论文检索

总访问量：5895179次

总访客量：421160人

所有论文

30681. 题目: Sulfur-isotope evidence for recovery of seawater sulfate concentrations from a PTB minimum by the Smithian-Spathian transition
文章编号: N18082408
期刊: Earth-Science Reviews
作者: Alan Stebbins, Thomas J. Algeo, Christian Olsen, Hiroyoshi Sano, Harold Rowe, Robyn Hannigan
更新时间: 2018-08-24
摘要: The Smithian-Spathian substage boundary (SSB) in the Early Triassic was an important time interval during the protracted recovery of marine faunas and ecosystems following the end-Permian mass extinction event. Although some Tethyan SSB sections have been studied, little information is available regarding environmental conditions in the Panthalassic Ocean, which comprised ~85% of the Early Triassic global ocean, during the Smithian-Spathian transition. Understanding changes in the carbon and sulfur cycles during the Early Triassic is important for deciphering the pattern and controls on the marine recovery. Our understanding of the Early Triassic sulfur cycle, in particular, is incomplete. In this study, we report carbonate carbon and oxygen, carbonate-associated sulfate (CAS) sulfur and oxygen, and pyritic sulfur isotopic ratios from the Jesmond section, Cache Creek Terrane, western Canada. This section, which formed as a tropical carbonate atoll in the middle of the Panthalassic Ocean, spans the latest Smithian to middle Spathian. Both δ³⁴S_CAS and δ¹⁸O_CAS increased through the SSB transition before decreasing in the early Spathian, matching variation in the δ¹³C_carb profile. We hypothesize that the sharp increase in δ³⁴S_CAS and δ¹⁸O_CAS at the SSB reflects a global increase in the amount of microbial sulfate reduction (MSR) and pyrite burial. Driving this increase in MSR and pyrite burial were cooling temperatures, increasing primary productivity, and increasing organic matter availability. The decreasing trend immediately following the SSB indicates that these environmental changes reached maxima and began to diminish or reverse in the early Spathian. The difference between δ³⁴S_CAS and δ³⁴S_pyr values (Δ³⁴S_CAS-pyr) remained relatively stable from the latest Smithian through the middle Spathian. This stability provides an estimate of MSR sulfur-isotope depletion allowing us to estimate paleo-seawater sulfate concentrations. Using the “MSR-trend” method, we estimate that Early Triassic seawater sulfate concentrations were between 2.5 and 9.1 mM. These estimates are higher than previously published values for the Permian-Triassic boundary, suggesting an overall increase in seawater sulfate by the late Early Triassic.

30682. 题目: Understanding the fate of soil organic matter in submerging coastal wetland soils: A microcosm approach
文章编号: N18082407
期刊: Geoderma
作者: Havalend E. Steinmuller, Kyle M. Dittmer, John R. White, Lisa G. Chambers
更新时间: 2018-08-24
摘要: Coastal wetland submergence can occur when rates of relative sea-level rise exceed that of soil elevation gain or landward transgression. In highly organic soils, the collapse of the wetland platform into open water can cause disarticulation of the soil structure, exposing previously protected anaerobic microzones to oxygenated seawater, which may accelerate mineralization rates. Nine soil cores (1 m deep) were collected from three sites within Barataria Bay, LA (USA), a region known for high rates of wetland submergence. Both the biogeochemical properties of the soils with depth were determined, as well as the impacts of the introduction of oxygenated seawater on carbon mineralization rates. Both field enzyme activity (β‑glucosidase, N‑acetyl‑beta‑d‑glucosaminidase, alkaline phosphatase, β‑xylosidase, and β‑cellobiosidase) and microbial biomass carbon (MBC) did not significantly change with depth until 50 cm, where activity increased dramatically, then gradually decreased. Total carbon (C), total nitrogen, and percent organic matter were highest between 50 and 100 cm. Following initial biogeochemical characterization, soil microcosms were created for 11 depth segments under anaerobic conditions (mimicking an intact wetland) and aerobic conditions (mimicking a submerging wetland mixing with oxygenated water); carbon dioxide (CO₂) production was measured within the bottles over 14 days. Carbon dioxide production averaged 66% greater in the aerobic treatment than the anaerobic treatment. Both treatments exhibited a general trend of increasing CO₂ production with depth (particularly from 40 to 100 cm), with the difference in CO₂ production between aerobic and anaerobic treatments being 4× greater at 90–100 cm than at the soil surface (0–5 cm). The increase in C mineralization rates observed at depth was positively correlated with indicators of greater microbial activity (i.e., higher enzyme activity and MBC) and greater nutrient availability. Study results indicate coastal wetland submergence into open water could significantly enhance CO₂ emissions, even in deep (40+ cm) soils, contrary to the typically observed pattern of soil microbial activity and soil quality decreasing with depth. These findings underline the need to analyze deeper soil samples (1+ m) in order to fully understand the implications of sea level rise on C loss from submerging coastal wetland soils.

