Dr Stephen Worrall

Lecturer in Chemistry Aston University

  • Birmingham

Dr Worrall's research interests are focused upon the interface between metal-organic frameworks and electrochemistry.

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Aston University pollution expert praises Clean Air Zone roll out plans across UK

Dr Stephen Worrall believes Birmingham’s Clean Air Zone is encouraging fewer drivers into city centre The pollution expert said statistics show motorists are ‘changing their behaviour’ He praised other cities for following suit but says changes need to come more quickly. A leading expert in air pollution from Aston University has examined available data on how many vehicles have paid to enter Birmingham’s Clean Air Zone (CAZ) and has said people’s behaviours are changing Atmospheric chemist, Dr Stephen Worrall, praised the introduction of Birmingham’s CAZ which launched on 1 June, saying it was an important step in tackling air pollution in the city and would have a considerable impact on people’s health. Whilst the full impact of the CAZ on pollution levels won’t become clear until 2022, Dr Worrall said since the “Go Live Date” the traffic data revealed that the number of non-compliant vehicles being driven in the zone was decreasing markedly. “In the first two weeks of June before charging was introduced, the daily number of non-compliant vehicles being driven within the CAZ was at an average of 18,787. “After charging was introduced, this dropped significantly to 11,850 for the remainder of June and this number has continued to fall, with the last reported daily average of 10,800 for August. “This isn’t just your average motorist with a car either, as the data shows similar trends for other categories of vehicles with the biggest improvement observed in light goods vehicles (LGVs). Over 75% of these vehicles were complying with the CAZ in August versus just 63% in June. This is a significant and sustained reduction which clearly demonstrates that people are modifying their behaviours,” he said. Dr Worrall added that the data was also able to hint at the manner in which people were modifying their behaviour, with a possible increase in public transport use, car sharing or a reduction in overall number of journeys. “Some people are upgrading their vehicles to newer, less polluting models as there has been a small rise of about 2,500 in the number of complaint vehicles entering the CAZ on a daily basis. However, this number is dwarfed by the approximately 8,500 reduction in the daily number of non-complaint vehicles. The upshot of this is that the total number of vehicles entering the CAZ every day has dropped by roughly 6,000 (around 6%). 6,000 fewer of the most polluting vehicles in our city centre is a real positive and a step in the right direction to improving our air quality and health,” he said. Air pollution particularly affects the most vulnerable in society, including children, and older people, and those with heart and lung conditions. The annual health cost to society of the impacts of particulate matter alone in the UK is estimated to be around £16 billion*. Levels of NO2 in Birmingham frequently exceed 45 to50 micrograms per cubic meter, mainly caused by road traffic emissions, with certain hotspots exhibiting even greater values such as the measuring site at St Chads Queensway where the last reported yearly average for the city centre was as high as 74 micrograms per cubic meter. The primary aim of the CAZ is to reduce the levels of NO2 to 40 micrograms per cubic meter. Dr Worrall said that although CAZs weren’t directly designed to address greenhouse gas emissions, if as suggested they result in less people using their vehicles for journey, then this would have an impact on emissions. “Whilst the CAZ target is to reduce nitrogen dioxide (NO2) levels, the knock-on effect of this reduction in car use will mean a reduction in pollution in general, including greenhouse gases such as CO2. This is really important and suggests that other cities need to be acting now rather than later. Bath has implemented a similar but less stringent system, London recently extended its ultra low emission zone (ULEZ) area and Portsmouth’s CAZ will be coming live shortly too, but other cities who have plans in the pipeline should really bring them forward as a matter of urgency,” he said. Dr Worrall added that with current COP26 discussions bringing pollution to the forefront, it was important to continue with awareness. “These policies are all small pieces in the puzzle for reducing emissions from transport and getting people to make wiser choices about the vehicles they own and buy, and as COP26 is making very clear we need to be doing all of these things now to save our planet” he said. Dr Worrall has great experience in the subject, having spent a portion of his post-doctoral research in Beijing where he took live air pollution measurements, monitored problematic levels and discussed with international colleagues’ ways to address these issues. Read more about the College of Engineering and Physical Sciences at Aston University, here: https://www.aston.ac.uk/eps ENDS Defra (2017) Air quality plan for nitrogen dioxide in the UK

Dr Stephen Worrall

3 min

Aston University atmospheric chemist praises introduction of Birmingham’s Clean Air Zone

