Size Distribution and Sources of Particles in Ambient Air

July 1, 2017

Particle Size and Distribution in Ambient Air

The particle sizes in the ambient air are ranged from 1 nanometer to slightly more than 10 micrometers. There are three modes: coarse, fine and nano. The course mode particles are road dusts, spores and pollens. The minimum sizes of these particles are 1 to 3 micrometers. The fine mode particles are generally secondary particles formed from reactions such as smoke, sulfates, nitrates, ammonium and lead. The minimum sizes of these particles are about 0.1 micrometers. Following Steinfeld & Pandis in 1998, a typical example of the size (volume) distribution of the urban & freeway is attached below.

Sources of Ambient Air Particles

EPA establishes air quality standards to protect public health, and also sets limits to protect public welfare including plants and animals, from harm, as well as protecting against decreased visibility and damage to crops, vegetation, and buildings. The followings are six common air pollutants:

nitrogen dioxide (NO2),
ozone (O3),
sulfur dioxide (SO2),
particulate matter (PM),
carbon monoxide (CO), and
lead (Pb)

Ozone is formed when oxides of nitrogen (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight.

There are 12 major source sectors. The table below provides more detail about which sources are included in each sector.

12 Major Source Sectors	Detailed Category Names
Fertilizer & Livestock	Livestock Waste
Fertilizer & Livestock	Fertilizer Application
Electricity Generation	Fuel Combustion – Electric Utilities
Fossil Fuel Combustion	Fuel Combustion – Industrial Boilers, Internal Combutions Engines
	Fuel Combustion – Commercial/Institutional
	Fuel Combustion – Residential Fossil
Residential Wood Combustion	Fuel Combustion – Residential Fireplaces
Residential Wood Combustion	Fuel Combustion – Residential Woodstoves
Waste Disposal	Waste Disposal
Waste Disposal	Waste Disposal – Open Burning
Fires	Wildfires
	Prescribed Fires
	Agricultural Field Burning
	Logging Slash Burning
Industrial Processes	Industrial Process – NEC
	Commercial Cooking
	Industrial Process – Metals
	Industrial Process – Chemical Manufacturing
	Industrial Process – Storage & Transfer
	Industrial Process – Petroleum Refineries
	Industrial Process – Oil & Gas Production
	Industrial Process – Pulp & Paper
	Industrial Process – Cement Manufacturing
On Road Vehicles	On-Road Vehicles – Gasoline
On Road Vehicles	On-Road Vehicles – Diesel
Non Road Equipment	Non-Road Equipment – Gasoline
	Non-Road Equipment – Diesel
	Planes, Trains, & Ships
Road Dust	Unpaved Roads
Road Dust	Paved Roads
Solvent Use	Solvent – Non-industrial
	Surface Coating – Industrial
	Degreasing
	Surface Coating – Architectural
	Graphic Arts
	Solvent – Not Classified Elsewhere
	Dry Cleaning
Miscellaneous	Agriculture – Crop Tilling & Livestock Dust
	Construction
	Gas Stations
	Bulk Gasoline Terminals
	Other Miscellaneous Sources

(EPA)

Particulate Matter (PM): The major source of PM10 is road dust and secondly source is miscellaneous. For PM2.5, there are various sources including road dust, miscellaneous, industrial processes, electricity generation, any combution related, waste disposal and vehicles.

Volatile organic compounds (VOCs): The sources of volatile organic compounds (VOCs) emissions are solvent use, vehicles, industrial processes, miscellaneous, any combustion related, and waste disposal.

Sulfur dioxide (SO2): The major source of SO2 is electricity generation and fossil fuel combustion and industrail processes are 2^nd and 3^rd sources, respectively.

Nitrogen oxides (NOx): The sources of nitrogen oxides emissions are vehicles, electricity generation and fossil fuel combustion, industrial processes and waste disposal.

Lead (Pb): The sources of lead emissions are off-highway vehicles, industrial processes, fossil fuel combustion, waste disposal and electricity generation.

Carbon monoxide (CO): The sources of carbon monoxide are vehicles and any combustion related.