30683. 题目: Influence of rice husk biochar and inorganic fertilizer on soil nutrients availability and rain-fed rice yield in two contrasting soils
文章编号: N18082406
期刊: Geoderma
作者: S.O. Oladele, A.J. Adeyemo, M.A. Awodun
更新时间: 2018-08-24
摘要: The co-application of biochar and inorganic N fertilizer has been shown to be a sustainable and environmental friendly technology for the improvement of soil fertility and crop yield. However, their interactive effects on nutrient availability and rain-fed rice productivity in contrasting soil types in the tropics have been scarcely studied. A field study was set up to investigate the effects of rice husk biochar and N-fertilizer applications at different rates on rain-fed rice yield and soil nutrient distribution in the 0–20 cm soil layer. Biochar was applied at four rates; 0, 3, 6, and 12 t/ha⁻¹, in combination with N fertilizer (urea) applied at four rates; 0, 30, 60 and 90 kg/ha⁻¹ to two different soil types (sandy clay loam Oxic-Paleustalf and sandy loam Oxic-Paleustult). In the Oxic-Paleustaif, biochar × N-fertilizer interaction significantly (p < 0.05) enhanced rain-fed rice yield and yield components such as number of panicles/m² by 71%, filled spikelet (%) by 24%, grain yield (t/ha⁻¹) by 78%, straw yield (t/ha⁻¹) by 74% and 1000 grain weight (g) by 16% when compared to the control. In the Oxic-Paleustult, interaction between biochar and N-fertilizer significantly (p < 0.05) increased number of panicles/m² by 73%, filled spikelet (%) by 24%, grain yield (t/ha⁻¹) by 83%, straw yield (t/ha¹) by 68% and 1000 grain weight (g) by 13% in the when compared to the control. Leaching of soil nitrate (NO₃-N) was mostly reduced in the Oxic-Paleustalf, while soil pH, soil organic carbon (SOC), total nitrogen (TN), available P and K content at the soil depth of 0–10 cm were significantly (p < 0.05) increased in both soil types. The result from this study suggest that biochar amendment and N fertilization have the potential to enhance rain-fed rice productivity and soil nutrient availability, while minimizing nitrate (NO₃-N) leaching.

30684. 题目: The chemical form of silicon in marine Synechococcus
文章编号: N18082405
期刊: Marine Chemistry
作者: Daniel C. Ohnemus, Jeffrey W. Krause, Mark A. Brzezinski, Jackie L. Collier, Stephen B. Baines, Benjamin S. Twining
更新时间: 2018-08-24
摘要: The widely distributed marine picocyanobacterium Synechococcus is found throughout the upper oceans. Recent observations that Synechococcus accumulates silicon indicate that it may influence the global cycle of this element. While diatoms, the organisms that dominate the marine Si cycle, have absolute Si requirements due to their precipitation of exoskeleton frustules composed of hydrated opal-A (i.e., biogenic silica), no requirements or biological roles are known for the Si associated with Synechococcus. Even less is known about the biochemical form(s) of Si in picocyanobacteria or whether it differs from diatomaceous silica. Using bulk X-ray absorption near-edge spectroscopy (XANES) across the Si K-edge, we investigated the chemical speciation of Si in dried Synechococcus laboratory isolates from several clades, representing both coastal and oligotrophic isolates grown at a range of Si(OH)₄ concentrations. Silicon associated with Synechococcus is bound to oxygen and is spectroscopically distinct from opal-A precipitated by diatoms. The closest XANES spectral analogues found in the literature are dried Mg-Si gels precipitated under basic conditions, suggesting that some Synechococcus Si may be present in vivo as a hydrated siliceous network with Mg and/or Ca cations. Slight spectral variations across isolates and growth conditions suggest strain-specificity in Si chemistry and the potential for siliceous phases to bind organic matter.

