Relationships Between Indoor and Outdoor Contaminants in Mechanically Ventilated Buildings

Abstract It is shown that comparing measured indoor and outdoor contaminant concentrations can be misleading if the concentrations vary with time and if the averaging periods are too short. In this article an alternative methodology aimed at estimating the internal source and sink effects in mechanically ventilated buildings is described. The methodology is based on both the results from continuous measurements, and calculations under transient conditions. The relative importance of indoor sources and outdoor sources is established by a comparison of the measured indoor concentration and a calculated indoor concentration of a compound. Furthermore, dynamic calculations are used to investigate how the indoor concentrations of contaminants originating outdoors and contaminants emitted from indoor sources are influenced by temporal reductions of the airflow rate. Reducing the outdoor airflow rate during periods with high outdoor concentrations can significantly reduce the indoor levels of pollutants for situations in which the outdoor sources are more important than the indoor sources.     

Contaminant flows in urban residential water systems

A contaminant balance for urban residential water systems has been performed for 12 pollutants. The characteristics of the residential site were based on Ellenbrook, a suburb of Perth, Australia. The sources of contaminants were identified and characterised using published literature values. A water balance was used to estimated flow data, and these results were used in conjunction with the contaminant source characteristics to calculate contaminant loads. The contaminants examined were total nitrogen, ammonia, total phosphorus, copper, zinc, lead, cadmium, suspended solids, dissolved solids, chemical oxygen demand, polycyclic aromatic hydrocarbons and oil and grease. Diagrams of contaminant flows through the water, wastewater and stormwater systems are presented. By identifying the sources of contaminants, the diagrams are a useful reference when considering the fate of contaminants in alternative urban water system configurations or how to better handle or reduce these contaminants.     

Downstream changes in the transport and storage of sediment-associated contaminants (P, Cr and PCBs) in agricultural and industrialized drainage basins

Samples of suspended, floodplain and channel bed sediment have been used to examine downstream changes in ediment-associated contaminant transport and storage in contrasting rivers in Yorkshire, UK. The concentrations of hosphorus, chromium and selected PCBs associated with sediment in the River Aire and its main tributary, the River Calder, which drain an urbanized and industrialized catchment, are considerably higher than those in the relatively unpolluted River Swale, which drains an agricultural catchment. Concentrations of sediment-associated contaminants in the Aire/Calder system increase downstream, reflecting the location of urban and industrial areas in the middle and lower reaches, and the location of point source inputs, such as sewage treatment works. The ontaminant concentrations associated with floodplain and channel bed sediment in the Rivers Aire and Calder are high, particularly in the lower reaches. This, combined with measurements of sediment storage on the floodplain and channel bed, indicate that significant storage of sediment-associated contaminants occurs in the Rivers Aire and Calder.     

Sorption phenomena in subsurface systems: Concepts, models and effects on contaminant fate and transport

The behavior, transport and ultimate fate of contaminants in subsurface environments may be affected significantly by their participation in sorption reactions and related phenomena. The degree to which the resulting effects can be quantified and predicted depends upon the extent to which certain fundamental aspects of sorption are understood, and upon the accuracy with which these phenomena can be characterized and modeled in complex subsurface systems. Current levels of understanding of the reactions and processes comprising sorption phenomena are discussed in this paper, as are the forms and utilities of different models used to describe them. Emphasis is placed on concept development, on the translation of these concepts into functional models for characterizing sorption rates and equilibria, and on the application of these concepts and models for explaining contaminant behavior in subsurface systems. Examples are provided to illustrate the impacts of sorption phenomena on contaminant transport.     

Determination and occurrence of phthalates, alkylphenols, bisphenol A, PBDEs, PCBs and PAHs in an industrial sewage grid discharging to a Municipal Wastewater Treatment Plant

Industrial and urban discharges release organic contaminants which might affect the quality of receiving waters if not properly eliminated in Wastewater Treatment Plants (WWTP). This study is aimed to evaluate the source, transport and fate of contaminants of industrial origin in a sewage grid discharging to a WWTP and finally to the sea. The sampling network covered an industrial and urban area and wastewaters, influents and effluents of a WWTP were analyzed using a newly developed multiresidual method to capture a wide range contaminants (phthalates, alkylphenols, bisphenol A, PBDEs, PCBs and PAHs). Alkylphenols and phthalates followed by PAHs were the main compounds detected at levels between 0.01 to 698 µg l^− 1 in the sewage pipelines. At the WWTP influent they were detected at concentrations up to 345 µg l^− 1. The contaminant load was eliminated in a 64-92% during the primary and secondary treatment of the plant. However, alkylphenols, phthalates bisphenol A and traces of PAHs were discharged with the effluent, producing a total net input of 825 g d^− 1 to the sea. The study of wastewaters herein proposed can be used to better predict the loads into WWTP to improve treatment conditions according to specific sewage inputs and to assess the risks associated with the continuous discharge of contaminants to receiving plants.     

