Direct measurements of urban pollutant emissions

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• Eiko Nemitz, CEH
• Monday 03 December 2018, 14:15-15:15
• Pfizer Lecture Theatre, Department of Chemistry.

If you have a question about this talk, please contact Dr Olalekan Popoola.

Predictions of air quality and air pollution impacts typically rely on numerical atmospheric chemistry and transport models. The performance of such model is never better than the underlying estimates of the emissions. Diffuse sources such as represented by urban areas are usually estimated through bottom-up emission inventories, where activity figures (e.g.: vehicle kilometres driven in each 1 km2 grid cell) are combined with emission factors (e.g.: grams of NO2 emitted per vehicle kilometre driven), which are often derived under non-representative (laboratory) conditions. As a result emission inventories are subject to considerable uncertainty. Independent verification of such emission inventories is difficult and usually done indirectly by assessing how well the models reproduce measured concentrations using a given estimate of emissions. This relies on good model performance and an accurate characterisation of background concentrations. Instead, we have pioneered the use of micrometeorological flux measurement techniques, more commonly applied to measure the pollutant exchange with vegetation, to quantify directly the vertical flux above the city. For this we mount fast-response chemical sensors on city flux towers; depending on the measurement height such flux measurements integrate the emission from several km2. This talk will introduce the concept and introduce examples of flux measurements of a range of pollutants (including greenhouse gases, aerosols, NH3 , VOCs, CO, O3, …) from a number of cities, with focus on Edinburgh, London and Beijing, together with some of the sometimes surprising results.

This talk is part of the Centre for Atmospheric Science seminars, Chemistry Dept. series.

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