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Atmospheric pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude because the atmospheric pressure decreases with increasing altitude. The change of atmospheric pressure with altitude can be obtained from this equation: [2]
mg/m 3 = milligrams of pollutant per cubic meter of air at sea level atmospheric pressure and T: ppmv = air pollutant concentration, in parts per million by volume T = ambient temperature in K = 273. + °C 0.082057338 = Universal gas constant in L atm mol −1 K −1: M = molecular mass (or molecular weight) of the air pollutant
A variant of the metric perm is used in DIN Standard 53122, where permeance is also expressed in grams per square meter per day, but at a fixed, "standard" vapor-pressure difference of 17.918 mmHg. This unit is thus 17.918 times smaller than a metric perm, corresponding to about 0.084683 of a U.S. perm.
A reference atmospheric model describes how the ideal gas properties (namely: pressure, temperature, density, and molecular weight) of an atmosphere change, primarily as a function of altitude, and sometimes also as a function of latitude, day of year, etc. A static atmospheric model has a more limited domain, excluding time.
= 205.196 548 3 mg carat (metric) ct ≡ 200 mg = 200 mg clove: ≡ 8 lb av = 3.628 738 96 kg: crith: ≡ mass of 1 L of hydrogen gas at STP: ≈ 89.9349 mg dalton: Da 1/12 the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest: ≈ 1.660 539 068 92 (52) × 10 −27 kg [20] dram (apothecary ...
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For carbon monoxide concentrations not exceeding 4 mg/m 3 24-hour mean. [ 2 ] Up to 30 % of Europeans living in cities are exposed to air pollutant levels exceeding EU air quality standards.
The daily light integral (DLI) is the number of photosynthetically active photons (photons in the PAR range) accumulated in a square meter over the course of a day. It is a function of photosynthetic light intensity and duration (day length) and is usually expressed as moles of light (mol photons) per square meter (m −2) per day (d −1), or: mol·m −2 ·d −1.