Experimental and theoretical investigation of particle-laden airflow under a prosthetic mechanical foot in motion

This research effort was aimed at understanding how foot motion affects air transport and thus how walking affects contaminant dispersion. Particle imaging velocimetry (PIV) showed that during a rotational motion of the foot (typical footstep), a draft corner flow develops that carries particles from heel to toe. Foot contact with the floor may result in one or both of two types of reentrainment: (1) particles become airborne due to detachment from the floor, and (2) particles are first collected by the foot cover (e.g., Tyvek) and then detached from the foot into the airflow produced by the foot rotation. The airflow under the rotating foot was modeled as a rotating corner flow, and it was shown that such modeling can capture major characteristics of the airflow generated by the rotating foot and can explain how rotational foot motion contributes to reentrainment and dispersion of contaminants.     

Contaminant dispersion with personal displacement ventilation,Part I: Base case study

Personal displacement ventilation (PDV) is a new ventilation concept that combines the positive features of displacement ventilation with those of task conditioning or personalized ventilation. PDV is expected to create a micro-environment around an occupant to control the environment individually. In this study, a base PDV case with a contaminant source at different locations was modeled for contaminant dispersion in a full-scale chamber. Computational fluid dynamics (CFD) was used to simulate the indoor airflow and pollutant transport, and the simulation results were validated against the experimental data. The contaminant concentration field for three different contaminant source locations was analyzed. Based on our results, it seems that this kind of PDV system cannot create the expected “micro-environment” to avoid the disturbance of the outside airflow. Further studies on how to improve the PDV performance are given in the companion paper.     

Assessing water quality impacts and cleanup effectiveness in streams dominated by episodic mercury discharges

Accurate pollutant mass budgets are needed for identifying contaminant sources and establishing cleanup goals. We monitored mercury discharges from an abandoned mine site in northern California with the objectives of: (1) estimating the mass loading of mercury from the site; (2) evaluating the factors that control the mercury discharges; (3) assessing the significance of peak flows in transporting contaminants; and (4) developing methods for measuring the effectiveness of cleanup efforts. We sampled water downstream from the mine site over a wide range of streamflows. Mercury concentrations varied over 2000-fold, from 485 to 1 040 000 ng/l, grossly exceeding the regulatory water quality objective of 12 ng/l at all times. Particulate mercury represented over 99.97% of the total mercury, and mercury concentrations were closely correlated to suspended sediment concentrations (r=0.98). Thus, we can use suspended sediment concentrations as a proxy for mercury concentrations, and calculate a continuous record of mercury flux from continuous monitoring of streamflow (using a small flume) and turbidity (using an optical backscatter sensor). Mercury fluxes inferred in this way are consistent with fluxes estimated from field samples. In January and February of 1998, our small abandoned mine site released approximately 82 kg of mercury to downstream waters. Most of the mercury was released during brief intense rainstorms. For example, in one 200-min period we recorded 3.4 cm of rain, a 2.6-fold increase in streamflow (460–1120 l/s), and an 82-fold increase in mercury flux (1.2–99 g/min). Over 75% of the total mercury flux during this 2-month period occurred in less than 10% of the total time. In systems such as this one, where contaminant transport is highly episodic, sampling programs that miss the high-flow episodes may greatly underestimate the actual water quality threat. In addition, changes in pollutant fluxes or concentrations in receiving waters may not reflect changes in pollutant sources (such as an environmental cleanup) if the stochastic forcing (e.g. intense rainstorms) varies through time. We propose that water quality trends can be more accurately measured by changes in the relationship between contaminant flux and stochastic driving factors, as expressed by contaminant rating curves.     

