ORCID Profile
0000-0001-5539-7293
Current Organisation
The University of Edinburgh
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Meteorological Society
Date: 05-2015
DOI: 10.1175/BAMS-D-12-00245.1
Abstract: Air quality and heat are strong health drivers, and their accurate assessment and forecast are important in densely populated urban areas. However, the sources and processes leading to high concentrations of main pollutants, such as ozone, nitrogen dioxide, and fine and coarse particulate matter, in complex urban areas are not fully understood, limiting our ability to forecast air quality accurately. This paper introduces the Clean Air for London (ClearfLo www.clearflo.ac.uk) project’s interdisciplinary approach to investigate the processes leading to poor air quality and elevated temperatures. Within ClearfLo, a large multi-institutional project funded by the U.K. Natural Environment Research Council (NERC), integrated measurements of meteorology and gaseous, and particulate composition/loading within the atmosphere of London, United Kingdom, were undertaken to understand the processes underlying poor air quality. Long-term measurement infrastructure installed at multiple levels (street and elevated), and at urban background, curbside, and rural locations were complemented with high-resolution numerical atmospheric simulations. Combining these (measurement–modeling) enhances understanding of seasonal variations in meteorology and composition together with the controlling processes. Two intensive observation periods (winter 2012 and the Summer Olympics of 2012) focus upon the vertical structure and evolution of the urban boundary layer chemical controls on nitrogen dioxide and ozone production—in particular, the role of volatile organic compounds and processes controlling the evolution, size, distribution, and composition of particulate matter. The paper shows that mixing heights are deeper over London than in the rural surroundings and that the seasonality of the urban boundary layer evolution controls when concentrations peak. The composition also reflects the seasonality of sources such as domestic burning and biogenic emissions.
Publisher: IOP Publishing
Date: 26-06-2019
Abstract: In much of the industrialised world, policy interventions to address the challenges of wide-spread air pollution as resulting from development and economic progress in the 2nd half of the 20th century have overall led to reductions in air pollution levels and related health effects since the 1970s. While overall improvements towards reducing health effects from ambient air pollution are recorded, comprehensive and consistent assessments of the long-term impact of policy interventions are still scarce. In this paper, we conduct a model assessment over a 40 year period of air pollution in the UK. In order to correct for the short and longer term variability of meteorological factors contributing to trends in ambient concentrations of priority air pollutants (nitrogen dioxide, sulphur dioxide, fine particulate matter and ozone), we use a fixed meteorological year for all model simulations. Hence, the modelled changes in air pollutant concentrations and related health effects are solely a function of the changes in emissions since 1970. These changes in emissions are primarily driven by policy interventions, ranging from phasing out of specific fuels or substances, to regulating the use of chemicals and driving the development of cleaner, more efficient technologies. Over the 40 year period, UK attributable mortality due to exposure to PM 2.5 and NO 2 have declined by 56% and 44% respectively, while ozone attributable respiratory mortality increased by 17% over the same period (however, with a slight decrease by 14% between 2000 and 2010).
