) analyses was applied to visually unravel the distribution and retention behavior of AgNPs on natural soils. Results and discussion: The results of batch retention experiments showed that Langmuir model well-approximated the retention isotherms of AgNPs and Ag+ on ten soils and that the Qmax value of AgNPs was generally lower than that of Ag+ on soils. The results of multiple regression analyses showed that the retention capacity of AgNPs on soils was positively correlated with the iron oxide content, which is visually confirmed by TEM-EDS observations, whereas retention capacity of Ag+ ions was mainly related to soil organic matter (SOM) content. Conclusions: Maximum retention capacity of AgNPs and Ag+ ion in soils varied with soil physicochemical properties, and particularly, iron oxide and SOM contents are two pivotal parameters controlling Qmax. These findings advance our current understanding of the mechanisms controlling retention and transport of AgNPs in natural soils, which represents an important step toward predicting the fate, transport, and potential toxicity of AgNPs in the subsurface environment.

29043. 题目: Sorption mechanism of zinc on reed, lignin, and reed- and lignin-derived biochars: kinetics, equilibrium, and spectroscopic studies
文章编号: N18070101
期刊: Journal of Soils and Sediments
作者: Ping Wu, Peixin Cui, Guodong Fang, Juan Gao, Dongmei Zhou, Yujun Wang
更新时间: 2018-07-01
摘要: Purpose: Biochar is considered as a substitute for stabilizing heavy metals, yet systematic studies regarding the stabilization mechanism of Zn on biochars from different biomass sources under different pyrolysis temperatures are still lacking. This study was endeavored to assess the sorption behavior and mechanism of Zn on pristine reed, lignin, and reed- and lignin-derived biochars at different pyrolysis temperatures (350, 450, and 550 °C). Materials and methods: Batch experiments were performed to investigate the Zn sorption on pristine reed, lignin, and their derived biochars. Major functional groups on the surface of samples were measured using Fourier transform infrared (FTIR) spectroscopy and Boehm titration method, while the speciation and binding mechanisms were elucidated using X-ray absorption near-edge structure (XANES). Results and discussion: The FTIR results showed an abrupt decline in the oxygen-containing functional groups with elevating pyrolysis temperature. The total amount of three acidic functional groups (carboxyl, lactone, phenol) was highest (2.39 mmol/g) in lignin, and it significantly decreased in reed- and lignin-derived biochars (0.05–0.94 mmol/g). Lignin exhibited the highest sorption capacity to Zn (qe = 3360 mg/kg) in the batch sorption experiments, while the sorption capacities for biochars were reduced with increasing pyrolysis temperature, irrespective of biomass sources. The XANES results indicated that soil organic matter (SOM), iron, and phosphate mineral components in the tested sorbents played an indispensable role in Zn immobilization. A large fraction of Zn-OM complex was observed in lignin due to its highest abundance of acidic functional group, leading to the highest sorption capacity for lignin toward Zn. The combination of XANES with FTIR, Boehm titration, batch sorption, and kinetic experiments altogether revealed that the decline in sorption capacity of Zn on reed- and lignin-derived biochars with elevating pyrolysis temperature was attributed to the loss in O-containing functional groups. Conclusions: The complexation of Zn with surface functional groups contributed to the Zn sorption on reed, lignin, and their derived biochars. The projected results will not only provide the detailed stabilization mechanism of Zn on lignin and reed- and lignin-derived biochars but also develop a novel and effective material (lignin) for heavy metal remediation.

29044. 题目: Efficient PFOA degradation by persulfate-assisted photocatalytic ozonation
文章编号: N18063022
期刊: Separation and Purification Technology
作者: Dan Wu, Xukai Li, Jingxian Zhang, Weirui Chen, Ping Lu, Yiming Tang, Laisheng Li
更新时间: 2018-06-30
摘要: ZnO-reduced graphene oxide (ZnO-rGO) was synthesized successfully at 423 K by a hydrothermal method. The presence of reduced graphene oxide significantly improved the photocatalytic performance of ZnO and its optimal loading ratio was 0.6 wt%. The XRD, SEM, UV–vis and FT-IR were applied to characterize the prepared catalyst. Comparative experiments were conducted to evaluate perfluorooctanoic acid (PFOA) degradation efficiency and the results showed that 99.2% PFOA was degraded in persulfate-assisted photocatalytic ozonation with low dosage of ozone and persulfate at room temperature. The impact factors on PFOA degradation efficiency including loading ratios of GO on ZnO, reaction temperatures and persulfate concentration were inspected and analyzed. The sodium persulfate and ammonium persulfate were compared as common oxidants in photocatalytic ozonation for PFOA degradation and sodium persulfate showed the better PFOA removal. Chloride and humic acid (HA) were common substances in natural water, and they showed inhibition effects on PFOA degradation. Conversion of persulfate to sulfate ion was studied and persulfate concentration during PFOA oxidation was monitored. PFHpA, PFHeA, PFPeA and PFBA were main intermediates during PFOA degradation.