Natural rates of sediment containment of PAH, PCB and metal inventories in Sydney Harbour, Nova Scotia

Analyses of metal and organic contaminants were carried out on 41 sediment cores, dated using ²¹⁰Pb and ¹³⁷Cs, from the heavily industrialized region of Sydney Harbour, N.S. to evaluate the history of contamination and to predict the rates of natural containment of the harbour by sediment burial. Geochronologies for metals (eg. Pb, As) and polycyclic aromatic hydrocarbons (PAHs) are correlated with the development of the steel and coke industries in the Sydney region while polychlorinated biphenyl (PCB) geochronologies reflect the disposal of electrical equipment used in the steel mill/coking operations. Pb was derived mainly from atmospheric emissions and its concentration has declined exponentially with time in harbour sediments since the closure of the steel mill/coke ovens in the 1980s with a time constant of about 15 years. This represents the time scale for the circulation of this particle-associated contaminant in transient catchment basins prior to permanent deposition in the sediments. PAH and PCB sediment concentrations have also declined exponentially with time since the 1980s, but with a smaller time constant of 10 years owing to the fact that they enter the harbour directly with steel mill and coke oven effluent rather than through atmospheric pathways. Since the time dependence for the burial of metal and organic inventories can be modeled by first order processes, future contaminant levels can be predicted for surface sediments in Sydney Harbour. Mean sediment concentrations of metal and organic contaminants in the upper 5 cm throughout most of the harbour are predicted to decline to levels below the effects range-medium (above which organisms are very likely to be negatively affected by the presence of a contaminant) by 2030.     

Outdoor Air Contaminants and Indoor Air Quality under Transient Conditions

The indoor concentrations of contaminants originating from outdoor sources have been measured and calculated under transient conditions. The results show that contaminants that are supplied to an office building via the ventilation system can reach considerably high concentration levels. The indoor/outdoor concentration ratio and time lag are dependent on the air change rate. In buildings with low air change rates the indoor concentration variations are smoothed out compared to buildings with high air change rates. The results from the theoretical model are compared to the results from both laboratory and field measurements and the model is verified for well mixed conditions in a 20 m³ test chamber. The model can be used to simulate different control strategies for reduction of indoor contaminant concentrations related to outdoor sources. One such control strategy is based on reduction of the outdoor air change rate during periods with peak outdoor contaminant concentrations.     

Factors influencing development of management strategies for the Abou Ali River in Lebanon I: spatial variation and land use

Surface water bodies are progressively subject to increasing stress as a result of environmentally degrading processes primarily related to anthropogenic activities. This study assesses and examines the impact of land use and land-based activities on the spatial variation in water quality of the Abou Ali River in North Lebanon. It is the first detailed study of its kind in Lebanon and adds to the existing knowledge by shedding light on a relatively small Mediterranean river in a developing country where there is a paucity of such studies. The assessment was conducted at the end of the dry season in 2002 and 2003 and the end of the wet season in 2003 and 2004. The study has demonstrated the importance of anthropogenic influences on the water quality of the Abou Ali River Basin, as concentrations of most contaminants were higher at locations with greatest human activity. The most adversely affected area was the section of the river that flows through an entirely urbanized and highly populated region, the Tripoli conurbation. Upstream rural sites were enriched by contaminants primarily from non-point sources such as agricultural runoff and poultry litter whereas contaminant concentrations at the urban sites were enriched by a combination of sewage discharge and flow of contaminants from upstream. If the Abou Ali River is to be utilized as a managed water resource and its water quality sustained, point source discharges will require treatment and land use management must be planned to minimize the impact of diffuse source pollution on the river. A high priority should be given to the implementation and enforcement of the precautionary and polluter pays principles. Moreover, an effective legal, economic and institutional framework is required to encourage investment in waste reduction and control and to introduce environmentally sound practices.     

Integrated modelling of eutrophication and organic contaminant fate & effects in aquatic ecosystems. A review

Eutrophication and contamination with micropollutants have been major problems in water quality management. Both problems have been subjected to extensive research and modelling but traditionally are treated separately. Traditional simulation models for aquatic systems can be categorised as eutrophication models, contaminant fate models, food web models and food chain bioaccumulation models. Because they are single issue models, many interactions and feedbacks between the food web, nutrient and toxicant cycles are missed. Linking these models is essential to evaluate the fate and risks of contaminants in systems with changing nutrient loading, to assess the natural attenuation of contaminants or to understand the selfpurifying capacity of ecosystems. Combination of the single issue models requires inclusion of 'interaction processes' to account for the coupling between the (sub-) model types, such as organic carbon cycling. toxicity, transport and accumulation of organic contaminants in the food chain, and bottom up versus top down control of primary production and nutrient cycling. This review first provides a brief overview of traditional approaches in modelling eutrophication, contaminant fate, food web dynamics and food chain bioaccumulation. Second, five existing integrated eutrophication, fate and/or effects models are reviewed. Third, the gaps and limitations in modelling the four types of interaction processes are discussed. It is concluded that these models are invaluable tools to focus attention to feedback mechanisms that are often overlooked, to identify dominating processes in ecosystems, to formulate counterintuitive hypotheses on ecosystem functioning, or to assess short term risks of acutely toxic stressors. However, the potential of integrated models for long term simulations of contaminant exposure. food chain bioaccumulation and effects to higher trophic levels remains limited, mainly because of principal limitations in food web modelling. In contrast, the potential of integrated models for long term simulations of contaminant fate is better because the environmental distribution of contaminants is mainly determined by the major abiotic compartments and by biotic compartments at the base of the food chain.     

