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所有论文

12541. 题目: Microbially Mediated Release of As from Mekong Delta Peat Sediments
文章编号: N19082115
期刊: Environmental Science & Technology
作者: Maria P. Asta, Yuheng Wang, Manon Frutschi, Karen Viacava, Luca Loreggian, Pierre Le Pape, Phu Le Vo, Ana María Fernández, Guillaume Morin, Rizlan Bernier-Latmani
更新时间: 2019-08-21
摘要: Peat layers within alluvial sediments are considered effective arsenic (As) sinks under reducing conditions due to the binding of As(III) to thiol groups in natural organic matter (NOM) and the formation of As-bearing sulfide phases. However, their possible role as sources of As for anoxic groundwaters remains unexplored. Here, we perform laboratory experiments to provide evidence for the role of a sediment peat layer in releasing As. Our results show that the peat layer, deposited about 8,000 years ago in a paleomangrove environment in the nascent Mekong Delta, could be a source of As to porewater under reducing conditions. X-ray absorption spectroscopy (XAS) analysis of the peat confirmed that As was bound to NOM thiol groups and incorporated into pyrite. Nitrate was detected in peat layer porewater, and flow-through and batch experiments evidenced the release of As from NOM and pyrite in the presence of nitrate. Based on poisoning experiments, we propose that the microbially mediated oxidation of arsenic-rich pyrite and organic matter coupled to nitrate reduction releases arsenic from this peat. Although peat layers have been proposed as As sinks in earlier studies, we show here their potential to release depositional- and/or diagenetically-accumulated As.

12542. 题目: Significant contribution of metastable particulate organic matter to natural formation of silver nanoparticles in soils
文章编号: N19082114
期刊: Nature Communications
作者: Ying-Nan Huang, Ting-Ting Qian, Fei Dang, Yong-Guang Yin, Min Li, Dong-Mei Zhou
更新时间: 2019-08-21
摘要: Particulate organic matter (POM) is distributed worldwide in high abundance. Although insoluble, it could serve as a redox mediator for microbial reductive dehalogenation and mineral transformation. Quantitative information on the role of POM in the natural occurrence of silver nanoparticles (AgNPs) is lacking, but is needed to re-evaluate the sources of AgNPs in soils, which are commonly considered to derive from anthropogenic inputs. Here we demonstrate that POM reduces silver ions to AgNPs under solar irradiation, by producing superoxide radicals from phenol-like groups. The contribution of POM to the naturally occurring AgNPs is estimated to be 11–31%. By providing fresh insight into the sources of AgNPs in soils, our study facilitates unbiased assessments of the fate and impacts of anthropogenic AgNPs. Moreover, the reducing role of POM is likely widespread within surface environments and is expected to significantly influence the biogeochemical cycling of Ag and other contaminants that are reactive towards phenol-like groups.

12543. 题目: Mechanism of biofouling enhancement in a membrane bioreactor under constant trans-membrane pressure operation
文章编号: N19082113
期刊: Journal of Membrane Science
作者: Phuc-Nguon Hong, Mana Noguchi, Norihisa Matsuura, Ryo Honda
更新时间: 2019-08-21
摘要: In a membrane bioreactor, flux and organic loading rate conditions essentially affect membrane fouling. In constant TMP mode, flux and organic loading rate dynamically changes, while they are rather static in constant flux mode. This study investigated fouling mechanism in MBR under these different filtration modes. Fouling development was more significant in constant TMP mode than in constant flux mode when MBR was operated under equal flux condition in average. In constant TMP mode, microbial community in cake sludge was distinct from bulk sludge and had higher abundance of biofilm-forming bacterial group. The cake sludge contained more SMP and LB-EPS with high polysaccharide contents in constant TMP mode. These results suggested that, in constant TMP mode, (i) initially high flux in a filtration cycle enhanced initial deposition of bacterial cells and rapid development of fouling layer, which resulted in distinct microbial community in cake sludge; (ii) the high abundance of the biofilm-forming bacteria in cake sludge and fluctuation of organic loading rate stimulated polysaccharide production, (iii) higher polysaccharide contents in cake layer caused faster development of fouling layer and increase of hydraulic resistance by compression.
图文摘要:

12544. 题目: Biochar alleviated the salt stress of induced saline paddy soil and improved the biochemical characteristics of rice seedlings differing in salt tolerance
文章编号: N19082112
期刊: Soil and Tillage Research
作者: Junhua Zhang, Zhigang Bai, Jie Huang, Sajid Hussain, Futao Zhao, Chunquan Zhu, Lianfeng Zhu, Xiaochuang Cao, Qianyu Jin
更新时间: 2019-08-21
摘要: Biochar is used mainly to alleviate salt stress in arid and semiarid soils, or to regulate acidification stress in paddy soils. However, the effects of biochar on paddy soil environments under salt stress and the biochemical characteristics of rice seedlings differing in salt tolerance are unclear. This study explored whether and how biochar is involved in alleviating salt stress in paddy soil and regulating the biochemical characteristics of rice seedlings. The trial was conducted under pot culture conditions, and NaCl was used as the salt stress agent in paddy soil. Two rice varieties were used in this trial: Jinyuan 85 (a salt-tolerant rice variety) and Nipponbare (a salt-sensitive rice variety). The salt stress included three treatments: 0 g NaCl kg−1 dry soil (control, S0), 1 g NaCl kg−1 dry soil (S1), and 3 g NaCl kg−1 dry soil (S3). Biochar produced by rice straw involved three treatments: no biochar (control, C0), biochar produced at 300℃ applied into soil (C300), and biochar produced at 600℃ applied into soil (C600). The results suggested that the adsorption ability of the biochar produced at 600℃ was significantly higher than that of the biochar produced at 300℃. Bulk density, electrical conductivity, exchangeable Na+ and exchangeable Cl- in the soil under salt stress were greatly decreased by the application of biochar, and the soil environment of C600 was more favorable for rice seedlings. The salt accumulations in the rice seedling, and the microstructure of the root and leaf of the rice seedlings under salt stress were significantly and positively affected by the biochar, and the biochemical characteristics of the rice seedlings also greatly improved in response to biochar application. The responses of Nipponbare to salt stress were more severe than those of Jinyuan 85, while the regulatory effects of biochar were more favorable for Jinyuan 85 than for Nipponbare. In conclusion, biochar, especially that produced at 600℃ in this trial played a positive role in alleviating the inhibitory effects of salt stress on rice seedlings, and might be useful as an amendment in saline soils to improve rice plant growth.
图文摘要:

12545. 题目: Urea/ZnCl 2 in situ hydrothermal carbonization of Camellia sinensis waste to prepare N-doped biochar for heavy metal removal
文章编号: N19082111
期刊: Environmental Science and Pollution Research
作者: Shasha Guo, Yuefang Gao, Yancheng Wang, Zhengjun Liu, Xingneng Wei, Pai Peng, Bin Xiao, Yajun Yang
更新时间: 2019-08-21
摘要: Environmental benefits of biochar require a simple and effective method for preparation of functional N-doped biochar. In this study, urea/ZnCl2 was developed to prepare N-doped biochar via in situ hydrothermal carbonization (HTC) of Camellia sinensis waste at 120–280 °C for 2 h under 1.0–9.8 MPa. Physicochemical and structural properties of the N-doped biochar were investigated by Raman spectra, elemental analysis, BET surface area, SEM, TEM, XRD, and XPS. The results showed that the N content in biochar could reach up to 7.79% at 280 °C. Surface chemistry suggested that pyridinic N, pyrollic N, and graphitic N were the major N species on the biochar. Moreover, the N-doped biochar was successfully employed to remove metal ions Cu2+, Pb2+, Zn2+, and Cr6+. Adsorption data fit closely to the pseudo-second-order kinetic equation and the Langmuir adsorption isotherm model for all metal ions.

12546. 题目: Freeze-thaw and dry-wet events reduce microbial extracellular enzyme activity, but not organic matter turnover in an agricultural grassland soil
文章编号: N19082110
期刊: Applied Soil Ecology
作者: Maki Miura, Timothy G. Jones, Paul W. Hill, Davey L. Jones
更新时间: 2019-08-21
摘要: Soils in temperate agroecosystems are frequently exposed to extremes of moisture and temperature during which time soil functioning may be negatively affected. The aim of this study was to directly compare the effects of a single dry-wet or freeze-thaw (−5 °C or −20 °C) cycle on extracellular enzyme activity and soil organic matter turnover. We measured the activity of six enzymes before and after imposing the freeze-thaw or dry-rewet events. Our results showed that drying had a much greater impact on total enzyme activity than a −20 °C freezing event (38 vs. 10% reduction, respectively), while freezing at −5 °C had no appreciable effect. Enzyme activity recovered back to control levels relatively quickly which we ascribe to de novo exoenzyme production (within 3 d for the −20 °C freeze-thaw treatment and 14 d for the dry-wet treatment). We added 14C-labelled plant residues to the soil prior to imposing the same thermal or moisture stress events. Monitoring residue decomposition before and after imposing the treatments indicated that none of the stress regimes greatly affected organic matter turnover rates. Our results did reveal, however, a pulse of 14CO2 which was produced during the drying and freezing events themselves. We ascribe this to a shift in microbial metabolism and the production of stress avoidance metabolites (e.g. osmo- and cryo-protectants, membrane lipids). Our work highlights that extreme weather events may affect exoenzyme activity, however, these responses are transitory and are unlikely to greatly affect soil organic matter cycling unless they occur at high frequency.

