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Alastair C Lewis  - - - 
Top co-authors
Mathew John Evans

109 shared publications

Wolfson Atmospheric Chemistry Laboratories, University of York, York, YO10 5DD, UK

Atallah El Zein

1 shared publications

Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, YO10 5DD, UK

Chunting Michelle Wang

1 shared publications

University of York

Publication Record
Distribution of Articles published per year 
(1995 - 2019)
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Article 0 Reads 0 Citations Variability of polycyclic aromatic hydrocarbons and their oxidative derivatives in wintertime Beijing, China Atallah El Zein, Rachel Ellen Dunmore, Martyn William Ward, ... Published: 05 March 2019
Atmospheric Chemistry and Physics Discussions, doi: 10.5194/acp-2019-120
DOI See at publisher website ABS Show/hide abstract
Ambient particulate matter (PM) can contain a mix of different toxic species derived from a wide variety of sources. This study quantifies the variation in diurnal and nocturnal abundance of 16 Polycyclic Aromatic Hydrocarbons (PAHs), 10 Oxygenated PAHs (OPAHs) and 9 Nitrated PAHs (NPAHs) in ambient PM in central Beijing during winter. Target compounds were identified and quantified using Gas Chromatography – time of flight mass spectrometry (GC-Q-TOF-MS). The total concentration of PAHs varied between 18 and 297&thinsp;ng&thinsp;m&minus;3 over 3&thinsp;h daytime filter samples and from 23 to 165&thinsp;ng&thinsp;m&minus;3 in 15&thinsp;h night-time samples. The total concentrations of PAHs over 24&thinsp;h varied between 37 and 180&thinsp;ng&thinsp;m&minus;3 (mean: 97&thinsp;ng&thinsp;m&minus;3). The total daytime concentrations during high particulate loading conditions for PAHs, OPAHs and NPAHs were 224, 54, and 2.3&thinsp;ng&thinsp;m&minus;3, respectively. The most abundant PAHs were fluoranthene (33&thinsp;ng&thinsp;m&minus;3), chrysene (27&thinsp;ng&thinsp;m&minus;3), pyrene (27&thinsp;ng&thinsp;m&minus;3), benzo(a)pyrene (27&thinsp;ng&thinsp;m&minus;3), benzo[b]fluoranthene (25&thinsp;ng&thinsp;m&minus;3), benzo[a]anthracene (20&thinsp;ng&thinsp;m&minus;3) and phenanthrene (18&thinsp;ng&thinsp;m&minus;3). 9,10-Anthraquinone (18&thinsp;ng&thinsp;m&minus;3), 1,8 Naphthalic anhydride (14&thinsp;ng&thinsp;m&minus;3) and 9-Fluorenone (12&thinsp;ng&thinsp;m&minus;3) were the three major OPAHs species, while 9-Nitroanthracene (0.84&thinsp;ng&thinsp;m&minus;3), 3-Nitrofluoranthene (0.78&thinsp;ng&thinsp;m&minus;3) and 3-Nitrodibenzofuran (0.45&thinsp;ng&thinsp;m&minus;3) were the three most abundant NPAHs. ∑PAHs and ∑OPAHs showed a strong positive correlation with the gas phase abundance of NO, CO, SO2, and HONO indicating that PAHs and OPAHs can be associated with both local and regional emissions. Diagnostic ratios suggested emissions from traffic road and coal combustion were the predominant sources for PAHs in Beijing, and also revealed the dominant source of NPAHs was secondary photochemical formation rather than primary emissions. PM2.5 and NPAHs showed a strong correlation with gas phase HONO. 9-Nitroanthracene appeared to undergo a photodegradation during the daytime and has shown a strong positive correlation with ambient HONO (R&thinsp;=&thinsp;0.90, P&thinsp;<&thinsp;0.001). The lifetime excess lung cancer risk for the species with available toxicological data (16 PAHs, 1 OPAH and 6 NPAHs) was calculated to be in the range 10&minus;5 to 10&minus;3 (risk per million people range from 26 to 2053).
Article 0 Reads 0 Citations Introduction to Special Issue – In-depth study of air pollution sources and processes within Beijing and its surrounding... ZongBo Shi, Tuan Vu, Simone Kotthaus, Sue Grimmond, Roy M. H... Published: 15 October 2018
Atmospheric Chemistry and Physics Discussions, doi: 10.5194/acp-2018-922
DOI See at publisher website ABS Show/hide 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&ndash;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 campaigns at two sites: (i) central Beijing, and (ii) rural Pinggu. The coordinated campaigns provided observations of the atmospheric chemistry and physics in and around Beijing during November&ndash;December 2016 and May&ndash;June 2017. The campaigns 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 campaigns. The winter campaign was characterized by high PM2.5 pollution events whereas the summer experienced high ozone pollution events. Air quality was poor during the winter campaign, 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.
