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| '''Air pollutant concentrations''', as measured or as calculated by [[air pollution dispersion modeling]], must often be converted or corrected to be expressed as required by the regulations issued by various governmental agencies. Regulations that define and limit the [[concentration]] of [[pollutant]]s in the ambient air or in gaseous [[Air pollutants|emission]]s to the ambient air are issued by various national and state (or provincial) [[United States Environmental Protection Agency|environmental protection]] and [[United States Occupational Safety and Health Administration|occupational health and safety]] agencies.
| | CMS provides the best platform to create websites that fulfill all the specifications of SEO. You may discover this probably the most time-consuming part of building a Word - Press MLM website. These templates are professionally designed and are also Adsense ready. Word - Press also provides protection against spamming, as security is a measure issue. It's as simple as hiring a Wordpress plugin developer or learning how to create what is needed. <br><br>Generally, for my private income-making market websites, I will thoroughly research and discover the leading 10 most worthwhile niches to venture into. Some of the Wordpress development services offered by us are:. This is the reason for the increased risk of Down Syndrome babies in women over age 35. So, if you are looking for some option to build a giant e-commerce website, then e-shopping preferable CMS tools will be helpful for you. Word - Press makes it possible to successfully and manage your website. <br><br>Digital photography is a innovative effort, if you removethe stress to catch every position and viewpoint of a place, you free yourself up to be more innovative and your outcomes will be much better. When a business benefits from its own domain name and a tailor-made blog, the odds of ranking higher in the search engines and being visible to a greater number of people is more likely. Are you considering getting your website redesigned. Storing write-ups in advance would have to be neccessary with the auto blogs. Have you heard about niche marketing and advertising. <br><br>The disadvantage is it requires a considerable amount of time to set every thing up. If you cherished this article and you simply would like to collect more info regarding [http://snipitfor.me/backup_plugin_6430930 wordpress backup plugin] generously visit our own site. This plugin allows a webmaster to create complex layouts without having to waste so much time with short codes. re creating a Word - Press design yourself, the good news is there are tons of Word - Press themes to choose from. IVF ,fertility,infertility expert,surrogacy specialist in India at Rotundaivf. Look for experience: When you are searching for a Word - Press developer you should always look at their experience level. <br><br>Many developers design websites and give them to the clients, but still the client faces problems to handle the website. If you operate a website that's been built on HTML then you might have to witness traffic losses because such a site isn't competent enough in grabbing the attention of potential consumers. You can select color of your choice, graphics of your favorite, skins, photos, pages, etc. You should stay away from plugins that are full of flaws and bugs. You can check out the statistics of page of views for your web pages using free tools that are available on the internet. |
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| Such regulations involve a number of different expressions of concentration. Some express the concentrations as ppmv ([[parts per million]] by volume) and some express the concentrations as mg/m<sup>3</sup> (milligrams per cubic meter), while others require adjusting or correcting the concentrations to reference conditions of moisture content, [[oxygen]] content or [[carbon dioxide]] content. This article presents methods for converting concentrations from ppmv to mg/m<sup>3</sup> (and vice versa) and for correcting the concentrations to the required reference conditions.
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| All of the concentrations and concentration corrections in this article apply only to air and other gases. They are not applicable for liquids.
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| ==Converting air pollutant concentrations==
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| The conversion equations depend on the temperature at which the conversion is wanted (usually about 20 to 25 °C). At an ambient sea level atmospheric pressure of 1 [[atmosphere (unit)|atm]] (101.325 [[Pascal (unit)|kPa]] or [[Bar (unit)|1.01325 bar]]), the general equation is:
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| :<math>\mathrm{ppmv} = \mathrm{mg}/\mathrm{m}^3\cdot \frac{(0.08205\cdot T)}{M}</math>
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| and for the reverse conversion:
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| :<math>\mathrm{mg}/\mathrm{m}^3 = \mathrm{ppmv}\cdot \frac{M}{(0.08205\cdot T)}</math>
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| {| border="0" cellpadding="2"
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| |align=right|where:
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| |align=right| '''mg/m<sup>3</sup>'''
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| |align=left|= milligrams of pollutant per cubic meter of air at sea level atmospheric pressure and '''''T'''''
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| |-
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| |align=right| '''ppmv'''
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| |align=left|= air pollutant concentration, in parts per million by volume
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| |-
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| |align=right| '''''T'''''
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| |align=left|= ambient temperature in K = 273.15 + °C
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| |align=right| '''0.08205'''
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| |align=left|= [[Molar gas constant|Universal gas constant]] in atm·m<sup>3</sup>/(kmol·K)
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| |-
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| |align=right| '''''M'''''
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| |align=left|= [[molecular mass]] (or molecular weight) of the air pollutant
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| |}
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| Notes:
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| * 1 atm = absolute pressure of 101.325 kPa or 1.01325 [[bar (unit)|bar]]
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| * mol = [[mole (unit)|gram mole]] and kmol = 1000 gram moles
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| * Pollution regulations in the United States typically reference their pollutant limits to an ambient temperature of 20 to 25 °C as noted above. In most other nations, the reference ambient temperature for pollutant limits may be 0 °C or other values.
