Direct N2O decomposition over La2NiO4-based perovskite-type oxides

Direct decomposition of N₂O by perovskite-structure catalysts including La₂NiO₄, LaSrNiO₄, and La_0.7Ce_0.3SrNiO₄ was investigated. The catalysts were prepared by the Pechini method and characterized by x-ray diffraction (XRD), BET, scanning electron microscopy (SEM), and O₂-TPD. Experimental results indicate that the properties of La₂NiO₄ are significantly improved by partially substituting La with Sr and Ce. N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ are 44 and 36%, respectively, at 400ºC. As the temperature was increased to 600ºC, N₂O decomposition efficiency achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ reached 100% at an inlet N₂O concentration of 1,000 ppm, while the space velocity was fixed at 8,000 hr^?1. In addition, effects of various parameters including oxygen, water vapor, and space velocity were also explored. The results indicate that N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ are not significantly affected as space velocity is increased from 8,000 to 20,000 hr^?1, while La_0.7Ce_0.3SrNiO₄ shows better tolerance for O₂ and H₂O_(g). On the other hand, N₂ yield with LaSrNiO₄ as catalyst can be significantly improved by doping Ce. At a gas hour space velocity of 8,000 hr^?1, and a temperature of 600ºC, high N₂O decomposition efficiency and N₂ yield were maintained throughout the durability test of 60 hr, indicating the long-term stability of La_0.7Ce_0.3SrNiO₄ for N₂O decomposition.

Implications:Nitrous oxide (N₂O) not only has a high global warming potential (GWP₁₀₀ = 310), but also potentially destroys ozone in the stratosphere. Pervoskite-type catalysts including La₂NiO₄, LaSrNiO₄, and La_0.7Ce_0.3SrNiO₄ are applied for direct N₂O decomposition. The results show that N₂O decomposition can be enhanced as Sr and Ce are doped into La₂NiO₄. At 600ºC, N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ reach 100%, demonstrating high activity and good potential for direct N₂O decomposition. Effects of O₂ and H₂O_(g) contents on catalytic activities are also evaluated and discussed.     

多环芳烃的几种理化参数与LC_(50)的相关性研究

对多环芳烃(PAHS)4种理化参数(K;W、Sw。X Vv。)与 LCO的相关关系进行了研究,建立了 4种一元线性回归方程。结果表明,4种参数的相关系数分别为:0.刀66、08083、09488、0.9570,经r检验,后两种属高度显著相关.用所建立的一元线性回归方程对7种PAHS的LC。进行估算,估算值与实测值相比,平均相对误差分别为58.84％、32.23％、1761％、198％,用l和V＊.H对LClj进行估算的估算精度也较高。经比较,提出用(。估算P＊比对麦穗鱼＊CO的新方法。     

人工神经网络方法用于城市环境空气质量综合评价

采用人工神经网络技术,建立了城市环境空气质量综合评价的ANN模型,并通过实例对建立的评价模型进行验证。结果证明,ANN模型用于区域环境空气质量评价,其评价结果比较直观。同时,对在建立和应用ANN模型时应注意的一些问题进行了讨论。     

Occurrence and behaviour of nonylphenol and octylphenol in Nanming River, Guiyang City, China

Occurrence, variation and behaviour of nonylphenol (NP) and octylphenol (OP) were studied in surface water and groundwater in Guiyang, Guizhou Province, southwestern China. Discharge of wastewater from Guiyang City was the main source of alkylphenols (APs) entering the aquatic environment. The concentrations of NP and OP in river water ranged from 40 to 1582 ng L(-1) and from below the lowest limit of detection (LOD) to 67 ng L(-1), respectively. NP and OP were also detected in groundwater. Both NP and OP exhibited spatial and temporal variations in river water and groundwater. It was found that concentrations of NP and OP in river water was low upstream and dramatically increased downstream, and higher concentration of NP was found in winter compared to that in summer. Proportions of NP and OP were trapped by suspended particulate matter (SPM), which accounted for 7.6-50.0% and 3.4-25.6% of their total concentration in the river water system, respectively. Seasonal changes in water flow were responsible for the temporal variations of APs. To determine the behaviour of APs along the river, a mass balance equation based on chloride was used. The results showed that a mixing process was the predominant factor to determine upstream APs concentrations; while the discharge of wastewater controlled the concentrations of APs downstream. Considering the adverse effect of APs on organisms, combined effect modeling was used to assess the toxicity to fish. It was found that the predicted mixture effect for APs in river water on fish vitellogenin induction was low upstream and medium downstream, respectively.     

DBD降解CF2ClBr过程中自由基与电子能量

利用介质阻挡放电方法对环境污染物CF2ClBr进行了等离子体降解的研究.在前人对该体系的降解产物分析及活性粒子推测的基础上,采用动态反应装置得到了等离子体的发射光谱,进一步确证了等离子体系中出现的CF2、CFCl、F、Cl、Br等主要自由基,并从中推出了等离子态气体可能发生的自由基反应.同时通过发射光谱的分析,近似得到该体系的平均电子能量约为2.42eV.     