12547. 题目: Biochar and rice husk ash assisted phytoremediation potentials of Ricinus communis L. for lead-spiked soils
文章编号: N19082109
期刊: Ecotoxicology and Environmental Safety
作者: Boda Ravi Kiran, M.N.V. Prasad
更新时间: 2019-08-21
摘要: Soil contamination with lead (Pb) is a serious global concern, adversely affecting crop production. Pot experiments were conducted to assess the efficacy of Prosopis biochar and rice husk ash for plant growth and mitigating Pb translocation in Ricinus communis. Physico-chemical characterization of both the amendments was carried out on a dry weight basis. Seedlings of R.communis were grown in 0, 400 and 800 mg kg−1 Pb spiked soil amended with Prosopis juliflora biochar (PJB) and rice husk ash (RHA) at 0, 2.5% and 5% (w/w) of soil for 60 days. Addition of biochar and rice husk ash to soils increased the Pb tolerance in R.communis, improved soil pH, nutrient intake, and antioxidant enzymatic activities. The biochar amendment significantly (p < 0.05) increased plant growth parameters (height, leaf diameter, nodes, and leaf number), protein (72%) and chlorophyll contents (38–52%), as did RHA to a lesser extent (increase of 10–31% in chlorophyll and 77% protein content) compared to unamended plants. Soil usage of RHA resulted in a more consistent decrease in Pb accumulation in the root, shoot, and leaf relative to PJB. Treatment with PJB at 5% decreased the accumulation of Pb in roots by 59% whereas RHA decreased Pb concentration in roots by 87%. The two distinct amendments significantly reduced the availability of soil Pb and decreased oxidative damage, as evidenced by the lower production of proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) in plants. Changes in infrared spectra confirmed that oxygenated phosphate, amide, ester and ether functional groups played a key role in binding accumulated Pb in roots as well as alleviation of Pb-induced phytotoxicity. Our findings conclude the amendments can be used as a stress regulator in mitigating Pb toxicity, which is important for all economic crop plants, including R.communis.
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12548. 题目: Valorization of alum sludge via a pyrolysis platform using CO2 as reactive gas medium
文章编号: N19082108
期刊: Environment International
作者: Dongho Choi, Jeong-Ik Oh, Jechan Lee, Young-Kwon Park, Su Shiung Lam, Eilhann E. Kwon
更新时间: 2019-08-21
摘要: In an effort to seek a new technical platform for disposal of drinking water treatment sludge (DWTS: alum sludge), pyrolysis of DWTS was mainly investigated in this study. To establish a more sustainable thermolytic platform for DWTS, this study particularly employed CO2 as reactive gas medium. Thus, this study laid great emphasis on elucidating the mechanistic roles of CO2 during the thermolysis of DWTS. A series of the TGA tests of DWTS in CO2 in reference to N2 revealed no occurrence of the heterogeneous reaction between CO2 and the sample surface of DWTS. As such, at the temperature regime before initiating the Boudouard reaction (i.e., ≥700 °C), the mass decay patterns of DWTS in N2 and CO2 were nearly identical. However, the gaseous effluents from lab-scale pyrolysis of DWTS in CO2 in reference to N2 were different. In sum, the homogeneous reactions between CO2 and volatile matters (VMs) evolved from the thermolysis of DWTS led to the enhanced generation of CO. Also, CO2 suppressed dehydrogenation of VMs. Such the genuine mechanistic roles of CO2 in the thermolysis of DWTS subsequently led to the compositional modifications of the chemical species in pyrolytic oil. Furthermore, the biochar composite was obtained as byproduct of pyrolysis of DWTS. Considering that the high content of Al2O3 and Fe-species in the biochar composite imparts a strong affinity for As(V), the practical use of the biochar composite as a sorptive material for arsenic (V) was evaluated at the fundamental levels. This work reported that adsorption of As(V) onto the biochar composite followed the pseudo-second order model and the Freundlich isotherm model.
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12549. 题目: Photocatalytic degradation of cephalexin by ZnO nanowires under simulated sunlight: Kinetics, influencing factors, and mechanisms
文章编号: N19082107
期刊: Environment International
作者: Jianzhou He, Yaozhong Zhang, Yang Guo, Geoff Rhodes, Junghoon Yeom, Hui Li, Wei Zhang
更新时间: 2019-08-21
摘要: Increasing concentrations of anthropogenic antibiotics and their metabolites in aqueous environments has caused growing concerns over the proliferation of antibiotic resistance and potential adverse impacts to agro-environmental quality and human health. Photocatalysis using novel engineered nanomaterials such as ZnO nanowires may be promising for removing antibiotics from waters. However, much remains to be learned about efficiency and mechanism for photocatalytic degradation of antibiotics by ZnO nanowires. This study systematically investigated photodegradation of cephalexin using ZnO nanowires under simulated sunlight. The degradation efficiency of cephalexin was substantially increased in the presence of ZnO nanowires especially at circumneutral and alkaline condition (solution pH of 7.2–9.2). The photodegradation followed the first-order kinetics with degradation rate constants (k) ranging between 1.19 × 10−1 and 2.52 × 10−1 min−1 at 20–80 mg L−1 ZnO nanowires. Radical trapping experiments demonstrated that hydroxyl radicals (OH) and superoxide radicals (O2) predominantly contributed to the removal of cephalexin. With the addition of HCO3 (1–5 mM) or Suwannee River natural organic matter (SRNOM, 2–10 mg L−1), the k values were substantially decreased by a factor of 1.8–70 to 1.69 × 10−3–6.67 × 10−2 min−1, probably due to screening effect of HCO3 or SRNOM sorbed on ZnO nanowires and scavenging of free radicals by free HCO3 or SRNOM in solution. Combining product identification by mass spectrometry and molecular computation, cephalexin photodegradation pathways were identified, including hydroxylation, demethylation, decarboxylation, and dealkylation. Overall, the novel ZnO nanowires have the potential to be used for removing antibiotics from contaminated waters.
图文摘要:

