How can cities detect, and avoid, peaks in particulate-matter air pollution?

Pollution over Lyon. Image: Getty.

In January 2017, France and a large part of Europe were struck by episodes of particulate matter pollution. These microscopic particles are known as PM2.5 and PM10 when they measure less than 2.5 or 10 micrometers (µm) in diameter respectively. The Conversation

They are proven to be harmful to human health because they enter our respiratory system, and the smallest can even enter our blood flow. According to the European Environment Agency, air pollution is the cause of 467,000 premature deaths annually in Europe.

These particles can come from natural sources (sea salt, volcanic eruptions, forest fires, etc.) or human activities (transport, heating, industry, etc.)

What is a pollution peak?

Pollution peaks occur when regulatory warning thresholds, as defined in 2008 by the European Union and transposed to French law in late 2010, are exceeded. In virtue of these regulations, the first level of severity (known as the “public information and warning threshold”) is reached for PM10 particles when there are ≥50 µg per cubic meter of air (m³) in the atmosphere; the warning level is reached at ≥80 µg/m³.

There is no trigger limit for PM2.5, but just a set maximum amount of 25 µg/m³ on average per year.

However, these regulations have serious limitations. The “mass” concentration thresholds which indicate the total mass of particles in the air and which are used to assess the danger of particulate matter pollution are higher than the levels recommended by the WHO; the latter have been set for PM10 at 20 µg/m³ on average per year and 50 µg/m³ on average per day, in order to take account of chronic and short-term exposure.

In addition, the only parameter taken into account in European and French regulations concerns mass concentration. The concentration in terms of number (i.e. the number of particles per m³ of air), and the chemical composition are not taken into account for the triggering of warnings.

Lastly, there are no regulations for very small particulate matter (less than 1 µm), which is mainly produced by human activity, even though it is potentially the most harmful.

Comparison of the size of microscopic particles with a hair and grain of sand. Image: EPA/creative commons.

How are they detected?

In France, the Ministry for the Environment has delegated the task of monitoring air quality and regulated pollutants across the country to certified associations united under Fédération Atmo France. They are supported in this task by the Central Laboratory for the Monitoring of Air Quality.

These associations put in place automatic measurements for the concentration of pollutants, as well as other monitoring measures to allow a better understanding of the phenomena observed, such as the chemical composition of particles, or weather conditions.

These measurements can be combined with approaches for modeling particle concentration, thanks in particular to Prevair, the French forecast platform. Calculating the history of air mass can also be used to reveal the origin of particles, and it is therefore now possible to describe the phenomena at the origin of the increase in concentrations in relative detail.

Explanation of a real case

The graph below, produced from observations by our research department and measurements by Atmo Hauts-de-France, illustrates an example of pollution peaks that affected the local area in January 2017.

During this period, anticyclonic weather conditions contributed to the stagnation of air masses above pollutant-emitting areas. In addition, cooler temperatures led to an increase in emissions (notably linked to domestic wood heating) and the formation of “secondary” particles which formed after chemical reactions in the atmosphere.

Image: Data V. Riffault/SAGE (Cappa and Climibio projects)/creative commons.

The graphs show changes in mass concentrations of PM10 and PM2.5 over a period of several days at the Lille Fives monitoring station, as well as changes in several chemical species measured in PM1 4 km away on the University of Lille campus.

We can see that almost all the particles fell within the PM2.5 proportion, something which rules out natural phenomena such as a dust being blown in from deserts, since such particles mainly fall within the range of 2.5 to 10 µm. Furthermore, the particles in question are generally smaller in size than 1 µm.

The pollution episode began on the evening of 21 January  and continued throughout the weekend, in spite of a lower level of road traffic. This can be explained by an increase in wood burning (as suggested by the m/z 60 tracer, which is a fragment of levoglucosan, a molecule emitted by pyrolysis of cellulose found in wood).

Wood burning and other forms of combustion (such as traffic or certain industries) also emit nitrogen dioxide (NO2) as a gas, which can turn into nitric acid (HNO3) through a reaction with hydroxyl radicals (•OH) in the atmosphere.

At sufficiently low temperatures, HNO3 combines with ammonia (NH3) produced by farming activity to form ammonium nitrate (NH4NO3) solid. These are known as “secondary particles”.