战略环境评价及其应用初探

概述了战略环境价的概念、产生原因、研究现状及其工作程序，结合川南矿肥工程项目对它进行了应用初探，提出了计划、规划层次ＳＥＡ的方法和指标，并对我国环评工作提出了建议。     

烟气脱硝技术及在我国的应用

氮氧化物气体是危害最大、最难处理的大气污染物之一。随着经济的发展,有效控制燃煤造成的大气污染已经刻不容缓,特别是控制燃煤过程中的氮氧化物,烟气脱硝技术显得相当重要。本文分析了几种常用的烟气脱硝技术（选择性催化还原脱硝技术、选择性非催化还原脱硝技术、碱性溶液吸收法和等离子体活化法等）的原理、技术特点以及在我国的应用情况。     

Characterization of on-road vehicle emission factors and microenvironmental air quality in Beijing,China

In this paper, we report the results and analysis of a recent field campaign in August 2007 investigating the impacts of emissions from transportation on air quality and community concentrations in Beijing, China. We conducted measurements in three different environments, on-road, roadside and ambient. The carbon monoxide, black carbon and ultrafine particle number emission factors for on-road light-duty vehicles are derived to be 95 g kg^?1-fuel, 0.3 g kg^?1-fuel and 1.8 × 10¹⁵ particles kg^?1-fuel, respectively. The emission factors for on-road heavy-duty vehicles are 50 g kg^?1-fuel, 1.3 g kg^?1-fuel and 1.1 × 10¹⁶ particles kg^?1-fuel, respectively. The carbon monoxide emission factors from this study agree with those derived from remote sensing and on-board vehicle emission testing systems in China. The on-road black carbon and particle number emission factors for Chinese vehicles are reported for the first time in the literature. Strong traffic impacts can be observed from the concentrations measured in these different environments. Most clear is a reflection of diesel truck traffic activity in black carbon concentrations. The comparison of the particle size distributions measured at the three environments suggests that the traffic is a major source of ultrafine particles. A four-day traffic control experiment conducted by the Beijing Government as a pilot to test the effectiveness of proposed controls was found to be effective in reducing extreme concentrations that occurred at both on-road and ambient environments.     

Part V—sorption of pharmaceuticals and personal care products

Background, aim, and scope  Pharmaceuticals and personal care products (PPCPs) including antibiotics, endocrine-disrupting chemicals, and veterinary pharmaceuticals are emerging pollutants, and their environmental risk was not emphasized until a decade ago. These compounds have been reported to cause adverse impacts on wildlife and human. However, compared to the studies on hydrophobic organic contaminants (HOCs) whose sorption characteristics is reviewed in Part IV of this review series, information on PPCPs is very limited. Thus, a summary of recent research progress on PPCP sorption in soils or sediments is necessary to clarify research requirements and directions. Main features  We reviewed the research progress on PPCP sorption in soils or sediments highlighting PPCP sorption different from that of HOCs. Special function of humic substances (HSs) on PPCP behavior is summarized according to several features of PPCP–soil or sediment interaction. In addition, we discussed the behavior of xenobiotic chemicals in a three-phase system (dissolved organic matter (DOM)–mineral–water). The complexity of three-phase systems was also discussed. Results  Nonideal sorption of PPCPs in soils or sediments is generally reported, and PPCP sorption behavior is relatively a more complicated process compared to HOC sorption, such as the contribution of inorganic fractions, fast degradation and metabolite sorption, and species-specific sorption mechanism. Thus, mechanistic studies are urgently needed for a better understanding of their environmental risk and for pollution control. Discussion  Recent research progress on nonideal sorption has not been incorporated into fate modeling of xenobiotic chemicals. A major reason is the complexity of the three-phase system. First of all, lack of knowledge in describing DOM fractionation after adsorption by mineral particles is one of the major restrictions for an accurate prediction of xenobiotic chemical behavior in the presence of DOM. Secondly, no explicit mathematical relationship between HS chemical–physical properties, and their sorption characteristics has been proposed. Last but not least, nonlinear interactions could exponentially increase the complexity and uncertainties of environmental fate models for xenobiotics. Discussion on proper simplification of fate modeling in the framework of nonlinear interactions is still unavailable. Conclusions  Although the methodologies and concepts for studying HOC environmental fate could be adopted for PPCP study, their differences should be highly understood. Prediction of PPCP environmental behavior needs to combine contributions from various fractions of soils or sediments and the sorption of their metabolites and different species. Recommendations and perspectives  More detailed studies on PPCP sorption in separated soil or sediment fractions are needed in order to propose a model predicting PPCP sorption in soils or sediments based on soil or sediment properties. The information on sorption of PPCP metabolites and species and the competition between them is still not enough to be incorporated into any predictive models.     

Incorporating layer- and local-scale heterogeneities in numerical simulation of unsaturated flow and tracer transport

This study characterizes layer- and local-scale heterogeneities in hydraulic parameters (i.e., matrix permeability and porosity) and investigates the relative effect of layer- and local-scale heterogeneities on the uncertainty assessment of unsaturated flow and tracer transport in the unsaturated zone of Yucca Mountain, USA. The layer-scale heterogeneity is specific to hydrogeologic layers with layerwise properties, while the local-scale heterogeneity refers to the spatial variation of hydraulic properties within a layer. A Monte Carlo method is used to estimate mean, variance, and 5th, and 95th percentiles for the quantities of interest (e.g., matrix saturation and normalized cumulative mass arrival). Model simulations of unsaturated flow are evaluated by comparing the simulated and observed matrix saturations. Local-scale heterogeneity is examined by comparing the results of this study with those of the previous study that only considers layer-scale heterogeneity. We find that local-scale heterogeneity significantly increases predictive uncertainty in the percolation fluxes and tracer plumes, whereas the mean predictions are only slightly affected by the local-scale heterogeneity. The mean travel time of the conservative and reactive tracers to the water table in the early stage increases significantly due to the local-scale heterogeneity, while the influence of local-scale heterogeneity on travel time gradually decreases over time. Layer-scale heterogeneity is more important than local-scale heterogeneity for simulating overall tracer travel time, suggesting that it would be more cost-effective to reduce the layer-scale parameter uncertainty in order to reduce predictive uncertainty in tracer transport.