Revisiting the contribution of land transport and shipping emissions to tropospheric ozone

Abstract

Abstract. We quantify the contribution of land transport and shipping emissions to tropospheric ozone for the first time with a chemistry-climate model including an advanced tagging method, which considers not only the emissions of NO x (NO and NO 2 ), CO or non-methane hydrocarbons (NMHC) separately but the competing effects of all relevant ozone precursors. For summer conditions a contribution of land transport emissions to ground level ozone of up to 18 % in North America and South Europe is estimated, which corresponds to 12 nmol mol 10A more in-depth analysis for the land transport emissions reveals that the two approaches give different results particularly in regions with large emissions (up to a factor of four for Europe). With respect to the contribution of land transport and ship traffic emissions to the tropospheric ozone burden we quantified values of 8 % and 6 % for the land transport and shipping emissions, respectively. Overall, the emissions from land transport contribute to around 20 % of the net ozone production near the source regions, while shipping emissions contribute up to 52 % to the net ozone production in the Northern Pacific. , respectively. Again these results are larger by a factor of 2-3 compared to previous studies using the perturbation approach, but largely agree with previous studies which investigated the difference between the tagging and the perturbation method. Overall our results highlight the importance of differing between the perturbation and the tagging approach, as they answer two different questions. We argue that only the tagging approach can estimate the contribution of emissions, while only 20 the perturbation approach investigates the effect of an emission change. To effectively asses mitigation options both approaches should be combined.

Current and Future Disease Burden From Ambient Ozone Exposure in India

“…Overestimated O 3 production in polluted regions may bias the source attribution of O 3 more toward local sources due to the shorter production time scales (Wild & Prather, ). The response of O 3 concentrations to changes in emissions is nonlinear, meaning an emission removal approach to quantify attributions can differ from a source tracking approach (Clappier et al, ; Mertens et al, ).…”

Source apportionment to support air quality planning: Strengths and weaknesses of existing approaches

“…In the case of Stockholm (Segersson et al, 2017), increments and impacts are used in combination. Mertens et al (2018) use impacts and contributions in complement, the first to assess the efficiency of mitigation measures on O 3 levels and the second to retrieve additional information on unmitigated emission sources (i.e. those not covered by the impacts ).…”

“…This was confirmed by Burr and Zhang (2011b) who noted that the omission of such indirect effects in the current formulation of tagging/labelling source apportionment approaches limit their use to support the planning of secondary PM species. Along the same line, Qiao et al (2018), Grewe et al (2010, 2012), Clappier et al (2017) and Mertens et al (2018) conclude that tagging approaches are not designed to assess the consequences of emission changes on air quality. Impacts (ERI) : Impacts are obtained by reducing emissions from the different precursors by a given percentage (α). In contrast with contributions , impacts account for indirect chemical effects that appear when emission are reduced.…”

“…Differences between contributions and impacts have been discussed in many studies (Burr and Zhang, 2011a; Kranenburg et al, 2013; Clappier et al, 2017; Grewe et al, 2010; Mertens et al, 2018). We highlight these differences with results obtained with a real-world modelling dataset over the Po-Valley (Italy) where both contributions and impacts are calculated consistently.…”

“…Mertens et al (2018) raised the point that although tagging contributions cannot assess and quantify the efficiency of mitigation measures on air quality, they are useful to assess the potential of additional unmitigated emission sources, i.e. the measures not covered by the ERI-LOW range.…”