Experimental and density functional theory study of the adsorption of N2O on ion-exchanged ZSM-5: Part II. The adsorption of N2O on main-group ion-exchanged ZSM-5

The adsorption and desorption of N2O on main-group ion-exchanged ZSM-5 was studied using temperature-programmed desorption (TPD) and density functional theory (DFT) calculations. TPD experiments were carried out to determine the desorbed temperature Tmax corresponding to the maximum mass intensity of N2O desorption peak and adsorption capacity of N2O on metal-ion-exchanged ZSM- 5s. The results indicated that Tmax followed a sequence of Ba2+ > Ca2+ > Cs+ > K+ > Na+ > Mg2+and the amount of adsorbed N2O on main-group metal cation followed a sequence of Ba2+ > Mg2+ > Ca2+ > Na+ > K+ > Cs+. The DFT calculations were performed to obtain the adsorption energy (Eads), which represents the strength of the interaction between metal cations and the N-end or O-end of N2O. The calculation results showed that the N-end of the N2O molecule was favorably adsorbed on ion-exchanged ZSM-5, except for Cs-ZSM-5. For alkali metal cations, the Eads of N2O on cations followed the order which was the same to that of Tmax: Cs+ > K+ > Na+. The calculated and experimental results consistently showed that the adsorption performances of alkaline-earth metal cations were better than those of alkali metal cations.     

Ambient air quality trends and driving factor analysis in Beijing, 1983-2007

The interaction between pollution sources change and implementation of air pollution control measures was the main driving factor that caused the variation in air quality.     

Ambient air quality trends and driving factor analysis in Beijing, 1983–2007

The rapid development in Beijing, the capital of China, has resulted in serious air pollution problems. Meanwhile great efforts have been made to improve the air quality, especially since 1998. The variation in air quality under the interaction of pollution and control in this mega city has attracted much attention. We analyzed the changes in ambient air quality in Beijing since the 1980’s using the Daniel trend test based on data from long-term monitoring stations. The results showed that different polluta...     

几种植物对水产养殖废水的修复效果

文章研究了凤眼莲、轮叶黑藻、香根草和水蕹菜四种水生植物在亚热带气候条件下净化水产养殖废水的效果,跟踪比较了一个月之内它们处理污水时,水体氮、磷、化学需氧量、pH值和溶解氧的变化,并对实验前后植物鲜重做了比较。结果表明:(1)4种植物均能强化水产养殖废水污染物的去除,但各有特点;(2)理论上凤眼莲和轮叶黑藻可在处理废水时相互搭配弥补不足,维持水体中性和较高的DO;(3)植物对废水经过2~3周的处理后,水质明显变好,而植物生长开始减退,应及时收割补种;(4)夏季用水生蕹菜处理废水,不仅改善了水质还能收菜创经济效益。研究结果为探索广东地区在构建人工湿地处理水产养殖废水时植物的选择提供了新的科学依据。     

电子鼻在环境监测中的应用与进展

电子鼻是一种模拟生物嗅觉工作原理的新形仿生检测系统,通常由交叉敏感的气体传感器阵列和适当的模式识别算法组成,可用于检测、分析和鉴别简单或复杂气味.作为新近发展的检测方法,它具有通用、快速、多功能、使用简单、低成本、便携、可自动化和在线监测等优势,在食品加工、环境临测、公共安全和医学诊断等诸多领域得到广泛的应用.随着在线...     

鄱阳湖生态经济区农村生活垃圾的处理主体及功能研究

鄱阳湖生态经济区农村生活垃圾处理现状不容乐观。本文通过对鄱阳湖生态经济区农村垃圾处置现状的调查分析,从农村生活垃圾处理的四个主体：政府、村民、企业、学校等出发,探索四类主体功能实现的途径及方式,即突出政府职能,强化村民主人意识,鼓励企业加入,夯实学校基础,长期坚持,持续推进,以解决垃圾的日益增长与垃圾处理的矛盾,实现政府、群众、企业与环境的共赢,经济、社会、环境效益的统一,共同造就鄱阳湖生态经济区的美好生活。     

渤海石油平台溢油清除专家系统的设计与开发

针对目前渤海石油平台溢油清除技术落后的问题,运用专家系统的理论知识,结合计算机技术、空间信息技术、数据库技术等,建立了相应的事实库、规则库和动态数据库,开发完成了渤海石油平台溢油清除专家系统.利用该系统专家系统的知识库及推理机制,不仅能协助溢油应急人员进行现场作业,而且能够整理和保存溢油清除领域出现的新知识,在渤海石油...     

粉煤灰对含铬废水的吸附研究

通过静态吸附实验,研究原状粉煤灰与粉煤灰滤料对Cr(Ⅵ)的吸附效果的影响,并通过正交实验进行实验结果对比。实验确定粉煤灰滤料的吸附平衡时间为90 min,在pH为3的条件下适于进行吸附实验;同时,粉煤灰滤料的吸附性能优于原状粉煤灰,六价铬溶液的初始浓度、滤料的投加量以及温度的改变对吸附性能具有显著影响,且粉煤灰滤料吸附时所受影响更为明显。     

原子吸收法测定土壤中铅含量的不确定度评定

以原子吸收法测定土壤中铅为例,本文分析了测试过程中不确定度的来源。对各不确定度分量进行评定及合成,并计算得出合成不确定度和扩展不确定度。结果表明,标准储备液配制过程引入的不确定度可以忽略不计。对本测试方法影响较大的不确定度分量是标准溶液稀释使用移液管的精度和微量进样器进样体积以及样品前处理和测定过程中的随机因素引起的相...     

洋山深水港海域水环境的周年变化

洋山深水港是上海国际航运中心的枢纽港,港口建设及外来船舶增加将对洋山深水港海域的水环境产生重要影响,因此,有必要对洋山深水港海域的水环境特征进行调研.2008年对洋山深水港海域的水环境因子进行了周年的调查研究.方差分析结果表明,洋山深水港海域表层水温、溶解氧、pH、盐度、电导率及悬浮物含量均存在明显的季节性变化(p < 0.01),季风和海流在洋山深水港海域水环境变化中具有重要的作用.相关分析结果显示,悬浮物含量与盐度之间没有显著相关性,长江口外泄泥沙的直接扩散,对洋山海区水体含沙量的影响较小,洋山深水港海域含沙量的大小,主要取决于波浪、潮汐及海流对当地浅滩的掀扬及输送.