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23541. 题目: Managing for soil carbon sequestration: Let’s get realistic
文章编号: N18113012
期刊: Global Change Biology
作者: William H. Schlesinger, Ronald Amundson
更新时间: 2018-11-30
摘要: Improved soil management is increasingly pursued to ensure food security for the world's rising global population, with the ancillary benefit of storing carbon in soils to lower the threat of climate change. While all increments to soil organic matter are laudable, we suggest caution in ascribing large, potential climate change mitigation to enhanced soil management. We find that the most promising techniques, including applications of biochar and enhanced silicate weathering, collectively are not likely to balance more than 5% of annual emissions of CO₂ from fossil fuel combustion.

23542. 题目: Impact of biochar coated with magnesium (hydr)oxide on phosphorus leaching from organic and mineral soils
文章编号: N18113011
期刊: Journal of Soils and Sediments
作者: Matthew Riddle, Lars Bergström, Frank Schmieder, Daniel Lundberg, Leo Condron, Harald Cederlund
更新时间: 2018-11-30
摘要: Purpose: Recent research suggests that Swedish organic arable soils have been under-recognized as a potential source of phosphorus (P) loading to water bodies. The aim of this study was to compare P losses through leaching from organic and high-fertility mineral soils. In addition, the effectiveness of a magnesium-salt-coated biochar applied below the topsoil as a mitigation strategy for reducing P losses was evaluated. Materials and methods: Phosphorus leaching was measured from four medium- to high-P arable soils, two Typic Haplosaprists (organic 1 and 2), a Typic Hapludalf (sand), and an unclassified loam textured soil (loam), in a 17-month field study utilizing 90-cm-long lysimeters. A magnesium-salt-coated biochar was produced and characterized using X-ray powder diffraction (XPD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and X-ray adsorption (XANES) spectroscopy, and its phosphate adsorption capacity was determined at laboratory scale. It was also applied as a 3-cm layer, 27 cm below the soil surface of the same lysimeters and examined as a mitigation measure to reduce P leaching. Results and discussion: Total-P loads from the 17-month, unamended lysimeters were in the order of organic 2 (1.2 kg ha⁻¹) > organic 1 (1.0 kg ha⁻¹) > sand (0.3 kg ha⁻¹) > loam (0.2 kg ha⁻¹). Macropore flow, humic matter competition for sorption sites, and fewer sorption sites likely caused higher P losses from the organic soils. Analysis by XRD and SEM revealed magnesium was primarily deposited as periclase (MgO) on the biochar surface but hydrated to brucite (Mg(OH)₂) in water. The Langmuir maximum adsorption capacity (Q_max) of the coated biochar was 65.4 mg P g⁻¹. Lysimeters produced mixed results, with a 74% (P < 0.05), 51% (NS), and 30% (NS) reduction in phosphate-P from the organic 1, organic 2, and sand, respectively, while P leaching increased by 230% (NS) from the loam. Conclusions: The findings of this study indicate that P leached from organic arable soils can be greater than from mineral soils, and therefore, these organic soils require further investigation into reducing their P losses. Metal-enriched biochar, applied as an adsorptive layer below the topsoil, has the potential to reduce P losses from medium- to high-P organic soils but appear to be less useful in mineral soils.

23543. 题目: Biomass waste components significantly influence the removal of Cr(VI) using magnetic biochar derived from four types of feedstocks and steel pickling waste liquor
文章编号: N18113010
期刊: Chemical Engineering Journal
作者: Yunqiang Yi, Guoquan Tu, Dongye Zhao, Pokeung Eric Tsang, Zhanqiang Fang
更新时间: 2018-11-30
摘要: Few studies have focused on the effects of biomass feedstocks on the structure-reactivity of magnetic biochar. In this study, four types of magnetic biochar were first prepared using steel pickling waste liquor (serving as iron salt) and sugarcane bagasse (SMBC), rice straw (RMBC), peanut shells (PMBC) and herb residue (HMBC). According to the Langmuir model, the maximum adsorption capacity of Cr(VI) by SMBC was 43.122 mg/g, which was approximately 1.298 times, 3.175 times and 3.677 times higher than that of RMBC, PMBC and HMBC, respectively. The mass balance of chromium indicated that Cr(VI) was removed mainly via reduction. However, the reduction capacity of Cr(VI) differed among the four types of magnetic biochar. The results of characterisations of those magnetic composites before and after reaction demonstrated that the Cr(VI) was electrostatically attracted to the surface of the materials. Consequently, most of the adsorbed Cr(VI) was reduced and the remainder of the Cr(VI) was complexed with C=O groups in magnetic biochar. Further, the total iron in magnetic biochar, especially Fe(II), played a dominant role in the removal and reduction of Cr(VI). Finally, correlation analysis showed that the cellulose and ash in the biomass were the main factors that induced the differences in the magnetic biochar’s total iron content. Therefore, this study may provide a reference for the use of magnetic biochar to remove Cr(VI) from aqueous solutions.