The accumulation levels of PAHs, PCBs and DDTs are related in an inverse way to the size of a benthic amphipod (Echinogammarus stammeri Karaman) in the River Po

The accumulation of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and DDTs were investigated in gammarids captured at three sites along the middle River Po; the first was located upstream and the other two were at increasing distances downstream of the confluence of a polluted tributary, the River Lambro. Using a GC-MS technique, the levels of PCBs, PAHs and DDTs were determined separately in large and small gammarids as well as in the fine fraction of sediment samples collected along the sites of capture. Results confirm the River Lambro as a source of these chemicals to the River Po, and show that bioaccumulation differences exist between small and large individuals, the former being more contaminated particularly by PCBs and DDTs. This is likely the result of several interacting factors such as contaminant bioavailability, gammarid-size effects on kinetic parameters and feeding selectivity. The bioaccumulation patterns of PCBs and DDTs, and their higher biota-sediment accumulation factors (BSAF), are consistent with chemical properties and suggest a dietary disequilibrium found only 10 km downstream from the tributary, and in smaller amphipods. Present results show that gammarids may represent an additional source of contaminants, particularly of chlorinated compounds, to the many organisms feeding on them, with a higher risk for those which prey selectively on smaller gammarids.     

重金属离子和LNAPLs在非饱和土中的运移规律研究

以重金属和轻非水相流体(LNAPLs)为例,介绍了清华大学开展非饱和土中污染物运移规律研究的部分工作成果。利用土工离心机对污染物的运移过程模拟,取样得到污染物的浓度分布特征。同时采用数值分析手段对污染物的长期运移规律和其影响因素进行分析。研究表明:离心模型试验可以有效模拟污染物的运移过程,离心模型试验和数值分析相结合,是研究污染物在非饱和土中运移规律的有效手段。     

Towards improved characterization of high-risk releases using heterogeneous indoor sensor systems

The sudden release of toxic contaminants that reach indoor spaces can be hazardous to building occupants. For an acutely toxic contaminant, the speed of the emergency response strongly influences the consequences to occupants. The design of a real-time sensor system is made challenging both by the urgency and complex nature of the event, and by the imperfect sensors and models available to describe it. In this research, we use Bayesian modeling to combine information from multiple types of sensors to improve the characterization of a release. We discuss conceptual and algorithmic considerations for selecting and fusing information from disparate sensors. To explore system performance, we use both real tracer gas data from experiments in a three-story building, along with synthetic data, including information from door-position sensors. The added information from door-position sensors is found to be useful for many scenarios, but not always. We discuss the physical conditions and design factors that affect these results, such as the influence of the door positions on contaminant transport. We highlight potential benefits of multisensor data fusion, challenges in realizing those benefits, and opportunities for further improvement.     

Fate and transport of particle matter during GEOTextile tube dewatering of a dioxin and furan (PCDD/F) contaminated sediment

Geotextile tube dewatering is a pre-treatment method utilized in the remediation of high-water content materials (i.e. sediments and slurries). However, given the association some contaminants (e.g. dioxins and furans, (i.e. PCDD/F)) have with particulate matter in these contaminated sediments, understanding the fate and transport of this particle matter in the dewatered effluent is essential. In this paper, pressure filtration tests (PFTs) were conducted to investigate the effect of pressure and filter cake formation on both geotextile filtration efficiency and effluent quality. Transport tests were then performed to evaluate the particle transport through the developed filter cake, as well as the hydraulic characteristics of the medium during dewatering. HYDRUS, a one-dimensional model contaminant transport model was then employed to simulate the experimental particle transport test results. Three different mechanisms of particle transport (i.e. attachment only, detachment only, both attachment and detachment) through saturated porous media were examined to identify the possible mechanisms of observed effluent particle concentration. HYDRUS modeling outputs suggest that both attachment and detachment mechanisms are involved in a given particle's fate and transport during geotextile dewatering. In addition, parameters such as confining pressure and filter cake properties affect the particle concentration in the effluent.     

