气候变化领域集成服务门户

We analyzed 2005-2017 data sets on ozone (O-3) concentrations in an area (the Vic Plain) frequently affected by the atmospheric plume northward transport of the Barcelona metropolitan area (BMA), the atmospheric basin of Spain recording the highest number of exceedances of the hourly O-3 information threshold (180 mu g m(-3)). We aimed at evaluating the potential benefits of implementing local-BMA short-term measures to abate emissions of precursors. To this end, we analyzed in detail spatial and time variations of concentration of O-3 and nitrogen oxides (NO and NO2, including OMI remote sensing data for the latter). Subsequently, a sensitivity analysis is done with the air quality (AQ) data to evaluate potential O-3 reductions in the north of the BMA on Sundays compared with weekdays as a consequence of the reduction in regional emissions of precursors.

The results showed a generalized decreasing trend for regional background O-3 as well as the well-known increase in urban O-3 and higher urban NO decreasing slopes compared with those of NO2. The most intensive O-3 episodes in the Vic Plain are caused by (i) a relatively high regional background O-3 (due to a mix of continental, hemispheric-tropospheric and stratospheric contributions); by (ii) intensive surface fumigation from mid-troposphere high O-3 upper layers arising from the concatenation of the vertical recirculation of air masses; but also by (iii) an important O-3 contribution from the northward transport/channeling of the pollution plume from the BMA. The high relevance of the local-daily O-3 contribution during the most intense pollution episodes is clearly supported by the O-3 (surface concentration) and NO2 (OMI data) data analysis.

A maximum decrease potential (by applying short-term measures to abate emissions of O-3 precursors) of 49 mu g O-3 M-3 (32 %) of the average diurnal concentrations was determined. Structurally implemented measures, instead of episodically, could result in important additional O-3 decreases because not only the local O-3 coming from the BMA plume would be reduced, but also the recirculated O-3 and thus the intensity of O-3 fumigation in the plain. Therefore, it is highly probable that both structural and episodic measures to abate NOx and volatile organic compound (VOC) emissions in the BMA would result in evident reductions of O-3 in the Vic Plain.