Publisher: Copernicus GmbH
Date: 30-11-2018
DOI: 10.5194/ACP-18-16953-2018
Abstract: Abstract. The increasing use of intensive agricultural practices can lead to damaging consequences for the atmosphere through enhanced emissions of air pollutants. However, there are few direct measurements of the surface–atmosphere exchange of trace gases and water-soluble aerosols over agricultural grassland, particularly of reactive nitrogen compounds. In this study, we present measurements of the concentrations, fluxes and deposition velocities of the trace gases HCl, HONO, HNO3, SO2 and NH3 as well as their associated water-soluble aerosol counterparts Cl−, NO2-, NO3-, SO42- and NH4+ as determined hourly for 1 month in May–June 2016 over agricultural grassland near Edinburgh, UK, pre- and postfertilisation. Measurements were made using the Gradient of Aerosols and Gases Online Registrator (GRAEGOR) wet-chemistry two-point gradient instrument. Emissions of NH3 peaked at 1460 ngm-2s-1 3 h after fertilisation, with an emission of HONO peaking at 4.92 ngm-2s-1 occurring 5 h after fertilisation. Apparent emissions of NO3- aerosol were observed after fertilisation which, coupled with a ergence of HNO3 deposition velocity (Vd) from its theoretical maximum value, suggested the reaction of emitted NH3 with atmospheric HNO3 to form ammonium nitrate aerosol. The use of the conservative exchange fluxes of tot-NH4+ and tot-NO3- indicated net emission of tot-NO3-, implying a ground source of HNO3 after fertilisation. Daytime concentrations of HONO remained above the detection limit (30 ng m−3) throughout the c aign, suggesting a daytime source for HONO at the site. Whilst the mean Vd of NH4+ was 0.93 mm s−1 in the range expected for the accumulation mode, the larger average Vd for Cl− (3.65 mm s−1), NO3- (1.97 mm s−1) and SO42- (1.89 mm s−1) reflected the contribution of a super-micron fraction and decreased with increasing PM2.5∕PM10 ratio (a proxy measurement for aerosol size), providing evidence – although limited by the use of a proxy for aerosol size – of a size dependence of aerosol deposition velocity for aerosol chemical compounds, which has been suggested from process-orientated models of aerosol deposition.
Publisher: Copernicus GmbH
Date: 20-03-2015
Abstract: Abstract. Determining the contribution of wood smoke to air pollution in large cities such as London is becoming increasingly important due to the changing nature of domestic heating in urban areas. During winter, biomass burning emissions have been identified as a major cause of exceedances of European air quality limits. The aim of this work was to quantify the contribution of biomass burning in London to concentrations of PM2.5 and determine whether local emissions or regional contributions were the main source of biomass smoke. To achieve this, a number of biomass burning chemical tracers were analysed at a site within central London and two sites in surrounding rural areas. Concentrations of levoglucosan, elemental carbon (EC), organic carbon (OC) and K+ were generally well correlated across the three sites. At all the sites, biomass burning was found to be a source of OC and EC, with the largest contribution of EC from traffic emissions, while for OC the dominant fraction included contributions from secondary organic aerosols, primary biogenic and cooking sources. Source apportionment of the EC and OC was found to give reasonable estimation of the total carbon from non-fossil and fossil fuel sources based upon comparison with estimates derived from 14C analysis. Aethalometer-derived black carbon data were also apportioned into the contributions from biomass burning and traffic and showed trends similar to those observed for EC. Mean wood smoke mass at the sites was estimated to range from 0.78 to 1.0 μg m−3 during the c aign in January–February 2012. Measurements on a 160 m tower in London suggested a similar ratio of brown to black carbon (reflecting wood burning and traffic respectively) in regional and London air. Peaks in the levoglucosan and K+ concentrations were observed to coincide with low ambient temperature, consistent with domestic heating as a major contributing local source in London. Overall, the source of biomass smoke in London was concluded to be a background regional source overlaid by contributions from local domestic burning emissions. This could have implications when considering future emission control strategies during winter and may be the focus of future work in order to better determine the contributing local sources.