浐河水质污染特征及水质改善措施分析

针对浐河水体遭受污染问题,通过对浐河水质特征断面的10项指标进行连续监测,分析了浐河水中污染物的组成和水质特征,对污染物的携入方式进行了调查,分析评价了浐河水体污染的原因,并提出了控制浐河水质污染的对策。结果表明,浐河水体中的物理指标水温、p H、重金属指标相对正常;重金属指标中只有少量的Fe、Zn、Cr元素;污染物主要为N、P等营养物质,水体的富营养化程度较为严重;河流水体浊度总体较高且与地表径流存在较高的相关性;污染的主要原因是浐河周边的水厂、污水处理厂所排出污水的点源污染;污染改善措施采用人工湿地、管网改建等适合不同断面特征的控制方式。     

Persistent organic pollutants in outmigrant juvenile chinook salmon from the Lower Columbia Estuary, USA

Although chemical contaminants are recognized as a potential factor contributing to the salmon declines in the Pacific Northwest, United States, information on contaminant concentrations in threatened and endangered salmon from the Columbia Estuary is limited. In this study we monitored exposure to several persistent organic pollutants [polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs) and other organochlorine pesticides] in outmigrant juvenile fall chinook salmon (Oncorhynchus tschawytscha) in the Lower Columbia River, and evaluated the potential for adverse effects on salmon and the estuarine food web. Contaminants were measured in whole bodies and stomach contents of subyearling to yearling chinook collected in 2001 and 2002 from sites near the confluence of the Columbia and Willamette Rivers, Longview, and within the lower Estuary. The contaminants detected at highest concentrations in salmon whole bodies were PCBs and DDTs. Average concentrations of PCBs in salmon from the sampling sites ranged from 1300 to 14,000 ng/g lipid, in some cases exceeding the recently estimated threshold for adverse health effects in juvenile salmonids of 2400 ng/g lipid. Average DDT concentrations ranged from 1800 to 27,000 ng/g lipid. These levels are among the highest measured in juvenile salmon from Pacific Northwest estuaries to date. Concentrations of PCBs and DDTs in salmon whole bodies showed no clear spatial gradient from the Willamette/Columbia Confluence to the mouth of the Columbia, but tended to be higher in larger fish and older fish, suggesting a correlation with estuarine residence time. PCBs, DDTs, and PAHs were all found in salmon stomach contents, indicating that prey is a source of exposure. Hatchery feed may have contributed to contaminant body burdens in those fish that were of hatchery origin. Contaminant body burdens in salmon were poorly correlated with contaminant concentrations previously measured in local bed sediments, suggesting that pelagic as well as benthic sources are important in determining salmon exposure.     

Comparison of underfloor and overhead air distribution systems in an office environment

This study compares thermal environment of two air distribution systems in an office setting. Airflow, heat and mass (water vapor and contaminant gas) transfer in steady-state condition are modeled for an underfloor air distribution system and an overhead air distribution system. The models include a typical cubicle in a large office floor with a chair, a desk with a personal computer on top, and heat sources such as seated person, desktop computer, and lights. For underfloor air distribution system, cool air enters the occupied zone through an inlet located at the floor level supplying a vertical upward inflow. Three different locations of the inlet diffuser are considered. For overhead air distribution, the inlet is located on the ceiling with slower and cooler inflow. Three inlet angles are considered. For both systems, the air return location is on the ceiling at the same place. Distributions of velocity, temperature, relative humidity, and contaminant concentration in various cases for both systems are computed. Thermal comfort factors are assessed for the two systems. The results are compared among cases of each system, as well as between two typical cases of the two systems and to experimental data for an actual office building given in literature. The results provide a detailed understanding of air transport and its consequence on thermal comfort and indoor air quality that are useful for office building air conditioner design. It is found that underfloor system gives better performance than overhead system in contaminant removal and significantly in energy saving while maintaining the same thermal comfort condition.     

Geographically distributed classification of surface water chemical parameters influencing fate and behavior of nanoparticles and colloid facilitated contaminant transport

The current production and use of nanomaterials in consumer products have increased the concern about the possibility that these enter the rivers during their entire life cycle. Further, many aquatic contaminants undergo partitioning to the ubiquitous aquatic colloids. Here is presented the development of a set of European water types for environmental risk assessment of chemicals transported as nanovectors as is the case of environmental fate of manufactured nanoparticles and colloid-bound contaminants.