Imperial College London

Dr Anja Tremper

Faculty of MedicineSchool of Public Health

Research Fellow
 
 
 
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Contact

 

anja.tremper

 
 
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Location

 

Sir Michael Uren HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

27 results found

Savadkoohi M, Pandolfi M, Favez O, Putaud J-P, Eleftheriadis K, Fiebig M, Hopke PK, Laj P, Wiedensohler A, Alados-Arboledas L, Bastian S, Chazeau B, María ÁC, Colombi C, Costabile F, Green DC, Hueglin C, Liakakou E, Luoma K, Listrani S, Mihalopoulos N, Marchand N, Močnik G, Niemi JV, Ondráček J, Petit J-E, Rattigan OV, Reche C, Timonen H, Titos G, Tremper AH, Vratolis S, Vodička P, Funes EY, Zíková N, Harrison RM, Petäjä T, Alastuey A, Querol Xet al., 2024, Recommendations for reporting equivalent black carbon (eBC) mass concentrations based on long-term pan-European in-situ observations., Environ Int, Vol: 185

A reliable determination of equivalent black carbon (eBC) mass concentrations derived from filter absorption photometers (FAPs) measurements depends on the appropriate quantification of the mass absorption cross-section (MAC) for converting the absorption coefficient (babs) to eBC. This study investigates the spatial-temporal variability of the MAC obtained from simultaneous elemental carbon (EC) and babs measurements performed at 22 sites. We compared different methodologies for retrieving eBC integrating different options for calculating MAC including: locally derived, median value calculated from 22 sites, and site-specific rolling MAC. The eBC concentrations that underwent correction using these methods were identified as LeBC (local MAC), MeBC (median MAC), and ReBC (Rolling MAC) respectively. Pronounced differences (up to more than 50 %) were observed between eBC as directly provided by FAPs (NeBC; Nominal instrumental MAC) and ReBC due to the differences observed between the experimental and nominal MAC values. The median MAC was 7.8 ± 3.4 m2 g-1 from 12 aethalometers at 880 nm, and 10.6 ± 4.7 m2 g-1 from 10 MAAPs at 637 nm. The experimental MAC showed significant site and seasonal dependencies, with heterogeneous patterns between summer and winter in different regions. In addition, long-term trend analysis revealed statistically significant (s.s.) decreasing trends in EC. Interestingly, we showed that the corresponding corrected eBC trends are not independent of the way eBC is calculated due to the variability of MAC. NeBC and EC decreasing trends were consistent at sites with no significant trend in experimental MAC. Conversely, where MAC showed s.s. trend, the NeBC and EC trends were not consistent while ReBC concentration followed the same pattern as EC. These results underscore the importance of accounting for MAC variations when deriving eBC measurements from FAPs and emphasize the necessity of

Journal article

Garcia-Marlès M, Lara R, Reche C, Pérez N, Tobías A, Savadkoohi M, Beddows D, Salma I, Vörösmarty M, Weidinger T, Hueglin C, Mihalopoulos N, Grivas G, Kalkavouras P, Ondráček J, Zíková N, Niemi JV, Manninen HE, Green DC, Tremper AH, Norman M, Vratolis S, Eleftheriadis K, Gómez-Moreno FJ, Alonso-Blanco E, Wiedensohler A, Weinhold K, Merkel M, Bastian S, Hoffmann B, Altug H, Petit J-E, Favez O, Dos Santos SM, Putaud J-P, Dinoi A, Contini D, Timonen H, Lampilahti J, Petäjä T, Pandolfi M, Hopke PK, Harrison RM, Alastuey A, Querol Xet al., 2024, Inter-annual trends of ultrafine particles in urban Europe., Environ Int, Vol: 185