23544. 题目: Activation of peroxymonosulfate by graphitized hierarchical porous biochar and MnFe₂O₄ magnetic nanoarchitecture for organic pollutants degradation: Structure dependence and mechanism
文章编号: N18113009
期刊: Chemical Engineering Journal
作者: Haichao Fu, Shuanglong Ma, Peng Zhao, Shengjun Xu, Sihui Zhan
更新时间: 2018-11-30
摘要: Three novel graphitized hierarchical porous biochar (MX) and MnFe₂O₄ magnetic composites (MnFe₂O₄/MX) have been prepared for degrading organic pollutants by peroxymonosulfate (PMS) activation. MX including MS, ML, MC synthesized using corn stems (S), leaves (L) and cores (C) as raw materials, respectively, possesses hierarchical porous structure, graphitization domains and tremendous surface area. The orange II removal effects of MX and MnFe₂O₄/MX outperform the corresponding carbonization products, despite that adsorption probably undertakes the major removal efficiency for MX and degradation contributes the most for MnFe₂O₄/MX. A structure-dependent degradation efficiency is discovered for MX and MnFe₂O₄/MX, among of which both MS and MnFe₂O₄/MS present the best removal effect, by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The lowest EIS owning to its better balance between graphitization degree and specific surface area and micropore volume of MnFe₂O₄/MS among MnFe₂O₄/MX explains its best catalytic activity. The catalytic degradation occurs by the following three ways. First, the radical-induced oxidation is attained by surface-bound •SO₄^– and •OH on MnFe₂O₄ nanoclusters and hierarchical porous carbon nanosheets generated by one-electron reduction of PMS under the participating and coupling of Mn(III)/Mn(II), Fe(III)/Fe(II), O₂/•O₂^-, and active sites on carbon surface. Second, non-radical pathway involves the contribution of ¹O₂, which is produced in a large quantity by promoted self-decomposition of PMS in presence of MnFe₂O₄/MS. Third, non-radical pathway is achieved through electron transfer from organic compounds as electron donator to PMS as electron acceptor mediated by graphitization structures. Taking into consideration the excellent degradation performance, easy magnetic separation, and bulk availability of MnFe₂O₄/MS, this work is expected to pave a new way for precision utilization of corn biomass-based biochar for environmental application.
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23545. 题目: Impacts of forests and forestation on hydrological services in the Andes: A systematic review
文章编号: N18113008
期刊: Forest Ecology and Management
作者: Vivien Bonnesoeur, Bruno Locatelli, Manuel R. Guariguata, Boris F. Ochoa-Tocachi, Veerle Vanacker, Zhun Mao, Alexia Stokes, Sarah-Lan Mathez-Stiefel
更新时间: 2018-11-30
摘要: Several Andean countries have planned to restore forest cover in degraded land to enhance the provision of multiple ecosystem services in response to international commitments such as the Bonn Challenge. Hydrological services, e.g. water supply, hydrological regulation and erosion mitigation, are particularly important to sustain the life of more than fifty million Andean people. While rapid and important forest cover changes have occurred during recent decades, critical information on the impact of forestation on hydrological services has not yet been synthesized in the context of Andean ecosystems. We define forestation as the establishment of forest by plantation or natural regeneration on areas that either had forest in the past or not. To help improve decision-making on forestation in the Andes, we reviewed the available literature concerning the impacts of forestation on water supply, hydrological regulation and mitigation of erosion and landslides. We also examined available data on the most relevant hydrological processes such as infiltration, evapotranspiration and runoff in forest stands. Hydrological services from native forests were also included as a reference state for comparing processes and services provided by forestation. Following systematic review protocols, we synthesized 155 studies using different methods, including meta-analyses and meta-regressions. Results show that forestation has had clear impacts on degraded soils, through reducing water erosion of soils and risk of moderate floods, increasing soil infiltration rate by 8 and topsoil organic matter (SOM). We found that 20 years of tree plantation was sufficient to recover infiltration rate and sediment yield close to the levels of native forests whereas SOM, soil water storage and surface runoff of native forests could not be recovered by forestation in the time scales examined. The benefits in terms of hydrological regulation are at the expense of a reduction in total water supply since forest cover was associated with higher water use in most Andean regions. Forestation with native species was underrepresented in the reviewed studies. The impact of forestation on landslides has also been largely overlooked in the Andes. At high elevations, exotic tree plantations on Andean grasslands (e.g. páramo and puna) had the most detrimental consequences since these grasslands showed an excellent capacity for hydrological regulation and erosion mitigation but also a water yield up to 40% higher than tree plantations. People engaged in forest restoration initiative should be aware that hydrological services may take some time for society and the environment to show clear benefits after forestation.