12550. 题目: Integrated use of straw mulch with nitrogen fertilizer improves soil functionality and soybean production
文章编号: N19082106
期刊: Environment International
作者: Kashif Akhtar, Weiyu Wang, Guangxin Ren, Ahmad Khan, Yongzhong Feng, Gaihe Yang, Haiyan Wang
更新时间: 2019-08-21
摘要: Mulching can effectively maintain and improve soil health and functionality. The mechanisms, however, have not been fully elucidated. Therefore, the effects of temperature on the biogeochemical properties of soil were investigated in the present study in relation to nitrogen management and soil functionality. The results of the 3-year field experiments showed that integrated straw mulch (S) and nitrogen fertilizer (N) treatments enhanced the activities of soil urease, invertase, alkaline phosphatase, and catalase by >1.8, 2.1, 2.0 and 1.4 fold, respectively, compared with the control treatment. Furthermore, these treatments increased soil available N by 28%, phosphorus by 45%, and potassium by 55%. In general, the soil organic carbon, dissolved carbon and labile organic carbon content in the treated plot were approximately 1.2–2.9 folds greater than in the control plot. These improvements in soil fertility and carbon indices increased the biomass and grain yield of soybean (67 and 75%, respectively) during the three-year study period. During 2015–2017, the straw mulch and nitrogen fertilizer treatment increased the soil moisture (23%) and decreased the soil temperature (8%) in comparison to the control in the 0–0.2 m soil depth and, therefore, improved soil enzyme activities, nutrient availability, and carbon stocks, and ultimately, soil functionality and sustainability, in the semiarid region.
图文摘要:

