Low-infiltration housing in Rochester, New York: A study of air-exchange rates and indoor air quality

A sample of 58 occupied homes in Rochester, NY, most of which incorporated special builder-designed weatherization components, were studied to assess (1) the effectiveness of construction techniques designed to reduce air leakage; (2) the indoor air quality and air-exchange rates in selected airtight houses, and (3) the impact on indoor air quality of mechanical ventilation systems employing air-to-air heat exchangers. The “specific leakage area” was measured in each house using the fan pressurization technique. Houses built with polyethylene vapor barriers and joint-sealing were as a group 50% tighter than a similar group of houses without such components. Mechanical ventilation systems with air-to-air heat exchangers were installed in nine relatively airtight houses, some of which had gas stoves and/or tobacco smoking occupants. Air-exchange rates and indoor concentrations of radon (Rn), formaldehyde (HCHO), nitrogen dioxide (NO₂), and humidity were measured in each house for 1-week periods with and without mechanical ventilation. More detailed measurements, including concentrations of carbon monoxide and inhalable particulates, were made in two of these houses by a mobile laboratory. In all nine houses, air-exchange rates were relatively low (0.2–0.5 ach) without mechanical ventilation, and yet indoor concentrations of Rn, HCHO, and NO₂ were below existing guidelines. Mechanical ventilation systems were effective in further reducing indoor contaminant concentrations. We conclude that when contaminant source strengths are low, acceptable indoor air quality can be compatible with low air-exchange rates.     

A CO2-controlled ventilation system

For buildings in which the emissions from people is the main source of pollution, the number of people is the limiting factor for air ventilation. When such buildings are not used at full capacity, the ventilation, and consequently the energy consumption, is unnecessarily high. A great deal of the energy could be saved if the ventilation system could be developed to adjust the air flow to the actual requirements. One possible system would allow the amount of CO₂ in the exhaust air to control the ventilation rate. To study if this principle is practicable and economic, a CO₂ indicator has been installed in an office building in Helsinki. The mixture of exterior air and recirculated air is adjusted so that the amount of CO₂ during working hours is kept on ca 700 ppm (μL/L). The equipment was used during winter 1981-82, and the variation of CO₂ and the exterior air flow has been registered. The proportion of CO₂ has also been measured locally in order to study occasional variations that may occur. The proportion of other pollutants in the room air has been studied simultaneously with a gas chromatograph. Different types of CO₂ indicators were used to study the efficiency of the control system. The successful results indicate that the system can be used in new constructions, as well as in existing buildings.     

Methods for control of indoor air quality

This report presents results of a review of available methods for control of environmental hazards applied to indoor air pollutants. Indoor air pollution originates from transport of ambient outdoor air contaminants into occupied spaces by natural infiltration ventilation, or by mechanical ventilation using outdoor makeup air, plus contributions from indoor emission sources. When air exchange with the external ambient environment is reduced to conserve energy, contributions from indoor emission sources may dominate indoor air pollutant levels. This paper identifies alternative methods available to control indoor air pollutant exposures. The performance characteristics of ventilation systems and of air cleaning devices used in mixed modes for ventilation of occupied spaces are described. Models for predicting effectiveness of several alternative modes are reviewed, with field trial validation results cited where available. Results of previous confined-space studies are briefly reviewed as points of departure for consideration of necessary air quality, ventilation, and air cleaning. Understanding of indoor air contaminant generation and controls is aided by examination of earlier studies of indoor air quality, using modern perspectives on occupational environmental health and hygiene.     

Analysis of priority pollutants at a primary aluminum production facility

This paper investigated the source of priority pollutants, assessment of the wastewater treatment plant, and priority pollutant removal efficiency for a single Soderberg-type primary aluminum plant.Forty-eight hour composite samples were collected from the following streams: (1) plant intake water; (2) wastewater from the primary air pollution control system (gas stream cooling water and wet ESPs); (3) secondary air pollution control system (room ventilation wet scrubber liquor); (4) paste plant briquette cooling water; and (5) final effluent after the wastewater treatment plant.Wastewater from the primary air pollution control system entered a conventional chemical coagulation (using slacked lime) — clarification plant. Clarified water from the clarifier was combined with the other three wastewater streams and flowed into a settling lagoon with a 20-h hydraulic retention time. Clarified lagoon water was finally discharged to the river.The principal source of organic compounds in the wastewater was from the primary and secondary air pollution control systems and results from the volatilization of petroleum coke and pitch in the Soderberg anode. Wastewater treatment plant removal efficiencies of greater than 85% were achieved for the majority of the organic priority pollutant species detected.     

