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25861. 题目: New U-Pb zircon age and carbon isotope records from the Lower Silurian Longmaxi Formation on the Yangtze Platform, South China: Implications for stratigraphic correlation and environmental change
文章编号: N19020503
期刊: Chemical Geology
作者: Yanfang Li, Tongwei Zhang, Deyong Shao, Baojian Shen
更新时间: 2019-02-05
摘要: The Ordovician–Silurian (O–S) transition was a period of dramatic climatic, environmental, and biological change. Numerous studies have documented the Late Ordovician glacial or mass extinction interval, but the Early Silurian has received significantly less attention. This study presents a U-Pb zircon age data and organic carbon isotope (δ¹³C_org) records from the Upper Ordovician to Lower Silurian succession of South China to better constrain carbon isotope perturbations and to evaluate their possible causes and relationships to paleoenvironmental change during Early Silurian time. A volcanic ash bed located at the top of the organic-rich Lower Silurian Longmaxi Formation yields a ²⁰⁶Pb/²³⁸U zircon age of 440 ± 3 Ma (MSWD = 1.4), which is consistent with the Rhuddanian–Aeronian (R–A) boundary age. The newly acquired age is similar to that documented an ash bed in Scotland (439.57 ± 1.13 Ma) perhaps indicating synchronous volcanism. The δ¹³C_org values show a negative excursion in the organic-rich lower Longmaxi Formation that is interrupted by a positive excursion in the organic-lean upper part of the unit. The positive excursion begins immediately above the dated ash bed thus assigning it to the R–A boundary. The documented δ¹³C_org trend is comparable to those of other sections throughout the world, and is suggestive of a global perturbation of carbon cycle. The negative δ¹³C_org excursion of the Rhuddanian stage was coeval with deposition of organic-rich shale under anoxic/euxinic conditions, whereas the subsequent positive δ¹³C_org excursion coincided with a change to suboxic conditions that could have diminished organic matter preservation. We propose that the negative δ¹³C_org excursion could be considered as the defining isotopic characteristic of the Rhuddanian oceanic anoxic event (Rhuddanian OAE). Results of the present study in tandem with published age data from the Guanyinqiao Bed immediately below the base of the Longmaxi Formation suggest that the negative δ¹³C_org excursion and associated Rhuddanian OAE persisted for approximately 3 Myr. This relatively long-lived event reflects a sustained addition of isotopically light carbon into the atmosphere-ocean system, possibly related to the release of volcanic CO₂. The enhanced burial of organic carbon in association with the Rhuddanian OAE could have removed the substantial ¹²C from the carbon reservoir and lowered atmospheric pCO₂ thus resulting in a subsequent positive δ¹³C excursion and global cooling at the R-A boundary.

25862. 题目: Hypoxic water mass in the highly turbid well-mixed macrotidal Rokkaku River Estuary, Ariake Sea, Japan
文章编号: N19020502
期刊: Estuarine, Coastal and Shelf Science
作者: Yuichi Hayami, Minoru Wada, Yu Umezawa, Naoki Fujii, Akito Nakamura, Fumiaki Mori
更新时间: 2019-02-05
摘要: Hypoxic water masses are usually formed in the bottom layer of stratified water columns. However, we found that hypoxia was formed throughout the water column in a well-mixed macrotidal estuary, the Rokkaku River Estuary, Japan. There was a spring-neap variation in the dissolved oxygen (DO) concentration where hypoxia developed during spring tides. Minimum DO concentration was observed 1 or a few days after the spring tide. When hypoxia developed, all the water column from bottom to surface became hypoxic (<2 mg l⁻¹ or < 30% saturation). The hypoxic water mass was associated with the estuarine turbidity maximum (ETM). Oxygen demand of water in this area was very large (>2 mg l⁻¹ day⁻¹). Potential oxygen consumption by microorganisms was positively correlated with turbidity. Concentration of suspended solid (SS) at the ETM exceeded 1000 mg l⁻¹. Furthermore, particulate organic carbon (POC) concentration in the estuary increased in spring tides. C/N ratio and δ¹³C of organic matter suggested that POC was transported from the sea into the estuary. These results suggest that the active resuspension of organic matter caused by the strong tidal current during spring tides enhanced the respiratory activity of microorganisms and the main source of the organic matter was detrital material from the sea. Such a large amount of organic matter should fuel microbial respiration effectively. Since microbial oxygen consumption was larger than the oxygen supply from the water surface even in the well mixed condition, a hypoxic water mass was formed in this estuary.