Article 0 Reads 0 Citations An improved low power measurement of ambient NO2 and O3 combining electrochemical sensor clusters and machine learning Kate R. Smith, Peter M. Edwards, Peter D. Ivatt, James D. Le... Published: 10 September 2018
Atmospheric Measurement Techniques Discussions, doi: 10.5194/amt-2018-285
DOI See at publisher website ABS Show/hide abstract
Low cost sensors (LCS) are an appealing solution to the problem of spatial resolution in air quality measurement, but they currently do not have the same analytical performance as regulatory reference methods. Individual sensors can be susceptible to analytical cross interferences, have random signal variability and experience drift over short, medium and long timescales. To overcome some of the performance limitations of individual sensors we use a clustering approach using the instantaneous median signal from six identical electrochemical sensors to minimise the randomised drifts and inter-sensor differences. We report here a low power analytical device (<200W) that comprises of clusters of sensors for NO2, OX, CO and total VOC, and that measures supporting parameters such as water vapour and temperature. This was tested in the field against reference monitors, collecting ambient air pollution data in Beijing, China. Comparisons were made of NO2 and OX clustered sensor data against reference methods for calibrations derived from factory settings, in-field simple linear regression (SLR) and then against three machine learning (ML) algorithms. The parametric supervised ML algorithms boosted regression trees (BRT) and boosted linear regression (BLR) and the non-parametric technique Gaussian Process (GP) used all available sensor data to improve the measurement estimate of NO2 and OX. In all cases ML produced an observational value that was closer to reference measurements than SLR alone. In combination, sensor clustering and ML generated sensor data of a quality that was close to that of regulatory measurements (using the RSME metric) yet retained a very substantial cost and power advantage.
Article 0 Reads 0 Citations Recent multivariate changes in the North Atlantic climate system, with a focus on 2005-2016 Jon Robson, Rowan T. Sutton, Alex Archibald, Fenwick Cooper,... Published: 05 September 2018
International Journal of Climatology, doi: 10.1002/joc.5815
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Major changes are occurring across the North Atlantic climate system, including in the atmosphere, ocean and cryosphere, and many observed changes are unprecedented in instrumental records. As the changes in the North Atlantic directly affect the climate and air quality of the surrounding continents, it is important to fully understand how and why the changes are taking place, not least to predict how the region will change in the future. To this end, this article characterizes the recent observed changes in the North Atlantic region, especially in the period 2005–2016, across many different aspects of the system including: atmospheric circulation; atmospheric composition; clouds and aerosols; ocean circulation and properties; and the cryosphere. Recent changes include: an increase in the speed of the North Atlantic jet stream in winter; a southward shift in the North Atlantic jet stream in summer, associated with a weakening summer North Atlantic Oscillation; increases in ozone and methane; increases in net absorbed radiation in the mid‐latitude western Atlantic, linked to an increase in the abundance of high level clouds and a reduction in low level clouds; cooling of sea surface temperatures in the North Atlantic subpolar gyre, concomitant with increases in the western subtropical gyre, and a decline in the Atlantic Ocean's overturning circulation; a decline in Atlantic sector Arctic sea ice and rapid melting of the Greenland Ice Sheet. There are many interactions between these changes, but these interactions are poorly understood. This article concludes by highlighting some of the key outstanding questions.
Article 1 Read 2 Citations The impacts of water vapour and co-pollutants on the performance of electrochemical gas sensors used for air quality mon... Xiaobing Pang, Marvin D. Shaw, Stefan Gillot, Alastair C. Le... Published: 01 August 2018
Sensors and Actuators B: Chemical, doi: 10.1016/j.snb.2018.03.144
DOI See at publisher website
Article 0 Reads 14 Citations Tropospheric Ozone Assessment Report: Present-day distribution and trends of tropospheric ozone relevant to climate and ... A. Gaudel, O. R. Cooper, G. Ancellet, B. Barret, A. Boynard,... Published: 10 May 2018
Elem Sci Anth, doi: 10.1525/elementa.291
DOI See at publisher website