Publications
12 results found
Dajnak D, Assareh N, Kitwiroon N, et al., 2023, Can the UK meet the World Health Organization PM2.5 interim target of 10 μg m-3 by 2030?, Environ Int, Vol: 181
The recent United Kingdom (UK) Environment Act consultation had the intention of setting two targets for PM2.5 (particles with an aerodynamic diameter less than 2.5 μm), one related to meeting an annual average concentration and the second to reducing population exposure. As part of the consultation, predictions of PM2.5 concentrations in 2030 were made by combining European Union (EU) and UK government's emissions forecasts, with the Climate Change Committee's (CCC) Net Zero vehicle forecasts, and in London with the addition of local policies based on the London Environment Strategy (LES). Predictions in 2018 showed 6.4% of the UK's area and 82.6% of London's area had PM2.5 concentrations above the World Health Organization (WHO) interim target of 10 μg m-3, but by 2030, over 99% of the UK's area was predicted to be below it. However, kerbside concentrations in London and other major cities were still at risk of exceeding 10 μg m-3. With local action on PM2.5 in London, population weighted concentrations showed full compliance with the WHO interim target of 10 μg m-3 in 2030. However, predicting future PM2.5 concentrations and interpreting the results will always be difficult and uncertain for many reasons, such as imperfect models and the difficulty in estimating future emissions. To help understand the sensitivity of the model's PM2.5 predictions in 2030, current uncertainty was quantified using PM2.5 measurements and showed large areas in the UK that were still at risk of exceeding the WHO interim target despite the model predictions being below 10 μg m-3. Our results do however point to the benefits that policy at EU, UK and city level can have on achieving the WHO interim target of 10 μg m-3. These results were submitted to the UK Environment Act consultation. Nevertheless, the issues addressed here could be applicable to other European cities.
Vu TV, Stewart GB, Kitwiroon N, et al., 2022, Assessing the contributions of outdoor and indoor sources to air quality in London homes of the SCAMP cohort, Building and Environment, Vol: 222, Pages: 1-8, ISSN: 0360-1323
Given that many people typically spend the majority of their time at home, accurate measurement and modelling of the home environment is critical in estimating their exposure to air pollution. This study investigates the fate and impact on human exposure of outdoor and indoor pollutants in London homes, using a combination of sensor measurements, outdoor air pollution estimated from the CMAQ-urban model and indoor mass balance models. Averaged indoor concentrations of PM2.5, PM10 and NO2 were 14.6, 24.7 and 14.2 μg m−3 while the outdoor concentrations were 14.4, 22.6 and 21.4 μg m−3, respectively. Mean infiltration factors of particles (0.6–0.7) were higher than those of NO2 (0.4). In contrast, higher loss rates were found for NO2 (0.5–0.8 h−1) compared to those for particles (0.1–0.3 h−1). The average concentrations of PM2.5, PM10 and NO2 in kitchen environments were 22.0, 33.7 and 20.8 μg m−3, with highest hourly concentrations (437, 644 and 136 μg m−3, respectively) during cooking times (6–7 pm). Indoor sources increased the indoor concentrations of particles and NO2 by an average of 26–37% in comparison to the indoor background level without indoor sources. Outdoor and indoor air exchange plays an important role in reducing air pollution indoors by 65–86% for particles and 42–65% for NO2.
Drysdale WS, Vaughan AR, Squires FA, et al., 2022, Eddy covariance measurements highlight sources of nitrogen oxide emissions missing from inventories for central London, Atmospheric Chemistry and Physics, Vol: 22, Pages: 9413-9433, ISSN: 1680-7316
During March–June 2017 emissions of nitrogen oxides were measured via eddy covariance at the British Telecom Tower in central London, UK. Through the use of a footprint model the expected emissions were simulated from the spatially resolved National Atmospheric Emissions Inventory for 2017 and compared with the measured emissions. These simulated emissions were shown to underestimate measured emissions during the daytime by a factor of 1.48, but they agreed well overnight. Furthermore, underestimations were spatially mapped, and the areas around the measurement site responsible for differences in measured and simulated emissions were inferred. It was observed that areas of higher traffic, such as major roads near national rail stations, showed the greatest underestimation by the simulated emissions. These discrepancies are partially attributed to a combination of the inventory not fully capturing traffic conditions in central London and both the spatial and temporal resolution of the inventory not fully describing the high heterogeneity of the urban centre. Understanding of this underestimation may be further improved with longer measurement time series to better understand temporal variation and improved temporal scaling factors to better simulate sub-annual emissions.