30685. 题目: Potential methane production and molecular characterization of bacterial and archaeal communities in a horizontal subsurface flow constructed wetland under cold and warm seasons
文章编号: N18082404
期刊: Science of The Total Environment
作者: Daniela López, Mario Sepúlveda-Mardones, Nathaly Ruiz-Tagle, Katherine Sossa, Enrica Uggetti, Gladys Vidal
更新时间: 2018-08-24
摘要: Organic matter removal in a horizontal subsurface flow constructed wetland (HSSF) treating wastewater is associated with the presence of bacteria and archaea. These organisms perform anaerobic microbial processes such as methanogenesis, which can lead to methane emissions. The aim of this study was to evaluate methane production and characterize the bacterial and archaeal communities found in HSSFs treating secondary urban wastewater during cold and warm seasons. The pilot system used in this study corresponds to four HSSFs, two planted with Phragmites australis (HSSF−Phr) and two planted with Schoenoplectus californicus (HSSF−Sch), the monitoring was carried out for 1335 days. Removal efficiencies for organic matter (biological and chemical oxygen demand) and total and volatile suspended solids were evaluated in each HSSF. Moreover, biomass from each HSSF was sampled during warm and cold season, and methane productions determined by Specific Methanogenic Activity assays_(maximum) (SMA_m). In the same samples, the quantification and identification of bacteria and archaea were performed. The results showed that the degradation of organic matter (53–67% BOD₅ and 51–62% COD) and suspended solids (85–93%) was not influenced by seasonal conditions or plant species. Potential methane production from HSSF-Sch was between 20 and 51% higher than from HSSF-Phr. Moreover, potential methane production during warm season was 3.4–42% higher than during cold season. The quantification of microorganisms in HSSFs, determined greater development of bacteria (38%) and archaea (50–57%) during the warm season. In addition, the species Schoenoplectus californicus has a larger number of bacteria (4–48%) and archaea (34–43%) than Phragmites australis. The identification of microorganisms evidenced the sequences associated with bacteria belong mainly to Firmicutes (42%), Proteobacteria (33%) and Bacteroidetes (25%). The archaea were represented primarily by Methanosarcinales, specifically Methanosaeta (75%) and Methanosarcina (16%). The community structure of the methanogenic archaea in HSSFs did not change throughout the seasons or plant species.
图文摘要:

30686. 题目: Land use shapes the resistance of the soil microbial community and the C cycling response to drought in a semi-arid area
文章编号: N18082403
期刊: Science of The Total Environment
作者: José Luis Moreno, Irene F. Torres, Carlos García, Rubén López-Mondéjar, Felipe Bastida
更新时间: 2018-08-24
摘要: The aim of this study was to understand the responses of the microbial community of soil under different land uses to drought in a semi-arid Mediterranean area. In a laboratory incubation, soil samples from different land uses (natural forest, drip-irrigated orchard, rain-fed almond tree cultivation and abandoned area) were maintained at 20% and 60% of the WHC. The microbial biomass and potential enzyme activities were determined after four and fifty days of soil incubation. The diversity and composition of the microbial community were studied after 50 days of incubation. The total mineralisation of soil organic C (SOC), as well as, the mineralisation of fresh organic matter (FOM) and the “priming effect” were analysed after addition of ¹³C-enriched plant tissue. Both land use and drought had significant effects in the soil microbial community, but the effect of land use was stronger than that of drought. The PLFA content (microbial biomass) of the forests soil was greater under drought. After 50 days of soil incubation, the microbial biomass and most of potential enzyme activities of the almond tree and abandoned soil samples were not significantly affected by drought contrary to those in orchard soil. The total and FOM mineralisation were on average lower in soil under drought than under optimal moisture for all land uses. However, the responses of the priming effect to drought were dependent on the land use. Overall, we conclude that the resistance to drought of the soil microbial community from an agroecosystem having a semi-arid climate is strongly influenced by the previous land use.
图文摘要:

30687. 题目: The transformation and migration of selenium in soil under different Eh conditions
文章编号: N18082402
期刊: Journal of Soils and Sediments
作者: Jianxin Fan, Yu Zeng, Jiaoxia Sun
更新时间: 2018-08-24
摘要: Purpose: Soil selenium (Se) sequestration and transformation, which are strongly controlled by soil redox conditions, are critical for understanding the mobility and bioavailability in the environment. Thus, the effect of redox potential on Se transformation was investigated for exploring the release mechanism of Se in soil. Materials and methods: Soils were incubated under anoxic condition in four treatments at room temperature over 56 days, and the soil solution pH, Eh, and Fe and Se concentrations were measured at given reaction time. The sequential extraction and X-ray photoelectron spectroscopy (XPS) were used to obtain the species distribution of Se in soil. High-resolution transmission electron microscopy (HR-TEM) was employed to observe morphology characteristic of soil. Results and discussion: Parts of soil Se can be released into solution, and Se speciation in soil changed during the incubation period. XPS and sequential extraction analyses revealed that the primary speciation of Se in soil was elemental Se, and metallic selenides were formed under aerobic condition. Moreover, XPS and HR-TEM data revealed the crystalline state of iron oxides in soil changed after anoxic incubation, and certain amorphous iron oxides were formed. Conclusions: Se release is activated by short-term incubation, whereas Se can be transformed into less soluble state after long-term incubation. Organic matter takes extremely an important role in Fe oxide reductive dissolution and Se transformation. This study is useful to understand the environmental behaviors of Se and enhance the application of Se fertilizers effectively and safely in Se deficiency area.

30688. 题目: The solid-solution distribution of copper added to soils: influencing factors and models
文章编号: N18082401
期刊: Journal of Soils and Sediments
作者: Xiaoqing Zhang, Jumei Li, Dongpu Wei, Bo Li, Yibing Ma
更新时间: 2018-08-24
摘要: Purpose: A series of empirical and mechanistic geochemical models were developed to describe the solid-solution partitioning of copper (Cu) in typical fresh spiked Chinese soils. Materials and methods: The influence of soil properties on Cu partitioning was assessed in a wide range of soils using multiple regression analysis. Geochemical models (WHAM VI and Visual MINTEQ) and simulation analyses in combination with experimental data (i.e., the bulk of soil properties and Cu contents) were performed in order to provide additional insight into the mechanisms controlling the Cu partitioning. Calculation of soluble Cu contents based on the two models was then simplified and optimized by adjusting input variables, and the calibrated outputs were used to produce reasonable predictions of soluble metal concentrations. Results and discussion: The results of the multiple regression analyses presented in this paper show strong correlations between soluble Cu concentrations and soil Cu concentrations and properties, with adjusted coefficients of determination (R_adj²) ranging between 0.84 and 0.91. Soil organic carbon (OC) content was an insignificant factor in most cases, but the active fraction of dissolved organic matter was important in improving model estimates. The best fit of root mean square error (RMSE) varied between 0.42 and 0.77 for the WHAM VI model and between 0.28 and 0.57 for the Visual MINTEQ model across all pH categories. Conclusions: The models presented in this paper are suitable for investigating and simulating Cu solid-solution partitioning in a wide range of Chinese soils.

30689. 题目: Removal of tetracycline from aqueous solution by biochar derived from rice straw
文章编号: N18082313
期刊: Water, Air, & Soil Pollution
作者: Shisuo Fan, Yi Wang, Yang Li, Zhen Wang, Zhengxin Xie, Jun Tang
更新时间: 2018-08-23
摘要: Antibiotic pollution has drawn considerable attention and the removal of antibiotic from water is crucial. In the present study, biochars were produced from rice straw under different pyrolytic temperatures of 300 °C, 500 °C, and 700 °C (RSBC300, RSBC500, and RSBC700, respectively). The biochars were used to remove tetracycline (TC) from aqueous solution and the influence of different experimental conditions on TC removal was investigated. The results showed that the order of adsorption was as follows: RSBC700 > RSBC500 > RSBC300. A pseudo-second-order model and Langmuir isotherm model described the adsorption process of TC on biochars. Maximum adsorption capacity could reach 50.72 mg g⁻¹ at 35 °C based on Langmuir fitting. Initial pH of the solution had little influence on TC removal. The inhibitory effect of Ca²⁺ on TC removal was greater than that of Na⁺. High system temperature was beneficial for TC removal. Minerals in RSBC500 affected TC removal and minerals in RSBC300 and RSBC700 had little influence on TC removal. TC removal rate decreased from 58.86 to 27.84% when the minerals were removed from RSBC500. The main mechanism involved in high-temperature biochar and TC adsorption included EDA π-π interactions and electrostatic interactions. Therefore, high-temperature biochar derived from rice straw has the potential to act as an adsorbent to remove tetracycline from aqueous solution.

