氮肥与DCD配施对棚室黄瓜土壤NH3挥发损失及N2O排放的影响

以传统水氮管理为对照,进行了优化水氮管理条件下氮肥与DCD配施对大棚黄瓜土壤氨挥发损失及氧化亚氮排放的影响研究.试验结果表明,与传统水氮管理相比,优化水氮管理减少了氮肥用量及灌水量,但黄瓜产量并没有降低.各水氮处理的NH3挥发速率峰值出现在施肥灌水后的第3d,添加DCD的各优化水氮处理与传统水氮处理相比,土壤氨挥发累积量分别减少55.97%、43.68%、66.47%,4次追肥后W2N2+DCD、W2N3+DCD和W2N4+DCD的氨挥发速率峰值与累积量变化范围较小.不同水氮处理的N2O排放通量的峰值均出现在施肥灌水后的第4d,各追肥时期W2N2+DCD、W2N3+DCD和W2N4+DCD处理,土壤N2O排放通量峰值与N2O累计排放量均显著低于传统水氮处理W1N1,并且3个处理之间不存在显著差异,充分表明优化水氮管理中将氮肥与DCD配施对减少N2O排放起到了显著作用.     

零价铁纳米颗粒对硫酸盐还原菌的杀灭作用研究

在实验条件下通过混合振荡的方式,探究了零价铁纳米颗粒（NZVI）对硫酸盐还原菌（SRB）的杀灭能力和杀灭效果;并通过电镜扫描等手段观察零价纳米铁颗粒与硫酸还原菌形态变化,推测杀灭机制.结果表明,当向油田回注水中分别加入0、1、2、5和10mg/mL的零价铁时,该纳米粒子对硫酸还原菌的杀灭效率分别为0、75.6%、90....     

长江口水环境中纳米颗粒物初探

利用抽滤及切向超滤（cross-flow ultrafiltration,CFUF）技术对长江口水环境中的纳米级颗粒物（NP）进行了有效地分离,对其理化性质进行表征,进而初步探讨了水环境因子对NP理化特性的影响机制.结果表明,长江口水环境中NP粒径变化范围为69.5～263.5 nm,平均值为157.3 nm;Zeta...     

Accumulation and elimination of iron oxide nanomaterials in zebrafish (Danio rerio) upon chronic aqueous exposure

A 52-day continuous semi-static waterborne exposure (test media renewed daily) regimen was employed to investigate the accumulation and elimination profiles of two iron oxide nanomaterials (nano-Fe₂O₃ and nano-Fe₃O₄) in zebrafish (Danio rerio). Adult zebrafish were exposed to nanomaterial suspensions with initial concentrations of 4.0 and 10.0 mg/L for 28 days and then were moved to clean water for 24 days to perform the elimination experiment. Fe content was measured in fish body and feces to provide data on accumulation and elimination of the two iron oxide nanomaterials in zebrafish. The experiment revealed that: (1) high accumulation of nano-Fe₂O₃ and nano-Fe₃O₄ were found in zebrafish, with maximum Fe contents, respectively, of 1.32 and 1.25 mg/g for 4.0 mg/L treatment groups and 1.15 and 0.90 mg/g for 10.0 mg/L treatment groups; (2) accumulated nanoparticles in zebrafish can be eliminated efficiently (the decrease of body burden of Fe conforms to a first-order decay equation) when fish were moved to nanoparticle-free water, and the elimination rates ranged from 86% to 100% by 24 days post-exposure; and (3) according to analysis of Fe content in fish excrement in the elimination phase, iron oxide nanomaterials may be adsorbed via the gastrointestinal tract, and stored for more than 12 days.     

Effects of surfactants on graphene oxide nanoparticles transport in saturated porous media

Transport behaviors of graphene oxide nanoparticles (GONPs) in saturated porous media were examined as a function of the presence and concentration of anionic surfactant (SDBS) and non-ionic surfactant (Triton X-100) under different ionic strength (IS). The results showed that the GONPs were retained obviously in the sand columns at both IS of 50 and 200 mmol/L, and they were more mobile at lower IS. The presence and concentration of surfactants could enhance the GONP transport, particularly as observed at higher IS. It was interesting to see that the GONP transport was surfactant type dependent, and SDBS was more effective to facilitate GONP transport than Triton X-100 in our experimental conditions. The advection–dispersion–retention numerical modeling followed this trend and depicted the difference quantitatively. Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction calculations also were performed to interpret these effects, indicating that secondary minimum deposition was critical in this study.     

Comparison studies of adsorption properties of MgO nanoparticles and ZnO–MgO nanocomposites for linezolid antibiotic removal from aqueous solution using response surface methodology

In this investigation, the adsorption measure of linezolid antibiotic onto MgO nanoparticles and ZnO–MgO nanocomposites were performed. The adsorbents were characterized by different techniques such as XRD, SEM, TEM and BET. The parameters influence such as the pH, adsorbent dosage and temperature was tested and evaluated by Box–Behnken Design combined with response surface methodology. Performing adsorption tests at optimal conditions set as 0.5 g L⁻¹ of adsorbent, pH 10 and 308 K make admit to obtain high adsorption turnover (123.45 and 140.28 mg g⁻¹ for MgO nanoparticles and ZnO–MgO nanocomposites, respectively). A good compromise between predicted and experimental data in this research was observed. The experimental equilibrium data fitting to Langmuir, Freundlich, Tempkin and Dubinin–Radushkevich models indicate that the Langmuir model is a best model for evaluation of adsorption behavior. Kinetic evaluation of experimental data indicated that the adsorption operations followed well pseudo-second-order models. The adsorption capacity of ZnO–MgO nanocomposites is higher than MgO nanoparticles that because of the ZnO–MgO nanocomposites have high specific surface area.     

