基于生命周期分析的电解铝清洁生产评价指标研究

本文利用生命周期评价对电解铝生产过程进行了全面分析,结合清洁生产的内涵和电解铝生产工艺的系统边界图,从炭素阳极、电解制铝、铝加工和烟气净化等四个子模块出发,把电解铝清洁生产评价指标体系分为五项一级指标,即管理与工艺设备指标、资源消耗指标、产品指标、环境指标、废物回收利用指标,一级指标又分解为13项二级指标和 28项三级指标。     

咸水中胶体迁移-沉积对砂介质渗透性损失的

采用室内土柱试验,研究咸水中胶体迁移引起砂介质渗透性变化的特征,通过胶体迁移-沉积作用的分析对砂介质渗透性损失的机理进行了探讨.结果表明:砂介质渗透性随孔隙体积数变化的动态特征符合Boltzmann函数;砂介质渗透性总的损失率为37.4%;渗透系数的损失量随孔隙体积数的增加而增加.胶体在砂介质中的穿透曲线呈“S”型,其中的2个拐点将曲线分成开始穿透、快速穿透和平稳穿透3个阶段,但并没有完全穿透,其迁移过程中发生了沉积. 胶体沉积作用是砂介质渗透性降低的主要原因.      

Macroinvertebrate and fish populations in a restored impounded salt marsh 21 years after the reestablishment of tidal flooding

During the last two decades, the State of Connecticut has restored tidal flow to many impounded salt marshes. One of the first of these and the one most extensively studied is Impoundment One in the Barn Island Wildlife Management Area in Stonington, Connecticut. In 1990, twelve years after the re-establishment of tidal flooding, the density of the marsh snail Melampus bidentatus, the numerically dominant macroinvertebrate of the high marsh, in Impoundment One was about half that in reference marshes below the breached impoundment dike. By 1999 the densities of Melampus above and below the dike were not significantly different, but the shell-free biomass was greater above the dike as a result of the somewhat larger number and size of the snails there. Twenty-one years after the renewal of tidal flooding, three marsh macroinvertebrates (the amphipods Orchestia grillus and Uhlorchestia spartinophila and the mussel Geukensia demissa) were significantly less abundant in the previously impounded marsh than in the reference marshes, whereas another amphipod (Gammarus palustris) was more abundant above the breached dike where conditions appeared to be somewhat wetter. In 1991 the fish assemblage in a mosquito-control ditch in Impoundment One was similar to that in a ditch below the breached dike; however, the common mummichog Fundulus heteroclitus appeared to be less abundant in the restoring marsh. By 1999 the number of mummichogs caught in ditches was significantly greater in Impoundment One than in the reference marsh, but the numbers of mummichogs trapped along the tidal creek were comparable above and below the dike. The results obtained in this study and those of other restoring marshes at Barn Island indicate the full recovery of certain animal populations following the reintroduction of tidal flow to impounded marshes may require up to two or more decades. Furthermore, not only do different species recover at different rates on a single marsh, but the time required for the recovery of a particular species may vary widely from marsh to marsh, often independently of other species.     

The Impact of Conifer Harvesting on Stream Water Quality: A Case Study in Mid-Wales

