期刊
NATURE GEOSCIENCE
卷 10, 期 12, 页码 914-+出版社
NATURE PORTFOLIO
DOI: 10.1038/s41561-017-0009-0
关键词
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资金
- Natural Environment Research Council (NERC) air quality studentships programme [NE/N007115/1]
- NCAS national capability programme
- NERC KE Fellowship
- NERC [ncas10008, ncas10006, ncas10005, NE/N005430/1] Funding Source: UKRI
- Natural Environment Research Council [NE/N005430/1, ncas10006, ncas10005, ncas10009, ncas10008] Funding Source: researchfish
Many European countries do not meet legal air quality standards for ambient nitrogen dioxide (NO2) near roads; a problem that has been forecasted to persist to 2030. Although European air quality standards regulate NO2 concentrations, emissions standards for new vehicles instead set limits for NOx-the combination of nitric oxide (NO) and NO2. From around 1990 onwards, the total emissions of NOx declined significantly in Europe, but roadside concentrations of NO2-a regulated species-declined much less than expected. This discrepancy has been attributed largely to the increasing usage of diesel vehicles in Europe and more directly emitted tailpipe NO2. Here we apply a data-filtering technique to 130 million hourly measurements of NOx, NO2 and ozone (O-3) from roadside monitoring stations across 61 urban areas in Europe over the period 1990-2015 to estimate the continent-wide trends of directly emitted NO2. We find that the ratio of NO2 to NOx emissions increased from 1995 to around 2010 but has since stabilized at a level that is substantially lower than is assumed in some key emissions inventories. The proportion of NOx now being emitted directly from road transport as NO2 is up to a factor of two smaller than the estimates used in policy projections. We therefore conclude that there may be a faster attainment of roadside NO2 air quality standards across Europe than is currently expected.
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