25863. 题目: Extreme weather events modulate processing and export of dissolved organic carbon in the Neuse River Estuary, NC
文章编号: N19020501
期刊: Estuarine, Coastal and Shelf Science
作者: Alexandria G. Hounshell, Jacob C. Rudolph, Bryce R. Van Dam, Nathan S. Hall, Christopher L. Osburn, Hans W. Paerl
更新时间: 2019-02-05
摘要: As the interface between riverine and coastal systems, estuaries play a key role in receiving, transporting, and processing terrestrial organic carbon prior to export to downstream coastal systems. Estuaries can switch from terrestrial organic carbon reactors under low river flow to pipelines under high flow, but it remains unclear how estuarine terrestrial organic carbon processing responds to the full spectrum of discharge conditions, which are bracketed by these high and low discharge events. The amount of terrestrial dissolved organic carbon and colored dissolved organic matter imported, processed, and exported was assessed for riverine discharge events spanning from 4th to 99th flow quantiles in the Neuse River Estuary, North Carolina, USA using spatially and temporally (July 2015–December 2016) resolved measurements. The extent of dissolved organic matter processing in the estuary under various flow conditions was estimated using a non-steady state box model to calculate estuary-wide terrestrial dissolved organic carbon and colored dissolved organic matter source & sink terms. Under mid-range riverine discharge conditions (4th to 89th flow quantiles), the Neuse River Estuary was a sink for terrestrial dissolved organic carbon, retaining and/or processing (i.e., flocculation; photochemical and microbial degradation) on average ∼29% of terrestrial dissolved organic carbon. Following floods due to extreme precipitation events (99th flow quantile), however, over 99% of the terrestrial dissolved organic carbon loaded from the riverine end-member was exported directly to the downstream coastal system. Following such extreme weather events, the estuary acts as a pipeline for direct export of terrestrial dissolved organic carbon, drastically altering the amount and quality of dissolved organic carbon loaded to downstream coastal systems. This has important implications under future climate scenarios, where extreme weather events are expected to increase.
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25864. 题目: Hydrochars produced with by-products from the sucroenergetic industry: a study of extractor solutions on nutrient and organic carbon release
文章编号: N19020409
期刊: Environmental Science and Pollution Research
作者: Daniely Reis Santos, Otávio da Mata Cunha, Márcia Cristina Bisinoti, Odair Pastor Ferreira, Altair Benedito Moreira, Camila Almeida Melo
更新时间: 2019-02-04
摘要: Hydrothermal carbonization transforms biomass into value-added material called hydrochar. The release of nutrients (P, N, Ca, Mg, and K) and organic carbon (TOC) from hydrochar in different extractive solutions was investigated in this study. Two sets of hydrochar were produced: (i) hydrochar prepared from sugarcane bagasse and vinasse mixture (BV-HC) and (ii) hydrochar prepared by the addition of H₃PO₄ to this mixture (BVA-HC). Both hydrochar types released significative amounts of nutrient and organic carbon, mainly Ca (5.0 mg g⁻¹) in the mixture (KCl, K₂SO₄, NaOH, 1:1:1) extractive solution and TOC (72.6 mg g⁻¹) in the NaOH extractive solution, for BV-HC. Nutrient release was influenced by pH and ionic strength. The release of P, Ca, and Mg was affected by the presence of insoluble phosphate phases in BVA-HC. The release of nutrients P, N, Ca, Mg, and K and organic carbon demonstrated that hydrochar has potential for soil application purposes.

25865. 题目: Enhanced adsorption for Pb(II) and Cd(II) of magnetic rice husk biochar by KMnO 4 modification
文章编号: N19020408
期刊: Environmental Science and Pollution Research
作者: Chen Sun, Tong Chen, Qunxing Huang, Jun Wang, Shengyong Lu, Jianhua Yan
更新时间: 2019-02-04
摘要: Novel KMnO₄-treated magnetic biochar (FMBC) was successfully synthesized by addition of Fe(NO₃)₃ during carbonization and KMnO₄ treatment following for Pb(II) and Cd(II) adsorption. SEM-EDS, XPS, and ICP-AES were used to evaluate the FMBC and magnetic biochar (FBC) on surface morphology, surface chemistry characteristics, surface functional groups, and Pb(II) and Cd(II) adsorption behavior. Results showed that the Langmuir maximum adsorption quantity of FMBC reached 148 mg/g for Pb(II) and 79 mg/g for Cd(II), nearly 7 times of that of FBC. The enhancement of FMBC for heavy metal adsorption was due to the successful load of manganese oxides and the increased oxygen functional groups consistent with XPS and FTIR results. The adsorption capacities of FMBC were maintained over 95% when the pH value was higher than 2.5 and 3.5 for Pb(II) and Cd(II), respectively. The adsorption performances of both heavy metals by FMBC were hardly influenced by ionic strength and humid acid. The adsorption capacities of FMBC could maintain over 50% and 87% after four cycles for Pb(II) and Cd(II), respectively. The saturation magnetization of FMBC was about 11.5 emu/g, which did not change after adsorption. This work proposed a new method to fabricate a magnetic biochar with high adsorption capacities of heavy metals Pb(II) and Cd(II).

