AMD stands for Air Monitoring Directive. Developed by Alberta Environment, the AMD sets the standards with which air monitoring operations must comply.
An anemometer is an instrument for measuring wind speed. There are two common types: rotating cup and propeller anemometers. In the WBEA network, rotating cup anemometers are used for horizontal wind speed measurement. Propeller anemometers are used for vertical wind speed measurement.
Air quality analyzers that measure low concentrations of pollutants are complex instruments that require periodic calibration. In most cases, regulation requires that they be calibrated at least once per month. During the period between calibrations, the output from the analyzers will drift. Because of the constant degradation of certain components (like lamps) over time, a negative drift is common. A reading of -2 ppb from an S02 analyzer is not uncommon.
Analyzers may also drift positive. The amount of drift is measured daily during the zero part of the zero/span cycle. Baseline correction is the process of using this zero data to correct the raw measurements from the analyzer.
Generally speaking, calibration is the process of ascertaining the outputs from a device for a set of known inputs. For air monitoring in Alberta, calibration means the monthly calibration of the air quality instruments. Typically this calibration requires four known input concentrations, including zero. Linearity checks and linear regression are done.
CO (Carbon Monoxide)
Carbon monoxide is a colourless, odorless, and tasteless gas produced by the incomplete combustion of carbon containing fuels. It has a strong affinity for haemoglobin and thus reduces the ability of blood to transport oxygen. Exposure to concentrations of 400 to 500 ppm for periods of one hour may not produce an appreciable effect, while concentrations in excess of 4000 ppm may cause asphyxiation. Long-term exposure to low concentrations may cause adverse effects in people suffering from cardiovascular disease.
Transportation is the major source of CO, with elevated concentrations during the morning and evening rush hours. Other sources include building heating systems, boiliers and industrial operations.
The Alberta Environment guidelines for the maximum permissible concentrations of carbon monoxide are based on prevention of adverse human health effects. The maximum permissible concentrations are:
- 1-hour average of 13.0 ppm
- 8-hour average of 5.0 ppb
COH (Coefficient of Haze)
COH stands for coefficient of haze which is a measure of particulate matter in the air. This type of measurement is becoming obsolete as new technology is being developed. There are no longer any COH instruments in the WBEA. Instead, PM2.5 and PM10 are measured.
Continuous and Non-Continuous
Continuous analyzers take measurements continuously. One minute, five minute, and one hour averages are calculated by regularly sampling (once per second or more often) the output of the analyzer. Non-continuous instruments do not have such an output. For example, passives simply absorb a pollutant over a time interval that may be several weeks long. Analysis of the passive will indicate an average concentration for the entire time period.
Critical load is the highest deposition load that will not cause chemical changes leading to long-term harmful effects on the most sensitive ecological systems.
Global radiation is a measure of the total radiation coming from the sun both directly and indirectly.
H2S and TRS
The term total reduced sulphur compounds (TRS) is used to collectively describe hydrogen sulphide and mercaptans. The major component is hydrogensulphide (H2S). It is a colourless gas with a characteristic rotten egg odour and is toxic at high concentrations.
Hydrogen sulphide is produced both naturally and through industrial processes. It is found naturally in coal, natural gas, oil, sulphur hot springs, sloughs, swamps, and lakes. The decomposition of organic matter by bacteria under anaerobic conditions results in the release of H2S and this results in the characteristic odor commonly associated with sewers, sewage lagoons, and swamps. Industrial sources are primarily petroleum refining, petrochemical complexes, and pulp and paper mills.
Sulphur is removed from bitumen by Oil Sand industries, first as H2S and then converted into elemental sulphur or burned to produce SO2. However, some H2S does escape from fugitive sources with the plant areas. H2S has been released from the tailings ponds on an intermittent basis as well.
Alberta guidelines for normal quantities of H2S in ambient air:
- 1-hour average of 10 ppb
- 24-hour average of 3.0 ppb
A leaf wetness sensor is mounted outside at ground level where it presents to the environment a surface like that of a leaf. The sensor outputs a reading of zero in conditions of dryness. As the dampness of its surface increases, its output increases. Although the leaf wetness sensor is most dramatically affected by precipitation, dampness caused by morning dew also creates an output.
NOx (Oxides of Nitrogen)
The oxides of nitrogen, most commonly in the form of nitrogen oxide, are produced by high temperature combustion of fossil fuels. Nitrogen oxide is the most predominant gas emitted by most combustion sources but it is rapidly oxidized to nitrogen dioxide in the atmosphere.
