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STUDYING THE POLLUTION FILTERING POTENTIAL OF DAMAS TREE WINDBREAKS
A British University in Dubai research team studied the efficiency of a Damas tree windbreak in filtering out larger particulate matter from the air, as a passive solution for sustainable urban development.
Urban development and general life in the UAE and wider Gulf region face a particular challenge in the form of dust. The UAE’s climate and terrain produce high levels of dust, which reduces air quality and impacts human health. In response to the need to reduce the impact of dust pollution, a British University in Dubai (BUiD) team has researched how to use a native tree species to reduce dust pollution in urban developments.
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While many people view dust as just a nuisance – something that accumulates on surfaces and requires regular removal – it is also a pollutant with health implications. In scientific terms, it is considered a type of particulate matter (PM), with the different particle sizes and compositions having varied environmental and health impacts.
There are two broad categories of PM. PM10 refers to coarser particles with a diameter greater than 2.5 micrometers (µm) and is the category in which dust typically falls. PM2.5 refers to finer particles with a diameter of less than 2.5µm. When we inhale, PM particles of both sizes can be deposited in our lungs.
The larger sized particles typically end up on the surface airways of the upper region of the lung, where they can induce tissue damage and inflammation, while the smaller particles can travel farther and even end up being absorbed into the bloodstream. This is why exposure to PM is considered a health hazard, with prolonged exposure contributing to coughing, wheezing, asthma attacks, high blood pressure, and even the risk of stroke and premature death.
WHILE MANY PEOPLE VIEW DUST AS JUST A NUISANCE – SOMETHING THAT ACCUMULATES ON SURFACES AND REQUIRES REGULAR REMOVAL – IT IS ALSO A POLLUTANT WITH HEALTH IMPLICATIONS.
The Middle East region is believed to be particularly impacted by the problem of dust pollution because of its natural dust sources, like windblown desert sand and sea spray, as well as human activity, like cement production and construction. The result is that the UAE has often recorded days of very high PM levels, with daily average values in the Western part of the country exceeding the national standard limit. In 2018, the UAE set a goal of increasing air purity to 90% by 2021 as part of its Vision 2021 goals. In light of the prevalence and risk of dust pollution in the UAE and the air purity goal, there is a need to improve air quality, and sustainable urban planning has been identified as one way to do that.
“One of the most pressing environmental issues today is sustainable urban planning. Because the landscape is so important to the quality of any urban environment, nature’s role is not only to beautify it but also to influence the shape of development and human wellbeing,” explained BUiD Faculty of Engineering and IT Associate Professor Dr. Hanan Taleb. She worked with BUiD Architecture and Sustainable Built Environment research associate and PhD student Mays Kayed to investigate the use of windbreaks as a sustainable urban planning solution to reduce dust pollution.
A windbreak is a row of shrubs, trees, or structures, planted or constructed to block and redirect wind flow. They are typically used to protect people’s homes, farmland, and animals from the damaging force of the wind, but the BUiD research team sought to explore their impact on PM levels.
“We aimed to investigate the role of adding windbreaks in order to lower the concentration of desert dust without compromising the natural ventilation in urban communities in Dubai. The effect of windbreaks was quantified by calculating the PM concentration in front of and behind the windbreak,” the authors wrote in a recently published paper in the journal Urban Forestry & Urban Greening.
While previous research had investigated the PM collection capabilities of specific tree species in other climates – like that of the hawthorn hedge in rural parts of the United Kingdom – no research had been done to measure the impact of green windbreaks on PM pollution in the UAE or to identify which type of tree would be best suited both for the PM filtering requirements and the UAE’s climate.
The researchers selected Al Furjan neighborhood in Dubai – an urban development that is surrounded by empty desert on three sides. They then located existing windbreaks within the development, which were formed using the hardy and popular Damas tree. The team analyzed the trees’ structure to understand its PM filtration effect and input the data into software that they used to determine the windbreak’s porosity. This was used to create a computational fluid dynamic analysis.
The team also collected PM10 data from the area for a year, as well as weather data on each month’s windiest days, and the hour of peak flux within each day. They then used data from that hour to simulate PM10 dispersal through two formations of Damas tree windbreaks – one placing the trees 20m apart, and another placing them 10m apart.
The resulting analysis showed that when the Damas trees are grown in a windbreak 20m apart, they are better able to block the flow of PM10. They also found that the angle of the wind had a significant impact on the effectiveness of the windbreaks in reducing PM10 concentration.
-Dr. Hanan Taleb Associate Professor British University in Dubai
“Our main findings were that the 20m tree spacing is more effective at reducing dust through a windbreak, compared to 10m spacing. Additionally, the windbreak’s effectiveness was increased when the wind was blowing perpendicular to the trees. If urban developers apply our findings and plant Damas windbreaks at 10m spacing between trees, they will achieve 19-22% dust reduction. This will result in a healthy community and pure ventilation. It will help UAE residents to enjoy the outdoors and will boost walkability,” Dr. Taleb shared, adding that her findings could also be applied to other countries with similar terrain and climate.
She has identified six further research questions relating to this topic, including investigating windbreak PM10 reduction in other climates, analyzing the PM10 filtration effects of other species of trees, and exploring the windbreaks’ filtration effects on PM2.5.