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| * Although ppmv and mg/m<sup>3</sup> have been used for the examples in all of the following sections, concentrations such as ppbv (i.e., parts per billion by volume), volume percent, mole percent and many others may also be used for gaseous pollutants.
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| *[[Atmospheric particulate matter|Particulate matter]] (PM) in the atmospheric air or in any other gas cannot be expressed in terms of ppmv, ppbv, volume percent or mole percent. PM is most usually (but not always) expressed as mg/m<sup>3</sup> of air or other gas at a specified temperature and pressure.
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| * For gases, volume percent = mole percent
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| * 1 volume percent = 10,000 ppmv (i.e., parts per million by volume) with a million being defined as 10<sup>6</sup>.
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| * Care must be taken with the concentrations expressed as ppbv to differentiate between the British billion which is 10<sup>12</sup> and the USA billion which is 10<sup>9</sup> (also referred to as the long scale and short scale billion, respectively).
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| ==Correcting concentrations for altitude==
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| Air pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m<sup>3</sup>, µg/m<sup>3</sup>, etc.) at sea level will decrease with increasing [[altitude]]. The concentration decrease is directly proportional to the pressure decrease with increasing altitude. Some governmental regulatory jurisdictions require industrial sources of air pollution to comply with sea level standards corrected for altitude. In other words, industrial air pollution sources located at altitudes well above sea level must comply with significantly more stringent air quality standards than sources located at sea level (since it is more difficult to comply with lower standards). For example, [[New Mexico]]'s Department of the Environment has a regulation with such a requirement.<ref>[http://www.complextransformationspeis.com/eis0236/vol4/v4c3.htm Draft Programmatic Environmental Impact Statement (EIS) for Stockpile Stewardship and Management](See section 03.05 of the EIS which involves the [[Los Alamos National Laboratory]] in New Mexico)</ref><ref>[http://www.blm.gov/pgdata/etc/medialib/blm/nm/field_offices/socorro/socorro_planning/socorro.Par.77588.File.dat/Final_Air_Quality_Impact_Analysis.pdf Air Quality Impact Analysis] (Developed for the [[United States Bureau of Land Management]], Socorro Field Office, New Mexico)</ref>
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| The change of atmospheric pressure with altitude (<20km) can be obtained from this equation:<ref>[http://www.atec.army.mil/publications/Mil-Std-810F/Mil-Std-810F.pdf United States Department of Defense MIL-STD-810F], 1 January, 2000. (See: Annex A, page 520.2A5 )</ref> | |
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| :<math>P_\mathrm h = P\,\cdot\bigg(\frac{288 - 6.5 h}{288}\bigg)^{5.2558}</math>
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| Given an air pollutant concentration at sea-level atmospheric pressure, the concentration at higher altitudes can be obtained from this equation:
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| :<math>C_\mathrm h = C\,\cdot\bigg(\frac{288 - 6.5 h}{288}\bigg)^{5.2558}</math>
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| {| border="0" cellpadding="2"
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| |align=right|where:
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| !align=right| '''h'''
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| |align=left|= altitude, in km
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| !align=right| '''''P'''''
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| |align=left|= atmospheric pressure at sea level
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| !align=right| '''''P'''''<sub>'''h'''</sub>
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| |align=left|= atmospheric pressure at altitude '''h'''
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| !align=right| '''''C'''''<br>
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| |align=left|= Air pollutant concentration, in mass per unit volume at sea level atmospheric pressure and specified temperature T
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| !align=right| '''''C'''''<sub>'''h'''</sub>
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| |align=left|= Concentration, in mass per unit volume at altitude '''h''' and specified temperature T
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| |}
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| As an example, given an air pollutant concentration of 260 mg/m<sup>3</sup> at sea level, calculate the equivalent pollutant concentration at an altitude of 2800 meters:
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| :'''''C'''''<sub>'''h'''</sub> = 260 × [ { 288 - (6.5)(2.8) } / 288]<sup> 5.2558</sup> = 260 × 0.71 = 185 mg/m<sup>3</sup>
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| Note:
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| * The above equation for the decrease of air pollution concentrations with increasing altitude is applicable only for about the first 10 km of altitude in the [[troposphere]] (the lowest atmospheric layer) and is estimated to have a maximum error of about 3 percent. However, 10 km of altitude is sufficient for most purposes involving air pollutant concentrations.
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| ==Correcting concentrations for reference conditions==
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| Many environmental protection agencies have issued regulations that limit the concentration of pollutants in gaseous [[Emission standards|emissions]] and define the reference conditions applicable to those concentration limits. For example, such a regulation might limit the concentration of [[Nitrogen oxide|NOx]] to 55 ppmv in a dry combustion exhaust gas (at a specified reference temperature and pressure) corrected to 3 volume percent [[Oxygen|O<sub>2</sub>]] in the dry gas. As another example, a regulation might limit the concentration of total particulate matter to 200 mg/m<sup>3</sup> of an emitted gas (at a specified reference temperature and pressure) corrected to a dry basis and further corrected to 12 volume percent [[Carbon dioxide|CO<sub>2</sub>]] in the dry gas.