12551. 题目: Carbon cycling in low temperature hydrothermal systems: The Dorado Outcrop
文章编号: N19082105
期刊: Geochimica et Cosmochimica Acta
作者: James McManus, C. Geoffrey Wheat, Wolfgang Bach
更新时间: 2019-08-21
摘要: We sampled low temperature (< 15°C) hydrothermal fluids that discharge from the Dorado Outcrop on the eastern flank of the Cocos Ridge. Our sampling techniques included discrete sample collection using DSV Alvin and autonomous time-series samplers deployed using RSV Jason II. The sampled fluids are enriched in dissolved inorganic carbon (DIC) by ∼0.10 mM and have a δ13CDIC that is on average between 0.2 and 0.5‰ lower than the surrounding bottom seawater. Assuming that the measured DIC enrichment is representative of low temperature hydrothermal systems, the magnitude of the DIC source to the ocean would be 1 x 1012 mol C/y, which is roughly the same magnitude as the high temperature hydrothermal source, but is more than a factor of three smaller than the estimated rate of carbon removal via carbonate precipitation within the ocean crust. Based on an isotope balance of the discharging fluids, which considers added sources of both basalt-derived inorganic and marine-derived organic carbon, the net DIC carbon isotope signature of vent fluids is most consistent with a primary carbon source from seawater (95.9%), plus a component from the weathering of basalt (3.4%) with a δ13C value of -6‰, and a component from organic matter degradation (0.7%), with a δ13C value of -22‰. This particular balance places the upper limit of organic carbon respiration at ∼0.3 x 1012 mol C/y; however, if our DIC input estimate is too high, then the isotope balance requires a larger organic carbon component, which is not consistent with the dissolved oxygen and nitrate data. Although low temperature hydrothermal systems are often thought to be important locations for carbonate precipitation, there is little evidence for current carbonate precipitation at Dorado Outcrop. Similar trends in DIC are observed at North Pond, another low temperature (< 15°C) ridge flank hydrothermal system. These data suggest that much of the current ridge flank discharge is a source of DIC to the ocean.

12552. 题目: Comparison of n-alkane concentrations and δD values between leaves and roots in modern plants on the Chinese Loess Plateau
文章编号: N19082104
期刊: Organic Geochemistry
作者: Jinzhao Liu, Zhisheng An, Huawu Wu, Yunlong Yu
更新时间: 2019-08-21
摘要: Sedimentary δDn-alkane values have been widely used as a valuable proxy for paleoenvironmental reconstruction. A number of studies have focused on δDn-alkane values that derived exclusively from leaves, while less attention has been paid to the root-derived n-alkanes and their impact on sedimentary δDn-alkane values. In this study, we sampled modern plant leaf and root materials from different growth contexts (slopes and seasons) on the Chinese Loess Plateau to compare leaf-derived n-alkanes with root-derived n-alkanes. Our results demonstrated that total n-alkane (C27-C33) concentrations varied substantially between leaf and root materials, with average values of 209 μg/g and 29.5 μg/g observed in leaves and roots respectively. The results suggest that ca. 12% of the n-alkane concentration in sediments derived from plant roots. Furthermore, leaf-derived δDn-alkane values for Stipa bungeana (grass), Artemisisa vestita (shrub) and Bothriochloa ischaemum (grass) averaged -184‰, -152‰ and -198‰, compared with their root-derived δDn-alkane values of -199‰, -179‰ and -163‰, respectively. These statistically significant differences in concentrations and δD values between leaf-derived and root-derived n-alkanes suggest that the contribution of n-alkanes derived from plant roots is important to evaluate the resultant n-alkane composition of sediments for paleoenvironmental reconstruction. Our finding indicates that the effects of root-derived n-alkanes on total sedimentary δDn-alkane values should be carefully considered in future paleoenvironmental reconstruction efforts.

12553. 题目: Changes in archaeal ether lipid composition in response to agriculture alternation in ancient and modern paddy soils
文章编号: N19082103
期刊: Organic Geochemistry
作者: Fengfeng Zheng, Yufei Chen, Xiaotong Tang, Jianqiang Su, Yongguan Zhu, Chuanlun Zhang
更新时间: 2019-08-21
摘要: Paddy soil is the consequence of human activity, which has exerted significant anthropogenic impacts on the global carbon cycle in recent earth history, particularly through the production of microbial methane from paddy soils. However, the anthropogenic impact of rice fields on the distribution of methanogenic archaea and methane emission during human history is poorly documented. Isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) are unique biomarkers for archaea, which can be used to examine changes in climate and environment during human evolution. This study aimed to reconstruct archaeal communities and evaluate how they might have been impacted by human activities during the development of two paddy soil profiles that recorded a cultivation history of over 6300 years in Zhejiang Province, southeastern China. Variations in archaeol, GDGT-0 and crenarchaeol strongly suggest that archaeal ether lipids deeply buried in the ancient paddy soil profiles are mainly fossil records rather than contemporary signals. Cluster analysis based on GDGT compositions revealed two major groups of GDGTs corresponding to different soil types, reflecting the shift of archaeal communities from Thaumarchaeota to methanogens. The archaeal ether lipids-based proxies (MI, archaeol/crenarchaeol and GDGT-0/crenarchaeol) related to methane-producing archaea varied remarkably in different soil types associated with the anthropogenic management. These proxies had significantly higher values in the buried paddy soils than currently cultivated paddy soils, implying that the earlier anthropogenic flooding may have resulted in considerable methane emission from paddy soils in southeastern China.