Hicks W, Beevers S, Tremper A, et al., 2021, Quantification of non-exhaust particulate matter traffic emissions and the impact of COVID-19 lockdown at London Marylebone Road, Atmosphere, Vol: 12, Pages: 1-19, ISSN: 2073-4433
This research quantifies current sources of non-exhaust particulate matter traffic emissions in London using simultaneous, highly time-resolved, atmospheric particulate matter mass and chemical composition measurements. The measurement campaign ran at Marylebone Road (roadside) and Honor Oak Park (background) urban monitoring sites over a 12-month period between 1 September 2019 and 31 August 2020. The measurement data has been used to determine the traffic increment (roadside – background) and covers a range of meteorological conditions, seasons and driving styles, as well as the influence of the COVID-19 ‘lockdown’ on non-exhaust concentrations. Non-exhaust PM10 concentrations are calculated using chemical tracer scaling factors for brake wear (barium), tyre wear (zinc) and resuspension (silicon) and as average vehicle fleet non-exhaust emission factors, using a CO2 ‘dilution approach’. The effect of lockdown, which saw a 32% reduction in traffic volume and a 15% increase in average speed on Marylebone Road, resulted in lower PM10 and PM2.5 traffic increments and brake wear concentrations, but similar tyre and resuspension concentrations, confirming that factors that determine non-exhaust emissions are complex. Brake wear was found to be the highest average non-exhaust emission source. In addition, results indicated that non-exhaust emission factors are dependent upon speed and road surface wetness conditions. Further statistical analysis incorporating a wider variability in vehicle mix, speeds and meteorological conditions, as well as advanced source apportionment of the PM measurement data, will be undertaken to enhance our understanding of these important vehicle sources.
Dajnak D, Stewart G, Beevers S, 2017, Policies for london nitrogen dioxide (NO<inf>2</inf>)compliance, Pages: 218-222
Over one tenth of the UK population live in London and since London’s air pollution concentrations are predicted to exceed legal NO2 limits until at least 2030 (DEFRA, 2015), London requires a bold combination of policies to tackle its air pollution problems. Road transport is the most significant source of NOX emissions in London with diesel vehicles the greatest contributor (TfL and GLA, 2013/2016). The current air pollution challenge, primarily caused by a shift from petrol to diesel vehicles over the last 15 years, needs to be recognised and reversed. Our study in partnership with Policy Exchange (PX), the Institute for Public Policy Research (IPPR) and Greenpeace (GP) builds on the Greater London Authority (GLA) implementation of the Ultra Low Emission Zone (ULEZ) in 2020 (TfL, 2014). Our ambitious air quality strategy proposes a comprehensive package of measures focusing on road transport policies such as phasing out diesel cars in inner London, moving toward more sustainable road transport alternatives, restricting the most polluting vehicles entering London, cleaning up taxi and bus fleets, promoting electric vehicles and car clubs. The proposed policies (the scenario) result in large reductions in NOX emissions (45%) across London, relative to the projected outcome of the ULEZ (TfL, 2014) from the previous administration (the baseline). Our modelling results suggest significant improvement bringing nearly the whole of London into compliance with legal NO2 limits by 2025 and decreasing NO2 concentration levels below 20 μgm-3 from 16% in the baseline to nearly 36% in the scenario. This is important since there are still health impacts below the 40 μgm-3 limit value. However, some key hotspots of pollution, on major roads, still remain non-compliant and will need additional localised targeted actions. These air quality improvements are projected to have a pronounced positive effect upon health outcomes in the capital. Life expectancy for all London
Popoola OAM, Stewart GB, Mead MI, et al., 2016, Development of a baseline-temperature correction methodology for electrochemical sensors and its implications for long-term stability, ATMOSPHERIC ENVIRONMENT, Vol: 147, Pages: 330-343, ISSN: 1352-2310
- Author Web Link
- Cite
- Citations: 75
Beevers SD, Carslaw DC, Dajnak D, et al., 2016, Traffic management strategies for emissions reduction: recent experience in London, Energy and Emission Control Technologies, Vol: 4, Pages: 27-39
