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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Line source</span></span>

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<p>A <b>line source</b>, as opposed to a <a href="Point_source" title="Point source">point source</a>, <a href="Area_source" class="mw-redirect" title="Area source">area source</a>, or <a href="Volume_source_(pollution)" title="Volume source (pollution)">volume source</a>, is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear (one-dimensional) geometry. The most prominent linear sources are <a href="Roadway_air_dispersion_modeling" title="Roadway air dispersion modeling">roadway air pollution</a>, <a href="Aircraft" title="Aircraft">aircraft</a> air <a href="Emission_standard" title="Emission standard">emissions</a>, <a href="Roadway_noise" title="Roadway noise">roadway noise</a>, certain types of <a href="Water_pollution" title="Water pollution">water pollution</a> sources that emanate over a range of river extent rather than from a discrete point, elongated light tubes, certain dose models in <a href="Medical_physics" title="Medical physics">medical physics</a> and electromagnetic <a href="Antenna_(radio)" title="Antenna (radio)">antennas</a>. While <a href="Point_source_(pollution)" class="mw-redirect" title="Point source (pollution)">point sources</a> of <a href="Pollution" title="Pollution">pollution</a> were studied since the late nineteenth century, linear sources did not receive much attention from scientists until the late 1960s, when environmental regulations for <a href="Highway" title="Highway">highways</a> and <a href="Airport" title="Airport">airports</a> began to emerge. At the same time, computers with the processing power to accommodate the data processing needs of the <a href="Computer_model" class="mw-redirect" title="Computer model">computer models</a> required to tackle these one-dimensional sources became more available.

</p><p>In addition, this era of the 1960s saw the first emergence of <a href="Environmental_scientist" class="mw-redirect" title="Environmental scientist">environmental scientists</a> who spanned the disciplines required to accomplish these studies. For example, meteorologists, chemists, and computer scientists in the air pollution field were required to build complex models to address <a href="Roadway_air_dispersion_modeling" title="Roadway air dispersion modeling">roadway air dispersion modeling</a>. Prior to the 1960s, these specialities tended to work within their own disciplines, but with the advent of <a href="NEPA" class="mw-redirect" title="NEPA">NEPA</a>, the <a href="Clean_Air_Act_(United_States)" title="Clean Air Act (United States)">Clean Air Act</a>, the <a href="Noise_Control_Act" title="Noise Control Act">Noise Control Act</a> in the United States, and other seminal legislation, the era of multidisciplinary environmental science had begun.

</p><p>For electromagnetic linear sources, the principal early advances in computer modeling arose in the <a href="Soviet_Union" title="Soviet Union">Soviet Union</a> and USA when the end of <a href="World_War_II" title="World War II">World War II</a> and the <a href="Cold_War" title="Cold War">Cold War</a> were fought partially by progress in <a href="Electronic_warfare" title="Electronic warfare">electronic warfare</a>, including the technologies of active antenna arrays.

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<div class="mw-heading mw-heading2"><h2 id="Linear_air_pollution_source">Linear air pollution source</h2></div>

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</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Roadway_air_dispersion_modeling" title="Roadway air dispersion modeling">Roadway air dispersion modeling</a></div>

<p>Air pollution levels near major highways and urban <a href="Arterial" class="mw-redirect" title="Arterial">arterials</a> are in violation of U.S. National Ambient Air Quality Standards where millions of Americans live or work. Even the interior of a building does not really protect inhabitants from adverse exterior air quality, since the exterior air is the intake supply, and it is well known that <a href="Indoor_air_quality" title="Indoor air quality">indoor air quality</a> is typically worse than exterior air.

</p><p>A roadway travelled by motor vehicles can be idealized by a line source emitting air pollutants. This mathematical problem was first solved in 1970 by a collaboration of <a href="Physics" title="Physics">physics</a>, <a href="Mathematics" title="Mathematics">mathematics</a> and <a href="Computer_science" title="Computer science">computer science</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The original theory assumed steady-state traffic conditions and meteorology on a perfectly straight roadway. Currently the models have evolved to treat variable meteorology, time-variant traffic operations and complex roadbed geometries. Current technology allows highway designers and city planners to analyze alternative roadway development plans and assess air quality impacts. The same basic model theory can be applied to airport operations, since the linear source is merely an inclined line. In the early 1970s these ESL models were refined into <a href="Area_source" class="mw-redirect" title="Area source">area source</a> models to account for the finite width of the roadway.