A slight decrease in concentrations of particulate matter was observed at the end of the weekend, with more favorable weather conditions for the dispersion and elimination of pollutants.

In this episode, the very low concentrations of sulfates rule out an impact from coal power stations in Germany and Eastern Europe. It is therefore definitely a question of local and regional pollution linked to human activity and which accumulated as a result of unfavorable weather conditions.


How can this be avoided?

Since we cannot control the weather conditions, levers of action are primarily based on reducing pollutant emissions.

For example, reducing the formation of secondary particles will entail limiting NO2emissions linked to road traffic through road space rationing measures; for NH3 emissions, action must be taken regarding farming practices (spreading and rearing methods).

Concerning emissions from wood heating, replacing older devices with cleaner ones will enable better burning and fewer particulate matter emissions; this could be accompanied by an investment in housing insulation.

But these measures should not make us forget populations’ chronic exposure to concentrations of particulate matter which exceed the recommended WHO thresholds. This type of pollution is insidious and is damaging to health in the medium and long term, notably with the development of cardio-vascular and respiratory diseases and lung cancer.

Véronique Riffault is professor of atmospheric science at IMT Lille Douai – Institut Mines-Télécom.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

To make electric vehicles happen, the government must devolve energy policy to councils

The future. Image: Getty.

Last week, the Guardian revealed that at least a quarter of councils have halted the roll-out of electric vehicle (EV) charging infrastructure with no plans to resume its installation. This is a fully charged battery-worth of miles short of ideal, given the ambitious decarbonisation targets to which the UK is rightly working.

It’s even more startling given the current focus on inclusive growth, for the switch to EVs is an economic advancement, on an individual and societal level. Decarbonisation will free up resources and push growth, but the way in which we go about it will have impacts for generations after the task is complete.

If there is one lesson that has been not so much taught to us as screamed at us by recent history, it is that the market does not deliver inclusivity by itself. Left to its own devices, the market tends to leave people behind. And people left behind make all kinds of rational decisions, in polling stations and elsewhere that can seem wholly irrational to those charged with keeping pace – as illuminted in Jeremy Harding’s despatch from the ‘periphery’ which has incubated France’s ‘gilet jaunes’ in the London Review of Books.

But what in the name of Nikola Tesla has any of this to do with charging stations? The Localis argument is simple: local government must work strategically with energy network providers to ensure that EV charging stations are rolled out equally across areas, to ensure deprived areas do not face further disadvantage in the switch to EVs. To do so, Ofgem must first devolve certain regulations around energy supply and management to our combined authorities and city regions.


Although it might make sense now to invest in wealthier areas where EVs are already present, if there isn’t infrastructure in place ahead of demand elsewhere, then we risk a ‘tale of two cities’, where decarbonisation is two-speed and its benefits are two-tier.

The Department for Transport (DfT) announced on Monday that urban mobility will be an issue for overarching and intelligent strategy moving forward. The issue of fairness must be central to any such strategy, lest it just become a case of more nice things in nice places and a further widening of the social gap in our cities.

This is where the local state comes in. To achieve clean transport across a city, more is needed than just the installation of charging points.  Collaboration must be coordinated between many of a place’s moving parts.

The DfT announcement makes much of open data, which is undoubtedly crucial to realising the goal of a smart city. This awareness of digital infrastructure must also be matched by upgrades to physical infrastructure, if we are going to realise the full network effects of an integrated city, and as we argue in detail in our recent report, it is here that inclusivity can be stitched firmly into the fabric.

Councils know the ins and outs of deprivation within their boundaries and are uniquely placed to bring together stakeholders from across sectors to devise and implement inclusive transport strategy. In the switch to EVs and in the wider Future of Mobility, they must stay a major player in the game.

As transport minister and biographer of Edmund Burke, Jesse Norman has been keen to stress the founding Conservative philosopher’s belief in the duty of those living in the present to respect the traditions of the past and keep this legacy alive for their own successors.

If this is to be a Burkean moment in making the leap to the transformative transport systems of the future, Mr Norman should give due attention to local government’s role as “little platoons” in this process: as committed agents of change whose civic responsibility and knowledge of place can make this mobility revolution happen.

Joe Fyans is head of research at the think tank Localis.