Can air quality be better monitored?

Can air quality be better monitored?
Some pollutant emissions, like smog, can be seen, but not all harmful substances are easily detectable.

Could the air quality of megacities be monitored better – more accurately, and yet inexpensively? Finnish atmospheric scientists have found a way to get reliable measurement results with low-cost devices.

The ever-growing population of megacities suffer from improper air quality. Some pollutant emissions, like smog, can be seen, but not all harmful substances are easily detectable. There are, of course, various monitoring and warning systems, but they are often expensive.

Finnish atmospheric researchers have therefore brought their expertise together with data scientists in order to alleviate the problem.

“We cannot immediately wipe out all pollutants from the atmosphere, but we could construct a new kind of monitoring method to make life easier and healthier for people living in big cities. Above all, we could make it more exhaustive but with lower costs than many cities do now.”

This is how Markku Kulmala, the head of the Institute of Atmospheric and Earth System Research INAR, describes his research interest with data scientists.

In other words, Kulmala and his colleagues have found an ingenious way of reaching accurate and reliable measurement results for air quality even when the sensors used are not up-to-date – and consequently, of lower cost. Thus, megacities in developing countries could also be able to afford a system which monitors air quality and provides alarms in advance for the tiniest amount of hazardous substances landing in the atmosphere.

Kulmala and his colleagues plan to combine masses of common off the shelf sensors to work in line with technically specific, up-to-date field stations, the so-called SMEAR-stations, for which Kulmala and his institute are world-famous. The actual station is, of course, expensive, but only one is needed for a large area like a megacity and its surrounding environment. The rest of the job could be performed by simple gadgets sold in ordinary stores like Amazon. The low-budget boxes could be fastened to traffic signs, buildings and public transport vehicles to sense the atmosphere and exchange data with the SMEAR-station. All this is ‘contained within’ a project called ‘Megasense’.

Artificial intelligence (AI) supports the calibration

The key for the successful co-operation of one up-to-date station and many low-quality sensors is calibration. Calibration, to put it very simply, refers to a method with which the differing measurement results of sensors and the station are made comparable.

In this very special case, the calibration is a demanding task. “We do not know yet whether we can make it work,” says Kulmala, but he is optimistic. He relies heavily on his partners, the data scientists of the University of Helsinki, who are headed by Professor Sasu Tarkoma.

“A dense network of low-cost sensors can be made to work together with one single high-quality station if the data transfer between them is effective, i.e., if a 5G-network is available. In addition to this, we are investigating artificial intelligence techniques for boosting the calibration,” explains Tarkoma. “We expect that the measurement station and the low-cost sensors form a matchless, real-time monitoring system for the air quality and, consequently, for the well-being of the citizens.”

At the moment, Tarkoma and his data experts test all the relevant equipment and software in Kumpula science campus, Helsinki, where one of the SMEAR stations is located.

Tarkoma and Kulmala are both experienced partners in various forums of Sino-Finnish scientific and industrial co-operation. As a consequence, Kulmala has been appointed to four honorary professorships in Chinese universities, with the latest being at Nanjing University.

The Megasense project may not only improve living conditions in the cities and create new industrial business, but also shed light on many purely scientific problems Kulmala and Tarkoma have been considering: basic research is, anyway, a matter closest to their hearts.

“But, of course, I must say there is another important motivator: the fact that millions of people die every year because of the polluted air,” they say. “Who wouldn’t like to work to bring about a change in it?”


What is SMEAR?

A SMEAR-station is kind-of well-equipped laboratory complex located in a forest, on a glacier or other terrain, or in urban area. It consists of several buildings, instruments and devices, including a measurement tower well over 100 meters in height, maintenance halls, power supplies such as generators, and residences for the researchers and technical staff.

All this is needed for the SMEAR-station to conduct its basic task, which is to measure the material and energy flows between the Earth’s surface and the atmosphere. There are, for example, gaseous chemical substances in the air emitted by vegetation which react with the molecular clusters already present in the air, thus forming new aerosol particles. In addition to the particles originating from Nature itself, pollutants also come from human action and industry. Together, they form a complex chemical mixture.

The energy flows, in turn, refer to the radiation of the Sun and the Earth’s surface. Radiation is always a nonmaterial, but it can, however, be measured and identified.

Altogether, there are myriads of different material and energy flows, concentrations and compositions. One fully equipped SMEAR station measures 1,200 of them every single second, around the clock and through the year.

The measurement data collected by the SMEAR stations is the cornerstone of all the scientific results reached by the Finnish Centre of Excellence. Many of the results are connected with the origin of the natural aerosol particles and, based on the discoveries, the centre’s researchers have founded three successful spin-off companies which manufacture, amongst other things, special sensors and particle counters.

The director of the Centre, Markku Kulmala, and his colleagues established the first SMEAR-station in 1991, and it has gone on to produce unbroken measurement data since then. Of the other stations, three are in Finland, one in Estonia, and one in China, with several others under construction. Kulmala and his team are aiming for a network of 400 stations around the world.

One station can cost up to €10m to establish, and to run it permanent technical staff are required.


Professor Sasu Tarkoma

Director, Department of

Computer Sciences

Academician Markku Kulmala

INAR director

Mai Allo

Institute of Atmospheric and Earth System Research (INAR)

University of Helsinki

This article will appear in SciTech Europa Quarterly issue 28, which will be published in September, 2018.

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