30690. 题目: Spatio‐temporal variation of the quality, origin and age of particulate organic matter transported by the Yangtze River (Changjiang)
文章编号: N18082312
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ying Wu, Timothy I. Eglinton, Jing Zhang, Daniel B. Montlucon
更新时间: 2018-08-23
摘要: Information on the age dynamics of particulate organic matter (POM) in large river systems is currently sparse, and represents an important knowledge gap in our understanding of the global carbon cycle. Here, we examine variations in organic geochemical characteristics of suspended sediments from the Changjiang (Yangtze River) system collected between 1997 and 2010. Higher POC% values were observed in the middle reach, especially after 2003, and are attributed to the increase of in situ (aquatic) primary production associated with decreased total suspended matter concentrations. Corresponding Δ¹⁴C values from, depth profiles taken in 2009 and 2010, indicate spatial and temporal variations in particulate organic carbon (POC) sources within the basin. Two isotopic mass balance approaches were explored to quantitatively apportion different sources of Changjiang POM. Results indicate that contributions of biomass and pre‐aged soil organic matter are dominant regardless of hydrological conditions, with soil‐derived OC comprising 17‐56% of POC based on a Monte Carlo three end‐member mixing model. In contrast, binary mixing model calculations suggest that up to 80% of POC (2009 samples only) derived from biospheric sources. The emplacement of the Three Gorges Dam and resulting trapping of sediment from the upper reach of the watershed resulted in a modification of POM ¹⁴C ages in the reservoir. With the resulting decline in sediment load and increase in the proportion of modern POC in lower reach, these changes in POM flux and composition of the Changjiang have significant implications for downstream carbon cycle processes.

30691. 题目: Spatial distribution characteristics of soil organic carbon in subtropical forests of mountain Lushan, China
文章编号: N18082311
期刊: Environmental Monitoring and Assessment
作者: Fazhan Yu, Zhongqi Zhang, Longqian Chen, Jinxin Wang, Zhengping Shen
更新时间: 2018-08-23
摘要: The study on the spatial distribution of forest soil organic carbon (SOC) is of great significance for accurate assessment of carbon storage in forest ecosystems. In the present study, by taking eight kinds of forest soils of Mountain Lushan in the subtropical area as the research object, we studied the spatial distribution characteristics of SOC in this mountainous area. The results showed that the SOC content and SOC density (SOCD) of main forest types in the Mountain Lushan were lower than the national and the world average. The soil layer of Lushan forest was thinner, and the SOC and active SOC (ASOC) contents of different forest types and SOCDs are the highest in the surface soil. SOCD of the topsoil accounts for 32.64–54.03% of the total SOCD in the whole soil profile. Surface litter is an important source of SOC, and the different vegetation types are the important reason for the different spatial distribution of SOC in this area. Soil SOC contents in the high-altitude forest (bamboo forest, deciduous broadleaf forest, Pinus taiwanensis forest, evergreen-deciduous forest, and coniferous-broadleaved mixed forest) were higher than those in the low-altitude forest (evergreen broadleaf forest, shrub, and Pinus massoniana forest). However, the difference in SOC content exhibited at the altitude gradient is significantly lower than that in SOC in the soil profile. This indicates that both soil depth and elevation are the important factors that affected SOC distribution. However, the influence of soil depth on spatial distribution of SOC may be more complex than that of altitude. Vegetation types and soil properties are the main reasons for the large differences of reduction rate in the contents of SOC and ASOC.

30692. 题目: Liming effects on soil pH and crop yield depend on lime material type, application method and rate, and crop species: a global meta-analysis
文章编号: N18082310
期刊: Journal of Soils and Sediments
作者: Yuan Li, Song Cui, Scott X. Chang, Qingping Zhang
更新时间: 2018-08-23
摘要: Purpose: The aim of this meta-analysis was to investigate the interactive effects of environmental and managerial factors on soil pH and crop yield related to liming across different cropping systems on a global scale. Materials and methods: This study examined the effects of liming rate, lime application method, and liming material type on various soil chemical properties and crop yield based on data collected from 175 published studies worldwide since 1980. Results and discussion: The most important variables that drive changes in soil pH and crop yield were liming rate and crop species, respectively. Soil conditions, such as initial soil organic matter and soil pH, were more important for increasing soil pH in field-based experiments, while lime material type and application method were more important for improving crop yield. To effectively neutralize soil acidity, the optimum liming duration, rate, and material type were < 3 years, 3–6 Mg ha⁻¹, and Ca (OH)₂, respectively. Averaged across different crop species, the application of CaO, CaCO₃, Ca (OH)₂, and CaMg (CO₃)₂ increased yield by 13.2, 34.3, 29.2, and 66.5%, respectively. Conclusions: This meta-analysis will help design liming management strategies to ameliorate soil acidity and thus improve crop yield in agroecosystems.