25866. 题目: Characterization of goethite-fulvic acid composites and their impact on the immobility of Pb/Cd in soil
文章编号: N19020407
期刊: Chemosphere
作者: Qianjun Liu, Xiang Li, Jiepeng Tang, Yangmei Zhou, Qintie Lin, Rongbo Xiao, Min Zhang
更新时间: 2019-02-04
摘要: The coprecipitation of organic matter (OM) and minerals is a relatively common phenomenon in soil, and it has a significant influence on the surface properties and reactivity of minerals. In turn, the fate of pollutants in soil is greatly affected by the organic-mineral composites. In this study, goethite-fulvic acid (Ge-FA) composites with varying FA mass ratios in the range of 0–15% were synthesized by coprecipitation. The sample properties were studied using XRD, FTIR, SEM-EDS and N₂ gas adsorption techniques. The influence of Ge-FA on the mobility of Pb/Cd in soil was investigated. The crystal forms of Ge-FA changed from goethite (FA≤4%) to hematite (FA≥5%), and the FA affected the FeO bond vibrations. These results demonstrated that FA was successfully introduced into the iron oxide. Ge-FA changed from a filamental morphology to an aggregate as the FA ratio increased. The coprecipitation resulted in blockages of iron oxides, thereby decreasing the specific surface area and pore volume. The adsorption amount of Pb(II) on Ge-FA increased as the FA ratio increased, but no significant change was observed for Cd(II). With the application of Ge-FA, the exchangeable concentrations of Pb and Cd in contaminated soil decreased by 42.4%–93.6% and 15.8%–43.7%, respectively. The exchangeable and carbonate bound fractions of Pb and Cd decreased and were transformed into the FeMn bound and residual fractions.
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25867. 题目: Combining biochar and sewage sludge for immobilization of heavy metals in mining soils
文章编号: N19020406
期刊: Ecotoxicology and Environmental Safety
作者: Evanise Silva Penido, Gabriel Caixeta Martins, Thiago Borges Matos Mendes, Leônidas Carrijo Azevedo Melo, Iara do Rosário Guimarães, Luiz Roberto Guimarães Guilherme
更新时间: 2019-02-04
摘要: Excess heavy metal concentrations in mining areas is a worldwide problem due to their toxicity and persistence. Applying amendments to those areas is a cost-effective remediation technique that would aid revegetation efforts. The aim of this work was to study the ability of sewage sludge-derived biochar (SSB), wood charcoal powder (hereafter named wood biochar – WB), raw sewage sludge (SS), and their blending (WB/SS) to improve soil properties and to immobilize Cd, Pb, and Zn after their addition to heavy-metal contaminated soils from a Zn-mining area. Biochar was prepared from dried sewage sludge and a greenhouse experiment was set using different amendment doses (WB = 30 and 60 g kg⁻¹, SS = 10 and 20 g kg⁻¹). Addition of wood biochar and sewage sludge-derived biochar to soils led to increased leachate and soil pH. Biochar materials were responsible for the greatest reduction of Cd, Pb, and Zn bioavailability. The use of sewage sludge-derived biochar or the combination of sewage sludge with wood biochar in mining areas are potential alternatives for reusing and aggregating value to these locally available wastes, offering an opportunity to solve both soil remediation and waste disposal problems at once.

25868. 题目: The role of hydrological conditions for riverine Hg species transport in the Idrija mining area
文章编号: N19020405
期刊: Environmental Pollution
作者: Carluvy Baptista-Salazar, Harald Biester
更新时间: 2019-02-04
摘要: Estimation of mercury (Hg) species fluxes in Hg contaminated rivers is crucial to predict Hg methylation in connected sediment sinks. Cinnabar (HgS) was mined and roasted for ∼500 years in the Idrija mining area, Slovenia, which is drained by the Idrijca River to the Gulf of Trieste (GT), Italy. Mining residues dumped into the Idrijca River caused high proportions of cinnabar in sediments, whereas soils containing high proportions of natural organic matter bound to Hg (NOM-Hg) are attributed to atmospheric Hg deposition. Previous calculations of Hg fluxes have been based on the erosion of cinnabar only, and neglected transport of NOM-Hg derived from soil. Here, we estimated NOM-Hg and cinnabar fluxes in the Idrijca River and evaluated the extent of variability under changing hydrological conditions. We estimated the discharge of NOM-Hg by Idrijca's tributaries and the importance of NOM-Hg fluxes for Hg methylation in the GT. Mass balance calculations reveal that approximately 11.2 Mg y⁻¹ of NOM-Hg and 38.9 Mg y⁻¹ of cinnabar are transported by the Idrijca River to the GT under median-flow conditions. In the past 520 years, a total of 53,000 tons of Hg have been released from the Idrija mining area, of which ∼32,000 tons were NOM-Hg. Under low-flow conditions, Idrijca's tributaries deliver more than 1280 kg y⁻¹ of NOM-Hg. This study highlights the importance of Hg species analyses and their flux calculations to estimate risks of biological Hg uptake in sedimentary Hg sinks connected to Hg mining areas.
