Molarity provides better clarity – using molar-based data when evaluating chlorinated volatile organic compound impacted sites

Abstract

Chlorinated volatile organic compounds are common constituents observed at many contaminated groundwater sites. Common industry practice has been to measure these constituents in groundwater on a weight concentration basis (e.g. µg/l, mg/l). This paper highlights the use of molar-based concentrations, especially in the case of parent-daughter degradation sequences commonly observed with the chloroethene, chloroethane, and chloromethane families of compounds. Converting to molar-based concentrations provides the practitioner greater insight into groundwater plume behavior including better evaluation of degradation processes, remedial progress, possible commingling, and/or sourcing. For example, this paper provides a tank analogy to evaluate whether the commonly misinterpreted observation of “DCE-stall” may be occurring at a site. Multiple examples of the benefits of using molar-based concentration data are also summarized in a project case study presented herein. As demonstrated in this paper, molarity does provide better clarity and can be a powerful evaluation tool in the groundwater practitioner’s toolbox.     

铁路运输安全的产权分析

由于我国铁路运输安全的复杂性 ,运输安全在改革过程中极有可能沦为“公地悲剧” ,对安全进行产权分析确有必要。分析了一些国家保证铁路运输安全的产权制度安排 ,如英国的“网运分离”后的私有产权路网公司完全负责制、美国的垂直一体化私有产权铁路公司负责和政府安全监管体制、瑞典的非赢利性组织管理和政府安全监管体制以及我国的垂直一体化国有垄断企业 (政府部门 )负责制。笔者认为我国铁路在改革过程中 ,不能忽视运输安全的产权问题 ,应建立适当的运输安全管制体系 ,政府更应该在确保铁路运输安全方面发挥重要作用。     

废水处理中的非传统脱氮途径

根据实验室小型SBR试验的结果，证实存在其它不同于传统的硝化和反硝化的脱氮途径。结合近几年来在生物脱氮理论方面新的研究进展，指出研究非传统脱氮途径的必要性和重要性，其中很有必要的一项工作是需对硝化、反硝化和脱氮过程作出明确的定义。     

气力管道输送在垃圾收运领域的应用研究

气力管道输送应用于垃圾收运在国内尚处于起步阶段,开发该项技术目前还存在一定的技术困难,但若该技术能在环境领域成功应用,它将完全改变传统的垃圾收运模式,大大提高垃圾收集的效率,减小垃圾收运过程中对环境造成的影响。本文主要对该技术的优势及在国内应用的技术困难进行探讨,并在此基础上提出了解决方法。     

上海城市交通建设中的可持续发展战略

城市交通设施建设和交通管理是保证城市可持续发展不可残缺的必要条件之一，故用可持续发展的概念来重新审视交通建设的历史和现状是十分必要的。文章提出了弱持续，中持续和强持续的概念，以此从宏观和微观，供给和需求等方面对上海的交通设施管理状况作了粗浅的分析。     

Multiscale Plume Transport from the Collapse of the World Trade Center on September 11, 2001

The collapse of the world trade center (WTC) produced enhanced levels of airborne contaminants in New York City and nearby areas on September 11, 2001 through December, 2001. This catastrophic event revealed the vulnerability of the urban environment, and the inability of many existing air monitoring systems to operate efficiently in a crisis. The contaminants released circulated within the street canyons, but were also lifted above the urban canopy and transported over large distances, reflecting the fact that pollutant transport affects multiple scales, from single buildings through city blocks to mesoscales. In this study, ground-and space-based observations were combined with numerical weather forecast fields to initialize fine-scale numerical simulations. The effort is aimed at reconstructing pollutant dispersion from the WTC in New York City to surrounding areas, to provide means for eventually evaluating its effect on population and environment. Atmospheric dynamics were calculated with the multi-grid Regional Atmospheric Modeling System (RAMS), covering scales from 250 m to 300 km and contaminant transport was studied using the Hybrid Particle and Concentration Transport (HYPACT) model that accepts RAMS meteorological output. The RAMS/HYPACT results were tested against PM2.5 observations from the roofs of public schools in New York City (NYC), Landsat images, and Multi-angle Imaging SpectroRadiometer (MISR) retrievals. Calculations accurately reproduced locations and timing of PM2.5 peak aerosol concentrations, as well as plume directionality. By comparing calculated and observed concentrations, the effective magnitude of the aerosol source was estimated. The simulated pollutant distributions are being used to characterize levels of human exposure and associated environmental health impacts.     