Dr Stephen Worrall has praised the introduction of the Clean Air Zone in Birmingham The expert in atmospheric chemistry said current levels within the city have to drop for the health of all Birmingham’s Clean Air Zone (CAZ) comes into effect on 1 June Dr Stephen Worrall is a lecturer in chemistry at Aston University A leading atmospheric chemist from Aston University has welcomed the introduction of Birmingham’s Clean Air Zone (CAZ) from 1 June 2021 and has said it will be an important step in tackling air pollution. Dr Stephen Worrall, a lecturer in chemistry in the College of Engineering and Physical Sciences, said the long-term effects of the change will be beneficial to people’s health throughout the city. Air pollution particularly affects the most vulnerable in society, including children and older people, and those with heart and lung conditions. The annual health cost to society of the impacts of particulate matter alone in the UK is estimated to be around £16 billion*. Dr Worrall said: “In my opinion the CAZ is undoubtedly a good idea. In many of our cities, but definitely in Birmingham, the levels of many types of pollution and especially nitrogen dioxide (NO2) are high and have been above the guideline levels for a very long time, so it is welcome that these changes are happening.” Dr Worrall said current levels of NO2 in Birmingham in May 2021 have frequently exceeded 45 – 50 micrograms per cubic meter, mainly caused by road traffic emissions. The last reported yearly average for the city centre was as high as 74 micrograms per cubic meter, taken from the measuring site at St Chads Queensway. The primary aim of the CAZ is to reduce the levels of NO2 to 40 micrograms per cubic meter. “What is interesting about 2020 is those levels were still quite high at times despite us being into lockdown, when there were significantly fewer vehicles on the road. The live, daily readings from this year are also often exceeding the recommended levels, both of which are telling,” he said. Dr Worrall has significant experience in the subject, having spent a portion of his post-doctoral research in Beijing where he took live air pollution measurements, monitored problematic levels and discussed with international colleagues’ ways to address these issues. He said: “I was working and living in a very polluted area of the city and it was very noticeable on a daily basis how polluted it was. The levels of NO2 in 2017 while I was there were on average 103 micrograms per cubic meter, which was very high.” Dr Worrall added he believed the CAZ would have a big impact on Birmingham’s overall health but that the situation needed to be closely monitored. “There is significant evidence to suggest that there are serious long term health issues that arise from breathing in high levels of NO2, as well as Particle Matter (PM), an air pollutant which is absorbed into the blood stream through penetrating the lungs. These include asthma, bronchitis, lung cancer, heart disease and strokes. “Whilst there is local concern about the economic impact of the CAZ which must be taken into account, reducing these levels will benefit all of us, particularly those living in areas of deprivation who have been shown to be most significantly harmed by these high levels of pollution, as Birmingham’s biggest cause of pollution is from cars,” he said. Read more about College of Engineering and Physical Sciences at Aston University, here.

Dr Stephen Worrall

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Biography

Dr Stephen David Worrall MRSC was appointed as a Lecturer in Chemistry, based in the Chemical Engineering and Applied Chemistry department of School of Engineering and Applied Science, in August 2019.

Prior to joining Aston University his research career had been based at the University of Manchester. Starting with an MChem in Chemistry under the supervision of Dr Andrew Horn in 2012 he then completed a PhD in Nanoscience in 2016 under the joint supervision of Professor Robert Dryfe and Dr Martin Attfield. This was followed by two post doctoral research positions. The first was in Atmospheric Chemistry, working for Professor Carl Percival and Professor Hugh Coe, as part of the APHH Beijing project. The second was in 2D material nanocomposites, working for Professor Sarah Haigh and Dr Steve Edmondson, as part of the DISCOVERER project.

His primary research interests are focused upon the interface between metal-organic frameworks (MOF) and electrochemistry.

1) In situ investigations of the mechanisms of electrochemical MOF coating formation.
2) Computationally guided synthesis of new MOFs via electrochemical techniques.
3) Electrochemical applications of MOFs; catalysis, charge storage and data storage.

He also has a supporting interest in developing coatings of two-dimensional materials; both for aerospace applications and for the synthesis of composite coatings with MOFs for electrochemical applications.

Additionally he has an ongoing collaboration focused upon the measurement and interpretation of solid state vapour pressure data towards improving the modelling of aerosols in the atmosphere.

Areas of Expertise

Thin Films and Nanotechnology
Nanomaterials Synthesis
Material Characterization
Material Characteristics
Thin Film Deposition
Advanced Materials
X-ray Diffraction
SEM Analysis
Nanomaterials
Materials

Education

University of Manchester

Ph.D.

Nanoscience

2016

University of Manchester

M.Chem.

Chemistry

2012

Affiliations

  • Member of the Royal Society of Chemistry

Media Appearances

Clean Air Zone: Birmingham reports drop in emissions

BBC News  online

2022-06-01

Dr Stephen Worrall a lecturer in chemistry at Aston University said the figures were encouraging, but a full-year cycle of data was required. "It's really positive news," he said. "We knew vehicle numbers in the city centre were looking positive anyway, but in the most polluting category they're dropping really steadily - it's the proportion that we needed, evidence on nitrous dioxide levels, so that's really good information from the council."

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CAZ: Driver numbers within Birmingham zone drop by 6,000

BBC News  online

2021-12-02

Although the full impact will not be clear until 2022, Dr Stephen Worrall - an atmospheric chemist at the university - said before charging was introduced, the number of daily non-compliant vehicles driving within the zone was an average of 18,787, but this dropped to 11,850 for the remainder of June with the last reported daily average of 10,800 for August.

