Air pollution in urban environments: a measurement campaign starts in the Ile-de-France region
A huge campaign to measure urban pollution from particulates has just been launched for the first time in Europe. The campaign is designed to help manage air quality more effectively.
The diversity and innovative range of resources used make the campaign to measure air pollution in urban environments, launched in the Ile-de-France region in July, something of a first. “It’s the largest campaign ever carried out in Europe,” explains scientist Matthias Beekmann, who specialises in modelling atmospheric pollution at the University Laboratory for Atmospheric Systems (LISA). The aim is to characterise pollution from particulates (concentration, chemical composition, optical properties, physical properties such as volatility, etc.) and their gaseous precursors. In the long term it involves validating hypotheses about how particulate pollution is formed – which has until now been tested only in the laboratory – and then focusing on management and prevention.
“Particulate pollution refers to the tiny particles of dust suspended in the air,” explains Matthias Beekmann. “These are invisible droplets, either liquid or solid, which are either released directly into the atmosphere by production processes, such as soot, in which case we call them primary emissions, or produced indirectly through the condensation of volatile organic compounds such as hydrocarbons, which we call secondary emissions. This second type of emission is complex and even now is still poorly understood and not very well quantified,” adds the researcher. Hence the problems in managing this kind of pollution.
Aware of the dreadful impact of particulate pollution, its harmful consequences on human health and its influence on the climate at a global and probably regional level, Europe has reacted. Big problems need big resources! Coordinated by two laboratories run by the National Institute for Universe Sciences (INSU) and the National Scientific Research Centre (CNRS) and carried out as part of the European MEGAPOLI project, the measurement campaign has brought together around 20 French and European teams.
Observations on the ground in three locations (one in the city and two others in the suburbs) have made it possible to study the variation in pollutants in the conurbation in different places and at different times. Measurement lorries have been used to measure the plume of pollution on the ground as well as the level of pollution in incoming air masses in Ile-de-France. A remote detection system has calculated the vertical distribution of some pollutants in the air over the region. Airborne observations by a French ATR-42 aircraft have assessed the process of secondary organic aerosol formation whilst a tethered balloon has concentrated on the vertical homogeneity of the pollution.
The first phase of the campaign ran for the whole of the month of July in the Ile-de-France region, which was selected because of its high population density, its relatively high pollution levels and its geographical location, which is representative of temperate latitudes. A second phase is scheduled for the winter, from 15 January to 15 February 2010. The first usable results should then be available in a year’s time, whilst the final results are expected in 2012. “In the meantime,” says Matthias Beekmann, “we are hoping to be able to supplement our data with measurements taken from other large conurbations, not only in Europe, in order to optimise the models that we will be developing as far as possible.” In the long term, this European project should make it possible to provide a better description of the impact of major metropolitan centres on air quality, the chemical composition of the troposphere and climate change at a regional level.
Delphine Barrais - Actualité en France No. 37 - October 2009
National Institute for Universe Sciences: www.insu.cnrs.fr
National Scientific Research Centre: www.cnrs.fr
Forecasts and observations of air quality in France and Europe: www.prevair.org
Information on air quality in the Ile-de-France region: www.airparif.asso.fr