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25869. 题目: Microbial kinetics and thermodynamic (MKT) processes for soil organic matter decomposition and dynamic oxidation-reduction potential: Model descriptions and applications to soil N₂O emissions
文章编号: N19020404
期刊: Environmental Pollution
作者: Soumendra N. Bhanja, Junye Wang, Narayan K. Shrestha, Xiaokun Zhang
更新时间: 2019-02-04
摘要: A conversion of the global terrestrial carbon sink to a source is critically dependent on the microbially mediated decomposition of soil organic matter (SOM). We have developed a detailed, process-based, mechanistic model for simulating SOM decomposition and its associated processes, based on Microbial Kinetics and Thermodynamics, called the MKT model. We formulated the sequential oxidation-reduction potential (ORP) and chemical reactions undergoing at the soil-water zone using dual Michaelis-Menten kinetics. Soil environmental variables, as required in the MKT model, are simulated using one of the most widely used watershed-scale models - the soil water assessment tool (SWAT). The MKT model was calibrated and validated using field-scale data of soil temperature, soil moisture, and N₂O emissions from three locations in the province of Saskatchewan, Canada. The model evaluation statistics show good performance of the MKT model for daily soil N₂O simulations. The results show that the proposed MKT model can perform better than the more widely used process-based and SWAT-based models for soil N₂O simulations. This is because the multiple processes of microbial activities and environmental constraints, which govern the availability of substrates to enzymes were explicitly represented. Most importantly, the MKT model represents a step forward from conceptual carbon pools at varying rates.
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25870. 题目: Impacts of timber harvest intensity and P fertilizer application on soil P fractions
文章编号: N19020403
期刊: Forest Ecology and Management
作者: José Henrique T. Rocha, Marcella L.C. Menegale, Marcos Rodrigues, Jose Leonardo de M. Gonçalves, Paulo S. Pavinato, Estela Couvre Foltran, Robert Harrison, Jason N. James
更新时间: 2019-02-04
摘要: Research has shown significant effects of timber harvest residue management on soil organic carbon (SOC), but less impact has been observed on the available P pool. The objectives of this study were: (1) to estimate the effects of different timber harvest intensities and P fertilization on soil labile P and P fate over time; and (2) to identify which soil P fractions supply P to Eucalyptus plantations cultivated in soils with low P availability. P fractions were assessed using Hedley’s sequential extraction methodology, which corresponds to differing degrees of soil P lability. Three timber harvest intensities (stemwood only, whole tree and whole tree plus litter) and two levels of P fertilization (0 and 44 kg ha⁻¹ of P) were used. A total of 70% of total soil P was found in a non-labile form in the whole tree plus litter removal treatment, while in the whole tree treatment only 66% was found in this form. Removal of harvesting and litter residues resulted in a 40% reduction in the labile P fraction when compared to stemwood only harvested treatment even with fertilizer application. Acid phosphatase activity, which is crucial in mobilizing P for plant uptake, was 45% higher in soils that did not receive P fertilizer, but it did not resulted in higher concentration of labile P. Timber harvest intensity and P fertilizer application did not influence the soil total P concentration over 12 years of Eucalyptus cultivation. However, there was an increase in non-labile and inorganic P fractions and a reduction of labile and organic P fractions with increasing timber harvest intensity. The organic, moderately labile P fraction was the main source of P to the trees under low P availability conditions. Acid phosphatase and low molecular weight organic acid excretion seem to be important strategies of Eucalyptus species to improve P uptake.

