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A normal cubic meter (Nm 3) is the metric expression of gas volume at standard conditions and it is usually (but not always) defined as being measured at 0 °C and 1 atmosphere of pressure. A standard cubic foot (scf) is the USA expression of gas volume at standard conditions and it is often ( but not always ) defined as being measured at 60 ...
= 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
In Bangladesh, the official permissible threshold level of salt in groundwater for the coastal districts is set at 1,000 ppm or 1,500 μS/cm, which is higher than the standard set at 600 ppm (or mg/L) for the rest of the country. [24] It is also higher than the standard set by the World Health Organization of 250 mg/L. [28]
Its units are in parts per million (ppm) for gases and in milligrams per cubic meter (mg/m 3) for particulates such as dust, smoke and mist. The basic formula for converting between ppm and mg/m 3 for gases is ppm = (mg/m^3) * 24.45 / molecular weight. This formula is not applicable to airborne particles.
PELs for chemicals are measured in mg/M 3 (milligrams per cubic meter). [2] Mg/M 3 is used to measure pollutant’s mass in the air. [ 13 ] PELs compliance is monitored through direct reading measurement tools, various sampling methods, and measuring biological markers in workers.
The World Health Organization guidelines were most recently updated in 2021. [1] The guidelines offer guidance about these air pollutants: particulate matter (PM), ozone (O 3), nitrogen dioxide (NO 2), sulfur dioxide (SO 2) and carbon monoxide (CO). [2]
Manual samplers draw a known volume of air through a filter.The filter is weighed on an analytical balance before and after sampling, and the difference in weight divided by the volume of air pulled through the filter gives the mass concentration of the particulate.
Arsenic contamination of the groundwater in Bangladesh is a serious problem. Prior to the 1970s, Bangladesh had one of the highest infant mortality rates in the world. Ineffective water purification and sewage systems as well as periodic monsoons and flooding exacerbated these problems.