Ultrafine particles (UFP, those with diameters ≤ 100 nm), have been reported to potentially penetrate deeply into the respiratory system, translocate through the alveoli, and affect various organs, potentially correlating with increased mortality. The aim of this study is to assess long-term trends (5-11 years) in mostly urban UFP concentrations based on measurements of particle number size distributions (PNSD). Additionally, concentrations of other pollutants and meteorological variables were evaluated to support the interpretations. PNSD datasets from 12 urban background (UB), 5 traffic (TR), 3 suburban background (SUB) and 1 regional background (RB) sites in 15 European cities and 1 in the USA were evaluated. The non-parametric Theil-Sen's method was used to detect monotonic trends. Meta-analyses were carried out to assess the overall trends and those for different environments. The results showed significant decreases in NO, NO2, BC, CO, and particle concentrations in the Aitken (25-100 nm) and the Accumulation (100-800 nm) modes, suggesting a positive impact of the implementation of EURO 5/V and 6/VI vehicle standards on European air quality. The growing use of Diesel Particle Filters (DPFs) might also have clearly reduced exhaust emissions of BC, PM, and the Aitken and Accumulation mode particles. However, as reported by prior studies, there remains an issue of poor control of Nucleation mode particles (smaller than 25 nm), which are not fully reduced with current DPFs, without emission controls for semi-volatile organic compounds, and might have different origins than road traffic. Thus, contrasting trends for Nucleation mode particles were obtained across the cities studied. This mode also affected the UFP and total PNC trends because of the high proportion of Nucleation mode particles in both concentration ranges. It was also found that the urban temperature increasing trends might have also influenced those of PNC, Nuc

Journal article

Liu X, Hadiatullah H, Zhang X, Trechera P, Savadkoohi M, Garcia-Marlès M, Reche C, Pérez N, Beddows DCS, Salma I, Thén W, Kalkavouras P, Mihalopoulos N, Hueglin C, Green DC, Tremper AH, Chazeau B, Gille G, Marchand N, Niemi JV, Manninen HE, Portin H, Zikova N, Ondracek J, Norman M, Gerwig H, Bastian S, Merkel M, Weinhold K, Casans A, Casquero-Vera JA, Gómez-Moreno FJ, Artíñano B, Gini M, Diapouli E, Crumeyrolle S, Riffault V, Petit J-E, Favez O, Putaud J-P, Santos SMD, Timonen H, Aalto PP, Hussein T, Lampilahti J, Hopke PK, Wiedensohler A, Harrison RM, Petäjä T, Pandolfi M, Alastuey A, Querol Xet al., 2023, Ambient air particulate total lung deposited surface area (LDSA) levels in urban Europe, Science of the Total Environment, Vol: 898, Pages: 1-11, ISSN: 0048-9697

This study aims to picture the phenomenology of urban ambient total lung deposited surface area (LDSA) (including head/throat (HA), tracheobronchial (TB), and alveolar (ALV) regions) based on multiple path particle dosimetry (MPPD) model during 2017-2019 period collected from urban background (UB, n = 15), traffic (TR, n = 6), suburban background (SUB, n = 4), and regional background (RB, n = 1) monitoring sites in Europe (25) and USA (1). Briefly, the spatial-temporal distribution characteristics of the deposition of LDSA, including diel, weekly, and seasonal patterns, were analyzed. Then, the relationship between LDSA and other air quality metrics at each monitoring site was investigated. The result showed that the peak concentrations of LDSA at UB and TR sites are commonly observed in the morning (06:00-8:00 UTC) and late evening (19:00-22:00 UTC), coinciding with traffic rush hours, biomass burning, and atmospheric stagnation periods. The only LDSA night-time peaks are observed on weekends. Due to the variability of emission sources and meteorology, the seasonal variability of the LDSA concentration revealed significant differences (p = 0.01) between the four seasons at all monitoring sites. Meanwhile, the correlations of LDSA with other pollutant metrics suggested that Aitken and accumulation mode particles play a significant role in the total LDSA concentration. The results also indicated that the main proportion of total LDSA is attributed to the ALV fraction (50 %), followed by the TB (34 %) and HA (16 %). Overall, this study provides valuable information of LDSA as a predictor in epidemiological studies and for the first time presenting total LDSA in a variety of European urban environments.

Journal article

Savadkoohi M, Pandolfi M, Reche C, V Niemi J, Mooibroek D, Titos G, Green DC, Tremper AH, Hueglin C, Liakakou E, Mihalopoulos N, Stavroulas I, Artinano B, Coz E, Alados-Arboledas L, Beddows D, Riffault V, De Brito JF, Bastian S, Baudic A, Colombi C, Costabile F, Chazeau B, Marchand N, Gomez-Amo JL, Estelles V, Matos V, Gaag EVD, Gille G, Luoma K, Manninen HE, Norman M, Silvergren S, Petit J-E, Putaud J-P, V Rattigan O, Timonen H, Tuch T, Merkel M, Weinhold K, Vratolis S, Vasilescu J, Favez O, Harrison RM, Laj P, Wiedensohler A, Hopke PK, Petaja T, Alastuey A, Querol Xet al., 2023, The variability of mass concentrations and source apportionment analysis of equivalent black carbon across urban Europe, ENVIRONMENT INTERNATIONAL, Vol: 178, ISSN: 0160-4120