For the purposes of air quality monitoring,oxides of nitrogen are considered to be the sum of nitric oxide and nitrogen dioxide. Most oxides of nitrogen are emitted in the form of nitric oxide. Nitric oxide will rapidly react with ozone in the atmosphere to form nitrogen dioxide.
In Alberta, about 43% of oxides of nitrogen emissions are produced by transportation (primarily vehicles), while 37% are due to industrial sources (oil and gas industries) and 18% are due to power plants (based on 1990 emission estimates). Smaller sources of oxides of nitrogen include natural gas combustion, heating fuel cumbustion, and forest fires. The largest urban source of oxides is emission from motor vehicles.
Nitrogen dioxide NO2 is a reddish-brown gas with a pungent irritating odour. It has been implicated in acute and chronic respiratory disease and as a source of acid rain. It plays a major role in atmospheric photochemical reactions and ground level ozone formation. Guidelines for nitrogen dioxide are based on prevention of human health effects.
Alberta guidelines for normal quantities of NO2 in ambient air:
- 1-hour average of 210 ppb
- 24-hour average of 110 ppb
- Annual average of 30 ppb
Ozone is both a natural component of the atmosphere and a major constituent of photochemical smog. At ambient concentrations, it is an odourless, colorless gas, but at high concentrations, such as found near photocopier machines and near electrical discharges, it has a sharp odor.
Ozone is a strong oxidizer and can irritate eyes, nose and throat. High concentrations can increase susceptibility to respiratory disease.
Unlike other pollutants, ozone is not emitted directly by man’s activities, but is generated by a photochemical reaction of oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Ozone is also transported to ground level from the upper atmosphere by natural meteorological mixing processes. Ozone and ozone precursors, such as NOx and VOCs, may also be carried from upwind sources such as urban centres and industrial complexes. A major source of VOCs in rural areas is natural emission from trees and vegetation. In Alberta, ozone concentrations are generally lower at urban locations than at rural locations. This is due to the destruction of ozone by nitric oxide which is emitted by vehicles.
In Alberta, maximum ozone values are generally recorded during the spring and summer months at all monitoring stations. During the late spring and summer, ozone production in the lower atmosphere is at a maximum due to a peak in incoming sunlight combined with stagnant weather conditions which may cause reactive pollutants to remain in the region for a prolonged period of time. During the early spring, high daily average ozone values may be influenced by transport of ozone from the upper atmosphere.
Alberta guidelines for normal quantities of O3 in ambient air are:
- 1-hour average of 82 ppb
- 24-hour average of 25 ppb
Passive monitoring systems are useful adjuncts to continuous air monitoring networks. They require no expensive shelters or power and can be deployed in remote locations. They provide average concentrations of pollutants over a previously selected monitoring period; usually one to three months. The WBEA uses a network of passive monitors to measure concentrations of sulphur dioxide, ozone, and nitrogen dioxide at remote forest locations.
pH is the measurement of the degree of acidity on a scale of 1 to 14. One is very acidic, 7 is neutral, and 14 is very alkaline. The natural pH of precipitation in the absence of pollution is thought to be 5.6.
Ambient particulate matter consists of a mixture of particles of varying size and chemical composition. Particles which are less that 10 micrometers in diameter (PM10) can be inhaled. The fraction of particles that are less than 2.5 micrometers in diameter (PM2.5) could be retained in the airways and lungs. Fine particles (PM2.5) also reduce visibility and contribute to soil acidification.
Sources of PM10 size particles include windblown soil, road dust and industrial activities. PM2.5 size particles are formed from gases released to the atmosphere by combustion processes such as from motor vehicles, gas plants, compressor stations, household heating appliances and forest fires.
There are currently no Alberta guidelines for normal quantities of PM10 or PM2.5 in ambient air. The Federal Government has proposed the following:
PM2.5 15 µg/m3
PM10 25 µg/m3
Air Quality Objectives
PM2.5 20 µg/m3
PM10 40 µg/m3
(µ = micrometre = micron)
ppb = parts per billion
ppm = parts per million
Precipitation is a measure of the water that has fallen from the sky. In the WBEA, tipping bucket rain gauges are used to measure precipitation during the non-winter months.
QAQC is the acronym for Quality Assurance Quality Control. In the WBEA, the term is used to refer to the process of adjusting and inspecting data to insure its quality. For example, data that is created by a malfunctioning analyzer is flagged as such and removed from the database.