25871. 题目: Comparison of the lead and copper adsorption capacities of plant source materials and their biochars
文章编号: N19020402
期刊: Journal of Environmental Management
作者: Myoung-Eun Lee, Jin Hee Park, Jae Woo Chung
更新时间: 2019-02-04
摘要: Lead (Pb) and Cu are the most common pollutants found in industrial effluents which affect ecosystem and human health. To remove Pb and Cu from aquatic system, cost-effective and environmentally friendly adsorbents are required. Therefore, the study evaluated the adsorption of Pb and Cu by waste plant materials and their biochars. The adsorption kinetics and isotherms were applied to compare the Pb and Cu adsorption capacities using the gingko (Spiraea blumei) leaf (GL), peanut shell (PS), and Metasequoia leaf (ML), and their derived biochars (GB, PB, and MB, respectively). The GB showed a significantly higher Pb adsorption capacity than the other adsorbents. Maximum Pb adsorption by GB was 138.9 mg/g followed by GL (117.6 mg/g). The highest Cu adsorption (59.9 mg/g) was also achieved by GB followed by GL (57.8 mg/g). The carbonates and the phosphate functional groups in the GB and higher affinity of Pb to the functional groups contributed to higher Pb adsorption. The Pb adsorption kinetics on the plant source materials and their biochars followed a pseudo-second order model. The Pb and Cu adsorption capacities, with the exception of the GL, ML, and GB, are better explained by Langmuir-isotherm models. The carbonization did not always lead to better heavy metal adsorption. The Pb and Cu adsorption significantly reduced with carbonization of ML because of disappearance of oxygen containing functional groups. Therefore, appropriate method to prepare metal adsorbent should be selected depending on feedstocks and metal removal mechanisms. The GL is the most-abundant fallen leaf in the streets of the Republic of Korea; therefore, the use of the GL biochar for heavy-metal adsorption will also reduce the cost for waste disposal.

25872. 题目: Corn waste valorization to generate activated hydrochar to recover ammonium nitrogen from compost leachate by hydrothermal assisted pretreatment
文章编号: N19020401
期刊: Journal of Environmental Management
作者: Tao Zhang, Xiaosha Wu, Xing Fan, Daniel C.W. Tsang, Guoxue Li, Yujun Shen
更新时间: 2019-02-04
摘要: Valorization of corn waste involves synthesis of hydrochar for use as a sorbent for ammonium nitrogen recovery from swine manure compost leachate. However, the inability to directly capture organic nitrogen and insoluble nitrogen, and the low sorption ability of hydrochar remain key issues. To overcome these issues, we used hydrothermal assisted pretreatment of compost leachate to promote the solubilization of nitrogen contained in feces, and the conversion of organic nitrogen into ammonium nitrogen in the compost leachate. The synthesis hydrochar was activated with KOH to enhance its sorption ability, and then characterized by SEM, FTIR, elemental analysis, specific surface area, pore volume and size analysis. The content of ammonium nitrogen in hydrolysis leachate at 210 °C increased by 22.3% compared with raw compost leachate. 3D-EEM analysis indicated that aromatic protein substances were rapidly hydrolyzed to gradually increase the content of ammonium nitrogen and produce considerable humic acids. The maximum adsorption capacity of ammonium nitrogen reached 140.3 mg/g at 45 °C for KOH-activated hydrochar of 260 °C. The Langmuir isotherm and pseudo second order kinetic models were good fit for the adsorption process of ammonium nitrogen at higher temperature (35 °C or 45 °C), and this reaction was mainly dominated by chemisorption. The adsorption of ammonium nitrogen was exothermic, spontaneous, and showed an increase in disorder at the solid–liquid interface. For resource recovery, the total release amount of ammonium nitrogen of five interval extractions could reach 12.2% of maximum adsorption capacity (140.3 mg/g) under alkaline (pH 8.0) condition. The nitrogen mass balance calculation revealed that 8.9% of total nitrogen in the compost leachate could be recovered.
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25873. 题目: Deep-sea oxygen depletion and ocean carbon sequestration during the last ice age
文章编号: N19020318
期刊: Global Biogeochemical Cycles
作者: Robert F. Anderson, Julian P. Sachs, Martin Q. Fleisher, Katherine A. Allen, Jimin Yu, Athanasios Koutavas, Samuel L. Jaccard
更新时间: 2019-02-03
摘要: Enhanced ocean carbon storage during the Pleistocene ice ages lowered atmospheric CO2 concentrations by 80 to 100 ppm relative to interglacial levels. Leading hypotheses to explain this phenomenon invoke a greater efficiency of the ocean's biological pump, in which case carbon storage in the deep sea would have been accompanied by a corresponding reduction in dissolved oxygen. We exploit the sensitivity of organic matter preservation in marine sediments to bottom water oxygen concentration to constrain the level of dissolved oxygen in the deep central equatorial Pacific Ocean during the last glacial period (18,000 – 28,000 years BP) to have been within the range of 20‐50 μmol/kg, much less than modern value of ca. 168 μmol/kg. We further demonstrate that reduced oxygen levels characterized the water column below a depth of ~1000 m. Converting the ice‐age oxygen level to an equivalent concentration of respiratory CO2, and extrapolating globally, we estimate that deep‐sea CO2 storage during the last ice age exceeded modern values by as much as 850 PgC, sufficient to balance the loss of carbon from the atmosphere (ca. 200 PgC) and from the terrestrial biosphere (ca. 300‐600 PgC). In addition, recognizing the enhanced preservation of organic matter in ice‐age sediments of the deep Pacific Ocean helps reconcile previously unexplained inconsistencies among different geochemical and micropaleontological proxy records used to assess past changes in biological productivity of the ocean.