Journal article

Baerenbold O, Meis M, MartínezHernández I, Euán C, Burr WS, Tremper A, Fuller G, Pirani M, Blangiardo Met al., 2023, A dependent Bayesian Dirichlet process model for source apportionment of particle number size distribution, Environmetrics, Vol: 34, ISSN: 1180-4009

The relationship between particle exposure and health risks has been well established in recent years. Particulate matter (PM) is made up of different components coming from several sources, which might have different level of toxicity. Hence, identifying these sources is an important task in order to implement effective policies to improve air quality and population health. The problem of identifying sources of particulate pollution has already been studied in the literature. However, current methods require an a priori specification of the number of sources and do not include information on covariates in the source allocations. Here, we propose a novel Bayesian nonparametric approach to overcome these limitations. In particular, we model source contribution using a Dirichlet process as a prior for source profiles, which allows us to estimate the number of components that contribute to particle concentration rather than fixing this number beforehand. To better characterize them we also include meteorological variables (wind speed and direction) as covariates within the allocation process via a flexible Gaussian kernel. We apply the model to apportion particle number size distribution measured near London Gatwick Airport (UK) in 2019. When analyzing this data, we are able to identify the most common PM sources, as well as new sources that have not been identified with the commonly used methods.

Journal article

Trechera P, Garcia-Marlès M, Liu X, Reche C, Pérez N, Savadkoohi M, Beddows D, Salma I, Vörösmarty M, Casans A, Casquero-Vera JA, Hueglin C, Marchand N, Chazeau B, Gille G, Kalkavouras P, Mihalopoulos N, Ondracek J, Zikova N, Niemi JV, Manninen HE, Green DC, Tremper AH, Norman M, Vratolis S, Eleftheriadis K, Gómez-Moreno FJ, Alonso-Blanco E, Gerwig H, Wiedensohler A, Weinhold K, Merkel M, Bastian S, Petit J-E, Favez O, Crumeyrolle S, Ferlay N, Martins Dos Santos S, Putaud J-P, Timonen H, Lampilahti J, Asbach C, Wolf C, Kaminski H, Altug H, Hoffmann B, Rich DQ, Pandolfi M, Harrison RM, Hopke PK, Petäjä T, Alastuey A, Querol Xet al., 2023, Phenomenology of ultrafine particle concentrations and size distribution across urban Europe, Environment International, Vol: 172, Pages: 1-17, ISSN: 0160-4120

The 2017-2019 hourly particle number size distributions (PNSD) from 26 sites in Europe and 1 in the US were evaluated focusing on 16 urban background (UB) and 6 traffic (TR) sites in the framework of Research Infrastructures services reinforcing air quality monitoring capacities in European URBAN & industrial areaS (RI-URBANS) project. The main objective was to describe the phenomenology of urban ultrafine particles (UFP) in Europe with a significant air quality focus. The varying lower size detection limits made it difficult to compare PN concentrations (PNC), particularly PN10-25, from different cities. PNCs follow a TR > UB > Suburban (SUB) order. PNC and Black Carbon (BC) progressively increase from Northern Europe to Southern Europe and from Western to Eastern Europe. At the UB sites, typical traffic rush hour PNC peaks are evident, many also showing midday-morning PNC peaks anti-correlated with BC. These peaks result from increased PN10-25, suggesting significant PNC contributions from nucleation, fumigation and shipping. Site types to be identified by daily and seasonal PNC and BC patterns are: (i) PNC mainly driven by traffic emissions, with marked correlations with BC on different time scales; (ii) marked midday/morning PNC peaks and a seasonal anti-correlation with PNC/BC; (iii) both traffic peaks and midday peaks without marked seasonal patterns. Groups (ii) and (iii) included cities with high insolation. PNC, especially PN25-800, was positively correlated with BC, NO2, CO and PM for several sites. The variable correlation of PNSD with different urban pollutants demonstrates that these do not reflect the variability of UFP in urban environments. Specific monitoring of PNSD is needed if nanoparticles and their associated health impacts are to be assessed. Implementation of the CEN-ACTRIS recommendations for PNSD measurements would provide comparable measurements, and measurements of <10 nm PNC are needed for full evalu