30693. 题目: Halogen Radical Oxidants in Natural and Engineered Aquatic Systems
文章编号: N18082309
期刊: Environmental Science & Technology
作者: Ke Zhang, Kimberly M. Parker
更新时间: 2018-08-23
摘要: Photochemical reactions contribute to the transformation of contaminants and biogeochemically important substrates in environmental aquatic systems. Recent research has demonstrated that halogen radicals (e.g., Cl^•, Br^•, Cl₂^•–, BrCl^•–, Br₂^•–) impact photochemical processes in sunlit estuarine and coastal waters rich in halides (e.g., chloride, Cl^–, and bromide, Br^–). In addition, halogen radicals participate in contaminant degradation in some engineered processes, including chlorine photolysis for drinking water treatment and several radical-based processes for brine and wastewater treatment. Halogen radicals react selectively with substrates (with bimolecular rate constants spanning several orders of magnitude) and via several potential chemical mechanisms. Consequently, their role in photochemical processes remains challenging to assess. This review presents an integrative analysis of the chemistry of halogen radicals and their contribution to aquatic photochemistry in sunlit surface waters and engineered treatment systems. We evaluate existing data on the generation, speciation, and reactivity of halogen radicals, as well as experimental and computational approaches used to obtain this data. By evaluating existing data and identifying major uncertainties, this review provides a basis to assess the impact of halogen radicals on photochemical processes in both saline surface waters and engineered treatment systems.
图文摘要:

30694. 题目: The fate of dichloroacetonitrile in UV/Cl2 and UV/H2O2 processes: implications on potable water reuse
文章编号: N18082308
期刊: Environmental Science: Water Research & Technology
作者: Ran Yin, Zhuozhi Zhong, Li Ling, Chii Shang
更新时间: 2018-08-23
摘要: This study investigated the fate of DCAN in UV/Cl₂ and UV/H₂O₂ processes under the conditions relevant to potable water reuse (e.g., two pH values and three oxidant dosages). At pH 6 and an oxidant dosage of 500 μM, the degradation of DCAN in the UV/Cl₂ process was attributed to UV photolysis (4.5%), HO⁻-assisted hydrolysis (10.5%), nucleophilic attack by ClO⁻ (32.2%), and oxidation by radicals (i.e., HO˙ and Cl˙) (52.8%), while that in the UV/H₂O₂ process was mainly attributed to HO₂⁻ (32%) and HO˙ (48%). In both processes, the DCAN degradation rates were higher with increasing solution pH from 5 to 6, because the increased HO⁻-assisted hydrolysis and nucleophilic attack of DCAN surpassed the decreased radical oxidation of DCAN. The DCAN degradation was enhanced with increasing chlorine or H₂O₂ dosage from 100 to 1000 μM, mainly due to the increased contribution from the nucleophilic attack. DCAN was mostly transformed into dichloroacetic acid (DCAA) through different pathways in the two processes. At the same pH and oxidant dosage conditions, the degradation rates of DCAN in the UV/Cl₂ process were higher than those in the UV/H₂O₂ process, due to the higher nucleophilic attack rates and radical oxidation rates in the former process. The cost of degrading 90% of DCAN using the UV/Cl₂ process is about 1/8 of that using the UV/H₂O₂ process, making the UV/Cl₂ process a more cost-effective UV-AOP in DCAN abatement for potable water reuse.
图文摘要:

30695. 题目: Potential formation of mutagenicity by low pressure-UV/H2O2 during the treatment of nitrate-rich source waters
文章编号: N18082307
期刊: Environmental Science: Water Research & Technology
作者: S. Semitsoglou-Tsiapou, M. R. Templeton, N. J. D. Graham, S. Mandal, L. Hernández Leal, J. C. Kruithof
更新时间: 2018-08-23
摘要: Mutagenicity formation by low pressure (LP)-UV/H₂O₂ treatment of nitrate-rich water containing natural organic matter (NOM) was investigated. Laboratory-grade water samples spiked with either Pony Lake NOM or Suwannee River NOM (4 mg L⁻¹ in both cases) and nitrate (50 mg L⁻¹) were irradiated with UV fluences of 0, 1500 and 2000 mJ cm⁻² and a H₂O₂ dose of 15 mg L⁻¹ and tested for mutagenicity with the Ames II assay. LP-UV photolysis of nitrate in the presence of Pony Lake NOM caused a significant increase in the Ames II assay response and low concentrations of nitrite (0.08–0.09 mg NO₂⁻ L⁻¹) and nitrophenols (0.014–0.046 μg L⁻¹) were detected. Suwannee River NOM produced the same nitrite levels but no significant responses in the Ames II assay were observed. Additionally, samples collected from a drinking water treatment plant in the UK using LP-UV/H₂O₂ treatment were analysed with the Ames II assay. LC-OCD fractionation and SUVA measurements were performed to observe any changes in the properties of NOM. Significant differences in the mutagenicity response were observed between the treatment steps as well as between the two sampling periods. However, with respect to standard thresholds, none of the samples were found to be mutagenic towards the Salmonella typhimurium strain TA98 used.
图文摘要:

30696. 题目: Enhanced enzymatic digestibility of mixed wood sawdust by lignin modification with naphthol derivatives during dilute acid pretreatment
文章编号: N18082306
期刊: Bioresource Technology
作者: Chenhuan Lai, Bo Yang, Juan He, Caoxing Huang, Xin Li, Xiangyang Song, Qiang Yong
更新时间: 2018-08-23
摘要: Effects of the addition of 2-naphthol and 2-naphthol-7-sulfonate on the dilute acid pretreatment of mixed wood sawdust were investigated, respectively. Compared to 2-naphthol, 2-naphtnol-7-sulfonate was more effective to enhance delignification and facilitate the enzymatic hydrolysis. The 72 h hydrolysis yield was improved by 47.8% for 2-naphthol-7-sulfone, while only 9.1% was observed for 2-naphthol. The surface charges, enzyme adsorption, and cellulose accessibility of dilute acid pretreated substrates with or without naphthol derivatives were examined. The improved enzymatic hydrolysis by adding 2-naphthol-7-sulfonate was ascribed to the higher negative surface charges, the lower enzyme non-productive binding, and the higher cellulose accessibility of pretreated substrates. Additionally, the HSQC NMR and ³¹P NMR analysis were carried out on both decomposed lignins and residual bulk lignins. It indicated that the addition of the naphthol derivatives during pretreatment could suppress the lignin repolymerization, which further mitigated the inhibition of residual lignins on enzymatic hydrolysis.
图文摘要:

30697. 题目: Effect of water-washing of wheat straw and hydrothermal temperature on its hydrochar evolution and combustion properties
文章编号: N18082305
期刊: Bioresource Technology
作者: Qiulin Ma, Lujia Han, Guangqun Huang
更新时间: 2018-08-23
摘要: In order to upgrade wheat straw, hydrothermal treatment at 160–240 °C was investigated. Meanwhile, the influence of temperature and leaching on the fuel’s physicochemical and combustion properties were explored. A temperature of 180–220 °C was found to benefit the generation of hydrochar, with solid and energy yields of at least 57.3% and 69.9%, respectively. When temperature increased to 160 °C, hemicellulose was hydrolyzed and this led to the formation of carbon microspheres. The diameter of the carbon microspheres reached 0.05–0.7 μm. Hydrochars obtained at 160, 180, and 200 °C exhibited better combustion performance with higher comprehensive combustibility index value. While leaching heavily impacted the hydrochar derived at 160 °C and increased its activation energy (178 kJ/mol) above those obtained for treatment at 180 °C (164 kJ/mol) and 200 °C (169 kJ/mol). Overall, the recommended hydrothermal temperature for production of fuel from wheat straw is 180–200 °C.

