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25221. 题目: Did early land plants produce a stepwise change in atmospheric oxygen during the Late Ordovician (Sandbian ~458 Ma)?
文章编号: N19082207
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Y. Datu Adiatma, Matthew R. Saltzman, Seth A. Young, Elizabeth M. Griffith, Nevin P. Kozik, Cole T. Edwards, Stephen A. Leslie, Alyssa M. Bancroft
更新时间: 2019-08-22
摘要: A stepwise change in atmospheric oxygen (O₂) levels during the Ordovician has been attributed to the emergence of land plants. This phenomenon is tied to a major baseline shift in the stable carbon isotope (δ¹³C) curve and inferred increase in nutrient delivery and enhanced primary productivity in nearshore settings, which led to high organic carbon burial. The timing and magnitude of this baseline shift, however, is still elusive in part because of the lack of high-resolution δ¹³C data that span this period. Much of the existing Ordovician δ¹³C literature is focused on isotopic excursions with less emphasis on identifying long-term shifts in baseline (pre- and post-excursion) values.This study presents new high resolution δ¹³C data from stratigraphic sections at Germany Valley (West Virginia) and Union Furnace (Pennsylvania) in the Central Appalachian Basin. These sections span the entire Sandbian Stage and continue into the lower Katian Stage. The δ¹³C data from both sections are characterized by relative stability carbon isotope values (mean = −0.61‰) in the lower Sandbian, followed by a + 1.2‰ shift in the upper Sandbian (mean = +0.62‰). Herein, we propose that the positive shift represents a long-term global shift in baseline δ¹³C values of dissolved inorganic carbon. The timing of this positive shift coinciding with the diversification of early land plants (i.e., bryophytes) supports earlier models that suggested enhanced organic carbon burial rates served as a mechanism for the stepwise oxygenation of the atmosphere during the Late Ordovician.

25222. 题目: Octadecylamine degradation through catalytic activation of peroxymonosulfate by FeMn layered double hydroxide
文章编号: N19082206
期刊: Science of The Total Environment
作者: Gong Chen, Li-chao Nengzi, Bo Li, Yingjie Gao, Guixian Zhu, Xiuwen Cheng
更新时间: 2019-08-22
摘要: A kind of heterogeneous catalyst, FeMn layered double hydroxide (Fe-Mn-LDH), was fabricated by coprecipitation process and used as PMS activator to degrade a novel organic pollutant octadecylamine (ODA). And the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microcopy (TEM), Mapping and X-ray photoelectron spectra (XPS) measurements were utilized to characterize the fresh and used Fe-Mn-LDH. After a serious of degradation experiments, it was clearly to see that the activator possessed excellent activation property for PMS and was capable of removing 85% ODA (10 mg·L⁻¹) within 25 min obviously higher than pure PMS. Moreover, the effect of some elements (such as PMS consumption, catalyst consistence and initial pH value), different reaction system and catalyst repeatability on ODA degradation were also explored. And by identification of main radical experiment, SO₄^— and HO were both confirmed the primary radicals. What's more, extra anion and nature organic matter (NOM) addition experiment displayed that NOM, NO₃^— and CO₃^2— perform a negative effect on ODA degradation but Cl^— could promote it. In addition, repeated experiments and metal leaching after degradation showed good stability of Fe-Mn-LDH. Finally, based on the XPS and Gas Chromatography-Mass Spectrometer (GS-MS) technology, the possible degradation mechanism and pathway were proposed.
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25223. 题目: Estimating soil organic carbon density in plains using landscape metric-based regression Kriging model
文章编号: N19082205
期刊: Soil and Tillage Research
作者: Zihao Wu, Bozhi Wang, Junlong Huang, Zihao An, Ping Jiang, Yiyun Chen, Yanfang Liu
更新时间: 2019-08-22
摘要: The spatial distribution of soil organic carbon density (SOCD) is crucial for understanding land use impact on carbon budget. The spatial estimation and accurate mapping of SOCD in plains remain challenging, partly due to the relatively invariant topography and the lack of consideration of landscape patterns. Here, we propose a novel landscape metric-based regression Kriging (LMRK) for the spatial estimation of SOCD in plains. Using 242 topsoil samples collected in the Jianghan Plain, China, we (i) investigate the scale-dependent relationship between SOCD and 24 landscape metrics and (ii) develop LMRK models with multi-scale buffers (100–1000 m) for SOCD estimation and compare their performance with ordinary Kriging (OK) and regression Kriging (RK) that integrates land use types. Results showed that LMRK outperformed other models. The relationships between SOCD and landscape metrics were found to be scale-dependent, and the buffer of 300 m exhibited the optimal scale in our case. The LMRK also revealed that a highly connected and water-sufficient landscape was conducive to the accumulation of soil organic carbon in farmlands. These results indicated that landscape metrics serve as good predictors, and the proposed LMRK method is effective for SOCD mapping in plains. Our findings highlight the scale-dependent relationship between landscape metrics and SOCD and provide a new perspective for soil mapping in plains.

