Source area

Compilation ofi Air Pollution Emission Factors, Vol. 1, Stationay Point and Area Sources, AP-42, 4th ed., Suppl. E, U.S. Environmental Protection Agency, Washiagton, D.C., 1993. 

Hazardous Air Pollutants. Tide 3 of the CAAA of 1990 addresses the release of hazardous air poUutants (HAPs) by requiring both the identification of major stationary sources and area source categories for 189 toxic chemicals and the promulgation of control standards. Major sources of air toxics, also referred to as HAPs, include any stationary source or group of sources emitting 10 or more tons/yr of any single Hsted toxic chemical or 25 tons/yr of a combination of any Hsted toxic. Area sources of HAPs include smaller plants that emit less than the 10 or 20 tons/yr thresholds. The major sources of HAPs are typically industrial faciHties. However, Tide 3 requites the EPA to study potential health affects associated with emissions of HAPs from electric UtiHty boilers (11). 

Parameters Affeeting Gas Dispersion A wide variety of parameters affect the dispersion of gases. These include (1) wind speed, (2) atmospheric stability, (3) local terrain characteristics, (4) height of the release above the ground, (5) release geometry, i.e. from a point, line, or area source, ( momentum of the material released, and (7) buoyancy of the material released. 

The geometry of the release also affects the resulting consequence. An ide release would occur at a point source. Real releases are more likely to occur as a hne source (from an escaping jet of material) or as an area source (from a boiling pool of liqmd). 

If it is necessary to consider short-term (hours or days) impact, the model PAL (4) will do a superior simulation of the area sources and a similar simulation of any point sources as done by the ISCLT model. 

The gradient transport model is most appropriate when the turbulence is confined to scales that are small relative to the pollutant volume. It is therefore most applicable to continuous line and area sources at ground... 

In estimating concentrations from area sources, it is important to know whether there is one source surrounded by areas of no emissions or whether the source is just one element in an area of conhnuous but varying emissions. 

If the receptor is within an area source, or if emission rates do not vary markedly from one area source to another over most of the simulation area, the narrow-plume hypothesis can be used to consider only the variation in emission rates from each area source in the alongwind direction. Calculations are made as if from a series of infinite crosswind line sources whose emission rate is assigned from the area source emission rate directly upwind of the receptor at the distance of the line source. The ATDL model (22) accomplishes this for ground-level area sources. The RAM model (8) does this for ground-level or elevated area sources. 

Using simplified techniques for estimating the concentrations from area sources, what is the annual average particulate matter concentration for a city with an average wind speed of 3.6 m s and area emission rate of 8 x 10 g s m" ... 

Fig. 21-11. Contributions to the annual sulfur dioxide concentration from each direction at a receptor in New York by area sources (lines) and point sources (rectangles) for 1969 using the Climatological Dispersion Model,...

EPA must promulgate a list of categories and subcategories of major sources and area sources of listed hazardous air pollutants. 

Within 6 months after enactment of the Qean Air Act Amendments of 1990, and at least every 3 years thereafter, the Administrator shall review and, if necessary, revise, the methods ( emission factors ) used for purposes of this Act to estimate the quantity of emissions of carbon monoxide, volatile organic compounds, and oxides of nitrogen from sources of such air pollutants (including area sources and mobile sources). In addition, the Administrator shall permit any person to demonstrate improved emissions estimating techniques, and following approval of such techniques, the Administrator shall authorise the use of such techniques. Any such technique may be approved only after appropriate public participation. Until the Administrator has completed the revision required by this section, nothing in this section shall be construed to affect the validity of emission factors established by the Administrator before the date of the enactment of the Clean Air Act Amendments of 1990. 

List five categories (such as hazardous waste incineration) that may be considered as major" or "area sources of hazardous air pollutants,... 

The law includes a list of 189 toxic air pollutants of which emissions must be reduced. The list of source categories includes (1) major sources emitting 10 tons/year of any one, or 25 tons/year of any combination of those pollutants and (2) area sources (smaller sources, such as dry cleaners). 

When running SCREEN for a point source, or for flare releases and area sources discussed below, you are first asked to provide a one line title (up to 79 characters) that will appear on the output file. You will then be asked to identify the source type, and should enter P or p for a point source (the model will identify either upper or lowercase letters and will repeat the prompt until a valid response is given). For a point source, you will be asked to provide the following inputs ... 

Italic - These options also apply to Area Sources... 

The third source type option in SCREEN is for area sources, which is selected by entering A or a for source type. The area source algorithm in SCREEN is based on a numerical integration approach, and allows for the area source to be approximated by a rectangular area. The inputs requested for area sources are as follows ... 

The range of directions used in the search is determined from a set of look-up tables based on the aspect ratio of the area source, the stability category, and the downwind distance. The SCREEN model also provides the user an option to specify a wind direction orientation relative to the long axis of the rectangular area. The second option may be used to estimate the concentration at a particular receptor location relative to the area. The output table for area sources includes the wind direction associated with the maximum concentration at each distance. 

The user has the same options for handling distances and the same choices of meteorology as described above for point sources, but no complex terrain, elevated simple terrain, building downwash, or fumigation calculations are made for area sources. Distances are measured from the center of the rectangular area. Since the numerical integration algorithm can estimate concentrations within the area source, the user can enter any value for the minimum distance. 

Note that for stable conditions and/or mixing heights greater than or equal to 10,000 m, unlimited mixing is assumed and the summation term is assumed to be zero, as noted by expressions presented earlier in this chapter. Equation (9) is used to model the plume impacts from point sources, flare releases, and volume releases in SCREEN. The SCREEN volume source option uses a virtual point source approach. The model uses a numerical integration algorithm for modeling impacts from area sources. 

The area source is assumed to be a rectangular shape, and the model can be used to estimate concentrations within the area. SCREEN examines a range of stability classes and wind speeds to identify the "worst case ... 

AREALTL.ZIP 7,787 bytes 09/18/95 (Area Source Test Case (Lahey))... 

The fire area is assumed to be rectangular, and estimated from the dimensions of the vessels and assuming they were within close proximity of each other. Area source inputs to the model are ... 

Most BEOs are situated at the end of a tube, but there are also basic openings situated in walls. BEOs can be used for nearly all kinds of sources, but are usually used for point sources. Use for line or area sources usually demands flexible or movable exhausts, or a slot placed along the line source or along the sides of an area source, or a very large (circular or rectangular) opening placed close to tlie source. A high flow rate is needed to get efficient exhaust in many cases. 

Rim exhausts are a specific application of slot hoods, which in turn are a type of exterior or capture hood. Rim exhausts are slot hoods placed along the rim or edge of an area source such as an open surface tank or vessel opening. Open surface tanks are widely used in indu.strial settings for cleaning, stripping. 

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