23546. 题目: Thermodynamic stability of methyldibenzothiophenes in sedimentary rock extracts: Based on molecular simulation and geochemical data
文章编号: N18113007
期刊: Organic Geochemistry
作者: Sibo Yang, Meijun Li, Xiaoqiang Liu, Qiuya Han, Jia Wu, Ningning Zhong
更新时间: 2018-11-30
摘要: The thermodynamic stabilities of methyldibenzothiophene(MDBT) isomers and the mechanisms of 1,2-methyl shift, methylation and demethylation have been systematically investigated by molecular modelling. Combining with the geochemical data from a set of lacustrine mudstone samples in the Liaohe Basin (East China), this study reveals the possible reaction mechanisms governing the formation and occurrence of MDBT isomers in source rocks. The Boltzmann distribution of MDBTs in gas, water and cyclohexane was calculated to show the relative thermal stability with the increasing of temperature (burial depth). A total of eight reaction pathways involving in 1,2-methyl shift, methylation and demethylation chemical processes via ionic and free radical reaction, and the transition states and energy barriers are calculated. The results show that three main reaction pathways (P1, P3 and P6) are three possible pathways for the transformation reactions between DBT and MDBTs during the onset of oil generation window to high maturity stages of sedimentary organic matter. The 1,2-methyl shift isomerization (P1) and low concentration of possible precursor (2-mehtylbiphenyl) for 1-MDBT cause the relative low abundance of 1-MDBT isomer during oil generative window. Methylation of DBT with methyl radical attack (P3), the formation of MDBTs with TMAB as methyl donor (P6), the prevailing degradation reactions and much higher thermodynamic stability of 4-MDBT relative to 1-MDBT makes the MDR maturity indicator regularly increase during oil generative window to high maturity stages. Therefore, previously proposed MDR maturity indicator was further confirmed by theoretical calculation, molecular simulation and the geochemical data of the lacustrine mudstone samples in this study.
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23547. 题目: The effect of biochar nanoparticles on rice plant growth and the uptake of heavy metals: Implications for agronomic benefits and potential risk
文章编号: N18113006
期刊: Science of The Total Environment
作者: Le Yue, Fei Lian, Yang Han, Qiongli Bao, Zhengyu Wang, Baoshan Xing
更新时间: 2018-11-30
摘要: The interaction between biochar nanoparticles (nano-BC) and plant roots in the rhizosphere is largely unknown, although it is crucial for understanding the role of BC in plant growth and bioavailability of pollutants. The effect of nano-BC produced at a series of temperatures (300–600 °C) on alleviating the phytotoxicity of Cd²⁺ to rice plants was investigated from the aspects of biochemical changes and Cd uptake in this study. The kinetics of Cd²⁺ fluxes in different root zones in the presence of nano-BC were also measured using a scanning ion-selective electrode technique. We found that the high-temperature nano-BC could more significantly alleviate the phytotoxicity of Cd²⁺ than the low-temperature and bulk BCs as reflected by the higher increased biomass, root vitality, chlorophyll content, and decreased MDA content as well as relative electrical conductivity of rice plants, which is due to the high adsorption affinity of nano-BC for Cd²⁺. Also, for the first time we demonstrated that nano-BC could differentially affect the net flux of Cd²⁺ in different zones of the root tips. However, nano-BC (especially that produced at higher temperatures) more significantly increased the contents of antioxidative enzyme activities (e. g., SOD, POD, and CAT) and soluble protein than the treatment only with Cd²⁺ (5.0 mg/L), indicating that nano-BC could induce oxidative stress in the rice plants. These results indicate that nano-BC could greatly reduce the uptake and phytotoxicity of Cd²⁺, but its potential risk should not be overlooked during the environmental and agricultural applications of biochar.