Distinguishing between healthy and sick preschools by chemical classification

The Swedish building code of 1975 emphasizes energy conservation and encourages the construction of tightly insulated structures with adequate ventilation systems. Some of the new buildings constructed along these guidelines have been labeled “sick,” because people working in them report an unusual number of health problems—e.g., eye irritation, skin rashes, and fatigue. One possible indicator of whether a building is “healthy” or “sick” may exist in the pattern of chemicals present in the air. This article outlines an approach designed to find sets of chemicals that can be used to separate buildings according to their designation as sick and healthy. Air samples were taken from a healthy and sick preschool and subsequently analyzed by gas chromatography. The prevalence of different chemical substances was determined and compared across 16 different locations from which air samples were obtained, including outdoor, supply, room, and exhaust air. In all, 158 different chemical substances were found; more in the healthy building than in the sick one. Cluster analysis, based on the pattern of presence and absence of chemicals, was able to separate locations within and between the two types of building. A large number of chemicals (approx. one-half the total) were effective in distinguishing among locations. The ten most critical chemicals in this respect were subjected to more complete statistical analysis in order to highlight further possible differences between the buildings. The general approach described may prove useful in recognizing the environmental conditions associated with the “sick building syndrome.”     

基于共同前沿SBM模型的农业用水效率测度及改善潜力

为了实现农业水资源可持续利用和保障国家粮食安全,地区必须提高农业用水效率。基于共同前沿下的非期望产出SBM模型,对中国31个省市1998~2015年农业用水效率进行了测算,在综合考虑各地农业资源承载力、环境容量、生态类型和发展基础等因素的基础上,将中国各地区进行分组,分别考虑了各组区域下农业用水效率的差异性、变动趋势以及改善潜力。结果表明：共同前沿下,各组农业用水效率值从高到低排列依次为保护发展区、优先发展区和适度发展区,其多年均值分别为0.623,0.568和0.432。这表明,如果采用潜在的最优生产技术,三大区域将分别平均有37.7%、43.2%和56.8%的效率提升空间,改善潜力巨大。管理无效和技术无效是导致地区农业用水效率损失的两大来源,优先发展区效率损失主要是由管理无效造成,完善管理制度和提高管理运营水平是促进农业用水效率改善的重要策略,保护发展区和适度发展区效率损失的原因则具有多样性,管理无效和技术无效二者皆有,因此需要结合技术和管理双角度来设计效率改善策略。     

Estimation of optimum requirements for indoor air quality and energy consumption in some residences in Kuwait.

Contrasting effects of the dilution of indoor generated pollutants and the energy efficiency of heating and ventilating air conditioning systems (HVAC) for indoor air quality (IAQ) and thermal comfort were studied for 10 Kuwaiti residences. The levels of volatile organic compounds (VOCs) and the calculated cooling load of the HVAC systems were used as indicators for the IAQ and for the energy consumption, respectively. Air exchange rates and VOCs levels (both indoor and outdoor) were measured. It was found that the outdoor VOC concentrations were always less than the indoor values. Therefore reduction of indoor VOC levels can be accomplished either by increasing the ratio of the makeup air to the recirculation air of the HVAC system or by increasing the infiltration airflow rate through openings. A single compartment IAQ model, modified by the authors, was used to test for the variation in the above two dilution modes and to test the performance sensitivity. Hence, the optimum parameters in terms of IAQ and energy consumption were determined. The results indicated that it was necessary to increase the ratio of the makeup air to the recirculation air from its typical design value of 0.5 to a range of 0.7-1.3 in order to reduce indoor VOC to acceptable levels.     