12554. 题目: An evaluation of measurement techniques for algal-derived organic nitrogen
文章编号: N19082102
期刊: Water Research
作者: X. Li, N.R.H. Rao, K.L. Linge, C.A. Joll, S. Khan, R.K. Henderson
更新时间: 2019-08-21
摘要: Algal-derived organic matter (AOM) from algal blooms in water supply systems contains dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) among other constituents. The DON and DOC are disinfection by-product (DBP) precursor compounds, and must be well characterised to facilitate effective removal, thus minimising DBP formation during disinfection. While DOC character has been studied extensively, DON analysis suffers from inaccuracies due to sample pre-treatment and instrument sensitivities. A liquid chromatography method that combines size exclusion chromatography with highly sensitive organic carbon and nitrogen detectors (LC-OCND)) has been widely adopted for DOC analysis; however, its potential for application for DON charactersation has been suggested as a viable alternative to existing DON characterisation techniquesnot been assessed despite its potential. Hence, the aim was to compare the effectiveness of conventional total dissolved N–dissolved inorganic N (TN–DIN), and LC-OCND methods for analysing DON in AOM. A suite of N-containing model compounds representative of DON and AOM extracted from Chlorella vulgaris CS-42/7 and Microcystis aeruginosa CS-555/1 were used to evaluate the techniques. The DON of both model compounds and AOM was first analysed using the conventional method and, then, via LC-OCND. It was observed that LC-OCND had a better precision for DON when TN contained more DIN. LC-OCND provided direct quantitative measurements for bulk and fractionated DON and DIN, with little interference caused by DIN. Additionally, LC-OCND provided information on MW distribution and protein content of the AOM. For example, LC-OCND results showed that M. aeruginosa AOM contained more HMW material than C. vulgaris AOM. However, as LC-OCND uses UV oxidation, it could not completely oxidise complex aromatic structures, and thus had a lower recovery for HMW model compounds and algal DON in comparison to the conventional method that used high temperature catalytic oxidation. Overall, it is advised that a combination of LC-OCND and TN analysis be used to provide a more detailed characterisation of N-containing AOM and other similar HMW aquatic NOM samples.
图文摘要:

12555. 题目: Global versus local processes during the Pliensbachian–Toarcian transition at the Peniche GSSP, Portugal: A multi-proxy record
文章编号: N19082101
期刊: Earth-Science Reviews
作者: Alicia Fantasia, Thierry Adatte, Jorge E. Spangenberg, Eric Font, Luís V. Duarte, Karl B. Föllmi
更新时间: 2019-08-21
摘要: The Toarcian Oceanic Anoxic Event (T-OAE, ~ 183 Ma) was an episode of extreme warmth, environmental changes and carbon cycle perturbation. We present a high-resolution study of the Peniche section (Lusitanian Basin, Portugal), recently defined as the Toarcian Global Stratotype Section and Point, to provide a review of the Pliensbachian–Toarcian (Pl–To) environmental and climatic changes. A large ~7‰-negative carbon-isotope excursion (CIE) is recorded within the T-OAE interval in bulk organic matter. Distinct small-scale δ13C negative shifts, modulating the T-OAE carbon isotope signal, are correlated across different European basins, which have implications on the estimation of the T-OAE duration. The increase in kaolinite content and chemical index of alteration from the Pl–To boundary up to the T-OAE interval is interpreted as reflecting a shift towards warmer and wetter climate conditions. The common occurrence of coarse-grained turbidites within the T-OAE interval is possibly linked with changes of the hydrological cycle and storm intensity. Low total organic carbon contents together with the absence of redox-sensitive trace element enrichments indicate oxygen-deficient conditions unfavourable for organic matter preservation. Mercury data show a clear increase at the base of the T-OAE CIE followed by a return to background values, providing further evidence that Karoo-Ferrar volcanism might have triggered the series of environmental disturbances during the early Toarcian. However, the highest mercury values are recorded in samples containing abundant pyritized wood fragments, highlighting the influence of local chemical processes on mercury enrichments, which should be considered before any interpretation of the Hg records.