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<div class="mw-heading mw-heading2"><h2 id="Linear_noise_source">Linear noise source</h2></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Roadway_noise" title="Roadway noise">Roadway noise</a></div>

<p>Roadway noise is the most important example of a linear noise source, since it comprises about 80 percent of the environmental noise exposure for humans worldwide. In the 1960s, when computer modeling of this phenomenon was perfected, the first applications of linear source noise modeling became systematic. After passage of the <a href="National_Environmental_Policy_Act" title="National Environmental Policy Act">National Environmental Policy Act</a> and Noise Control Act,<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> the demand for detailed analysis soared, and decision makers began to look to acoustical scientists for answers regarding the planning of new roadways and the design of <a href="Noise_mitigation" class="mw-redirect" title="Noise mitigation">noise mitigation</a>. The intensity of roadway noise is governed by the following variables: <a href="Traffic" title="Traffic">traffic</a> operations (speed, <a href="Truck" title="Truck">truck</a> mix, age of <a href="Vehicle" title="Vehicle">vehicle</a> fleet), roadway surface type, tire types, roadway geometrics, terrain, micrometeorology and the geometry of area structures.

</p><p>Due to the complexity of the variables, a line source acoustic model must be a computer model that can analyze sound levels in the vicinity of roadways. The first meaningful models arose in the late 1960s and early 1970s. Two of the leading research teams were <a href="BBN_Technologies" class="mw-redirect" title="BBN Technologies">BBN</a> in <a href="Boston" title="Boston">Boston</a> and <a href="ESL_Inc." class="mw-redirect" title="ESL Inc.">ESL Inc.</a> of Sunnyvale, California. Both of these groups developed complex <a href="Mathematical_model" title="Mathematical model">mathematical models</a> to allow the study of alternate roadway designs, traffic operations and <a href="Noise_mitigation" class="mw-redirect" title="Noise mitigation">noise mitigation</a> strategies in an arbitrary setting.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Later model alterations have come into widespread use among state <a href="Department_of_Transportation" class="mw-redirect" title="Department of Transportation">Departments of Transportation</a> and city planners, but the accuracy of early models has had little change in 40 years.

</p><p>Generally line source acoustic models trace sound ray bundles and calculate spreading loss along with ray bundle divergence (or convergence} from refractive phenomena. <a href="Diffraction" title="Diffraction">Diffraction</a> is usually addressed by establishing secondary emitters at any points of <a href="Topographic" class="mw-redirect" title="Topographic">topographic</a> or <a href="Anthropomorphic" class="mw-redirect" title="Anthropomorphic">anthropomorphic</a> “sharpness” (such as <a href="Noise_barrier" title="Noise barrier">noise barriers</a> or building surfaces. <a href="Meteorology" title="Meteorology">Meteorology</a> can be addressed in a statistical manner allowing for actual <a href="Wind_rose" title="Wind rose">wind rose</a> and <a href="Wind_speed" title="Wind speed">wind speed</a> statistics (along with <a href="Thermocline" title="Thermocline">thermocline</a> data).

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<div class="mw-heading mw-heading2"><h2 id="Water_pollution_line_source">Water pollution line source</h2></div>

<p>Less common are line source applications in the field of water pollutant dispersal. This phenomenon generally arises when <a href="Surface_runoff" title="Surface runoff">surface runoff</a> scours <a href="Soil_contaminants" class="mw-redirect" title="Soil contaminants">soil contaminants</a> from upper soil layers and transports these pollutants to a linear receiving water, such as a river. The underlying land management practices which lead to such sources of water pollution are <a href="Logging" title="Logging">logging</a>, <a href="Pesticide" title="Pesticide">pesticide</a> application, <a href="Construction" title="Construction">construction</a> grading, <a href="Slash-and-burn" class="mw-redirect" title="Slash-and-burn">slash-and-burn</a> activity and urban <a href="Stormwater" title="Stormwater">stormwater</a> runoff.

</p><p>Again computer models are needed to address the complexity of such an extended linear discharge into a dynamic medium such as flowing water. The resulting surface runoff water carrying pollutants may be considered a line source discharging into a river or stream. The chemical composition of this surface runoff may be characterized by a surface runoff model such as the USGS runoff precipitation algorithm,<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> while the instream transport may be analyzed by a dynamic river pollutant model such as <a href="DSSAM" class="mw-redirect" title="DSSAM">DSSAM</a>.