Journal article

Chen G, Canonaco F, Tobler A, Aas W, Alastuey A, Allan J, Atabakhsh S, Aurela M, Baltensperger U, Bougiatioti A, De Brito JF, Ceburnis D, Chazeau B, Chebaicheb H, Daellenbach KR, Ehn M, El Haddad I, Eleftheriadis K, Favez O, Flentje H, Font A, Fossum K, Freney E, Gini M, Green DC, Heikkinen L, Herrmann H, Kalogridis A-C, Keernik H, Lhotka R, Lin C, Lunder C, Maasikmets M, Manousakas MI, Marchand N, Marin C, Marmureanu L, Mihalopoulos N, Močnik G, Nęcki J, O'Dowd C, Ovadnevaite J, Peter T, Petit J-E, Pikridas M, Matthew Platt S, Pokorná P, Poulain L, Priestman M, Riffault V, Rinaldi M, Różański K, Schwarz J, Sciare J, Simon L, Skiba A, Slowik JG, Sosedova Y, Stavroulas I, Styszko K, Teinemaa E, Timonen H, Tremper A, Vasilescu J, Via M, Vodička P, Wiedensohler A, Zografou O, Cruz Minguillón M, Prévôt ASHet al., 2022, European aerosol phenomenology - 8: Harmonised source apportionment of organic aerosol using 22 Year-long ACSM/AMS datasets, Environment International, Vol: 166, ISSN: 0160-4120

Organic aerosol (OA) is a key component of total submicron particulate matter (PM1), and comprehensive knowledge of OA sources across Europe is crucial to mitigate PM1 levels. Europe has a well-established air quality research infrastructure from which yearlong datasets using 21 aerosol chemical speciation monitors (ACSMs) and 1 aerosol mass spectrometer (AMS) were gathered during 2013-2019. It includes 9 non-urban and 13 urban sites. This study developed a state-of-the-art source apportionment protocol to analyse long-term OA mass spectrum data by applying the most advanced source apportionment strategies (i.e., rolling PMF, ME-2, and bootstrap). This harmonised protocol was followed strictly for all 22 datasets, making the source apportionment results more comparable. In addition, it enables quantification of the most common OA components such as hydrocarbon-like OA (HOA), biomass burning OA (BBOA), cooking-like OA (COA), more oxidised-oxygenated OA (MO-OOA), and less oxidised-oxygenated OA (LO-OOA). Other components such as coal combustion OA (CCOA), solid fuel OA (SFOA: mainly mixture of coal and peat combustion), cigarette smoke OA (CSOA), sea salt (mostly inorganic but part of the OA mass spectrum), coffee OA, and ship industry OA could also be separated at a few specific sites. Oxygenated OA (OOA) components make up most of the submicron OA mass (average = 71.1%, range from 43.7 to 100%). Solid fuel combustion-related OA components (i.e., BBOA, CCOA, and SFOA) are still considerable with in total 16.0% yearly contribution to the OA, yet mainly during winter months (21.4%). Overall, this comprehensive protocol works effectively across all sites governed by different sources and generates robust and consistent source apportionment results. Our work presents a comprehensive overview of OA sources in Europe with a unique combination of high time resolution (30-240 min) and long-term data coverage (9-36 months), providing essential information

Journal article

Manousakas M, Furger M, Daellenbach KR, Canonaco F, Chen G, Tobler A, Rai P, Qi L, Tremper AH, Green D, Hueglin C, Slowik JG, El Haddad I, Prevot ASHet al., 2022, Source identification of the elemental fraction of particulate matter using size segregated, highly time-resolved data and an optimized source apportionment approach, Atmospheric Environment: X, Vol: 14, ISSN: 2590-1621