A new approach to graphical and numerical analysis of links between plant chemotaxonomy and secondary metabolism from HPLC data smoothed by a simplex mixture design

Summary. HPLC analysis of secondary metabolites represents an efficient tool for the studying of plant chemical diversity under different aspects: chemotaxonomy, metabolomics, adaptative responses to ecological factors, etc. Statistical analyses of HPLC databases, e.g. correlation analysis between HPLC peaks, can reliably provide information on the similarity/dissimilarity degrees between the chemical compounds. The similarities, corresponding to positive correlations, can be interpreted in terms of analogies between chemical structures, synchronic metabolisms or co-evolution of two compounds under certain environment conditions, etc. . In terms of metabolism, positive correlations can translate precursor-product relationships between compounds; negative correlations can be indicative of competitive processes between two compounds for a common precursor(s), enzyme(s) or substrate(s). Furthermore, the correlation analysis under a metabolic aspect can help to understand the biochemical origins of an observed polymorphism in a plant species. With the aim of showing this, we present a new approach based on a simplex mixture design, Scheffé matrix, which provides a correlation network making it possible to graphically visualise and to numerically model the metabolic trends between HPLC peaks. The principle of the approach consisted in mixing individual HPLC profiles representative of different phenotypes, then from a complete mixture set, a series of average profiles were calculated to provide a new database with a small variability. Several iterations of the mixture design provided a smoothed final database from which the relationships between the secondary metabolites were graphically and numerically analysed. These relationships were scale-dependent, namely either deterministic or systematic: the first consisted of a monotonic global trend covering the whole variation field of each metabolites’ pair; the second consisted of repetitive monotonic variations which gradually attenuated or intensified along a global trend. This new metabolomic approach was illustrated from 404 individual plants of Astragalus caprinus (Leguminoseae), belonging to four chemical phenotypes (chemotypes) on the basis of flavonoids analysed in their leaves. After smoothing, the relationships between flavonoids were numerically fitted using linear or polynomial models; therefore the co-response coefficients were easily interpreted in terms of metabolic affinities or competitions between flavonoids which would be responsible of the observed chemical polymorphism (the four chemotypes). The statistical validation of the approach was carried out by comparing Pearson correlations to Spearman correlations calculated from the smoothed and the crude HPLC database, respectively. Moreover, the signs of the smoothed relationships were finely supported by analogies and differences between the chemical structures of flavonoids, leading to fluent interpretation in relation to the pathway architecture.     

Lack of theoretical basis for predicting rate and pathways of recovery

An inadequate basis for precisely predicting the outcome of lotic ecosystem recovery, whether due to unaided natural processes or management techniques or both, exists because: (1) the field of ecology has not yet matured as a rigorous predictive science; (2) the precise sequence of events, including climatic occurrences, affecting the recovery process may be unique events and thus rarely or never repeated; and (3) even when attempts are made to control the recolonization process through introduction of species, etc., the interaction of these species may not follow deterministic models. Although this symposium focuses on lotic ecosystems, such systems are influenced strongly by exports from the surrounding land mass and, under certain circumstances, this may be the overriding influence on the recovery process; therefore, unless the boundary conditions are determined realistically, the recovery process may not follow desirable pathways. Despite the lack of a robust theoretical support base for lotic ecosystem recovery, some remarkable and rapid recoveries have occurred to either a close approximation of the original condition or to a condition ecologically superior to the damaged condition. In some cases, the recovery was due entirely to natural processes and, in others, often followed relatively straightforward management practices. There is evidence indicating that lotic ecosystem restoration is both cost effective and likely to produce satisfying results relatively rapidly. It is both fortunate that this is the case, since society is likely to support such efforts when the results have been extraordinarily successful, and unfortunate since restoration ecology needs a predictive capability.     

Transport and degradation of pesticides in a biopurification system under variable flux, part I: A microcosm study

The efficiency of a biopurification system, developed to treat pesticide contaminated water, is to a large extent determined by the chemical and hydraulic load. Insight into the behaviour of pesticides under different fluxes is necessary. The behaviour of metalaxyl, bentazone, linuron, isoproturon and metamitron was studied under three different fluxes with or without the presence of pesticide-primed soil in column experiments. Due to the time-dependent sorption process, retention of the pesticides with intermediate mobility was significantly influenced by the flux. The higher the flux, the slower pesticides will be sorbed, which resulted in a lower retention. Degradation of the intermediate mobile pesticides was also submissive to variations in flux. An increase in flux, led to a decrease in retention, which in turn decreased the opportunity time for biodegradation. Finally, the presence of pesticide-primed soil was only beneficial for the degradation of metalaxyl.     

A longitudinal study of the links between Local Air Quality Management and Local Transport Planning policy processes in England

The second round of the Local Transport Plan (LTP2) process in England presents unique challenges and opportunities for integrating Local Air Quality Management (LAQM) within current transport planning policy. Using content analysis of LTP2 documents from nine English authorities, and results from a questionnaire survey of local government officers undertaken in late 2007, this paper charts the changes in the integration of air quality management within the transport planning process since 1997. While substantial improvements in policy integration were observed within the selected case studies, the paper demonstrates that such improvements are often constrained by institutional complexities that create implementation gaps between national objectives and local decision-making outcomes.