25874. 题目: The potential hidden age of dissolved organic carbon exported by peatland streams
文章编号: N19020317
期刊: Journal of Geophysical Research: Biogeosciences
作者: Joshua F. Dean, Mark H. Garnett, Evangelos Spyrakos, Michael F. Billett
更新时间: 2019-02-03
摘要: Radiocarbon (¹⁴C) is a key tracer for detecting the mobilization of previously stored terrestrial organic carbon (C) into aquatic systems. Old C (>1,000 y B.P.) may be ‘masked’ by post‐bomb C (fixed from the atmosphere post‐AD1950), potentially rendering bulk aquatic dissolved organic C (DOC) ¹⁴C measurements insensitive to old C. We collected DOC with a modern ¹⁴C signature from a temperate Scottish peatland stream and decomposed it to produce CO₂ under simulated natural conditions over 140 days. We measured the ¹⁴C of both DOC and CO₂ at seven time‐points and found that while DOC remained close to modern in age, the resultant CO₂ progressively increased in age up to 2356 ± 767 y B.P. The results of this experiment demonstrate that the bulk DO¹⁴C pool can hide the presence of old C within peatland stream DOC export, demonstrating that bulk DO¹⁴C measurements can be an insensitive indicator of peatland disturbance. Our experiment also demonstrates that this old C component is biologically and photochemically available for conversion to the greenhouse gas CO₂, and as such bulk DO¹⁴C measurements do not reflect the ¹⁴C signature of the labile organic C pool exported by inland water systems more broadly. Moreover, our experiment suggests that old C may be an important component of CO₂ emissions to the atmosphere from peatland aquatic systems, with implications for tracing and modeling interactions between the hydrological and terrestrial C cycles.

25875. 题目: Drought-induced decline of productivity in the dominant grassland species Lolium perenne L. depends on soil type and prevailing climatic conditions
文章编号: N19020316
期刊: Soil Biology and Biochemistry
作者: Alexandre Buttler, Pierre Mariotte, Marco Meisser, Thomas Guillaume, Constant Signarbieux, Amarante Vitra, Sara Preux, Géraldine Mercier, Juan Quezada, Luca Bragazza, Konstantin Gavazov
更新时间: 2019-02-03
摘要: Severe constraints on grasslands productivity, ecosystem functions, goods and services are expected to result from projected warming and drought scenarios under climate change. Negative effects on vegetation can be mediated via soil fertility and water holding capacity, though specific mechanisms are fairly complex to generalise. In field drought experiments, it can be difficult to disentangle a drought effect per se from potential confounding effects related to vegetation or soil type, both varying along with climate. Furthermore, there is the need to distinguish the long-term responses of vegetation and soil to gradual climate shift from responses to extreme and stochastic climatic events. Here we address these limitations by means of a factorial experiment using a single dominant grassland species (the perennial ryegrass Lolium perenne L.) grown as a phytometer on two soils types with contrasted physicochemical characteristics, placed at two elevation sites along a climatic gradient, and exposed to early or late-season drought during the plant growing season.Warmer site conditions and reduced precipitation along the elevational gradient affected biogeochemistry and plant productivity more than the drought treatments alone, despite the similar magnitude in volumetric soil moisture reduction. Soil type, as defined here by its organic matter content (SOM), modulated the drought response in relation to local site climatic conditions and, through changes in microbial biomass and activity, determined the seasonal above and belowground productivity of L. perenne. More specifically, our combined uni- and multivariate analyses demonstrate that microbes in a loamy soil with low SOM are strongly responsive to change in climate, as indicated by a simultaneous increase in their C,N,P pools at high elevation with cooler temperatures and wetter soils. Contrastingly, microbes in a clay-loam soil with high SOM are mainly sensitive to temperature, as indicated by a strong increase in microbial biomass under warmer temperatures at low elevation and a concomitant increase in C:N, C:P and N:P ratios. High SOM promoted a better annual yield of the phytometer grass under warmer climate and the effect of drought on productivity was transient. In contrast, low SOM reduced cumulative yield under warmer conditions and root production strongly decreased, enduring a lasting drought effect. Microbes in soils with high organic matter remained more active during warmer and drier conditions, ensuring soil fertility and stimulating a higher overall plant nutrient availability and productivity.Our study highlights the important role of soil type for grassland responses to both stochastic climatic extremes and long-term climate change. Management practices enhancing SOM accumulation via organic residue incorporation seem a promising way to mitigate the effects of increased temperature and drought on plants and soil microbes alike promoting thereby a sustainable ecosystem functioning.