Using radon-222 as indicator for the evaluation of the efficiency of groundwater remediation by in situ air sparging

A common approach for remediation of groundwater contamination with volatile organic compounds (VOCs) is contaminant stripping by means of in situ air sparging (IAS). For VOC stripping, pressurized air is injected into the contaminated groundwater volume, followed by the extraction of the contaminant-loaded exhaust gas from the vadose soil zone and its immediate on-site treatment. Progress assessment of such remediation measure necessitates information (i) on the spatial range of the IAS influence and (ii) on temporal variations of the IAS efficiency. In the present study it was shown that the naturally occurring noble gas radon can be used as suitable environmental tracer for achieving the related spatial and temporal information. Due to the distinct water/air partitioning behaviour of radon and due to its straightforward on-site detectability, the radon distribution pattern in the groundwater can be used as appropriate measure for assessing the progression of an IAS measure as a function of space and time. The presented paper discusses both the theoretical background of the approach and the results of an IAS treatment accomplished at a VOC contaminated site lasting six months, during which radon was applied as efficiency indicator.     

长江经济带大气环境效率的时空异质性与驱动因素研究

将大气污染物视为“坏”产出,基于SBM-Undesirable模型与Global Malmqusit-Luenberger（GML）生产率指数实证测算2006~2015年间长江经济带11省市的大气环境效率与大气环境全要素生产率,并考察其时空异质特征与驱动因素,利用泰尔指数分解方法揭示大气环境效率地区差距的形成根源,通过构建“效率-生产率”矩阵分析长江经济带各省市大气环境效率提升的优势与不足。结果表明：长江经济带大气环境效率整体水平偏低,不同地区差异较大且在考察期间维持了下降趋势,大气污染减排潜力巨大;长江上游、中游与下游三大地区之间差距与长江上游地区内部省市之间差距是长江经济带大气环境效率地区差距形成的主要根源;大气环境全要素生产率提升完全依靠技术进步来驱动,技术效率恶化是长江经济带大气环境生产率提升的主要障碍;不同省市大气环境效率提升的优势与不足存在差异,因而必须因地制宜地制定大气污染防治对策。研究结论可以为长江经济带改善大气环境质量、促进经济社会可持续发展提供决策依据。 关键词： 长江经济带;大气环境效率;时空异质性;驱动因素     

基于DEA的中国农地非农化效率及其变化

基于DEA和Malmquist TFP指数模型方法研究分析2000～2008年我国省域和区域层面农地非农化效率及其变化,为优化土地利用提供参考。研究结果表明：（1）省域层面各项平均效率水平一般,超过80%的省份农地非农化综合效率未达到有效状态;（2）农地非农化效率总体呈现东部地区>东北地区>中部地区>西部地区的状态,区域差距呈现缩小趋势;（3）农地非农化平均综合效率的提升主要源于纯技术效率的贡献,而生产效率的明显改善得益于技术进步;（4）东部和东北地区农地非农化综合效率有所下降,中西部地区综合效率呈现上升趋势,西部地区上升显著。通过研究发现：现阶段我国农地非农化存在要素资源的利用不充分现象,效率提升潜力较大;西部地区农地非农化规模集聚能力与其他地区差距较大;东部地区存在农地非农化效率损失;虽然中西部地区农地非地化效率变化提升明显,但能否成为农地非农化指标增加的依据还值得进一步探讨     

Efficient ventilation in office rooms

Results from a two-box model for calculation of tracer gas concentrations in rooms are given and consequences of different definitions of “ventilation efficiency” are discussed. Results from three different series of experiments are presented. The first two series were dilution experiments; examples of the results are given and discussed. The third series of tests was performed with one person working at a desk in the test room. Above the person;s head, a tracer gas (N₂O) was injected into the convection plume, with as low momentum as possible. Starting with zero concentration, a test continued until steady-state conditions were established for the concentration levels in the different parts of the room. The tests included simulation of summer, autumn/spring, and winter daytime conditions. The results indicate a tendency towards lower tracer gas concentrations in the “breathing zone” when the supply air (typical flow rate equivalent to two air changes per hour) is brought into the room at a low level as compared to a high level close to the ceiling. The exhaust air terminal device in all tests was situated high in the “corridor” wall.     