Relative humidity is the ratio of the amount of moisture in the air to the amount of moisture in saturated air at the same temperature, pressure, and volume.
SO2 (Sulphur Dioxide)
Sulphur dioxide is formed during the processing and combustion of fossil fuels containing sulphur. It is a colorless gas with a pungent odour at low concentrations. Sulphur reacts in the atmosphere to form sulphuric acid and acidic aerosols which contribute to acid rain. Sulphur dioxide combines with other gases to produce aerosols which may reduce visibility.
Brief exposure to high concentrations of sulphur dioxide and its products can produce human health effects, irritating the upper respiratory tract and aggravating existing cardiac and respiratory disease. Long-term exposure may increase the risk of developing chronic respiratory disease.
In Alberta, it is estimated that 42% of sulphur dioxide emissions are emitted by natural gas processing plants while oil sands and power plants produce about 26% and 18%, respectively based on 1990 emission inventory). Other sources include gas plants flares, oil refineries, pulp and paper mills and fertillizer plants.
Alberta Environmental Protection has adopted Environmental Canada’s most rigorous objectives for sulphur dioxide. The guidelines are based on prevention of effects to vegetation.
Alberta guidelines for normal quantities of SO2 in ambient air:
- 1-hour average of 170 ppb
- 24-hour average of 60 ppb
- Annual average of 10 ppb
The WBEA measures lots of temperatures. The internal temperature of each of stations is monitored to insure that the heating/cooling systems are working. Analyzers do not give accurate readings if they are running in ambient temperatures that are either too hot or too cold. Many external temperatures are also measured. At Lower Camp (Station 3) and Mannix (Station 5) temperature gauges are mounted at various heights so that temperature differences may be calculated.
THC (Total Hydrocarbons)
Total Hydrocarbons are colourless, flammable, non-toxic gases with characteristic odours. This includes methane, ethane, propane and butane. They often occur in petroleum, natural gas and coal.
There are currently no Alberta guidelines for normal quantities of THC in ambient air.
The term “total hydrocarbons” refers to a broad family of chemicals that contain carbon and hydrogen atoms. Methane, a non-reactive hydrocarbon, is the most common hydrocarbon in the earth’s atmosphere. Reactive hydrocarbons such as alkenes, alkynes and aromatics are important because they can: (1) react with oxides of nitrogen in the presence of sunlight to form ozone; and (2) be toxic to humans, animals or vegetation. Sources of hydrocarbons include vehicular emissions, gasoline marketing and storage tanks, petroleum and chemical industries, vegetation, dry cleaning, fireplaces, natural gas combustion and aircraft traffic. Alberta does not have guidelines for ambient (outdoor) concentrations of total hydrocarbons.
Tipping Bucket Rain Gauge
This gauge measures rainfall and is only operational during the months when it rains. In this instrument, the rain water is fed into a small container that tips whenever the weight of the water exceeds a set amount. The tipping action sends an electrical pulse that is counted by the data acquisition system. Each tip corresponds to 0.1 mm of rain.
VOC (Volatile Organic Compounds)
Volatile Organic Compounds can be emitted naturally or as byproducts of industrial processes. Examples are terpenes produced by forests, ethylene from industrial and natural sources, and chloroform from industry.
Three aspects of the wind are measure in the WBEA. At each station, horizontal wind speed and wind direction are measured. At Lower Camp (Station 3) and Mannix (Station 5), vertical wind speed is also measured. For horizontal wind, the speed and direction are combined to form a velocity vector. The averages calculated by the data acquisition system are vector averages. In addition, standard deviation of wind speed and wind direction are calculated. Average vertical wind speed tends to be near zero. The important measure regarding vertical wind is its standard deviation.
Part of the QAQC process for many of the continuous analyzers is the daily zero/span cycle. Each day, usually in the early hours of the morning, the normal sample port is closed to the analyzer and, for about 20 minutes, zero air is fed to the analyzer. Zero air is air from a cylinder or air that has been filtered so that it contains almost no pollutant. The analyzer should read zero. If the analyzer does not read zero, then the data is adjusted by a corresponding amount.
This common procedure is known as baseline correction. After the zero air comes the span gas. Span gas is air with a known high concentration of pollutant. The analyzer should output a reading that is within 10 percent of the known concentration. If it does not, then the analyzer must be calibrated. After the zero and span gases have been passed through the analyzer, the sample port is again opened. About 10 minutes is allowed for the analyzer to recover before readings are accepted again as real.