Air pollution strategies in London over the last 12 years have centered upon the congestion charging scheme, and at the same time, the fitting of particle traps to London buses, the low emissions zone (LEZ), and the Mayor’s Air Quality Strategy (MAQS). The 2003 congestion charging scheme achieved much of the scheme’s aims, but the demand to travel and the need for road space eroded the initial benefits. While fitting particle traps on buses was predicted to reduce particulate matter (PM) exhaust emissions, the introduction of phases 1 and 2 of the LEZ and MAQS strategies were both predicted to have modest emission impacts. Reliance on new Euro-standard vehicles to reduce emissions, and as a way of designing LEZs, has been problematic, with oxides of nitrogen (NOx) and nitrogen dioxide (NO2) emissions from diesel vehicles reducing less than predicted. Consequently, the UK has not met annual NO2 European Union (EU) limit values, necessitating a time extension application. A mismatch between PM10 ambient trends and emissions has also been reported, with the long-term performance of PM particle filters remaining an important question. Assessing London’s traffic management schemes has relied upon emission inventories and dispersion models, and to date, there has been no confirmation of the effects of the schemes using ambient data, a challenging and important area of research. However, measurements of ambient NOx, NO2, ozone, PM species, and roadside vehicle emissions have all contributed to the improvement of road traffic emission inventories in London, and it remains important to undertake ambient monitoring to assess future schemes. Looking forward, the real-world emissions performance of Euro 6/VI vehicles, selective catalytic reduction, and the ultra-low emissions zone in London will play a critical role in meeting EU limit values for ambient NO2, and in light of the increasing health evidence of urban air pollution, policy makers should aim to red
Heimann I, Bright VB, McLeod MW, et al., 2015, Source attribution of air pollution by spatial scale separation using high spatial density networks of low cost air quality sensors, ATMOSPHERIC ENVIRONMENT, Vol: 113, Pages: 10-19, ISSN: 1352-2310
- Author Web Link
- Cite
- Citations: 86
Carslaw DC, Priestman M, Williams ML, et al., 2015, Performance of optimised SCR retrofit buses under urban driving and controlled conditions, ATMOSPHERIC ENVIRONMENT, Vol: 105, Pages: 70-77, ISSN: 1352-2310
This work presents the first comprehensive real-world emissions results from urban buses retrofitted with an optimised low-NO2 selective catalytic reduction (SCR) system. The SCRT system combines a CRT (Continuously Regenerating Trap) to reduce particle emissions and SCR to reduce NOx emissions. The optimised low-NO2 SCRT was designed to work under urban conditions where the vehicle exhaust gas temperature is often too low for many SCR systems to work efficiently. The system was extensively tested through on-road and test track measurements using a vehicle emission remote sensing instrument capable of measuring both nitric oxide (NO) and nitrogen dioxide (NO2). Over 700 on-road measurements of the SCRT system were made in London. Compared with identical buses operating under the same conditions fitted with a CRT, NO2 emissions were reduced by 61% and total NOx by 45%. Under test track conditions reductions in NOx of 77% were observed. The test track results do reveal however that compared with an original Euro III bus without a CRT, the SCRT retrofit bus emissions of NO2 are 50% higher. Engine-out and tailpipe measurements of several important engine parameters under test track conditions showed the important effect of SCR inlet temperature on NOx conversion efficiency. Overall, we conclude that retrofitting urban buses to use low-NO2 SCRT systems is an effective method for delivering NOx and NO2 emissions reduction.
Mueller MD, Hasenfratz D, SaUKh O, et al., 2014, Statistical modelling of pollutant concentration in the urban environment at high spatial and temporal resolution by utilizing data from sensor networks, Pages: 374-378
We developed a statistical modelling approach for the generation of pollutant concentration maps at high spatio-temporal resolution (30 minutes, 10 m) focusing on the application in the urban environment. The statistical models rely on data from sensor networks and georeferenced information. We explore the potential of this modelling approach by using data sets originating from the OpenSense mobile sensor network in Zurich and the Cambridge air pollution sensor network.
Mead MI, Popoola OAM, Stewart GB, et al., 2013, The use of electrochemical sensors for monitoring urban air quality in low-cost, high-density networks, ATMOSPHERIC ENVIRONMENT, Vol: 70, Pages: 186-203, ISSN: 1352-2310
- Author Web Link
- Cite
- Citations: 495
Bennett M, Christie SM, Graham A, et al., 2013, Abatement of an Aircraft Exhaust Plume Using Aerodynamic Baffles, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 47, Pages: 2346-2352, ISSN: 0013-936X
- Author Web Link
- Cite
- Citations: 3
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.