Pollutant pathways

Pathways one or more pollutant pathways connect the pollutant source to the occupants and a driving force exists to move pollutants along the pathway(s). Occupants building occupants are present. 

Even when the building as a whole is maintained under positive pressure, there is always some location (for example, the outdoor air intake) that is under negative pressure relative to the outdoors. Entry of contaminants may be intermittent, occurring only when the wind blows from the direction of the pollutant source. The interaction between pollutant pathways and intermittent or variable driving forces can lead to a single source causing lAQ complaints in areas of the building that are distant from each other and from the source. 

An initial walkthrough of the problem area provides information about all four of the basic factors influencing indoor air quality (occupants, HVAC system, pollutant pathways, and contaminant sources). The initial walkthrough may provide enough... 

If the hypothesis or model does not seem to be a good predictor of what is happening in the building, you probably need to collect more information about the occupants, HVAC system, pollutant pathways, or contaminant sources. Under some circumstances, detailed or sophisticated measurements of pollutant concentrations or ventilation quantities may be required. Outside assistance may be needed if repeated efforts fail to produce a successful hypothesis or if the information required calls for instruments and procedures that are not available in-house. Analysis of the information collected during the LAQ investigation could produce any of the following results ... 

If there is substantial airflow through the pathway, the peppermint oil odor could be diluted so that it is imperceptible. Tracer gases such as sulfur hexafluoride (SF ) can provide qualitative and quantitative information on pollutant pathways and ventilation rates. Use of tracer gases to obtain quantitative results requires considerable technical expertise. If it appears that a sophisticated study of pathways (or ventilation rates) is required, you need to use trained investigators. 

Pollutant pathway information helps the investigator to understand airflow patterns in and around the complaint area. The pollutant pathway data may indicate a need to enlarge the complaint area, or may direct attention toward contaminant sources that deserve close study. 

Evaluate airflow patterns into and within the complaint area. Because of the complexity and variability of airflow patterns, investigators cannot be expected to understand how air moves within the building under all potential operating conditions. However, data on pathways and driving forces can help to locate potential pollutant sources and to understand how contaminants are transported to building occupants. The discovery of unexpected pollutant pathways can show a need to study areas of the building that may be distant from the original complaint area. 

Bonazountas, M. et al. (1981). Evaluation of seasonal soil/groundwater pollutant pathways via SESOIL Office of Water Regulations and Standards, U.S. Environmental Protection Agency, Washington, DC. 

Bonazountas, M. I. Wagner and B. Goodwin "Evaluation of Seasonal Soil/Ground Water Pollutant Pathways," Arthur D. Little, Inc., Final Report, prepared for U.S. EPA, Monitoring and Data Support Division, EPA Contract No. 68-01-5949/9. 

Monitoring. As suggested above, the Part IIA enforcement process can require action to be taken to monitor sites after remedial treatment action has been carried out. This obligation covers significant pollutant linkages that have already been identified, and is intended to pick up any changes that may occur in the condition of their component pollutants, pathways or receptors. 

The overall risk estimation should cover all the pollutant linkages identified, broken into site zones as appropriate. Details should be provided of source concentrations, with estimated confidence limits, the receptor characteristics and confirmation of the viability of the pollutant pathway. If generic guideline values are used, then their applicability should be supported. Clearly, full details need to be recorded of any models and data used to generate site-specific values for unacceptable risk, together with a commentary on assumptions that have been made in their application. 

The Control of Industrial Pollution Water Quality and Health Aspects of the Chemistry and Analysis of Substances of Concern in the Water Cycle The Role of Wastewater Treatment Processes in the Removal of Toxic Pollutants Sewage and Sewage Sludge Treatment The Chemistry of Metal Pollutants in Water Effects of Pollutants on the Aquatic Environment Important Air Pollutants and Their Chemical Analysis Pollutant Pathways and Modelling of Air Pollution Legislation and the Control of Air Pollution Catalyst Systems for Emission Control from Motor Vehicles Evaluating Pollution Effects on Plant Productivity A Cautionary Tale Epidemics of Non-infectious Disease Systems Methods in the Evaluation of Environmental Pollution Problems Organometallic Compounds in the Environment. 

More recently there has been an increased emphasis on air pollution since episodes of pollution have been correlated with increased morbidity and mortality in susceptible groups. Here EM coupled with image analysis and microanalytical techniques gives information at different levels in the pollution pathway (Table 4). The morphology and elemental composition of particles collected from ambient air can be identified and the number and composition of particles present in bronchial lavage fluids and in alveolar macrophages determined. The technique of EELS with its ability to differentiate between oxidative states of metals such as iron, and thus assist in determination of their hazard potential, has great potential in this area. 

The nitric oxide gas formed in this way is an important species in several pollution pathways and is itself an irritant molecule. For example, NO(g) reacts further with oxygen to form nitrogen dioxide, whose brown color is largely responsible for the dark haze typical of urban smog. Example Problem 9.10 shows how this type of equation can be used to determine heats of reaction of specific quantities of substances. 

Analytical chemistry plays an important role in the protection of the environment. This branch of chemistry finds application in the determination of pollutant concentration - both qualitative and quantitative - in the biosphere, in determining the pollutant pathway from the source to man (or other object of interest) and also in elucidating further transformations into other substances along this pathway, e.g. as a result of the interaction among various pollutants, as a result of metabolism etc. Analytical chemistry is also a means for evaluation of the effectiveness of various processes that prevent the formation of pollutants, or that remove those already formed. 

A fourth and sometimes critical factor affecting indoor air quality involves pollutant pathways and naturally occurring driving forces. Pollutant pathways can most commonly be referred to as pressure differentials which occur throughout the inside of a building. 

These differentials can be caused from an oversupply of conditioned air being provided to one room while limited quantities of return air are being allowed. When this occurs, a positive pressure differential happens. If this room as described were a laboratory, kitchen, or other source of potential contaminants, those contaminants could then be deUvered throngh a pollutant pathway to other occnpied areas in the bnilding. 

Information on site drainage and other man-made potential pollutant pathways, e.g. underground services Yes D/No ... 

S. J. Rooklidge, Environmental antimicrobial contamination from terr-accumulation and diffuse pollution pathways, Sci.Total Environ., 2004, 325, 1-13. 

Some pollutants, such as carbon monoxide, sulfur dioxide, and lead, are produced in specific locations and then move through the environment. However, the pollution pathways for other components, such as ozone and nitrogen dioxide, are dependent on chemical transformations that occur in the atmosphere. They are impacted by temperature and the presence of sunlight and are therefore more difficult to assess. Figure 3.2 presents the most common air pollution pathways. 

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