Publisher: Copernicus GmbH
Date: 05-08-2021
DOI: 10.5194/ACP-21-11655-2021
Abstract: Abstract. Air pollution in urban environments has been shown to have a negative impact on air quality and human health, particularly in megacities. Over recent decades, Delhi, India, has suffered high atmospheric pollution, with significant particulate matter (PM) concentrations as a result of anthropogenic activities. Organic aerosols (OAs) are composed of thousands of different chemical species and are one of the main constituents of submicron particles. However, quantitative knowledge of OA composition, their sources and their processes in urban environments is still limited. This is important particularly in India, as Delhi is a massive, inhomogeneous conurbation, where we would expect the apportionment and concentrations to vary depending on where in Delhi the measurements/source apportionment is performed, indicating the need for multisite measurements. This study presents the first multisite analysis carried out in India over different seasons, with a focus on identifying OA sources. The measurements were taken during 2018 at two sites in Delhi, India. One site was located at the India Meteorological Department, New Delhi (ND). The other site was located at the Indira Gandhi Delhi Technical University for Women, Old Delhi (OD). Non-refractory submicron aerosol (NR-PM1) concentrations (ammonium, nitrate, sulfate, chloride and organic aerosols) of four aerosol mass spectrometers were analysed. Collocated measurements of volatile organic compounds, black carbon, NOx and CO were performed. Positive matrix factorisation (PMF) analysis was performed to separate the organic fraction, identifying a number of conventional factors: hydrocarbon-like OAs (HOAs) related to traffic emissions, biomass burning OAs (BBOAs), cooking OAs (COAs) and secondary OAs (SOAs). A composition-based estimate of PM1 is defined by combining black carbon (BC) and NR-PM1 (C-PM1= BC + NR-PM1). No significant difference was observed in C-PM1 concentrations between sites, OD (142 ± 117 µg m−3) compared to ND (123 ± 71 µg m3), from post-monsoon measurements. A wider variability was observed between seasons, where pre-monsoon and monsoon showed C-PM1 concentrations lower than 60 µg m−3. A seasonal variation in C-PM1 composition was observed SO42- showed a high contribution over pre-monsoon and monsoon seasons, while NO3- and Cl− had a higher contribution in winter and post-monsoon. The main primary aerosol source was from traffic, which is consistent with the PMF analysis and Aethalometer model analysis. Thus, in order to reduce PM1 concentrations in Delhi through local emission controls, traffic emission control offers the greatest opportunity. PMF–aerosol mass spectrometer (AMS) mass spectra will help to improve future aerosol source apportionment studies. The information generated in this study increases our understanding of PM1 composition and OA sources in Delhi, India. Furthermore, the scientific findings provide significant information to strengthen legislation that aims to improve air quality in India.
Publisher: Copernicus GmbH
Date: 31-10-2014
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.ENVINT.2013.09.010
Abstract: Exposure to surface ozone (O3), which is influenced by emissions of precursor chemical species, meteorology and population distribution, is associated with excess mortality and respiratory morbidity. In this study, the EMEP-WRF atmospheric chemistry transport model was used to simulate surface O3 concentrations at 5km horizontal resolution over the British Isles for a baseline year of 2003, for three anthropogenic emissions scenarios for 2030, and for a +5°C increase in air temperature on the 2003 baseline. Deaths brought forward and hospitalisation burdens for 12 UK regions were calculated from population-weighted daily maximum 8-hour O3. The magnitude of changes in annual mean surface O3 over the UK for +5°C temperature (+1.0 to +1.5ppbv, depending on region) was comparable to those due to inter-annual meteorological variability (-1.5 to +1.5ppbv) but considerably less than changes due to precursor emissions changes by 2030 (-3.0 to +3.5ppbv, depending on scenario and region). Including population changes in 2030, both the 'current legislation' and 'maximum feasible reduction' scenarios yield greater O3-attributable health burdens than the 'high' emission scenario: +28%, +22%, and +16%, respectively, above 2003 baseline deaths brought forward (11,500) and respiratory hospital admissions (30,700), using O3 exposure over the full year and no threshold for health effects. The health burdens are greatest under the 'current legislation' scenario because O3 concentrations increase as a result of both increases in background O3 concentration and decreases in UK NOx emissions. For the +5°C scenario, and no threshold (and not including population increases), total UK health burden increases by 500 premature deaths (4%) relative to the 2003 baseline. If a 35ppbv threshold for O3 effects is assumed, health burdens are more sensitive to the current legislation and +5°C scenarios, although total health burdens are roughly an order of magnitude lower. In all scenarios, the assumption of a threshold increases the proportion of health burden in the south and east of the UK compared with the no threshold assumption. The study highlights that the total, and geographically-apportioned, O3-attributable health burdens in the UK are highly sensitive to the future trends of hemispheric, regional and local emissions of O3 precursors, and to the assumption of a threshold for O3 effect.
