Environmental Parameters

When people talk about air quality monitoring they tend to think about the measurement of gaseous and particulate pollution in the atmosphere. Indeed that is the main reason why people invest in air monitoring systems like the AQM 65 compact air monitoring system.

But that is only half the story.

There is a very close relationship between air pollution and other environmental conditions at the monitoring site. To fully understand this relationship it is important to measure other environmental parameters such as temperature, humidity and wind. There is also a close link between air quality and other forms of environmental pollution such as noise or vibration. In some applications, such as construction, all three are regulated and must be reported on simultaneously.

That’s why we designed the AQM 65 to be a complete environmental monitoring station. Sensors for environmental parameters like wind, rain, solar radiation and noise can plug straight in and are logged and reported simultaneously with the system’s gas and particulate measurements.

Below is a summary of the main environmental measurements that can be integrated with the AQM 65 air monitoring system and a brief explanation of why it is important to measure them alongside gases and particulate.

Air temperature

Measuring air temperature can help explain the presence of certain gaseous and particulate pollutants. Ozone is formed by the reaction of NOx and VOCs with solar radiation. At higher temperatures, such as in the summer months, there is going to be more ozone present. Conversely, in the winter months when the air is cooler less NOx and VOCs are being converted to ozone resulting in higher concentrations of NOx and VOCs.

Furthermore, during the colder months there is often an increase in particulate matter due to a rise in use of fireplaces and wood stoves. This coupled with the chance of a temperature inversion will cause air pollutants to remain trapped at ground levels during colder days. In the warmer months, hot air will sit near the ground allowing air to rise easily carrying away pollutants. A temperature inversion is when cold air is trapped near the ground by a layer of warm air. During these events particulate and gaseous pollutants can rise to unhealthy levels.

Although the temperature of the air does not appear to have a direct effect on air pollution it can be used to make certain assumptions such as, higher temperatures mean higher solar radiation which results in more ozone present.

Relative humidity

Relative humidity is defined as the amount of moisture in the air compared to what the air can “hold” at that temperature. It is strongly associated with temperature and solar radiation in regards to its interaction with air pollution. Water vapour plays a crucial role in many thermal and photochemical reactions that take place in the atmosphere.

For example, water molecules can attach to corrosive gases such as sulphur dioxide resulting in an acidic solution that can damage property, crops and human health. Furthermore, water molecules can also attach to particles and significantly increase the amount of light scattered creating a haze.

Measuring relative humidity can help highlight the change in air pollution behaviour in relation to seasonal variation. In general, relative humidity is higher during the summer months when temperature and rainfall are at their highest.

Precipitation

The term precipitation refers to any weather condition where substances fall from the sky. This therefore includes rain, snow, sleet and hail. Similar to areas with high relative humidity, precipitation can dissolve acidic gaseous pollutants resulting in the creation of acidic rain. However, areas with high precipitation, in particular rainfall, tend to have better air quality. Rain can wash particulate matter and gaseous pollutants out of the atmosphere improving visibility and reducing pollutant concentrations.

It is worth mentioning that precipitation, relative humidity and air temperature are closely related. Although increased rainfall can help clean the air, if it is combined with high temperatures it can increase the humidity. It is beneficial to measure all 3 of these parameters to fully understand the mechanics at play.

Wind

Wind speed and direction should always be measured when air quality monitoring is taking place. Having this data available will help to improve your understanding of air pollution movement in and around the monitoring location. Wind can transport and disperse both gaseous and particulate pollution in the atmosphere. Understanding the direction of flow will help to determine the source of the pollution as well as gain a better insight into what is happening with the air.  Wind speed can then be used to estimate the level of dispersion.

To put it simply, the faster the wind speed the more ground level gaseous pollutants are dispersed and as a result, the lower the overall concentration of the gas in a given area. However, high wind speeds can also cause re-suspension of dust particles, increasing the concentration of particulate matter.

How wind affects air pollution behaviour is a complex subject which cannot be fully explained in a blog post! However, ensuring it gets measured will help explain some of the variations that may be seen in the pollution data.

Solar radiation

Sundown in desert.

Solar radiation is an important parameter to consider measuring as it is a contributing factor to the formation of photochemical smog events. The increase in pollution from combustion processes, such as vehicle emissions, has caused an increase in nitrogen oxides and volatile organic compounds present in the atmosphere. When these gases interact in the presence of solar radiation a chemical reaction takes place and ground level ozone is generated. This is a primary component of photochemical smog and is particularly harmful to humans.  By measuring solar radiation at locations close to combustion processes you can compare the ozone concentration against solar radiation and notice any notable correlations.

Measuring solar radiation can also be used to understand the phenomena of global dimming. This is a term used to describe the gradual reduction in direct solar intensity on the earth’s surface. An increase in particulate matter, caused by industrial processes, is absorbing solar radiation or reflecting it back into the atmosphere. Consequently, the amount of solar radiation hitting the earth’s surface is reduced.

As you can see, solar radiation is closely intertwined with the behaviour of both gaseous and particulate air pollution. It is therefore a useful parameter to be measuring to help explain changes in atmospheric conditions.

Noise

Although noise pollution does not impact air quality directly it can have significant and detrimental impact on people, wildlife or the environment. Noise exceeding safe limits (over 50 decibels) can be detrimental to hearing and has been seen to contribute to high blood pressure, strokes and heart attacks. Noise pollution has also been associated with reduced crop quality and changes in animal behaviour.

Many industrial sites where air quality monitoring is essential will also have regulation requirements for noise monitoring. The most common sources of noise pollution include transportation vehicles and construction site equipment. Therefore industries such as mining, quarrying and construction, as well as urban roadside applications, will all need noise pollution controls.

AQM 65, environmental monitoring system

Vaisala WXT520 Weather Sensor

The Vaisala WXT520, one of many sensors that plugs in to the AQM 65 air monitoring system.

At Aeroqual we realize the importance of being able to measure and report environmental parameters together with gaseous and particulate matter. That is why we designed our air quality monitoring systems to seamlessly integrate a suite of environmental sensors.

Our AQM 65 and Dust Monitors both come with a pre-configured auxiliary module which acts as an interface between ‘third party’ sensors and the instrument operating system. This means environmental sensors can be added without any additional configuration. Because we fit and test them at the factory and ship out a fully integrated package, you can be assured of their compatability with your air monitoring system. It also reduces the cost of on-site integration, installation and commissioning. Plus you get all your data from a single software interface – including on our web-based data acquisition system, Aeroqual Cloud.

The sensors we offer include:

Our instruments can provide simultaneous air quality and environmental monitoring. As a result, the Aeroqual design ensures you receive a complete environmental monitoring system.

To find out more please contact us.