Sources Of Particulate Matter Essay.
A brief summary of the sources of particulate matter (PM) will be presented. The will be a brief overview of ‘particulate matter’ in regard to sources, history and additionally there will informative discussion such as PM levels as set by authoritative regulations.Sources Of Particulate Matter Essay.
Discussion will include the different sources of particulate matter and with specific attention to emission vehicle fuel sources, since they are the largest contributors of PM in the environment (1, 2). Lastly, A brief discussion of the different metals found in ambient PM will be discussed and their health effects, these include copper, zinc and iron (4).
There are several sources from which particulate matter finds itself into the environment and ultimate humans, inhalation is the typical mechanism in which PM enters the body and is then absorbed during gas-exchange in the lungs (3). Therefore there will be a brief summary of the health effects of particulate matter (PM).Sources Of Particulate Matter Essay.
Discussion – Overview and a brief history
Particulate matter (PM) is a world wide problem; one of the major sources of PM is vehicle traffic and as a result it has been the subject of various epidemiological studies (1). Studies on PM have shown that particle size plays a key role on the adverse effects cause by PM concentrations (1). For example, studies have shown that children living near higher have larger risk of developing asthma and allergies from dust (2). Studies have also shown that the density of vehicles traffic does not account for differences in PM toxicity between similar communities; it therefore indicates that particle chemistry also plays a role in health effects (1, 2).
Particulate matter is typically composed of organic and inorganic materials and source are both natural and anthropogenic (1). Thus particulate matter can be divided in to two groups, Primary PM and Secondary PM: Primary PM can be the direct result of fossil fuel combustion, natural wood combustion, volcanoes, soil dust, pollen, smelting, mining and milling process (3). Secondary PM are created by chemical reaction of primary PM such as SO2, nitrogen oxides (NOx) and Ammonia (NH3), for example the formation of ammonium nitrate (NH4NO3) (3). However, Volcanoes, wildfires and other can contribute to both primary and secondary PM (3). Other natural sources include volatile organic compounds (VOC) from trees, vegetation and emission of gases such as sulfur from wet lands (3, 8).
Particle size pertaining to both primary and secondary PM can be subdivided into size fractions: Large particles are > 30µm and smaller particles are divided into PM2.5 (<2.5 µm) and PM10 (<10 µm) and lastly there are ultrafine particles of (<100 µm) (1,2). In the atmosphere, Total suspended particles (TSP) concentrations usually have higher concentrations of PM2.5 and PM10 than larger particles (> 30µm) since these are only suspended for short periods of time (1) (see figure 1 (6. PM of sizes smaller then 1 µm are consider to cause the most adverse effect since these can penetrate the pulmonary alveoli (part of the respiratory system for gas-exchange in the lungs) (1). Although particle size is a factor in the penetration capabilities of PM into the alveoli, another factor is the chemical composition of the PM (1). Some of the pollutants that are part of PM composition include heavy metals, polycyclic aromatic hydrocarbons (PAHs), and acid aerosols among others (1).
PM is considered one of the 6 criteria pollutants by the Environmental Protection agency (7). Additionally, The U.S. Clean Air Act and set by the EPA has established that the primary standard for the protection of human heath is PM10 at 150µg/m3 (24 hrs) and PM2.5 at 35µg/m3 (24 hrs) and 15µg/m3 (Annual) (7). The EPA recognizes that there is no threshold for the adverse health effects from long term exposure to PM10 therefore the annual PM10 standard has not been accepted (7).
In Canada, Air Quality objectives where first established in the 1970s and revised in 1980 under the knowledge that PM could cause adverse effect only in severe pollution loads (8, 9). However, it was not until the 1990s that serious health effects where identified for low levels of fine particles such as PM2.5 and PM10 (8, 9). As result, PM10 and PM2.5 where consider to be toxic and where included in the Canadian Environmental protection Act (CEPA, 1999), the Canada-Wide Standard (CWS) goal (set in 2000) for Canada ambient air quality are PM2.5 < 30µg/m3 (24 hrs) by 2010 (9) (see figure 2 and table 1 for CWS across Canada). Additionally, in 2003 the secondary pollutants forms of PM2.5 such as sodium oxides, nitrogen oxides and volatile organic compounds where consider to be toxic and added to CEPA (7). Lastly, Canada and the United States joined together to corporate in the reduction of PM under the Canada-United States Border Air Quality
Strategy (1991) (12).
As mention above, urban traffic is one of the major sources of PM; some studies in Copenhagen found that traffic accounts for about 13% for PM10 and 35% to 50% of PM2.5 (1). Most of vehicles today run on combustion engines using fossil fuel such as gasoline and diesel (diesel engines are known to contribute significantly in greater quantities to PM concentrations then gasoline engines) (1). Other sources of PM from vehicle traffic include brake pad wear, tire wear, and by physical resuspension of dust (1).
One of the challenges of studies on PM is to identify the source of the PM (1). Researches know that PAH and some of its derivatives are created via combustion of fossil fuel (1, 2). It is a selection of PAH derivates together with other organics chemicals such as hopanes and steranes (from lube oil) that are used in the identification of PM from traffic sources (1,2). Dynamometer test which is used for the measurement of HP and torque of engines provide a good control environment to adequately measure PM from engines, since exhaust lines are attached to collection and detection instruments (2). The only difficulty or limitation in dynamometer test is that real life environment of urban traffic has other factors that contribute to the overall PM concentrations, these include the age of the vehicle, maintenance history, size of engines (expensive to test every size engine), atmospheric interactions/reactions with other chemicals and other dust contributors like brakes dust etc (2).
Vehicle Emission a source of PM – Los Angeles, CA study
Because of the challenges presented for vehicle emissions there have been studies conduction in traffic tunnels, these present researchers with unique control environment (2). The only limitation of tunnel test is that it does not account for cold start emission since it only measures the vehicles through the driving conditions of the tunnel, secondly the tunnel may present different conditions than ambient conditions such as dilution with air, temperature and humidity (2).Sources Of Particulate Matter Essay.
Gas chromatography-mass spectrometry (GC-MS)) is the preferred method for the detection of atmospheric PM in the environment (2). The methods for identifying primary PM from gasoline and diesel engines has been to identify for example hapanes & steranes and tracing back of these chemicals using a chemical mass balance (CMB) (2). Other tracers include high molecular weight benzo perylene (BgP) for high powered gasoline vehicles and light molecular weight PAHs for diesel vehicles (2).
A study was conducted in two freeways: 1. the Interstate 710 (I-170) who’s traffic compositions is a mixture of gasoline power vehicles with a percentage of heavy-duty diesel vehicles. 2. The California freeway 110 (CA-110) in which traffic is normally composed of mainly gasoline power vehicles (2). During the study it was found that concentration level of hapanes, steranes, BgP and high molecular weight PAHs where similar comparable in both CA-110 and I-710 (2). However, there was higher level of elemental carbon (EC) and low molecular PAHs in I-710 as is expected due to the higher concentration of diesel vehicles (2). Measurements on site for CA-110 and I-710 locations where conducted using a custom built collection sampler able to measure 450 liter/minute (lpm) (2). The samples where then separated into:Sources Of Particulate Matter Essay.