Publisher: Copernicus GmbH
Date: 05-06-2019
Abstract: Abstract. The Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) programme is an international collaborative project focusing on understanding the sources, processes and health effects of air pollution in the Beijing megacity. APHH-Beijing brings together leading China and UK research groups, state-of-the-art infrastructure and air quality models to work on four research themes: (1) sources and emissions of air pollutants (2) atmospheric processes affecting urban air pollution (3) air pollution exposure and health impacts and (4) interventions and solutions. Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3 provide scientific data for Theme 4 to develop cost-effective air pollution mitigation solutions. This paper provides an introduction to (i) the rationale of the APHH-Beijing programme and (ii) the measurement and modelling activities performed as part of it. In addition, this paper introduces the meteorology and air quality conditions during two joint intensive field c aigns – a core integration activity in APHH-Beijing. The coordinated c aigns provided observations of the atmospheric chemistry and physics at two sites: (i) the Institute of Atmospheric Physics in central Beijing and (ii) Pinggu in rural Beijing during 10 November–10 December 2016 (winter) and 21 May–22 June 2017 (summer). The c aigns were complemented by numerical modelling and automatic air quality and low-cost sensor observations in the Beijing megacity. In summary, the paper provides background information on the APHH-Beijing programme and sets the scene for more focused papers addressing specific aspects, processes and effects of air pollution in Beijing.
Publisher: Springer Science and Business Media LLC
Date: 31-08-2023
Publisher: BMJ
Date: 02-2016
Publisher: Copernicus GmbH
Date: 15-10-2018
DOI: 10.5194/ACP-2018-922
Abstract: Abstract. APHH-Beijing (Atmospheric Pollution and Human Health in a Chinese Megacity) is an international collaborative project to examine the emissions, processes and health effects of air pollution in Beijing. The four research themes of APHH-China are: (1) sources and emissions of urban atmospheric pollution (2) processes affecting urban atmospheric pollution (3) exposure science and impacts on health and (4) interventions and solutions to reduce health impacts. Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3 provide scientific data for Theme 4 on the development of cost-effective solutions. A key activity within APHH-Beijing was the two month-long intensive field c aigns at two sites: (i) central Beijing, and (ii) rural Pinggu. The coordinated c aigns provided observations of the atmospheric chemistry and physics in and around Beijing during November–December 2016 and May–June 2017. The c aigns were complemented by numerical air quality modelling and air quality and meteorology data at the 12 national monitoring stations in Beijing. This introduction paper provides an overview of (i) APHH-Beijing programme, (ii) the measurement and modelling activities performed as part of it in Beijing, and (iii) the air quality and meteorological conditions during the two field c aigns. The winter c aign was characterized by high PM2.5 pollution events whereas the summer experienced high ozone pollution events. Air quality was poor during the winter c aign, but less severe than in the same period in 2015 when there were a number of major pollution episodes. PM2.5 levels were relatively low during the summer period, matching the cleanest periods over the previous five years. Synoptic scale meteorological analysis suggests that the greater stagnation and weak southerly circulation in November/December 2016 may have contributed to the poor air quality.