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23548. 题目: Synthesis of biochar from chili seeds and its application to remove ibuprofen from water. Equilibrium and 3D modeling
文章编号: N18113005
期刊: Science of The Total Environment
作者: R. Ocampo-Perez, E. Padilla-Ortega, N.A. Medellin-Castillo, P. Coronado-Oyarvide, C.G. Aguilar-Madera, S.J. Segovia-Sandoval, R. Flores-Ramírez, A. Parra-Marfil
更新时间: 2018-11-30
摘要: In this work chili seeds (Capsicum annuum) were used as raw material in the synthesis of biochar at temperatures between 400 and 600 °C. The samples were chemically, texturally and morphologically characterized and their properties were correlated with the calcination temperature. The adsorption mechanism of IBP was elucidated by analyzing the effect of solution pH, ionic strength and temperature, whereas that, the intraparticle diffusion mechanism was clarified through the application of a 3D diffusional model. The results evidenced that raising the pyrolysis temperature promotes a greater content of disordered graphitic carbon (51.6–85.02%) with small surface area (0.52–0.18 m²/g) and low quantity of functional groups. The adsorption study demonstrated that the biochar synthesized at 600 °C (C600) enhances the adsorption capacity >50 folds compared with chili seeds. Moreover, at pH = 7 the adsorption mechanism is governed by π-acceptor and attractive electrostatic interactions, whereas at basic pH the main adsorption mechanism is π-acceptor. Additionally, hydrophobic interactions become important by increasing the presence of NaCl. The application of 3D diffusional model based on surface diffusion interpreted clearly the kinetic curves obtaining values of D_s ranging from 2.31 × 10⁻⁸–2.51 × 10⁻⁸ cm² s⁻¹. Besides, it was determined that intraparticle mass flux is larger along the shortest axis of the seed, and always directed toward the particle center. The maximum mass flux takes place in the center of particle, and it advances like a moving front as time was increased.
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23549. 题目: Response of ammonia volatilization to biochar addition: A meta-analysis
文章编号: N18113004
期刊: Science of The Total Environment
作者: Zhipeng Sha, Qianqian Li, Tiantian Lv, Tom Misselbrook, Xuejun Liu
更新时间: 2018-11-30
摘要: There has been increasing interest in and use of biochar as a soil amendment. However, the effects of biochar addition on ammonia volatilization (AV) appeared contradictory from the many reported studies and the main influencing factors remain unclear. Here, we conducted a comprehensive meta-analysis of 41 published articles with 144 observations to reveal the effects of biochar addition on AV and used a boosted regression tree modelling approach to further interpret the contribution of biochar characteristics, soil properties and experimental conditions to this process. On average, biochar addition did not impact on AV, but this varied greatly under different soil, biochar and experimental conditions. The pH of soil and biochar were important factors impacting AV. Biochar application to acidic soil could stimulate AV, and addition of biochar with a high pH and at a low application rate also showed the same trend. In contrast, combining biochar with urea or organic fertilizer, or using wood-based or acidified biochar at appropriate rates had benefits in reducing AV. These findings have major implications for biochar management strategies in agricultural systems, where an important consideration is the mitigation of potentially detrimental environmental consequences.
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23550. 题目: Insight into complexation of Cu(II) to hyperthermophilic compost-derived humic acids by EEM-PARAFAC combined with heterospectral two dimensional correlation analyses
文章编号: N18113003
期刊: Science of The Total Environment
作者: Jia Tang, Li Zhuang, Zhen Yu, Xiaoming Liu, Yueqiang Wang, Ping Wen, Shungui Zhou
更新时间: 2018-11-30
摘要: Hyperthermophilic composting has been demonstrated to overcome the disadvantages of conventional composting in products with better quality. However, the complexation of heavy metals to hyperthermophilic compost (HTC)-derived HA remains unclear. In the present work, using Cu(II) as the representative heavy metal, we investigated the binding process of Cu(II) to HAs derived from HTC, thermophilic compost (TC), and sewage sludge (SS). The complexation ability of three HAs was analyzed by the method of parallel factor (PARAFAC) coupled with hetero two-dimensional correlation spectroscopy (hetero-2DCOS) analyses. Results showed that HTC-derived HA has the greater complexation ability (log K_M = 5.68, CC_M = 1.21) than both TC-derived HA (log K_M = 5.27, CC_M = 0.94) and SS-derived HA (log K_M = 5.19, CC_M = 0.586), likely due to the higher humification degree, as well as the faster response of carboxyl and phenols to Cu(II) binding with HTC-derived HA. This study demonstrated that the utilization of HTC might provide an effective approach for remediation of Cu(II)-polluted soils. Moreover, PARAFAC analysis integrated with hetero-2DCOS offers a unique insight into understanding the correlation between HAs fractions and functional groups during the Cu(II) binding process.