25876. 题目: Sediment trapping and carbon sequestration in floodplains of the lower Atchafalaya Basin, LA: Allochthonous vs. autochthonous carbon sources
文章编号: N19020315
期刊: Journal of Geophysical Research: Biogeosciences
作者: Cliff R. Hupp, Daniel E. Kroes, Gregory B. Noe, Edward R. Schenk, Richard H. Day
更新时间: 2019-02-03
摘要: Recent studies suggest that about 2 Pg of organic C is stored on floodplains worldwide. The present study indicates the Atchafalaya River, fifth largest river in the United States in terms of discharge, traps 30 mm/y of sediment on average within its floodplain, which is the highest average non‐episodic rate of fluvial deposition on the U.S. Coastal Plain. We installed sediment sampling stations at 23 sites, normally in transect, in the Atchafalaya Basin; these sites represent the range of hydrogeomorphic conditions on the floodplain based on hydrologic connectivity with the river main stem. The rate of sedimentation translates into about 12.5 Tg/y and includes 694 Mg/y of organic C. Highest sedimentation rates are associated with areas of high connectivity to channels and prograding deltaic processes. The δ¹³C content suggests that 35% of deposited C is derived from river‐suspended sediment compared to litterfall in the Basin. Thus, much of the organic C sequestered is allochthonous material. However, isolated interior sites with limited connectivity to the channel may generate and sequester large amounts of autochthonous C. The substantial trapping of both auto‐ and allochthonous C (392 Mg/y) make this freshwater‐forested floodplain critical in storage of material before reaching the coastal delta and estuary. This C deposition rate (340 g C m^‐2y^‐1) exceeds all other rates reported in recent Blue Carbon and Tidal Freshwater Forested Wetland studies. Atchafalaya C sequestration occurs in/near areas with tidal influence and like other coastal systems is an important site for trapping mineral and organic sediment and in global C cycling.

25877. 题目: Comparison of Pb stabilization in a contaminated calcareous soil by application of vermicompost and sheep manure and their biochars produced at two temperatures
文章编号: N19020314
期刊: Applied Geochemistry
作者: Hamid Reza Boostani, Mahdi Najafi-Ghiri, Ailsa G. Hardie, Dariush Khalili
更新时间: 2019-02-03
摘要: Soil contamination with potentially toxic elements (PTEs) is increasing due to human activities including the widespread use of chemical fertilizers, sludge and industrial wastewater in agriculture. In situ stabilization of soil PTEs using organic amendments is a cost effective and efficacious method. A laboratory experiment was conducted to investigate the effect of two organic materials (sheep manure (SM) and vermicompost (VC)) and their biochars (SMB and VCB) produced at two pyrolysis temperatures (300 and 500 °C) at 2 wt. % on Pb immobilization in a contaminated calcareous soil. A sequential extraction procedure, mobility factor and release kinetics were used for evaluating efficiency of the amendments. Addition of the biochars resulted in a significant decrease in exchangeable (10.4–19.6%) and carbonate (3.8–10.5%) forms of soil Pb, while Pb bound to amorphous Fe oxides (4.3–52.9%) was increased. The application of VCB produced at 500 °C resulted in the greatest mobility factor reduction (11%), likely due to its characteristics such as high pH (10.5), high P (0.39%) and ash content (67.7%). Two first-order reactions model best fitted the Pb release data extracted by EDTA, indicating Pb release took place from two sections of the soil with different adsorption and solubility properties. The lowest amount of Pb extracted in Q₁ and Q₂ phases were observed in VCB (115.2 mg kg⁻¹) and SMB (105.5 mg kg⁻¹) produced at 500 °C treatments, respectively. Generally, the effect of biochars produced at higher temperature (500 °C) on the soil Pb stabilization was greater than those produced at lower temperature (300 °C), while the feedstocks (SM and VC) had no significant effect in stabilizing soil Pb.

25878. 题目: Rare earth elements in soil profiles of various ecosystems across Germany
文章编号: N19020313
期刊: Applied Geochemistry
作者: Julia Mihajlovic, Albrecht Bauriegel, Hans-Joachim Stärk, Niko Roßkopf, Jutta Zeitz, Gerhard Milbert, Jörg Rinklebe
更新时间: 2019-02-03
摘要: Rare earth elements (REEs) are of emerging interest. In the environment, they occur in minerals, however, they are also used in many key technologies and in agriculture. In consequence, REEs are released into the environment and have thus an impact on it. However, our knowledge regarding REEs in soils is incomplete. We selected eight soil profiles across Germany aiming to determine REE contents (aqua regia) and potential mobilization (hydroxylammonium chloride and hot water extractable) and to explore relations between REEs and soil properties. The composition of the parent material strongly influenced by the ice ages during the Pleistocene (especially in northeastern Germany) is a crucial factor differentiating the content of REEs in our studied soils. The silty, clayey soils in the western part of Germany possessed higher REE contents than the sandy and peaty soils in the northeast (average REE content Cambisols: 825 μmol kg⁻¹, Retisols: 407 μmol kg⁻¹, Arenosol 180 μmol kg⁻¹, Histosols 122 μmol kg⁻¹) because REE can adsorb onto clay minerals. The characteristic soil genetic processes of each soil type were reflected by the vertical distribution of the REE content. The vertical distribution of REEs and the hydroxylammonium chloride-extractable REE contents were mainly controlled by Al, Fe, Mn and their oxides (additional to clay) which provide important sorption sites for REEs. High contents of clay, Al/Fe/and Mn oxides caused high REE contents. The hydroxylammonium chloride-extractable REE contents varied in average from 266 to 8 μmol kg⁻¹ in the soils. The hot water extractable REE contents (in average 0.94 μmol kg⁻¹) tended to be higher in horizons which were rich in organic matter. In future, mechanistic experiments concerning the dynamics of REE mobilization should be performed as well as monitoring in plants and wildlife to improve our knowledge about REEs in the environment.