29045. 题目: Distribution of dissolved organic carbon in the Bay of Bengal: Influence of sediment discharge, fresh water flux, and productivity
文章编号: N18063021
期刊: Marine Chemistry
作者: Chinmay Shah, A.K. Sudheer, Ravi Bhushan
更新时间: 2018-06-30
摘要: Dissolved organic carbon (DOC) plays an important role in the oceanic carbon cycle, with its distribution and variation primarily controlled by in situ productivity. The vertical and spatial distribution of DOC measured during two cruises has been investigated to decipher the processes controlling DOC in the Bay of Bengal (BoB). The terrestrial DOC flux to the BoB constitutes a significant fraction of the total DOC and has implications for the carbon budget of the northern Indian Ocean. High concentrations of DOC were observed in the northern BoB, which is primarily due to high flux of terrestrially derived fresh water from various rivers draining to the BoB. Compared to surface DOC concentration of the world oceans, BoB surface water generally has a higher DOC concentration (75–100 μM), which can be attributed to the high DOC content of the riverine flux. Stratification of surface water helps to maintain DOC content due to inhibited vertical mixing in the BoB as a result of the fresh water lens. High subsurface DOC concentration is due to the remineralisation of biogenic sinking particles brought along with the sediments. Subsurface DOC concentrations in the BoB exhibit a conspicuous decreasing trend southwards due to reduced influence of riverine biogenic flux. This study demonstrates that the average contribution of apparent oxygen utilization (AOU) to the DOC remineralisation in the BoB was ~18%.

29046. 题目: Distribution of thiol, humic substances and colored dissolved organic matter during the 2015 Canadian Arctic GEOTRACES cruises
文章编号: N18063020
期刊: Marine Chemistry
作者: Zhiyuan Gao, Céline Guéguen
更新时间: 2018-06-30
摘要: Organic sulfur and humics play a key role in the biogeochemistry of metals in natural waters but their distribution is not well understood. In this study, we measured the concentrations of thiol-like, humic substance (HS) -like and fluorescent dissolved organic matter (FDOM) during the 2015 Canadian Arctic GEOTRACES cruises in the Canada Basin and Canadian Arctic Archipelago (CAA). Concentrations of thiol-like (7–85 nM, expressed as equivalent to glutathione concentration) and HS-like (19 to 190 μg C/L) determined by cathodic stripping voltammetry (CSV) were congruent with previous marine CSV-based studies. Three humic-like (C1-C3) and one protein-like (C4) components identified and validated using excitation-emission matrix (EEM) and parallel factor analysis (PARAFAC) have been reported in previous ocean studies. The distributions of HS-like and humic-like components (C1 and C2) in the CAA were similar, whereas thiol-like and protein-like component C4 were closely related in the study area. Maximum CSV-based thiol-like levels were associated with chlorophyll-a maximum, confirming the biogenic origin of thiols. The distribution and concentrations of CSV-based thiol- and HS-like, and FDOM varied between four distinct water masses (i.e. surface waters, Arctic outflow waters, Arctic intermediate waters and North Atlantic deep waters) with the lowest levels associated with the surface waters, likely due to photobleaching and sea ice melt dilution. The concentrations in CSV-based HS-like and FDOM in the Arctic outflow waters decreased from western to eastern CAA, reflecting the influence of DOM-rich Pacific derived waters.

29047. 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.

29048. 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.

29049. 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.

29050. 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.

29051. 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.

29052. 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.

29053. 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.

29054. 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.

29055. 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.

29056. 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.

29057. 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.

29058. 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.

29059. 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).

29060. 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.