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<div class="mw-heading mw-heading2"><h2 id="Light_emission_line_source">Light emission line source</h2></div>

<p>In the study of illumination, a variety of sources are linear in nature, most commonly the <a href="Fluorescent_tube" class="mw-redirect" title="Fluorescent tube">fluorescent tube</a>, During the process of interior lighting design it is important to calculate the light intensity at work stations or other user areas, not only to ensure sufficient light is present, but more importantly to avoid <a href="Over-illumination" class="mw-redirect" title="Over-illumination">over-illumination</a> and its attendant <a href="Energy_conservation" title="Energy conservation">energy wastage</a> as well as adverse health effects. Thus the scientists involved in light transmission calculations employ computer models that recognize linear sources when fluorescent fixtures are used. In a typical setting there may be hundreds of finite length light sources that comprise the light output in an office environment. A related concept are the <a href="Ultraviolet" title="Ultraviolet">ultraviolet</a> tubes used in <a href="Phototherapy" class="mw-redirect" title="Phototherapy">phototherapy</a>, where output radiation from the tube can be accurately modeled by treating the tube as a line source.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> On a larger scale, an illuminated <a href="Roadway" class="mw-redirect" title="Roadway">roadway</a> may act as a line source of <a href="Light_pollution" title="Light pollution">light pollution</a>.

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<ul><li><a href="Air_pollution_dispersion_terminology" class="mw-redirect" title="Air pollution dispersion terminology">Air pollution dispersion terminology</a></li>

<li><a href="Area_source_(pollution)" class="mw-redirect" title="Area source (pollution)">Area source (pollution)</a></li>

<li><a href="Atmospheric_dispersion_modeling" title="Atmospheric dispersion modeling">Atmospheric dispersion modeling</a></li>

<li><a href="Effluent" title="Effluent">Effluent</a></li>

<li><a href="Fenceline_community" title="Fenceline community">Fenceline community</a></li>

<li><a href="Line_array" title="Line array">Line array</a></li>

<li><a href="List_of_atmospheric_dispersion_models" title="List of atmospheric dispersion models">List of atmospheric dispersion models</a></li>

<li><a href="Phased_array" title="Phased array">Phased array</a></li>

<li><a href="Point_source_(pollution)" class="mw-redirect" title="Point source (pollution)">Point source (pollution)</a></li>

<li><a href="Roadway_noise" title="Roadway noise">Roadway noise</a></li>

<li><a href="Surface_runoff" title="Surface runoff">Surface runoff</a></li>

<li><a href="Volume_source_(pollution)" title="Volume source (pollution)">Volume source (pollution)</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

<li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text">Michael Hogan, <i>Theoretical basis for atmospheric diffusion from a linear source</i>, ESL Inc., Environmental Systems Laboratory, Publication IR-29, Sunnyvale, Ca., May 4, 1970</span>

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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">Richard J. Venti, <i>Atmospheric diffusion models for roadway sources</i>, ESL Inc., Environmental Systems Laboratory, Publication ET-22, Sunnyvale, Ca., October 5, 1970.</span>

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<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><i>Public Law No. 92-574, 86 Stat. 1234 (1972) Noise Pollution and Abatement Act of 1972</i>, codification amended at 42 U.S.C. 4901-4918 (1988)</span>

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<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">John Shadely, <i>Acoustical analysis of the <a href="New_Jersey_Turnpike" title="New Jersey Turnpike">New Jersey Turnpike</a> widening project between Raritan and East Brunswick</i>, Bolt Beranek and Newman, 1973</span>

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<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://eco.wiz.uni-kassel.de/model_db/mdb/prms.html">United States Geological Survey runoff precipitation algorithm</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070610235807/http://eco.wiz.uni-kassel.de/model_db/mdb/prms.html">Archived</a> 2007-06-10 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><a href="David_Robert_Grimes" title="David Robert Grimes">David Robert Grimes</a>, Chris Robbins, Neil John O'Hare. <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pubmed/21089759"><i>Dose Modeling in Ultraviolet phototherapy</i>, Medical Physics, <b>37(10)</b> October 2010</a></span>

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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://www.epa.gov./scram001/">EPA Support Center for Regulatory Atmospheric Modeling</a></li>

<li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060926155730/http://www.fhwa.dot.gov/environment/rcnm.htm">U.S. Federal Highway Administration Roadway Construction Noise Model</a></li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2024-08-05" href="https://en.wikipedia.org/wiki/?title=Line_source&oldid=1238659253">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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