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25879. 题目: Photoconversion of U(VI) by TiO₂: An efficient strategy for seawater uranium extraction
文章编号: N19020312
期刊: Chemical Engineering Journal
作者: Ping Li, Jingjing Wang, Yun Wang, Jianjun Liang, Bihong He, Duoqiang Pan, Qiaohui Fan, Xiangke Wang
更新时间: 2019-02-03
摘要: Uranium extraction from seawater is of significant importance for the sustainable utilization of uranium in the near future; however, several challenges remain owing to the low uranium concentration and high salinity of seawater. In this work, for the first time, photocatalysis by TiO₂ was introduced for U(VI) extraction from seawater. The photocatalysis method achieved a high uranium extraction capacity of 3,960 mg/g without saturation. To evaluate the performance of the photocatalysis in the potential real applications, the influence of environmental factors was systematically studied. The results showed that H⁺ in solution competed with U(VI) ions for the photogenerated e^-, inhibiting U(VI) photoreduction. Inversely, U(VI) photoreduction was facilitated at pH > 6.0 and was adequate for U(VI) extraction from seawater. The efficiency of U(VI) photoreduction can also be inhibited by the high initial U(VI) concentration, high salinity, and high TiO₂ dose. Methanol can accelerate U(VI) photoreduction by consuming photogenerated holes. Similarly, humic acid can promote U(VI) photoreduction at acidic conditions, and the reaction efficiency was slightly hindered over pH ∼6.5. Although the photoactivity was inhibited to some extent under specific conditions, it was proven that U(VI) could be completely extracted in all systems by increasing the irradiation time. X-ray photoelectron spectroscopy, X-ray diffraction and X-ray absorption near edge structure confirmed that U(VI) was transformed into U(IV) during photocatalysis and that UO₂ was mainly formed on the TiO₂ surface. The extraction of uranium in real seawater is also feasible and the deposited uranium could be easily recovered using a Na₂CO₃ solution after standing in air for several hours. Therefore, photocatalysis is demonstrated to be an eco-friendly, facile, economical and sustainable approach for uranium extraction from seawater.
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25880. 题目: Graphene based ZnO nanoparticles to depolymerize lignin-rich residues via UV/iodide process
文章编号: N19020311
期刊: Environment International
作者: Mahmoud Mazarji, Merlin Alvarado-Morales, Panagiotis Tsapekos, Gholamreza Nabi-Bidhendi, Niyaz Mohammad Mahmoodi, Irini Angelidaki
更新时间: 2019-02-03
摘要: In this work, potassium iodide (KI) and graphene oxide (GO) were utilized to promote the selectivity of photocatalytic process for alkali lignin oxidation over ZnO. Different concertation of GO was added during the microwave synthesis procedure of ZnO, and the characterization results revealed that graphene can shift the conduction band to more reducing potential, resulting to higher production of superoxide anion radicals (O₂⁻) compared to OH. Response Surface Methodology revealed the most suitable interaction among loading of GO, KI and irradiation time on lignin and total phenolic compound (TPC) degradation. Specifically, the optimal conditions (i.e. maximum lignin (52%) and minimum TPC (55%) degradation) were at [KI] = 0.64 mM; GO content into ZnO 1.2 mg/mL; 240 min of irradiation time. The results showed that higher addition of graphene into structure of ZnO could preserve more phenolics from degradation due to less production of OH. Furthermore, the addition of KI at optimized conditions could enhance the selectivity of degradation of lignin and phenolics via producing I radicals and quenching the excess amount of generated OH, respectively. The lower generation of OH at optimized conditions was quantitatively confirmed by a photoluminescence simplified technique. In addition, the effect of the photocatalytic process on substrate's anaerobic degradability was examined in order to evaluate the suitability of the pretreated solution for energy recovery. Indeed, besides the higher TPC concentration, the biogas production of treated straw at optimized conditions was increased by 35% compared to the untreated sample.
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