30698. 题目: The influence of pH, co-existing ions, ionic strength, and temperature on the adsorption and reduction of hexavalent chromium by undissolved humic acid
文章编号: N18082304
期刊: Chemosphere
作者: Samuel Barnie, Jia Zhang, Hui Wang, Huilin Yin, Honghan Chen
更新时间: 2018-08-23
摘要: The retention of Cr(VI) in subsurface environment is highly dependent on humic acid (HA), however, the undissolved form is poorly investigated, the amount of which can be of two magnitude higher compared with the dissolved one in soils and sediments. In this study, the effects of time, initial concentration, pH, ionic strength, ion species and temperature on the adsorption and reduction respective processes by undissolved self-extracted peat soil HA from Northeast China (EHA) and from Sigma Aldrich (CHA) were investigated by batch experiments. Cr(VI) removal rates by EHA were higher than CHA and the maximum Cr(VI) removal amount for EHA and CHA were 0.77 (±0.01) and 0.61 (±0.02) mmol/g. Of these, 98% and 54% were reduced to Cr(III) by EHA and CHA respectively, which were related to the phenolic group content of HA. With time, the adsorbed Cr(VI) on HA increased to a maximum level (equilibrium) beyond which Cr(VI) reduction dominated the removal process. Cr(VI) adsorption and reduction by undissolved HA increased as pH decreased. Co-existing ion species had varying effect on Cr(VI) adsorption and indirectly on reduction especially divalent cations which was suggestive of cation bridging between Cr anions and ionized carboxyl group of HA. The positive effect of ionic strength (Ca²⁺) on Cr(VI) adsorption through complexation corroborated the cation bridge effect of divalent cations. Temperature increased both Cr(VI) adsorption (complexation) and reduction with enhancing reduction rate constants and partitioning. ΔH^o, ΔS^o, and ΔG⁰ parameters showed that Cr(VI) adsorption and reduction processes were endothermic, irreversible and spontaneous.

30699. 题目: Selective preservation among bacterial alkyl glycerol ether lipid structures during long term oxic and anoxic incubation
文章编号: N18082303
期刊: Organic Geochemistry
作者: Arnauld Vinçon-Laugier, Cristiana Cravo-Laureau, Vincent Grossi
更新时间: 2018-08-23
摘要: Bacterial mono- and dialkyl glycerol ether lipids (MAGEs and DAGEs) are potential powerful lipid biomarkers whose respective diagenetic fate still needs to be precisely assessed. To do so, the lipid content of cultures of an anaerobic bacterium synthetizing both MAGEs and DAGEs was analyzed at different growth stages and after long-term incubation under aerobic or anaerobic conditions. The proportions of the different lipid classes (fatty acids, MAGEs and DAGEs) as well as their structural distribution did not significantly vary during anaerobic growth under optimal conditions until the stationary phase. Long-term exposure to oxygen (up to 480 days) induced the preferential degradation of fatty acids and MAGEs relative to DAGEs and of sn-1 relative to sn-2 positional isomers of MAGEs. The degradation of fatty acids and MAGEs appeared slower under anaerobic conditions and no specific structures appeared preferentially degraded. All DAGE structures were very well preserved whatever the redox conditions and the time of incubation considered (480 days and 13 years under oxic and anoxic conditions, respectively). The results highlight the excellent diagenetic stability of DAGEs and the much lower potential of preservation of MAGEs, warranting caution for an eventual use of those latter compounds as tracers of environmental or microbial community changes.

30700. 题目: Multiple sulfur isotopes (δ34S, Δ33S) of organic sulfur and pyrite from Late Cretaceous to Early Eocene oil shales in Jordan
文章编号: N18082302
期刊: Organic Geochemistry
作者: Katharina Siedenberg, Harald Strauss, Olaf Podlaha, Sander van den Boorn
更新时间: 2018-08-23
摘要: We present the first multiple sulfur isotope study (³²S, 33S, ³⁴S, ³⁶S) of bulk kerogen sulfur (KS) and disulfides (’chromium-reducible sulfur’, CRS) from the oil shale of the Umm Rijam Chert-Limestone and Muwaqqar Chalk Marl Formation, Jordan (Late Cretaceous to Early Eocene, appr. 50 to 70 Ma). Analysis of the sulfur isotopic composition of KS (δ34S_KS) shows values ranging from 0.3 to 17.9  ‰, which are ³⁴S-enriched compared to the δ34S_CRS ranging from -23.5 to -3.7  ‰. Values for CRS and KS are significantly ³⁴S-depleted compared to seawater sulfate sulfur which suggests a major input of early-diagenetic, microbially-generated sulfide. A minor contribution of assimilated seawater sulfate to KS is assumed. The ³⁴S-enrichment of KS compared to CRS can be partly explained by (1) sulfide oxidation to intermediate sulfur species prior to its incorporation into organic material, by (2) fractionations during organic sulfur generation, as well as by (3) a post-depositional timing of formation. Additionally, we hypothesize, based on parallel depth trends of maturity parameters (e.g., vitrinite reflectance) and δ34S_CRS and δ34S_KS values, that the sulfur isotopic compositions were influenced by thermal maturation (catagenesis). We suggest that the CRS pool comprises a contribution of sulfide released during the thermal decomposition of KS. Overall, our study highlights the importance of organic sulfur in sulfur isotopic studies and the potential of multiple sulfur isotope analyses in maturated sedimentary successions.