The general objectives of the research are:

Evaluating the impact which the decrease in NO_x emissions has had on the atmosphere oxidative capacity, and thus, on the air quality in the main European cities throughout the last years.
Contrasting the influence of the NO_x decrease on the chemistry of the main atmospheric processes in which they are involved:
(i) ozone photochemical production.
(ii) effect on the day and night atmosphere oxidative capacity which is controlled by OH and NO₃ radicals.
(iii) contribution to secondary organic aerosols (SOA) formation, and (iv) Implication related to acidification eutrophication of ecosystems by deposit of nitrogenous substances.
Reaching conclusions which may be relevant for the design of environmental strategies to support the competent authorities in environmental policies to be able to keep on making progresses in their implementation.

Specific objectives/tasks planned:

In order to fulfil the general objectives, the specific objectives for each of the subprojects were planned.

SUB-PROJECT 1

1.A Simulation of representative scenes of characteristic different urban conditions (variations in NO, NO₂, O₃ and other oxidants and ratios NO_x/VOC_s) in EUPHORE chambers, both in day and night conditions.

1.B Analysing and integrating the results obtained throughout different techniques ‘in situ’, ‘on-line’ and ‘off-line’.

1.C Assessing the results from numerical simulations, especially as regards species whose routine measurements are not available, such as OH and NO₃, PAN, OVOC_s, SOA, etc. radicals. Determining of critical variables and recommendations for the revision of models and for the implementation of plans and measures.

SUB-PROJECT 2

2.A Quantifying the variation in the atmosphere oxidative capacity in Europe in the period of time 2007-2015 through mesoscale simulations with the WRF-CMAQ system.

2.B Analysing the results obtained and evaluating how they have affected:
-The photochemical ozone production and the increase of their levels in different backgrounds (urban, suburban and rural).
-The variation in the oxidants concentration in day and night conditions in the main cities (with a special interest in OH and NO₃, respectively).
– The impact on the secondary organic aerosols (SOA) formation. -The impact on the rates of deposit of nitrogenous substances in different backgrounds (urban, suburban and rural).

2.C Spreading at a regional scale, within the European continent, those implications previously obtained, and which will serve as a basis for studies in other parts of the world and which will be considerably useful for the development of environmental policies aimed at improving air quality throughout a decrease in emissions in urban areas in the future. The project conclusions will be elaborated so that they are useful for administrations and managers of air quality to set new strategies to improve air quality in a more efficient way.

Project funded by the Spanish Ministry of Science and Innovation

(RTI2018-097768-B-C21)