Source emissions with high covariance degrade the performance of multivariate models, and often highly-time resolved data is needed to accurately extract the contribution of different emissions. Here, we use highly time-resolved size segregated elemental composition data to apportion the sources of the elemental fraction of PM in Zürich (May 2019–May 2020). For data collection, we have used an ambient metals monitor, Xact 625i, equipped with a sampling inlet alternating between PM2.5 and PM10. By implementing interpolation and a newly proposed uncertainty estimation methodology, it was possible to obtain and use in PMF a combined dataset of PM2.5 and PMcoarse (PM10-2.5) having data from only one instrument. The combination of the inlet switching system, the instrument's high time resolution, and the use of advanced source apportionment approaches yielded improved source apportionment results in terms of the number of identified sources, as the model, additionally to the diurnal and seasonal variation of the dataset, also utilizes the variation from the size segregated data. Thirteen sources of elements were identified, i.e., sea salt (5.4%), biomass burning (7.2%), construction (4.3%), industrial (3.3%), light-duty vehicles (5.4%), Pb (0.7%), Zn (0.7%), dust (22.1%), transported dust (9.5%), sulfates (15.4%), heavy-duty vehicles (17%), railway (6.6%) and fireworks (2.4%). The Covid-19 lockdown effect in PM sources in the area was also quantified. High-intensity events disproportionally affect the PMF solution, and in many cases, they are getting discarded before analysis, removing thus valuable information from the dataset. In this study, a three-step source apportionment approach was used to get a well-resolved unmixed solution when firework data points were included in the analysis. This approach can also be used for other sources and/or events with very high contributions that distort source apportionment analysis. Optimized source apportionment techni

Journal article

Tremper A, Jephcote C, Gulliver J, Hibbs L, Green D, Font A, Priestman M, Hansell A, Fuller Get al., 2022, Sources of particle number concentration and noise near London Gatwick Airport, Environment International, Vol: 161, ISSN: 0160-4120

There is increasing evidence of potential health impacts from both aircraft noise and aircraft-associated ultrafine particles (UFP). Measurements of noise and UFP are however scarce near airports and so their variability and relationship are not well understood. Particle number size distributions and noise levels were measured at two locations near Gatwick airport (UK) in 2018–19 with the aim to characterize particle number concentrations (PNC) and link PNC sources, especially UFP, with noise. Positive Matrix Factorization was used on particle number size distribution to identify these sources. Mean PNC (7500–12,000 p cm−3) were similar to those measured close to a highly trafficked road in central London. Peak PNC (94,000 p cm−3) were highest at the site closer to the runway. The airport source factor contributed 17% to the PNC at both sites and the concentrations were greatest when the respective sites were downwind of the runway. However, the main source of PNC was associated with traffic emissions. At both sites noise levels were above the recommendations by the WHO (World Health Organisation). Regression models of identified UFP sources and noise suggested that the largest source of noise (LAeq-1hr) above background was associated with sources of fresh traffic and urban UFP depending on the site. Noise and UFP correlations were moderate to low suggesting that UFP are unlikely to be an important confounder in epidemiological studies of aircraft noise and health. Correlations between UFP and noise were affected by meteorological factors, which need to be considered in studies of short-term associations between aircraft noise and health.

Journal article

Green D, 2022, Source attribution and quantification of atmospheric nickel concentrations in an industrial area in the United Kingdom (UK), Environmental Pollution, Vol: 293, Pages: 1-10, ISSN: 0269-7491

Pontardawe in South Wales, United Kingdom (UK), consistently has the highest concentrations of nickel (Ni) in PM10 in the UK and repeatedly breaches the 20 ng m−3 annual mean EU target value. Several local industries use Ni in their processes. To assist policy makers and regulators in quantifying the relative Ni contributions of these industries and developing appropriate emission reduction approaches, the hourly concentrations of 23 elements were measured using X-ray fluorescence alongside meteorological variables and black carbon during a four-week campaign in November–December 2015. Concentrations of Ni ranged between 0 and 2480 ng m−3 as hourly means. Positive Matrix Factorization (PMF) was used to identify sources contributing to measured elements. Cluster analysis of bivariate polar plots of those factors containing Ni in their profile was further used to quantify the industrial processes contributing to ambient PM10 concentrations. Two sources were identified to contribute to Ni concentrations, stainless-steel (which contributed to 10% of the Ni burden) and the Ni refinery (contributing 90%). From the stainless-steel process, melting activities were responsible for 66% of the stainless-steel factor contribution.