Publisher: Copernicus GmbH
Date: 11-07-2018
DOI: 10.5194/ACP-2018-603
Abstract: Abstract. The increasing use of intensive agricultural practices can lead to damaging consequences for the atmosphere through enhanced emissions of air pollutants. However, there are few direct measurements of the surface–atmosphere exchange of trace gases and water-soluble aerosols over agricultural grassland, particularly of reactive nitrogen compounds. In this study, we present measurements of the concentrations, fluxes and deposition velocities of the trace gases HCl, HONO, HNO3, SO2 and NH3, and their associated water-soluble aerosol counterparts Cl−, NO2−, NO3−, SO42−, NH4+ as determined hourly for one month in May–June 2016 over agricultural grassland pre- and post-fertilisation. Measurements were made using the Gradient of Aerosols and Gases Online Registration (GRAEGOR) wet–chemical two–point gradient instrument. Emissions of NH3 peaked at 1460 ng m−2 s−1 three hours after fertilisation, with an emission of HONO peaking at 4.92 ng m−2 s−1 occurring five hours after fertilisation. Apparent emissions of NO3− aerosol were observed after fertilisation which, coupled with a ergence of HNO3 deposition velocity (Vd) from its theoretical maximum value, suggested the reaction of emitted NH3 with atmospheric HNO3 to form ammonium nitrate aerosol. The use of the conservative exchange fluxes of tot-NH4+ and tot-NO3− indicated net emission of tot-NO3−, implying a ground source of HNO3 after fertilisation. Daytime concentrations of HONO remained above the detection limit (30 ng m−3) throughout the c aign, suggesting a daytime source for HONO at the site. Whilst the mean Vd of NH4+ was with 0.93 mm/s in the range expected for the accumulation mode, the larger average Vd for Cl− (3.65 mm/s), NO3− (1.97 mm/s), SO42− (1.89 mm/s) reflected the contribution of a super-micron fraction and decreased with increasing PM2.5 / PM10 ratio (a proxy measurement for aerosol size), providing direct evidence of a size-dependence of aerosol deposition velocity for aerosol chemical compounds.
Publisher: Copernicus GmbH
Date: 31-10-2014
DOI: 10.5194/ACPD-14-27459-2014
Abstract: Abstract. Determining the contribution of wood smoke to air pollution in large cities such as London is becoming increasingly important due to the changing nature of domestic heating in urban areas. During winter, biomass burning emissions can exceed the contributions from traffic emissions, and have been identified as a major cause of exceedences of European air quality limits. The aim of this work was to quantify the contribution of biomass burning in London to concentrations of PM2.5 and determine whether local emissions or regional contributions were the main source of biomass smoke. To achieve this, a number of biomass burning chemical tracers were analysed at a site within central London and two sites in surrounding rural areas. Concentrations of levoglucosan, elemental carbon (EC), organic carbon (OC) and K+ were generally well correlated across the three sites. At all the sites, biomass burning was found to be a source of OC and EC, with the largest contribution of EC from traffic emissions, while for OC the dominant fraction likely included contributions from secondary organic aerosols, primary biogenic and cooking sources. Source apportionment of the EC and OC using average source ratios from published data was found to give reasonable estimation of the total carbon from non-fossil and fossil fuel sources based upon comparison with estimates derived from 14C analysis. Black carbon (BC) data from 2 and 7 wavelength Aethalometers were also apportioned into the contributions from biomass burning and traffic, based upon the enhanced absorption of wood smoke at UV wavelengths compared to BC. While the source apportionment of BC using this approach found similar trends to that observed for EC, higher percentage contributions of wood burning to BC were estimated. Based on a wood smoke mass conversion factor for levoglucosan, mean wood smoke mass at the sites was found to range from 0.78–1.0 μg m−3 during the c aign in January–February 2012. Measurements on a 160 m tower in London suggested a similar ratio of brown to black carbon (reflecting wood burning and traffic respectively) in regional and London air. Peaks in the levoglucosan and K+ concentrations were observed to coincide with low ambient temperature, consistent with domestic heating as a major contributing local source in London. Overall, the source of biomass smoke in London was concluded to be a background regional source overlaid by contributions from local domestic burning emissions. This could have implications when considering future emission control strategies during winter and may be the focus of future work in order to better determine the contributing local sources.
