The role of long-range transport and domestic emissions in determining atmospheric secondary inorganic particle concentrations across the UK

Abstract

Abstract. Surface concentrations of secondary inorganic particle components over the UK have been analysed for 2001-2010 using the EMEP4UK regional atmospheric chemistry transport model and evaluated against measurements. Gas/particle partitioning in the EMEP4UK model simulations used a bulk approach, which may lead to uncertainties in simulated secondary inorganic aerosol. However, model simulations were able to accurately represent both the long-term decadal surface concentrations of particle sulfate and nitrate and an episode in early 2003 of substantially elevated nitrate measured across the UK by the AGANet network. The latter was identified as consisting of three separate episodes, each of less than 1 month duration, in February, March and April. The primary cause of the elevated nitrate levels across the UK was meteorological: a persistent high-pressure system, whose varying location impacted the relative importance of transboundary versus domestic emissions. Whilst long-range transport dominated the elevated nitrate in February, in contrast it was domestic emissions that mainly contributed to the March episode, and for the April episode both domestic emissions and long-range transport contributed. A prolonged episode such as the one in early 2003 can have substantial impact on annual average concentrations. The episode led to annual concentration differences at the regional scale of similar magnitude to those driven by long-term changes in precursor emissions over the full decade investigated here. The results demonstrate that a substantial part of the UK, particularly the south and southeast, may be close to or exceeding annual mean limit values because of import of inorganic aerosol components from continental Europe under specific conditions. The results reinforce the importance of employing multiple year simulations in the assessment of emissions reduction scenarios on particulate matter concentrations and the need for international agreements to address the transboundary component of air pollution.

Water soluble aerosols and gases at a UK background site – Part 1: Controls of PM<sub>2.5</sub> and PM<sub>10</sub> aerosol composition

“…Graph produced using the plotting routine of Crippa et al (2014). time that NO − 3 has been found to be a dominating species during pollution events in the UK. Vieno et al (2014) reported NO − 3 as a dominating fraction during pollution events at a site (Bush) approximately 10 km NE from the Auchencorth Moss field site. They show that the NO − 3 during pollution events at this site arise from a combination of emissions from the UK and continental Europe but that the relative importance depends on synoptic conditions and differs greatly between episodes with the UK contribution ranging from 35 and 80 % (Vieno et al, 2014).…”

“…Vieno et al (2014) reported NO − 3 as a dominating fraction during pollution events at a site (Bush) approximately 10 km NE from the Auchencorth Moss field site. They show that the NO − 3 during pollution events at this site arise from a combination of emissions from the UK and continental Europe but that the relative importance depends on synoptic conditions and differs greatly between episodes with the UK contribution ranging from 35 and 80 % (Vieno et al, 2014). The Auchencorth measurements demonstrate the importance of controlling the emissions of NH 4 NO 3 precursor gas concentrations (NH 3 and NO x ) in both the UK and the rest of Europe for controlling the high pollution episodes.…”

The sensitivities of emissions reductions for the mitigation of UK PM<sub>2.5</sub>

“…Although it is well-known that much of the ambient PM 2.5 in the UK derives from transboundary emissions and transport into the UK (Vieno et al, 2014;AQEG, 2015), a pertinent policy question to address is what additional surface PM 2.5 reductions could the UK unilaterally achieve, at least in principle? In other words, what are the sensitivities of UK PM 2.5 to UK reductions in emissions of relevant components?…”

Air quality simulations for London using a coupled regional-to-local modelling system

“…The main EMEP MSC-W model has been widely used for both scientific studies and for policymaking in Europe, with references to evaluation and application studies available in Simpson et al (2012), Schulz et al (2013) and at http://www.emep.int (last access: 1 August 2018). EMEP4UK is described in Vieno et al (2010Vieno et al ( , 2014Vieno et al ( , 2016a; the version used here is based on EMEP MSC-W rv4.5. It uses one-way nesting from a 50 km × 50 km resolution greater European domain (standard EMEP domain) to an inner 5 km × 5 km domain which covers the British Isles and nearby parts of continental Europe, both in a polar stereographic projected coordinate system, as shown in Fig.…”