12556. 题目: Net additions of recalcitrant dissolved organic carbon in the deep Atlantic Ocean
文章编号: N19082011
期刊: Global Biogeochemical Cycles
作者: Cristina Romera‐Castillo, Marta Álvarez, Josep Lluís Pelegrí, Dennis A. Hansell, Xosé Antón Álvarez‐Salgado
更新时间: 2019-08-20
摘要: Most dissolved organic carbon (DOC) sequestered in the deep ocean has residence times of decades to thousands of years, with clear implications for climate regulation, though some net removal is typically observed with increasing water mass age. Here, a high quality–high resolution dataset has allowed us to identify net additions of recalcitrant DOC in specific water masses of the deep South Atlantic. Overall, the South Atlantic is a net source of recalcitrant DOC, adding 0.027 ± 0.019 Pg C y–1, while the North Atlantic is a net sink that removes 0.298 ± 0.141 Pg C y–1. We find that the balance of addition/removal of recalcitrant DOC depends not only on the origin, but also on the temperature, age and depth of the water masses that circulate and mix in the Atlantic Ocean. Future changes in the water mass composition and circulation patterns due to climate change would eventually affect that balance, altering the carbon cycle.

12557. 题目: Short‐term (5 years) impact of conservation agriculture on soil physical properties and organic carbon in a rice‐wheat rotation in Indo‐Gangetic plains of Bihar
文章编号: N19082010
期刊: European Journal of Soil Science
作者: Surajit Mondal, S.P. Poonia, J.S. Mishra, B.P. Bhatt, K.K. Rao, Kirti Saurabh, Rakesh Kumar, Debashis Chakraborty
更新时间: 2019-08-20
摘要: Short‐term (5 yrs) impact of tillage and residue management practices on physical properties and organic carbon (OC) of a silty clay soil was evaluated in a rice‐wheat rotation in the Indo‐Gangetic Plains of Bihar. The experiment had three conservation agriculture (CA) practices: one full (direct‐seeded rice (DSR)‐no‐tilled wheat (NTW)‐no‐tilled mung bean (NTMB); fCA), and two partial (puddled transplanted rice (PTR)‐NTW‐conventionally tilled mung bean (CTMB); pCA1 and unpuddled transplanted rice (UPTPR)‐conventionally tilled potato+maize (CTP + M)‐NTMB; pCA2), which were evaluated against full conventional practice (puddled transplanted rice (PTR)‐conventionally tilled wheat (CTW); TA). Subsurface compaction reduced and soil aggregation improved under both full and partial CA. Macro‐ and water‐stable aggregates increased to a large extent (26 and 11%, respectively) in full CA, and to a lesser extent in partial CA, mostly due to increase in coarse macroaggregate (2–8 mm) contents in 0–10 and 10–20 cm layers. Steady‐state infiltration rate nearly doubled under full CA, with larger pore volume recorded in 10–20 and 20–30 cm layers. The CA increased OC associated with all size fractions of aggregates in the surface layer (0–10 cm), but a higher amount of C was associated with macroaggregates indicating relative stabilization of OC in the soil under the CA. Change in bulk soil OC was larger at 0–10 cm layer in favour of CA, which also had an 11% increase in OC stock in 0–30 cm layer. Improvement in soil physical condition did not effectively translate into rice or wheat yields, but the system productivity increased largely.

12558. 题目: Determination of soil properties using thermogravimetry under laboratory conditions
文章编号: N19082009
期刊: European Journal of Soil Science
作者: JiŘí Kučerík, Karel SvatoŇ, Stanislav Malý, Martin Brtnický, Helena Doležalová‐Weismannová, Michael Scott Demyan, Christian Siewert, David Tokarski
更新时间: 2019-08-20
摘要: Analysis of soil properties and soil organic matter dynamics requires the use of reliable and rapid analytical techniques. Included in such applicable techniques is thermogravimetry (TG), which, typically, measures mass losses of soil heated during a temperature ramping. Previous work revealed relationships between mass losses of 10°C intervals (TG indicators) and total organic carbon (SOC), total nitrogen (TN), clay content, and mass losses at higher temperatures (TG fractions) with interactions between SOC, TN, and clay. However, widespread application of these relationships is hampered by the requirement to equilibrate soils at 76% relative humidity (RH) prior to and during TG measurements. In this study we tested whether the relationships between mass losses and soil properties can be observed at 43% RH by analyzing 37, mostly arable and grassland soils. It was found that at 43% RH the same TG indicators correlated significantly with soil properties as at 76% RH, but the correlations with TN and clay contents were observed at lower temperatures. New equations were developed for rapid analysis of soil properties using TG indicators and for determination of TG fractions at 43% RH. The results indicated that for routine application of these TG approaches in soil science, it is necessary to include a RH parameter which accounts for potential shifts in diagnostic temperatures when modeling the relationships between TG data and soil properties.