A 12-year record of water quality data for runoff from a spruce forested hillslope with podzolic soils shows the impacts of conifer harvesting and replanting in relation to nitrate generation and its influence on surface water acidification. With felling, nitrate increases from a background of 18 Eq/l to about 50 Eq/l after 1 to 2 years and then declines to background levels over the next 1 to 2 years and to lower concentrations thereafter. This change is mirrored by an acidification process as manifest by a change in Gran alkalinity, acid neutralization capacity (ANC) and aluminium concentrations as well as pH. For example, Gran alkalinity and ANC, which start at negative concentrations prior to felling (about –20 and –50 Eq/l, respectively), become more negative (–30 and –100 Eq/l, respectively) at high nitrate concentrations. Correspondingly, pH decreases from about 4.7 to 4.5 and aluminium concentrations increase from about 14 to 16 M. Subsequently, the acidification is reversed as nitrate concentrations decline and after five years post-felling the system has higher pH, Gran alkalinity and ANC together with lower aluminium concentrations than even before the felling took place (the post-felling values are about 4.9, -15 Eq/l, –20 Eq/l and 7 M/l, respectively).Other determinands show clear changes over time. For example, there is a marked increase in sodium and chloride prior to and around the time of felling (200 to 300 and 230 to 400 Eq/l, respectively), with a subsequent decline in concentration to pre-felling and to lower values of around 160 and 170 Eq/l, respectively, thereafter. This change is probably associated with abnormally high inputs of sea-salts from the atmosphere during the first quarter of the year of felling, and dilution thereafter, rather than a direct consequence of the felling activity itself: this change in sea salt loading has had an impact on stream acidity. Dissolved organic carbon and iron also change with concentrations increasing over time (60 to 200 and 1.0 to 1.5 M/l, respectively) and this mirrors a general pattern observed across the Plynlimon catchments irrespective of whether or not there has been felling activity.The implications of the findings are discussed in relations to environmental management and hydrochemical processes.     

天然气再燃添加有机酸盐同时降低SO2及NOx的机理研究

对天然气再燃过程中添加的有机酸盐同时脱硫、脱氮反应途径及机理进行了详细的分析.探讨了有机酸盐(钙镁醋酸盐CMA)分解的CHi还原NO的主要机理,研究了CMA固硫的反应机理,分析了脱硫过程影响HCN、NH3还原NO的因素.提出了天然气再燃添加CMA同时脱硫、脱氮时,也要综合考虑CaO对SO2的脱除和对NO生成的促进作用.     

膜蒸馏淡化西部苦咸水应用技术研究

膜蒸馏是将膜与蒸馏过程相结合的分离方法,是一种节能高效的分离技术。本文从其过程机理出发,展望了该技术在苦咸水淡化技术中应用的前景。     

无机盐对表面活性剂淋洗疏水性有机污染物的影响机理

表面活性剂淋洗法是去除土壤中疏水性有机污染物的一种有效方法。在简要介绍表面活性剂淋洗法去除作用机理的基础上,从增流和增溶两方面,讨论了无机盐对表面活性剂淋洗法去除疏水性有机污染物的影响机理。     

使用融雪剂除雪给环境带来的危害分析

针对北方城市冬季普遍使用融雪剂来融化道路上的积雪、有效改善雪后道路交通状况,但同时也带来了一系列的环境污染问题的现状,依据相关资料,并结合丹东市具体情况,对使用融雪剂除雪给环境带来的危害进行分析,并提出对策建议。     

提高柠檬酸钠净化甲苯废气效率的实验研究

以柠檬酸钠溶液为吸收剂,添加三种不同的添加剂在填料塔中进行了吸收法净化含甲苯有机废气的实验研究。在相同的工艺条件下,分别研究了添加柠檬酸,无机盐助剂、聚乙二醇(PEG200)以及三者的组成对柠檬酸钠吸收剂去除甲苯效果的影响。实验结果表明,当5%柠檬酸钠吸收剂分别添加柠檬酸时pH=6,无机盐0.05%硅酸钠、0.1%磷酸钠和0.1%碳酸钠,0.5%聚乙二醇时,对甲苯净化效率及吸收容量都有显著提高。当三种添加剂组合时效果更佳。     

海盐粒子含量测定方法对比研究

为了探讨海盐粒子含量采用不同测定方法的变化趋势和规律,采用纱布法和湿烛法这2种采集分析方法,测定了海南三亚、万宁、厦门和青岛4类大气环境中海盐粒子含量。通过对测定数据的讨论与研究,分析了在不同海域、不同环境气候条件下海盐粒子含量变化趋势和变化规律,探讨了2种采集分析方法之间的相关关系。