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23551. 题目: Sources and dry deposition of carbonaceous aerosols over the coastal East China Sea: Implications for anthropogenic pollutant pathways and deposition
文章编号: N18113002
期刊: Environmental Pollution
作者: Fengwen Wang, Ting Feng, Zhigang Guo, Yuanyuan Li, Tian Lin, Neil L. Rose
更新时间: 2018-11-30
摘要: 75 paired TSP and PM_2.5 samples were collected over four seasons on Huaniao Island (HNI), an island that lies downwind of continental pollutants emitted from mainland China to the East China Sea (ECS). These samples were analyzed for organic carbon (OC) and elemental carbon (EC), with a special focus on char-EC (char) and soot-EC (soot), to understand their sources, and the scale and extent of pollution and dry deposition over the coastal ECS. The results showed that char concentrations in PM_2.5 and TSP averaged from 0.13 to 1.01 and 0.31–1.44 μg m⁻³; while for soot, they were from 0.03 to 0.21 and 0.16–0.56 μg m⁻³, respectively. 69.0% of the char and 36.4% of the soot were present in PM_2.5. The char showed apparent seasonal variations, with highest concentrations in winter and lowest in summer; while soot displayed maximum concentrations in fall and minimum in summer. The char/soot ratios in PM_2.5 averaged from 3.29 to 17.22; while for TSP, they were from 1.20 to 7.07. Both of the ratios in PM_2.5 and TSP were highest in winter and lowest in fall. Comparisons of seasonal variations in OC/EC and char/soot ratios confirmed that char/soot may be a more effective indicator of carbonaceous aerosol source identification than OC/EC. Annual average atmospheric dry deposition fluxes of OC and EC into ECS were estimated to be 229 and 107 μg m⁻² d⁻¹, respectively, and their deposition fluxes significantly increased during episodes. It was estimated that the loadings of OC + EC and EC accounted for 1.3% and 4.1% of the total organic carbon and EC in ECS surface sediments, respectively, implying a relatively small contribution of OC and EC dry deposition to organic carbon burial. This finding also indicates a possibly more important contribution of wet deposition to organic carbon burial in sediments of ECS, and this factor should be considered for future study.
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23552. 题目: Effect of salinity and humic acid on the aggregation and toxicity of polystyrene nanoplastics with different functional groups and charges
文章编号: N18113001
期刊: Environmental Pollution
作者: Jiayi Wu, Ruifen Jiang, Wei Lin, Gangfeng Ouyang
更新时间: 2018-11-30
摘要: Studies regarding the effect of environmental factors on the environmental behaviour and potential toxicity of nanoplastics (NPs) are limited but important. In this study, four polystyrene NPs with different functional groups and charges (PS, PS-COOH, n-PSNH₂, p-PSNH₂) were selected to investigate the effect of humic acid (HA) and salinity on their aggregation behaviour and toxicity. The results showed that salinity significantly accelerated the aggregation of the four NPs, while HA mainly exerted a stabilizing effect on the three negatively charged NPs. In contrast, the positively charged p-PSNH₂ aggregated significantly at first but remained stable as HA concentration further increased. The joint effect mainly depended on their concentration ratio. The aggregation phenomena can be explained by the Derjaguin - Landau - Verwey - Overbeek (DLVO) theory. Also, the acute toxicity of NPs on Daphnia magna was affected by the surface charge of NPs, and the positively charged p-PSNH₂ showed the lowest toxicity among the selected NPs. Furthermore, the presence of HA effectively alleviated the toxicity of PS and p-PSNH₂, as the survival rates increased from 15% to 45%–95% and 100% respectively. Our results demonstrate that the surface properties of NPs significantly influence their aggregation and toxicity.
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23553. 题目: Distributing sulfidized nanoscale zerovalent iron onto phosphorus-functionalized biochar for enhanced removal of antibiotic florfenicol
文章编号: N18112914
期刊: Chemical Engineering Journal
作者: Jiang Xu, Zhen Cao, Yan Wang, Yilin Zhang, Xiaoyu Gao, Mohammad Boshir Ahmed, Jing Zhang, Yi Yang, John L. Zhou, Gregory V. Lowry
更新时间: 2018-11-29
摘要: Aggregation of nZVI and sulfur-modified nZVI (S-nZVI) can lower its reactivity with contaminants in water. To overcome this limitation, we synthesized biochar-supported nZVI and S-nZVI using a phosphate pretreatment of the biochar (pBC) to uniformly distribute the nZVI and S-nZVI onto the biochar support. The participation of phosphorus groups in the synthesis, and the good distribution of S-nZVI on the pBC were confirmed by FTIR, SEM, XRD, and XPS. Pretreatment of the biochar led to smaller well-dispersed S-nZVI compared to S-nZVI supported on untreated biochar. This increased the surface area of the S-nZVI and the reaction rate with the antibiotic florfenicol (FF). The removal rate of FF by pBC-S-nZVI was 4.3 times higher than that by unsupported S-nZVI. Even though FF strongly adsorbed to the pBC support, FF was fully degraded based on the mass balance results. Surface area normalized reaction rate constants (k_SA) for FF removal by S-nZVI, BC-S-nZVI, and pBC-S-nZVI were similar, suggesting that the enhanced reactivity is due to the greater dispersion of S-nZVI on the treated biochar. These results provide a simple pretreatment method for dispersing nZVI or S-nZVI onto biochar supports.