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| Environmental agencies in the USA often use the terms "dscf" or "scfd" to denote a "standard" cubic foot of dry gas. Likewise, they often use the terms "dscm" or "scmd" to denote a "standard" cubic meter of gas. Since there is no universally accepted set of "standard" temperature and pressure, such usage can be and is very confusing. It is strongly recommended that the reference temperature and pressure always be clearly specified when stating gas volumes or gas flow rates.
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| ===Correcting to a dry basis===
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| If a gaseous emission sample is analyzed and found to contain water vapor and a pollutant concentration of say 40 ppmv, then 40 ppmv should be designated as the "wet basis" pollutant concentration. The following equation can be used to correct the measured "wet basis" concentration to a "[[dry basis]]" concentration: | |
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| :<math>C_\mathrm{dry\, basis} = \frac{C_\mathrm{wet\, basis}}{1 - w}</math>
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| {| border="0" cellpadding="2"
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| |align=right|where:
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| !align=right|'''''C'''''
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| |align left|= Concentration of the air pollutant in the emitted gas
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| !align=right|'''''w'''''
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| |align=left|= fraction, by volume, of the emitted gas
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| |}
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| As an example, a wet basis concentration of 40 ppmv in a gas having 10 volume percent water vapor would have a:
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| :'''''C'''''<sub>'''dry basis'''</sub> = 40 ÷ ( 1 - 0.10 ) = 44.4 ppmv.
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| ===Correcting to a reference oxygen content===
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| The following equation can be used to correct a measured pollutant concentration in a dry emitted gas with a measured O<sub>2</sub> content to an equivalent pollutant concentration in a dry emitted gas with a specified reference amount of O<sub>2</sub>:<ref name=Lewandowski>{{cite book|author=David A. Lewandowski|title=Design of Thermal Oxidation Systems for Volatile Organic Compounds|edition=1st Edition|publisher=CRC Press|year=1999|isbn=1-56670-410-3}}</ref>
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| :<math>C_\mathrm r = C_\mathrm m\cdot\frac{(20.9 - \mathrm{reference\,volume\, %\, O_2})}{(20.9 - \mathrm {measured\,volume\, %\, O_2})}</math>
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| {| border="0" cellpadding="2"
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| |align=right|where:
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| !align=right| '''''C'''''<sub>'''r'''</sub>
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| |align=left|= corrected concentration of a dry gas with a specified reference volume % O<sub>2</sub>
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| |-
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| !align=right| '''''C'''''<sub>'''m'''</sub>
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| |align=left|= measured concentration in a dry gas having a measured volume % O<sub>2</sub>
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| |}
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| As an example, a measured NOx concentration of 45 ppmv in a dry gas having 5 volume % O<sub>2</sub> is:
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| :45 × ( 20.9 - 3 ) ÷ ( 20.9 - 5 ) = 50.7 ppmv of NOx
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| when corrected to a dry gas having a specified reference O<sub>2</sub> content of 3 volume %.
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| Note:
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| * The measured gas concentration '''''C'''''<sub>'''m'''</sub> must first be corrected to a dry basis before using the above equation.
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| ===Correcting to a reference carbon dioxide content===
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| The following equation can be used to correct a measured pollutant concentration in an emitted gas (containing a measured CO<sub>2</sub> content) to an equivalent pollutant concentration in an emitted gas containing a specified reference amount of CO<sub>2</sub>:<ref name=Lewandowski/>
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| :<math>C_\mathrm r = C_\mathrm m\cdot\frac {(\mathrm{reference\,volume\,%\,CO_2})}{(\mathrm{measured\,volume\,%\,CO_2})}</math>
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| {| border="0" cellpadding="2"
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| |-
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| |align=right|where:
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| !align=right| '''''C'''''<sub>'''r'''</sub>
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| |align=left|= corrected concentration of a dry gas having a specified reference volume % CO<sub>2</sub>
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| |-
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| !align=right| '''''C'''''<sub>'''m'''</sub>
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| |align=left|= measured concentration of a dry gas having a measured volume % CO<sub>2</sub>
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| |}
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| As an example, a measured particulates concentration of 200 mg/m<sup>3</sup> in a dry gas that has a measured 8 volume % CO<sub>2</sub> is:
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| :200 × ( 12 ÷ 8 ) = 300 mg/m<sup>3</sup>
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| when corrected to a dry gas having a specified reference CO<sub>2</sub> content of 12 volume %.
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| ==References==
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| {{Citizendium}}
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| {{reflist}}
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| {{DEFAULTSORT:Air Pollutant Concentrations}}
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| [[Category:Chemical engineering]]
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| [[Category:Air pollution]]
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| [[Category:Environmental engineering]]
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