Ventilation for control of indoor air quality: A case study

Dilution of indoor air contaminants with less contaminated outdoor air is the most common strategy for control of indoor air quality. Unfortunately this strategy frequently imposes a substantial energy burden. If the contaminants are associated with occupants and their activities, a ventilation control system based on the carbon dioxide level in the controlled space is shown to relieve this energy burden. A test was carried out in the Fridley, MN, Junior High School Music Department to obtain air quality, energy, and subjective response data on an Automatic Variable Ventilation System. A control system with both CO₂ and temperature inputs was devised to control the use of outdoor air. Infiltration measurements lead to a quantitative measure of ventil3tion efficiency. This in turn led to recommendations for air circulation patterns in rooms. The measured ventilation efficiency enabled energy and CO₂ models to fit measured data. Energy savings of approximately 20% were found for this application. Subjective response of the occupants also was measured. A special questionnaire, subjected to statistical analysis, showed that the subjects felt warmer with increased CO₂ in the room air.     

Rethinking the contribution of indigenous management in small-scale water provision among selected rural communities in Cameroon

This paper describes the pro-active role of rural communities in negotiating livelihood and sustenance through the improvement of some of their local water sources. It discusses the strategies put in place to ensure the availability of water, one of the world’s scarcest natural resources. Despite some external assistance, local communities are increasingly shouldering the responsibility of ensuring the availability of water through self-reliant efforts. These attempts are being undermined by a high incidence of waterborne and water-related diseases, which are impacting on health, and hygiene and other health care delivery systems. The management of potable water is proving to be a herculean task for most communities after the departure of funding partners. To guarantee the proper maintenance of pipe borne water schemes, communities are rethinking their strategies as they grapple with difficulties to put in place viable techniques for sustainability of water supply schemes.     

Filtration efficiencies in electrostatically augmented granular beds

Fine particle filtration efficiencies of electrically enhanced granular beds are computed and compared with available experimental data. Collection efficiencies of a single bed sphere in a gaseous flow are first calculated by numerically solving the equations of particle motion. The collection mechanisms incorporated here are inertial impaction, interception, and charged fine particle-imposed electric field interaction. The approach is based upon a “unit cell” model which enables one to include the effects of surrounding bed particles on the collection process. Stokes' flow and potential flow are used to model the gas flow around the bed particle. Total efficiency is computed by integrating the single-sphere collection efficiency over the bed volume. These calculated total bed efficiencies compare satisfactorily with data obtained from an existing granular bed facility over a range of parameter values. Both theory and experimental data show that the electrical force significantly enhances particulate collection in granular beds.     

Future directions of meteorology related to air-quality research

Meteorology is one of the major factors contributing to air-pollution episodes. More accurate representation of meteorological fields has been possible in recent years through the use of remote sensing systems, high-speed computers and fine-mesh meteorological models. Over the next 5-20 years, better meteorological inputs for air quality studies will depend on making better use of a wealth of new remotely sensed observations in more advanced data assimilation systems. However, for fine mesh models to be successful, parameterizations used to represent physical processes must be redesigned to be more precise and better adapted for the scales at which they will be applied. Candidates for significant overhaul include schemes to represent turbulence, deep convection, shallow clouds, and land-surface processes. Improvements in the meteorological observing systems, data assimilation and modeling, coupled with advancements in air-chemistry modeling, will soon lead to operational forecasting of air quality in the US. Predictive capabilities can be expected to grow rapidly over the next decade. This will open the way for a number of valuable new services and strategies, including better warnings of unhealthy atmospheric conditions, event-dependent emissions restrictions, and now casting support for homeland security in the event of toxic releases into the atmosphere.     

A procedure to estimate worst-case air quality in complex terrain

Using a straightforward synoptic climatological analysis scheme, it is shown that the potential for an area to experience air quality degradation due to local sources is highest under polar subtropical highs. With respect to polar highs, the problem is most severe when the sun angle is low and snow covers the ground, and the polar high persists for a long period of time. A simple algorithm is introduced which is designed to estimate worst-case impact in a trapping valley. The potential for the accumulation of air pollution in such valleys due to the persistence of a polar high in a region, is ignored in current regulatory air quality assessments. Trapping valleys and synoptic flow stagnation often occur in wilderness areas. Refined air quality assessments are shown to be possible using a mesoscale meteorological model and a pollution dispersion model. These tools permit quantitative assessments of pollution build-up from local sources as a result of the recirculation of the local air. This tool, along with the synoptic climatological classification scheme, also permits an evaluation of the fractional contribution of long range versus local sources in the air quality degradation in a region. Areas near the center of a polar or subtropical surface high pressure system, for instance, appear to be dominated by local sources, if they exist, whereas in the vicinity of extratropical cyclones, long-range transport is usually much more important.     