Publisher: Copernicus GmbH
Date: 13-07-2020
DOI: 10.5194/ACP-2020-586
Abstract: Abstract. The Amazon rainforest presents a unique, natural laboratory for the study of surface-atmosphere interactions. Its alternation between a near-pristine, marine-influenced atmosphere during the wet season, and a vulnerable system affected by periodic intrusions of anthropogenic pollution during the dry season, provides an opportunity to investigate some fundamental aspects of boundary-layer chemical processes. This study presents the first simultaneous hourly measurements of concentrations, fluxes and deposition velocities of the inorganic trace gases NH3, HCl, HONO, HNO3 and SO2 and their water-soluble aerosol counterparts NH4+, Cl−, NO2−, NO3− and SO42− over the Amazon. Species concentrations were measured in the dry season (from 6 October to 5 November 2017), at the Amazon Tall Tower Observatory (ATTO) in Brazil, using a two-point gradient, wet-chemistry instrument (Gradient of Aerosols and Gases Online Registration, GRAEGOR) s ling at 42 m and 60 m. Fluxes and deposition velocities were derived from the concentration gradients using a modified form of the aerodynamic gradient method corrected for measurement within the roughness sub-layer. Findings from this c aign include observations of elevated concentrations of NH3 and SO2 partially driven by long-range transport (LRT) episodes of pollution, and the substantial influence of coarse Cl− and NO3− particulate on overall aerosol mass burdens. From the flux measurements, the dry season budget of total reactive nitrogen dry deposition at the ATTO site was estimated as −2.9 kg N ha−1 a−1. HNO3 and HCl were deposited continuously at a rate close to the aerodynamic limit. SO2 was deposited with an average daytime surface resistance (Rc) of 28 s m−1, whilst aerosol components showed average surface deposition velocities of 2.8 and 2.7 mm s−1 for SO42− and NH4+. Deposition rates of NO3
Publisher: Copernicus GmbH
Date: 15-12-2020
DOI: 10.5194/ACP-20-15551-2020
Abstract: Abstract. The Amazon rainforest presents a unique, natural laboratory for the study of surface–atmosphere interactions. Its alternation between a near-pristine marine-influenced atmosphere during the wet season and a vulnerable system affected by periodic intrusions of anthropogenic pollution during the dry season provides an opportunity to investigate some fundamental aspects of boundary-layer chemical processes. This study presents the first simultaneous hourly measurements of concentrations, fluxes, and deposition velocities of the inorganic trace gases NH3, HCl, HONO, HNO3, and SO2 as well as their water-soluble aerosol counterparts NH4+, Cl−, NO2-, NO3- and SO42- over the Amazon. Species concentrations were measured in the dry season (from 6 October to 5 November 2017), at the Amazon Tall Tower Observatory (ATTO) in Brazil, using a two-point gradient wet-chemistry instrument (GRadient of AErosols and Gases Online Registration, GRAEGOR) s ling at 42 and 60 m. Fluxes and deposition velocities were derived from the concentration gradients using a modified form of the aerodynamic gradient method corrected for measurement within the roughness sub-layer. Findings from this c aign include observations of elevated concentrations of NH3 and SO2 partially driven by long-range transport (LRT) episodes of pollution and the substantial influence of coarse Cl− and NO3- particulate on overall aerosol mass burdens. From the flux measurements, the dry season budget of total reactive nitrogen dry deposition at the ATTO site was estimated as −2.9 kg N ha-1a-1. HNO3 and HCl were deposited continuously at a rate close to the aerodynamic limit. SO2 was deposited with an average daytime surface resistance (Rc) of 28 s m−1, whilst aerosol components showed average surface deposition velocities of 2.8 and 2.7 mm s−1 for SO42- and NH4+, respectively. Deposition rates of NO3- and Cl− were higher at 7.1 and 7.8 mm s−1, respectively, reflecting their larger average size. The exchange of NH3 and HONO was bidirectional, with NH3 showing emission episodes in the afternoon and HONO in the early morning hours. This work provides a unique dataset to test and improve dry deposition schemes for these compounds for tropical rainforest, which have typically been developed by interpolation from conditions in temperate environments. A future c aign should focus on making similar measurements in the wet season in order to provide a complete view of the annual pattern of inorganic trace gas and coarse aerosol biosphere–atmosphere exchange over tropical rainforest.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Mathew Heal.