Distributed generation by energy from waste technology: A life cycle perspective

Municipal Solid Waste in general and its organic fraction in particular is a potential renewable and non-seasonal resource. In this work, a life cycle assessment has been performed to evaluate the environmental impacts of two future scenarios using biogas produced from the organic fraction of municipal solid waste (OFMSW) to supply energy to a group of dwellings, respectively comprising distributed generation using solid oxide fuel cell (SOFC) micro-CHP systems and condensing boilers. The London Borough of Greenwich is taken as the reference case study. The system is designed to assess how much energy demand can be met and what is the best way to use the digestible waste for distributed energy purposes.The system is compared with two alternative scenarios fuelled by natural gas: a reference scenario, where the electricity is supplied by the grid and the heat is supplied from condensing boilers, and a fuel cell micro-CHP system. The results show that, although OFMSW alone can only supply between 1% and 4% of the total energy demand of the Borough, a saving of ∼130 tonnes of CO₂ eq per year per dwelling equipped with micro-CHP is still achievable compared with the reference scenario. This is primarily due to the surplus electricity produced by the fuel cell when the micro-CHP unit is operated to meet the heat demand. Use of biogas to produce heat only is therefore a less desirable option compared with combined heat and power production. Further investigation is required to identify locally available feedstock other than OFMSW in order to increase the proportion of energy demand that can be met in this way.     

Intracellular biosynthesis of Au and Ag nanoparticles using ethanolic extract of Brassica oleracea L. and studies on their physicochemical and biological properties

In this present study, we reported broccoli (Brassica oleracea L.) as a potential candidate for the synthesis of gold and silver nanoparticles (NPs) in green chemistry method. The synthesized metal nanoparticles are evaluated their antimicrobial efficacy against different human pathogenic organisms. The physico-chemical properties of gold nanoparticles were analyzed using different analytical techniques such as a UV-Vis spectrophotometer, Field Emission Scanning Electron Microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and a Fourier Transform Infrared spectrophotometer. In addition, gold and silver NP antimicrobial efficacy was checked by disc diffusion assay. UV-Vis color intensity of the nanoparticles was shown at 540 and 450 nm for gold and silver nanoparticles respectively. Higher magnification of the Field Emission Scanning Electron Microscopy image shows the variable morphology of the gold nanoparticles such as spherical, rod and triangular shapes and silver nanoparticles were seen in spherical shapes. The average spherical size of the particles was observed in 24- 38 nm for gold and 30-45 nm for silver NPs. X-ray diffraction pattern confirmed the presence of gold nanoparticles and silver nanoparticles which were crystalline in nature. Additionally, the functionalmetabolites were identified by the Fourier TransformInfrared spectroscopy. IR spectra revealed phenols, alcohols, aldehydes (sugar moieties), vitamins and proteins are present in the broccoli extract which are accountable to synthesize the nanoparticles. The synthesized gold and silver NPs inhibited the growth of the tested bacterial and fungal pathogens at the concentration of 50 μg/mL respectively. In addition, broccoli mediated gold and silver nanoparticles have shown potent antimicrobial activity against human pathogens. © 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.     

Methane and nitrous oxide emissions from a subtropical coastal embayment (Moreton Bay,Australia)

Surface water methane (CH₄) and nitrous oxide (N₂O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010–2012. Water–air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH₄ and N₂O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH₄ and N₂O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH₄ varied between 500% and 4000% saturation while N₂O varied between 128 and 255% in the two bays. Average seasonal CH₄ fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH₄/(m²·day) while N₂O varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N₂O/(m²·day). Weighted emissions (t CO₂-e) were 63%–90% N₂O dominated implying that a reduction in N₂O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas (GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH₄ and N₂O and puts the estimated fluxes into the global context with measurements done from other climatic regions.     

Role of nitric oxide in the genotoxic response to chronic microcystin-LR exposure in human–hamster hybrid cells

Microcystin-LR (MC-LR) is the most abundant and toxic microcystin congener and has been classified as a potential human carcinogen (Group 2B) by the International Agency for Research on Cancer. However, the mechanisms underlying the genotoxic effects of MC-LR during chronic exposure are still poorly understood. In the present study, human–hamster hybrid (A_L) cells were exposed to MC-LR for varying lengths of time to investigate the role of nitrogen radicals in MC-LR-induced genotoxicity. The mutagenic potential at the CD59 locus was more than 2-fold higher (p < 0.01) in A_L cells exposed to a cytotoxic concentration (1 μmol/L) of MC-LR for 30 days than in untreated control cells, which was consistent with the formation of micronucleus. MC-LR caused a dose-dependent increase in nitric oxide (NO) production in treated cells. Moreover, this was blocked by concurrent treatment with the NO synthase inhibitor N^G-methyl-l-arginine (l-NMMA), which suppressed MC-LR-induced mutations as well. The survival of mitochondrial DNA-depleted (ρ⁰) A_L cells was markedly decreased by MC-LR treatment compared to that in A_L cells, while the CD59 mutant fraction was unaltered. These results provided clear evidence that the genotoxicity associated with chronic MC-LR exposure in mammalian cells was mediated by NO and might be considered as a basis for the development of therapeutics that prevent carcinogenesis.