基于数量视角的耕地保护政策绩效评价

耕地保护政策的绩效评价是我国粮食安全及土地调控的重要课题。本文基于数量保护的视角,采用数据包络分析法(DataEnvelopment Analysis,简称DEA)评价了我国2000-2007年的耕地保护政策绩效,测度对象主要为耕地总量动态平衡、土地用途管制、耕地执法监管政策。研究结果显示,耕地保护政策在数量保护上具有总体效率高(2002年除外)、规模效率递增或保持、纯技术效率高的表征,但是,规模效率、纯技术效率与总体效率不能很好拟合且三项效率的综合具有分层性,只有耕地总量动态平衡达到了最佳产出。进而得出结论:2000-2007年,耕地保护政策取得了耕地总量平衡、耕地基本数量维持、建设占用耕地趋缓、耕地违法减少的显著效果,然而,耕地保护政策绩效的年度差异、政策时滞及体制等影响因素的复杂、投入和产出的部分饱和亦表明绩效的不充分。为促进我国耕地保护政策绩效的提升,提出强化土地利用总体规划作用、建立耕地保护责任制度等建议,并对进一步研究作了展望。     

A method for supporting the design of efficient heating systems using EU product policy data

The design of heating, ventilation and air conditioning systems is still a challenging engineering task which requires experienced and informed decision-making. These systems have a great energy-saving potential at the system level rather than at the level of the individual products of which they are composed. European environmental product policies have been very useful in facilitating a homogeneous rating scheme which can be used to compare the energy performance of different products that provide the same service. This paper proposes a simplified design method which uses the performance of components that are regulated by European product policies to obtain the overall performance of heating systems in residential buildings. It is a flexible method and allows different product configurations to be assessed so as to optimise the system performance during the design phase. The method is tested on a real case study with domestic hot water and space heating systems. The case study shows the potential for improving the heating systems according to the performance levels of its products currently available in the market. Results of the domestic hot water system show that upgrading its storage tank to the maximum energy class (A⁺) could bring the highest energy savings ( 4162 kWh/y).     

可达性视角下中国高铁线路空间效率与供需关系研究

透过可达性视角解析我国高铁线路空间效率和供需关系。首先,以我国2008～2017年高铁线路为对象,根据日常可达性(DA)增量描述高铁线路可达性空间演变特征。其次,通过人口加权可达性(PWA)增量刻画我国高铁线路空间效率和高铁线路供给水平的空间特征。第三,以高铁客运班次数表示高铁需求程度,通过因子叠加法与多元回归方程探讨高铁可达性的供需关系。结果显示:(1)在PWA增量及其效率中,干线高,延伸线低,东中部地区线路高,全国高铁网络外围和末端线路低,PWA增量及其效率自东向西整体递减,高铁线路PWA空间效率呈现出"树状结构"、"核心-外围结构"和区域梯度差异,2012年以后高铁PWA增量及其效率出现逐年递减趋势。(2)高需求线路主要是东中部地区高铁干线,低需求线路主要为中西部地区高铁干线和延伸线。(3)高铁线路供需匹配程度高。"双高型"线路为少数高铁主干线,"双低型"线路数量比重高,包括西部地区高铁线路、高铁延伸线以及网络末梢线路。(4)城市PWA增量是高铁客运量高低的关键因素,能够用来预测规划高铁城市客运规模。     

The optimization of wastewater treatment via combined techniques: Part II: Combined biological—Dissolved air flotation

Optimum operating conditions for sewage treatment via combined biological-physico chemical treatment has been studied. The biological unit was a trickling filter. The non-settled biological effluent was subjected to coagulation followed by rapid solid-liquid separation via dissolved air flotation. The impact of organic load on the over-all efficiency of the system has been investigated using three different organic loads namely, 9.48, 20.0, and 27.85 g BOD₅m^?2d^?1. The coagulants used were ferric chloride and alum. Calcium oxide was used as a coagulant aid with ferric chloride. Factors affecting the efficiency of dissolved air flotation process such as detention time, air solids ratio, and position of coagulant's addition have been investigated. The results obtained showed that the use of biological, extended physico-chemical technique leads to the removal of organic as well as inorganic contaminants. Moreover, sludge with high solids content can be obtained.