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23554. 题目: Chemostratigraphic resolution of widespread reducing conditions in the southwest Pacific Ocean during the Late Paleocene
文章编号: N18112913
期刊: Chemical Geology
作者: Benjamin R. Hines, Michael F. Gazley, Katie S. Collins, Kyle J. Bland, James S. Crampton, G. Todd Ventura
更新时间: 2018-11-29
摘要: Paleogene strata throughout much of the southwest Pacific is comprised of thick successions of fine-grained siliceous to calcareous sediments. However, during the Late Paleocene the south Pacific experienced widespread deposition of organic-rich and δ¹³C_org-enriched sediments that are recorded in the Waipawa Formation and the correlative Waipawa Organofacies. The mechanisms responsible for the elevated input and preservation of organic matter are still poorly understood. Using a multi-proxy chemostratigraphic approach we assess paleoceanographic conditions, including paleo-redox states and paleo-productivity of the Waipawa Formation. Eight key sections from the East Coast Basin, New Zealand were sampled and analysed for multi-element geochemistry and bulk pyrolysis. Sedimentological, stratigraphic and chemostratigraphic evidence indicates the south Pacific underwent an abrupt regression event during the Late Paleocene resulting in on-shelf erosion and/or bypassing of continental sourced sediments from the shelf into deeper waters. The change in sediment delivery further increased nutrients and terrestrial organic matter loading to the site of deposition. Coeval excursions in Ti/Zr and Rb/Sr indicate a shift to an aluminosilicate-dominated sediment supply, resulting in a modest increase in marine productivity that cannot account for the anomalous organic matter enrichment. Changes in the hydrogen index show a transition from terrestrial to mixed terrestrial–marine organic matter occurred during the Late Paleocene, in which high concentration of Type II-III kerogens were buried and preserved in association with enhanced water column reducing conditions in deep marine settings. Elevated concentrations of redox-sensitive trace elements (e.g. U, Mo, Fe, S) are consistent with alternating phases of dysoxic to oxic conditions suggesting an expansion of an oxygen minimum zone, enhancing preservation and delivery of organic matter to the seafloor, leading to the subsequent burial and preservation of organic matter within anoxic sediments. These new data provide insight into the depositional conditions and the petroleum potential of prospective source rocks in this basin using an integrated organic and inorganic geochemical approach to refine our knowledge of the depositional environment and paleoceanographic changes in shelfal to bathyal marine sediments of the Late Paleocene.

23555. 题目: Condensate refractory inclusions from the CO3.00 chondrite Dominion Range 08006: Petrography, mineral chemistry, and isotopic compositions
文章编号: N18112912
期刊: Geochimica et Cosmochimica Acta
作者: S.B. Simon, A.N. Krot, K. Nagashima, L. Kööp, A.M. Davis
更新时间: 2018-11-29
摘要: We have found two refractory inclusions in the CO3.00 carbonaceous chondrite Dominion Range (DOM) 08006 that appear to be primary condensates from the early solar nebula. One, inclusion 56-1, contains the first four phases predicted to form by equilibrium gas-solid condensation: corundum; hibonite; grossite; and perovskite. The other, 31-2, contains nine predicted condensate phases: hibonite; grossite; perovskite; melilite; spinel; FeNi metal; diopside; forsterite; and enstatite. Except for melilite/spinel, the phases occur in the predicted sequence from core to rim of the inclusion, which has an irregular shape inconsistent with a molten stage. This inclusion preserves the most complete record of condensation in the early solar nebula that has yet been found. The physical evidence reported here supports equilibrium condensation calculations that predict the observed sequence as well as the assumptions upon which they are based, such as total pressure (∼10^–3 atm), bulk system composition (solar), and C-O-H proportions. All phases in both inclusions and the associated ferromagnesian silicates are ¹⁶O-rich, with Δ¹⁷O between –25 and –20‰, implying that this is the original composition of the vast majority of primary condensates and that ¹⁶O-poor compositions observed in many isotopically heterogeneous inclusions are largely due to subsequent isotopic exchange. While the nebula was well-mixed with respect to oxygen isotopic composition, clearly resolved anomalies in Ca and Ti isotopic compositions indicate that some isotopic heterogeneity existed early and was preserved during condensation. Inclusion 31-2 did not incorporate live ²⁶Al and and has nucleosynthetic anomalies in the heavy Ca and Ti isotopes (i.e., δ⁴⁸Ca=4.3±1.9‰; δ⁵⁰Ti=8.8±2.0‰). In contrast, inclusion 56-1 has radiogenic ²⁶Mg excesses yielding a (²⁶Al/²⁷Al)₀ ratio of (1.0±0.1) × 10^–5 and negative nucleosynthetic isotopic anomalies in Ca (δ⁴⁸Ca=–10.3±4.2‰) and Ti (δ⁵⁰Ti=–4.3±2.9‰). Thus, it represents a deviation from the mutual exclusivity relationship between ²⁶Al incorporation and large nucleosynthetic anomalies. The reservoirs in which these inclusions formed had similar O-isotopic and different Al-, Ca– and Ti-isotopic compositions, suggesting that while the CAI-forming region was well-mixed with respect to oxygen isotopic composition, clearly resolved anomalies in Ca and Ti isotopic compositions indicate that some isotopic heterogeneity existed and was preserved during condensation.