25224. 题目: Effects of long-term application of organic fertilizer on improving organic matter content and retarding acidity in red soil from China
文章编号: N19082204
期刊: Soil and Tillage Research
作者: Hanxi Wang, Jianling Xu, Xuejun Liu, Di Zhang, Longwei Li, Wei Li, Lianxi Sheng
更新时间: 2019-08-22
摘要: Long-term fertilization causes declines in soil quality and crop yield, hindering current agricultural development. This paper is about the effect of long-term fertilization (20 years) in Hunan’s Qiyang County. It was found that chemical nitrogen, phosphorus, and potassium (NPK) fertilizer lowered soil pH by an annual average of 0.07, while organic fertilizer increased soil pH by about 0.04. Furthermore, organic fertilizer and chemical fertilizer both increased total soil organic carbon (SOC). Long-term chemical NPK and organic fertilizer increased straw and grain yield of wheat and maize to a greater extent than did other fertilization methods. Thus, our results suggest that mixing organic fertilizer with chemical NPK fertilizer should prevent soil acidification and elevate crop yield.

25225. 题目: Biochar increases nitrate removal capacity of woodchip biofilters during high-intensity rainfall
文章编号: N19082203
期刊: Water Research
作者: Alexander W. Berger, Renan Valenca, Yu Miao, Sujith Ravi, Shaily Mahendra, Sanjay K. Mohanty
更新时间: 2019-08-22
摘要: Stormwater biofilters have been increasingly used to mitigate the impact of climate change on the export of contaminants including nitrate to water bodies. Yet, their performance is rarely tested under high-intensity rainfall events, which are predicted to occur more frequently under climate change scenarios. We examined the potential of biochar to improve the resilience of woodchip biofilters under simulated high-intensity rainfall events and linked denitrification to biochar-mediated changes in hydrological (physical), chemical, and biological properties of woodchip biofilters. Results showed that nitrate removal capacity of woodchip biofilters decreased with increases in rainfall intensity or duration and decreases in antecedent drying time. However, adding biochar to woodchips significantly decreased the exhaustion rate of woodchips, only when the hydraulic residence time (HRT) was less than 5 h. At longer HRT (>5 h), the benefits of biochar became less apparent. We attributed the improved denitrification during high nitrate loading to biochar's ability to decrease dissolved oxygen in pore water and increase water holding capacity and retention of dissolved organic carbon and nitrate—all of which could increase nitrate utilization. Biochar increased the net microbial biomass but did not affect the relative abundance of denitrifying genes, which indicates that a shift in microbial biomass could not fully explain the observed increase in nitrate removal in biochar-augmented woodchip biofilters. Overall, the results showed that biochar could increase the resiliency of woodchip biofilters for denitrification in high-intensity rainfall events, a worst-case scenario, thereby mitigating the water quality degradation.
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25226. 题目: Evaluating the contributions of different organic matter sources to urban river water during a storm event via optical indices and molecular composition
文章编号: N19082202
期刊: Water Research
作者: Mi-Hee Lee, Yun Kyung Lee, Morgane Derrien, Kwangsoon Choi, Kyung Hoon Shin, Kyoung-Soon Jang, Jin Hur
更新时间: 2019-08-22
摘要: Dissolved organic matter (DOM) in river water dynamically changes with respect to its major sources during heavy rain events. However, there has been no established tool to estimate the relative contributions of different organic sources to river water DOM. In this study, the evolution in the contributions of ten different organic matter (OM) sources to storm water DOM was explored with a selected urban river, the Geumho River in South Korea, during storm events via an end-member mixing analysis (EMMA) based on fluorescence indices and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The OM source materials included treated effluent, road runoff, groundwater, topsoil, deep soil, leaves, reeds, riparian plants, attached algae, and suspended algae. The EMMA results provided quantitative estimates of the variations in the dominant OM sources with the progress of storms. Treated effluent was the prevailing source at the beginning period of the storm, while topsoil, leaves, riparian plants, and groundwater predominated during and after the peak period. The fluorescence indices-based evaluation was consistent with the statistical comparison of the molecular formulas derived from FT-ICR-MS conducted on the ten potential OM sources and the storm samples. The observed variations in the OM sources agreed with the typical characteristics of urban rivers in connection with anthropogenic inputs and the impact of surrounding impervious surfaces. This study demonstrates the application of intuitive and facile tools in estimating the relative impacts of OM sources in urban watersheds.