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Articles

Chemical characterisation of benzene oxidation products under high- and low-NOx conditions using chemical ionisation mass spectrometry

Atmospheric Chemistry and Physics

Michael Priestley, Thomas J Bannan, Michael Le Breton, Stephen D Worrall, Sungah Kang, Iida Pullinen, Sebastian Schmitt, Ralf Tillmann, Einhard Kleist, Defeng Zhao, Jürgen Wildt, Olga Garmash, Archit Mehra, Asan Bacak, Dudley E Shallcross, Astrid Kiendler-Scharr, Åsa M Hallquist, Mikael Ehn, Hugh Coe, Carl J Percival, Mattias Hallquist, Thomas F Mentel, Gordon McFiggans

Aromatic hydrocarbons are a class of volatile organic compounds associated with anthropogenic activity and make up a significant fraction of urban volatile organic compound (VOC) emissions that contribute to the formation of secondary organic aerosol (SOA). Benzene is one of the most abundant species emitted from vehicles, biomass burning and industry. An iodide time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) and nitrate ToF-CIMS were deployed at the Jülich Plant Atmosphere Chamber as part of a series of experiments examining benzene oxidation by OH under high- and low-NOx conditions, where a range of organic oxidation products were detected. The nitrate scheme detects many oxidation products with high masses, ranging from intermediate volatile organic compounds (IVOCs) to extremely low volatile organic compounds (ELVOCs), including C12 dimers. In comparison, very few species with C≥6 and O≥8 were detected with the iodide scheme, which detected many more IVOCs and semi-volatile organic compounds (SVOCs) but very few ELVOCs and low volatile organic compounds (LVOCs). A total of 132 and 195 CHO and CHON oxidation products are detected by the iodide ToF-CIMS in the low- and high-NOx experiments respectively...

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Effect of methacrylic acid and pendant vinyl groups on the mechanical properties of highly stretchable core–shell nanostructured films deposited from water

Polymer Chemistry

James Turton, Stephen Worrall, Muhamad S Musa, Amir H Milani, Yichao Yao, Peter Shaw, David Ring, Brian R Saunders

2021

With the continued drive to develop elastomers, improved methods are required to decrease the environmental impact of their preparation. Previously, such systems used Zn-based salts to form nanostructured ionomeric elastomers which had high modulus values, but only limited stretchability. Here, we investigate highly stretchable, additive-free, nanostructured films that are formed simply by casting aqueous core–shell nanoparticle dispersions and drying. The nanoparticles have a poly(n-butylacrylate) (PBA) core and the shell contains a crosslinked copolymer of BA, acrylonitrile (AN), methacrylic acid (MAA) and 1,4-butanediol diacrylate (BDDA). The nanostructured films are shown to be highly stretchable (up to 1300%) and their toughness increases linearly with MAA content. The latter is due to hydrogen-bonding between the –COOH groups and AN. The core–shell nanoparticles are subsequently functionalised using glycidyl methacrylate (GMA) and the films heated to provide additional covalent crosslinking. We show that the vinyl group content can be evaluated using Raman spectroscopy. The latter also enables the monitoring of nanoparticle functionalisation by the reaction with GMA. Radical coupling of the vinyl groups upon heating of the films is shown to increase both the modulus and toughness of the films. Our new nanostructured films provide an alternative, additive-free, environmentally friendly approach for the preparation of highly stretchable water-based elastomers.

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Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO_x in Beijing

Atmospheric Chemistry and Physics

Lisa K Whalley, Eloise J Slater, Robert Woodward-Massey, Chunxiang Ye, James D Lee, Freya Squires, James R Hopkins, Rachel E Dunmore, Marvin Shaw, Jacqueline F Hamilton, Alastair C Lewis, Archit Mehra, Stephen D Worrall, Asan Bacak, Thomas J Bannan, Hugh Coe, Carl J Percival, Bin Ouyang, Roderic L Jones, Leigh R Crilley, Louisa J Kramer, William J Bloss, Tuan Vu, Simone Kotthaus, Sue Grimmond, Yele Sun, Weiqi Xu, Siyao Yue, Lujie Ren, W Joe F Acton, C Nicholas Hewitt, Xinming Wang, Pingqing Fu, Dwayne E Heard

2021

Measurements of OH, HO2, complex RO2 (alkene-and aromatic-related RO2) and total RO2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2:8 × 107 molecule cm-3, HO2 peaking at 1 × 109 molecule cm-3 and the total RO2 concentration reaching 5:5×109 molecule cm-3. OH reactivity (k.OH/) peaked at 89 s-1 during the night, with a minimum during the afternoon of 22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbvh-1) under the very low NO conditions (< 0:5ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC) emissions and low NO loadings...

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