23556. 题目: Carbon Cycling of Subsurface Organic Matter Recorded in Speleothem ¹⁴C Records: Maximizing Bomb-Peak Model Fidelity
文章编号: N18112911
期刊: Geochimica et Cosmochimica Acta
作者: Peter E. Carlson, Jay L. Banner, Kathleen R. Johnson, Richard C. Casteel, Daniel O. Breecker
更新时间: 2018-11-29
摘要: From 1955 to 1963, atmospheric testing of nuclear weapons caused a significant rise in atmospheric radiocarbon activity. This “bomb peak” has been used to calculate turnover rates of organic carbon in soils and other recent sedimentary deposits. Some speleothems contain precise and independently dated records of radiocarbon activity. These records can be used to understand, through inverse modeling, the processes and rates of turnover of subsurface organic carbon in karst regions. This approach is complicated, however, by the contribution of radioactively “dead” carbon to the stalagmite by the dissolution of host-rock limestone or by the respiration of relatively old soil organic matter. Previously published inverse models of the radiocarbon bomb peak in speleothems constrain the dead carbon proportion (DCP, in percent) by comparing measurements of speleothem radiocarbon activity from before the onset of the bomb peak to measurements of coeval atmospheric radiocarbon. This approach precludes modeling of speleothems that began growing after the onset of atmospheric nuclear weapons testing in 1955. Here, we advance the inverse modeling framework to calculate DCP using the entire length of the speleothem record, allowing for the modeling of speleothems that began growing after the initiation of atmospheric nuclear weapons testing. We test the sensitivity and resolution of this model and find that it can precisely resolve the turnover times and relative contributions of subsurface organic matter pools with residence times of less than a decade. The model fails to resolve turnover times or relative contributions of organic matter pools on millennial or greater timescales. These results also hold for the previously published models from which the current model is derived. We find that imprecise estimates of slow-turnover carbon add significant uncertainty to the calculated average age of respired carbon, which is a common metric of subsurface carbon cycling. The high precision and resolution attainable between sub-decadal carbon pools will allow researchers to differentiate the (sub-) annual pool, which is likely dominated by root/rhizosphere respiration, from the 2- to 10-year pools, which is likely dominated by microbial decomposition of labile organic carbon. The high precision attainable in fast-turnover pools also suggests that when there are multiple viable chronological interpretations for the same speleothem, bomb peak models could be used to help select which chronology is most likely to be accurate. This is important for high-resolution (sub-annual) speleothem climate records, where even single-year chronological offsets can result in misleading calibrations to the instrumental record.

23557. 题目: Fouling resistant functional blend membrane for removal of organic matter and heavy metal ions
文章编号: N18112910
期刊: Journal of Environmental Management
作者: C. Lavanya, R. Geetha Balakrishna, Khantong Soontarapa, Mahesh S. Padaki
更新时间: 2018-11-29
摘要: This study investigates the removal of heavy metal ions and humic acid using Cellulose acetate (CA) and Poly (methyl vinyl ether-alt-maleic acid) (PMVEMA) blend membranes. Antifouling properties of blend membranes were also investigated. Flat sheet membranes were prepared by phase inversion technique using different concentrations of CA and PMVEMA. The prepared membranes were characterized and their performance was evaluated by measuring pure water flux, water uptake capacity and humic acid removal. Rejection of humic acid (HA) was observed to be around 97% for all the blend membranes because of electrostatic interactions between the functional groups of HA and blends. The fouling characteristics of the membranes was assessed using HA as a foulant and the antifouling capacity of blend membranes was observed to be greater with a flux recovery ratio of almost 95% when compared to bare CA, commercial CA (TechInc) and other reported CA blends used for HA rejection. Also, the blend membranes were very effective in removing heavy metal ions (Pb²⁺, Cd²⁺ and Cr⁺⁶) and humic acid simultaneously. Overall, the PMVEMA modified CA membranes can open up new possibilities in enhancing the hydrophilicity, permeability and antifouling properties.
