Since 2004, the Northern Territory Government has conducted particulate monitoring in the Darwin region. In late 2010 monitoring was expanded to include a full ambient air quality monitoring station located near Palmerston. Another station was installed at Winnellie in mid 2012. In accordance with the National Environment Protection (Ambient Air Quality) Measure 1998 (Air NEPM) each station houses the following instruments:
- Dichotomous Tapered Element Oscillating Microbalance (TEOM) particulate monitor for near real time analysis of particulates less than 10 microns and less than 2.5 microns.
- Carbon Monoxide (CO) analyser
- Oxides of Nitrogen (NOX, NO and NO2) analyser
- Ozone (O3) analyser
- Sulfur Dioxide (SO2)
To assist in interpretation of the air quality data meteorological data is also collected from instruments on the same site.
In general the primary pollutant in Darwin and Palmerston is smoke from distant and local vegetation burning during the Dry season and is represented by particulates less than 2.5 microns. The gases CO, NO2 and SO2 all occur at very low levels compared to large cities in other parts of Australia while Ozone occurs at moderate levels, typically due to natural processes. A website displaying live and historical data from the two stations is available for public access and can be accessed via the link below:
About Air Pollutants
Ozone - 03
Near the ground, ozone is a colourless, gaseous secondary pollutant. It is formed by chemical reactions between reactive organic gases and oxides of nitrogen in the presence of sunlight. Ozone is one of the irritant secondary pollutants in photochemical smog and is often used as a measure of it.
The formation of ozone in the upper levels of the atmosphere or 'stratosphere' is by a different process. Ozone there is not regarded as a pollutant because it is produced naturally. It is important in absorbing harmful ultraviolet radiation and preventing it from reaching the earth. Ozone is strongly oxidising and can irritate the eyes and the respiratory tract. It also damages plants.
Ozone is more readily formed during the summer months and reaches its highest concentrations in the afternoon or early evening. If we breathe in too much ozone, it can irritate the lungs. Breathing ozone can affect lung function and worsen asthma. You may notice difficulty in breathing, coughing, and throat irritation if you are exercising outdoors when ozone levels are high.
Nitrogen dioxide - NO2
The main oxides of nitrogen present in the atmosphere are nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O). Nitrous oxide occurs in much smaller quantities than the other two, but is of interest as it is a powerful greenhouse gas and thus contributes to global warming.
The major human activity which generates oxides of nitrogen is fuel combustion, especially in motor vehicles. Oxides of nitrogen form in the air when fuel is burnt at high temperatures. This is mostly in the form of nitric oxide with usually less than 10% as nitrogen dioxide. Once emitted, nitric oxide combines with oxygen ('oxidises') to form nitrogen dioxide, especially in warm sunny conditions.
These oxides of nitrogen may remain in the atmosphere for several days and during this time chemical processes may generate nitric acid, and nitrates and nitrites as particles. These oxides of nitrogen play a major role in the chemical reactions which generate photochemical smog.
Nitrogen dioxide is found at highest concentrations near busy roads and can also be high indoors when unflued gas appliances are used. Nitrogen dioxide irritates the lungs and makes people with asthma more susceptible to lung infections and asthma triggers like pollen and exercise.
Carbon monoxide - CO
Carbon monoxide is an odourless, colourless gas produced by incomplete oxidation (burning). As well as wildfires, carbon monoxide is produced naturally by oxidation in the oceans and air of methane produced from organic decomposition. In cities, the motor vehicle is by far the largest human source, although any combustion process may produce it.
Carbon monoxide usually remains in the atmosphere for a month or two. It is removed by oxidation to form carbon dioxide, absorption by some plants and micro-organisms, and rain.
When inhaled, carbon monoxide binds to the oxygen-carrying site on the blood's haemoglobin, which reduces oxygen transport in the body. At high concentrations it is very toxic, causing headaches, dizziness, reduced ability to think, and nausea.
Carbon monoxide enters the bloodstream through the lungs and prevents the normal transport of oxygen by blood. This can reduce the amount of oxygen reaching the body's organs and tissues, especially the heart. People suffering from heart disease are most at risk. They may experience chest pain if they are exposed to carbon monoxide, particularly while exercising.
Sulfur dioxide - SO2
Sulfur dioxide in the atmosphere arises from both natural and human activities. Natural processes which release sulfur compounds include decomposition and combustion of organic matter; spray from the sea; and volcanic eruptions. The main human activities producing sulfur dioxide are the smelting of mineral ores containing sulfur and the combustion of fossil fuels.
Sulfur dioxide dissolves in water to form sulfuric acid. This is a corrosive substance that damages materials and the tissue of plants and animals.
Sulfur dioxide irritates the airways of the lungs. People with asthma who are physically active outdoors are most likely to experience the health effects of sulfur dioxide. This may include wheezing, chest tightness, and shortness of breath.
Particles - PM10, PM2.5
Not only are there gaseous pollutants, there are also solid or liquid particles that may be suspended in the air and may reduce visual amenity and adversely impact health.
The NT EPA measures particles as PM10 (particles less than 10 micrometers in diameter) and PM2.5 (particles less than 2.5 micrometers in diameter).
Examples of particles in the air include dust, smoke, plant spores, bacteria and salt. Particulate matter may be a primary pollutant, such as smoke particles, or a secondary pollutant formed from the chemical reaction of gaseous pollutants.
Human activities resulting in particulate matter in the air include mining; burning of fossil fuels; transportation; agricultural and hazard reduction burning; the use of incinerators; and the use of solid fuel for cooking and heating.
Particulate matter can be usefully classified by size. Large particles usually settle out of the air quickly while smaller particles may remain suspended for days or months. Rainfall is an important mechanism for removing particles from the air.
The size of a particle also determines its potential impact on human health. Larger particles are usually trapped in the nose and throat and swallowed. Smaller particles may reach the lungs and cause irritation there. Fine particles can be carried deep into the lungs and irritate the airways. When exposed to particle pollution, people suffering from heart disease may experience symptoms such as chest pain, and shortness of breath. Particle pollution can aggravate existing respiratory diseases such as asthma and chronic bronchitis.
These are based on validated data and are as presented to the National Environment Protection Council.
- Air Quality Monitoring Plan (PDF | 1.5 MB)
- Air Quality Study (PDF | 1.2 MB)
- Explanation of pollution wind rose charts (PDF | 209 KB)
- Reports submitted to the NEPC from the NT and other jurisdictions can be found at