Coarse particulate organic matter

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. 

Fiber-bed scrubbers are used to collect fine or soluble particulate matter or as mist eliminators to collect liquid aerosols, including inorganic (e.g., sulfuric acid mist) and volatile organic compounds. Insoluble or coarse PM will clog the fiber bed with time, and VOCs that are difficult to condense will not be collected efficiently. 

Particles that can be inhaled, those less than 10 p,m (10,000 nm PMIO) can be separated by the high volume cascade impactor (HVCI) into four fractions. When the HVCI was used to collect organic urban aerosols presumably from transportation, combustion, and the Earth s crust, the breathable particulate matter (PM) was divided into PM 10 to 2.5 p.m (coarse aerosols, which are mechanically produced), and the PM 2.5 to 1 p.m (intermodal) fiaclion, which is expected to have particles that contain properties of both coarse (larger) and fine (smaller) aerosols. In addition it separates the PM 1 to 0.2 p,m (1000 to 200 nm accumulation) fraction (just larger than nano- or ultrafine particles with properties similar to those particles) and PM 0.2 (particles <200 run diameter in air) firaction. The cutoff size (200 nm) was chosen for convenience. 

Turbidity is the measure of fine suspended matter in water, which is mostly caused by clay, silt, organic particulates, plankton, and other microscopic organisms, ranging in size from colloidal to coarse dispersion. Turbidity in the water is measured in nephelometric turbidity units (NTUs), which measure the amount of light scattered or reflected from the water. Officially reported in standard units or equivalent to milligrams per liter of silica of diatoma-ceous earth that could cause the same optical effect, turbidity testing is not required for groundwater sources. 

Environment Canada has collected inhalable partides (<10 pm in diameter) in 15 Canadian cities since May 1984. Restdts for the period from May 1984 to December 1987 show that average inhalable particulate levels ranged fi om 17 pg/m in St. John s to 49 pg/m at a site in Montreal. Analysis has shown that the finest of the inhalable particles— those with a diameter less than about 2.5 pm— are different in origin and composition from the coarser particles in the 2.5- to 10-pm-diameter range. The coarse particles are mostly of natural origin (minerals from Earth s crust, sea salt, and plant material), whereas the fine particles consist of lead, sulfates, nitrates, carbon, and a variety of organic compoimds, mainly resulting from man-made pollution. At eastern Canadian sites, fine particulate matter accounted for more than 60 percent of the inhalable particles at sites in the Prairie provinces, the fine fraction was usually less than 40 percent of the inhalable particles. 

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