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23558. 题目: Lipid biomarker distributions in Oligocene and Miocene sediments from the Ross Sea region, Antarctica: Implications for use of biomarker proxies in glacially influenced settings
文章编号: N18112909
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Bella Duncan, Robert McKay, James Bendle, Timothy Naish, Gordon N. Inglis, Heiko Moossen, Richard Levy, G. Todd Ventura, Adam Lewis, Beth Chamberlain, Carrie Walker
更新时间: 2018-11-29
摘要: Biomarker-based climate proxies enable climate and environmental reconstructions for regions where other paleoclimatic approaches are unsuitable. The Antarctic Cenozoic record consists of widely varying lithologies, deposited in rapidly changing depositional settings, with large lateral variations. Previous sedimentological and microfossil studies indicate that the incorporation of reworked older material frequently occurs in these sediments, highlighting the need for an assessment of biomarker distribution across a range of depositional settings and ages to assess the role reworking may have on biomarker-based reconstructions. Here, we compare sedimentary facies with the distribution of n-alkanes and hopanoids within a terrestrial outcrop, two glaciomarine cores and a deep sea core, spanning the Late Oligocene to Miocene in the Ross Sea. Comparisons are also made with n-alkane distributions in Eocene glacial erratics and Mesozoic Beacon Supergroup sediments, which are both potential sources of reworked material. The dominant n-alkane chain length shifts from n-C₂₉ to n-C₂₇ between the Late Eocene and the Oligocene. This shift is likely due to changing plant community composition and the plastic response of n-alkanes to climate cooling. Samples from glaciofluvial environments onshore, and subglacial and ice-proximal environments offshore are more likely to display reworked n-alkane distributions, whereas, samples from lower-energy, lacustrine and ice-distal marine environments predominantly yield immature/contemporaneous n-alkanes. These findings emphasise that careful comparisons with sedimentological and paleontological indicators are essential when applying and interpreting n-alkane-based and other biomarker-based proxies in glacially-influenced settings.

23559. 题目: Frequent euxinia in southern Neo-Tethys Ocean prior to the end-Permian biocrisis: Evidence from the Spiti region, India
文章编号: N18112908
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Alan Stebbins, Jeremy Williams, Michael Brookfield, Steven W. Nye, Robyn Hannigan
更新时间: 2018-11-29
摘要: In this study, we reconstruct water-column oxygen availability during the deposition of Late Permian shales (Wuchiapingian to approximately early Changhsingian) using the geochemistry and morphology of sedimentary pyrite (FeS₂). Deposition of the shales occurred prior to the end-Permian mass extinction within the southern Neo-Tethys Ocean (Spiti region, Himachal Pradesh, India). We found that the variability of pyritic sulfur to organic carbon (S_pyr/C_org) and the pyritic sulfur isotopic composition (δ³⁴S_pyr) did not record changes in oxygen availability at Spiti sections. This was due to the removal of original pyritic sulfur by modern oxidative weathering and diagenetic pyrite formation which overwhelmed the original δ³⁴S_pyr values. However, pyrite framboid size distributions was a reliable recorder of paleoredox conditions. The degree of oxygen limitation varied with multiple transient euxinic events interrupting a predominantly oxic-dysoxic trend near the top of the Gungri Formation upper member (approximately late Wuchiapingian to early Changhsingian). These transient euxinic intervals provide important insight and regional evidence of environmental stress and instability in the southern Neo-Tethys well prior to the end-Permian mass extinction.

23560. 题目: Release of polycyclic aromatic hydrocarbons from biochar fine particles in simulated lung fluids: Implications for bioavailability and risks of airborne aromatics
文章编号: N18112907
期刊: Science of The Total Environment
作者: Xinlei Liu, Rong Ji, Yu Shi, Fang Wang, Wei Chen
更新时间: 2018-11-29
摘要: Airborne carbonaceous fine particles, such as soot and biochar, represent a significant fraction of air particulate matter and have received widespread concern due to their health effects. Atmospheric carbonaceous particles can contain high concentration of polycyclic aromatic hydrocarbons (PAHs), and may pose significant health risks when carried into respiratory system from inhalation of particulates. In this study, the bioaccessibility of two PAH compounds, phenanthrene and pyrene, bound to biochar fine particles was assessed by examining their release in two simulated lung fluids: Gamble's solution and artificial lysosomal fluid (ALF). We observed that only 0.47 to 0.75% of biochar-bound PAHs were released in the simulated lung fluids, most likely due to the physical entrapment of PAH molecules in the micropore regimes of biochar, resulting in strong desorption hysteresis, even though apparent desorption equilibrium was reached within 30 min, well within the average clearance time of particulate matter in lung system. The inorganic and organic salts in the simulated lung fluids were found to inhibit the release of PAHs by exerting the pore blockage effect and salting-out effect. Moreover, the low molecular weight organic acids (LMWOAs) in the lung fluids further inhibited PAH release by increasing the micropore volume and surface area of biochar fine particles. When taking into account the inhibited release, the estimated carcinogenic risks of biochar-bound PAHs are typically low, even under extreme conditions wherein both biochar concentrations and PAH loadings on biochar are very high. An important implication is that contaminant bioavailability needs to be taken into account when assessing the risks of the contaminants bound to airborne carbonaceous materials.
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