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25227. 题目: Assessment of the chlorine demand and disinfection byproduct formation potential of surface waters via satellite remote sensing
文章编号: N19082201
期刊: Water Research
作者: Yiling Chen, William A. Arnold, Claire G. Griffin, Leif G. Olmanson, Patrick L. Brezonik, Raymond M. Hozalski
更新时间: 2019-08-22
摘要: The ability of satellites to assess surface water quality indicators such as colored dissolved organic matter (CDOM) suggests that remote sensing could be a useful tool for evaluating water treatability metrics in considering potential drinking water supplies. To explore this possibility, 24 surface water samples were collected throughout Minnesota, USA with wide ranging values of CDOM (a₄₄₀; 0.41–27.9 m^-1), dissolved organic carbon (DOC; 5.5–47.6 mg/L) and specific ultraviolet absorbance at 254 nm (SUVA₂₅₄; 1.3–5.1 L/mg-M). Laboratory experiments were performed to quantify chlorine demand and the formation of two classes of halogenated disinfection byproducts (DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), using the uniform formation conditions (UFC) test. Chlorine demand and THM_UFC were linearly correlated with CDOM (R² = 0.97 and 0.91, respectively), indicating that CDOM is a useful predictor of these parameters. On the other hand, data comparing di- and tri-HAA_UFC with CDOM were best fit by a logarithmic relationship (R² = 0.73 and 0.87, respectively), while mono-HAA_UFC was linearly correlated with CDOM (R² = 0.46) but only for low-to moderately-colored waters (a₄₄₀ ≤ 11 m⁻¹). The correlations relating chlorine demand and DBP_UFC values with CDOM were coupled with satellite CDOM assessments to estimate chlorine demand and DBP_UFC values for all surface waters larger than 0.05 km² in the state of Minnesota, USA. The resulting maps suggest that only 21.8% of Minnesota lakes would meet both the THM and HAA maximum contaminant levels, but only when pre-disinfection treatment removes 75% of DBP precursors. There are limitations to determining CDOM using satellites for high color surface waters (a₄₄₀ > 11 m⁻¹), however, leading to underpredicted values for CDOM, chlorine demand, and DBP_UFC. Overall, the results demonstrate the potential benefits of satellite remote sensing for assessing potential drinking water sources and water treatability metrics.
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25228. 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.

25229. 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.

25230. 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.
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25231. 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.
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25232. 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.

25233. 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.

25234. 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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25235. 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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25236. 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.
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25237. 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.
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25238. 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 δ¹³C_DIC 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.

25239. 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 δD_n-alkane values have been widely used as a valuable proxy for paleoenvironmental reconstruction. A number of studies have focused on δD_n-alkane values that derived exclusively from leaves, while less attention has been paid to the root-derived n-alkanes and their impact on sedimentary δD_n-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 δD_n-alkane values for Stipa bungeana (grass), Artemisisa vestita (shrub) and Bothriochloa ischaemum (grass) averaged -184‰, -152‰ and -198‰, compared with their root-derived δD_n-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 δD_n-alkane values should be carefully considered in future paleoenvironmental reconstruction efforts.

25240. 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.