Atmosphere, ambient, dust levels

Airborne particulate matter, which includes dust, dirt, soot, smoke, and liquid droplets emitted into the air, is small enough to be suspended in the atmosphere. Airborne particulate matter may be a complex mixture of organic and inorganic substances. They can be characterized by their physical attributes, which influence their transport and deposition, and their chemical composition, which influences their effect on health. The physical attributes of airborne particulates include mass concentration and size distribution. Ambient levels of mass concentration are measured in micrograms per cubic meter (mg/m ) size attributes are usually measured in aerodynamic diameter. Particulate matter (PM) exceeding 2.5 microns (/i) in aerodynamic diameter is generally defined as coarse particles, while particles smaller than 2.5 mm (PMj,) are called fine particles. 

In summary, improper e-waste recycling operations are the major contributors of dioxin and dioxin-like compounds to the terrestrial environment in China [7]. The lower concentrations of dioxin and dioxin-like compounds at reference sites than at e-waste recycling sites suggest the likelihood for these chemicals to transport atmospherically from where they are generated to distant areas. We can also infer that dioxin and dioxin-like compounds initially derived from burning of e-waste can enter ambient air and dust and finally deposit into soil. This notion is supported by the significant positive correlation between the levels of PCDD/Fs in dust and soil samples from Taizhou. 

Plutonium deposited on soil surfaces may be resuspended in the atmosphere especially in areas that have low soil moisture levels, such as the Nevada Test Site. In drier areas, the levels of ambient airborne dust are expected to be higher than in areas with normal rainfall (Harley 1980). The highest concentrations of plutonium are likely to be found in the fine silt-clay particle size range. Particles of this size tend to be transported the farthest distance by wind and water (WHO 1983). 

Industrial stationary compressors are normally installed in separate rooms, drawing in air from the outside atmosphere, free of factory contaminants. When the level of dust concentration in the intake air is likely to be of the order of 10-50 mg/m, it is standard practice to fit the compressor with an intake filter (usually a panel filter or a paper cartridge type, depending on the size of the compressor), having an efficiency of 99.9% based on the dust concentration present in the ambient air. The air intake filter can, therefore, be expected to pass all particles smaller than 5 pm, as well as a proportion of larger ones, in addition to atmospheric water vapour. It will also pass all gases, vapours, odours, bacteria and viruses. 

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