12559. 题目: Thermal oxidation of carbon in organic matter rich volcanic soils: insights into SOC age differentiation and mineral stabilization
文章编号: N19082008
期刊: Biogeochemistry
作者: Katherine E. Grant, Valier V. Galy, Oliver A. Chadwick, Louis A. Derry
更新时间: 2019-08-20
摘要: Radiocarbon ages and thermal stability measurements can be used to estimate the stability of soil organic carbon (OC). Soil OC is a complex reservoir that contains a range of compounds with different sources, reactivities, and residence times. This heterogeneity can shift bulk radiocarbon values and impact assessment of OC stability and turnover in soils. Four soil horizons (Oa, Bhs, Bs, Bg) were sampled from highly weathered 350 ka Pololu basaltic volcanics on the Island of Hawaii and analyzed by Ramped PyrOX (RPO) in both the pyrolysis (PY) and oxidation (OX) modes to separate a complex mixture of OC into thermally defined fractions. Fractions were characterized for carbon stable isotope and radiocarbon composition. PY and OX modes yielded similar results. Bulk radiocarbon measurements were modern in the Oa horizon (Fm = 1.013) and got progressively older with depth: the Bg horizon had an Fm value of 0.73. Activation energy distributions (p(E)) calculated using the ‘rampedpyrox’ model yielded consistent mean E values of 140 kJ mol−1 below the Oa horizon. The ‘rampedpyrox’ model outputs showed a mostly bimodal distribution in the p(E) below the Oa, with a primary peak at 135 kJ mol−1 and a secondary peak at 148 kJ mol−1, while the Oa was dominated by a single, higher E peak at 157 kJ mol−1. We suggest that mineral-carbon interaction, either through mineral surface-OC or metal-OC interactions, is the stabilization mechanism contributing to the observed mean E of 140 kJ mol−1 below the Oa horizon. In the Oa horizon, within individual RPO analyses, radiocarbon ages in the individual thermal fractions were indistinguishable (p > 0.1). The flat age distributions indicate there is no relationship between age and thermal stability (E) in the upper horizon (> 25 cm). Deeper in the soil profile higher µEf values were associated with older radiocarbon ages, with slopes progressively steepening with depth. In the deepest (Bg) horizon, there was the largest, yet modest change in Fm of 0.06 (626 radiocarbon years), indicating that older OC is slightly more thermally stable.

12560. 题目: Synthesis of graphene oxide nano-materials coated bio-char using carbonaceous industrial waste for phenol separation from water
文章编号: N19082007
期刊: Colloids and Surfaces A: Physicochemical and Engineering Aspects
作者: Suvendu Manna, Snigdha Prakash, Papita Das
更新时间: 2019-08-20
摘要: This article presents the process of synthesizing a value added product from a carbonaceous industrial waste. For this a carbonaceous industrial waste was coated with graphene oxide (GO) and then thermally activated at 800°C. The GO and the GO-coated biochar were characterized with atomic force microscope, raman spectroscope, fourier transform infrared spectroscopy, field-emission scanning electron microscope, x-ray Diffraction and transmission electron microscope. This GO-coated biochar was then utilized to investigate removal capacity of phenol present in wastewater. The data indicated that the GO-coated biochar showed better phenol removal efficacy then that of the GO itself. The isotherm analysis indicated that the data could be described best with Langmuir isotherm indicating that the phenol separation was a monolayer surface adsorption. The kinetic analysis indicated that the phenol separation process was followed by pseudo second order kinetics. Also, it was evident from the intra-particle diffusion kinetic analysis that diffusion plays a significant role in phenol separation. From thermodynamic analysis it was evident that the phenol separation process was endothermic as well as spontaneous in nature. The GO-coated biochar showed better separation efficacy in the presence of salt.
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