Journal article

Manousakas M, Diapouli E, Tremper AH, 2022, Editorial: Physicochemical Characterization of Aerosols in Diverse Environments and Climatic Conditions, FRONTIERS IN ENVIRONMENTAL SCIENCE, Vol: 9

Journal article

Weiss D, Resongle E, harrison R, Dietze V, Green D, Tremper A, Ochoa Ret al., 2021, Strong evidence for the continued contribution of lead deposited during the 20th century to the atmospheric environment of today, Proceedings of the National Academy of Sciences of USA, Vol: 118, ISSN: 0027-8424

Although leaded gasoline was banned at the end of the last century, lead (Pb) remains significantly enriched in airborne particles in large cities. The remobilization of historical Pb deposited in soils from atmospheric removal has been suggested as an important source providing evidence for the hypothetical long-term persistency of lead, and possibly other pollutants, in the urban environment. Here, we present data on Pb isotopic composition in airborne particles collected in London (2014 to 2018), which provide strong support that lead deposited via gasoline combustion still contributes significantly to the lead burden in present-day London. Lead concentration and isotopic signature of airborne particles collected at a heavily trafficked site did not vary significantly over the last decade, suggesting that sources remained unchanged. Lead isotopic composition of airborne particles matches that of road dust and topsoils and can only be explained with a significant contribution (estimate of 32 ± 10 to 43 ± 9% based on a binary mixing model) of Pb from leaded gasoline. The lead isotopes furthermore suggest significant contributions from nonexhaust traffic emissions, even though isotopic signatures of anthropogenic sources are increasingly overlapping. Lead isotopic composition of airborne particles collected at building height shows a similar signature to that collected at street level, suggesting effective mixing of lead within the urban street canyon. Our results have important implications on the persistence of Pb in urban environments and suggest that atmospheric Pb reached a baseline in London that is difficult to decrease further with present policy measures.

Journal article

Hicks W, Beevers S, Tremper A, Stewart G, Priestman M, Kelly F, Lanoisellé M, Lowry D, Green Det 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.

Journal article

Font A, Tremper AH, Lin C, Priestman M, Marsh D, Woods M, Heal MR, Green DCet al., 2020, Air quality in enclosed railway stations: Quantifying the impact of diesel trains through deployment of multi-site measurement and random forest modelling, ENVIRONMENTAL POLLUTION, Vol: 262, ISSN: 0269-7491

Journal article

Barratt BM, Fuller GW, Kelly FJ, Priestman M, Tremper AH, Green DCet al., 2020, PM2.5 on the London Underground, Environment International, Vol: 134, ISSN: 0160-4120

Introduction: Despite the London Underground (LU) handling on average 2.8 million passenger journeys per day, the characteristics and potential health effects of the elevated concentrations of metal-rich PM2.5 found in this subway system are not well understood. Methods: Spatial monitoring campaigns were carried out to characterise the health-relevant chemical and physical properties of PM2.5 across the LU network, including diurnal and day-to-day variability and spatial distribution (above ground, depth below ground and subway line). Population-weighted station PM2.5 rankings were produced to understand the relative importance of concentrations at different stations and on different lines. Results: The PM2.5 mass in the LU (mean 88 μg m−3, median 28 μg m−3) was greater than at ambient background locations (mean 19 μg m−3, median 14 μg m−3) and roadside environments in central London (mean 22 μg m−3, median 14 μg m−3). Concentrations varied between lines and locations, with the deepest and shallowest submerged lines being the District (median 4 μg m−3) and Victoria (median 361 μg m−3 but up to 885 μg m−3). Broadly in agreement with other subway systems around the world, sampled LU PM2.5 comprised 47% iron oxide, 7% elemental carbon, 11% organic carbon, and 14% metallic and mineral oxides. Although a relationship between line depth and air quality inside the tube trains was evident, there were clear influences relating to the distance from cleaner outside air and the exchange with cabin air when the doors open. The passenger population-weighted exposure analysis demonstrated a method to identify stations that should be prioritised for remediation to improve air quality. Conclusion: PM2.5 concentrations in the LU are many times higher than in other London transport Environments. Failure to include this environment in epidemiological studies of the relationship between PM2.5 and health in

Journal article

Gulliver J, Chen Y, Fuller G, Tremper A, Hibbs L, Soussan J, Vineis P, Hansell Aet al., 2019, Do ultrafine particles confound studies on noise and cardiovascular disease?, Pages: 3040-3047, ISSN: 2226-7808

Ultrafine particles (UFP) are emitted by both jet engine aircraft and road traffic and may potentially confound associations between noise and health outcomes. However, neither UFP or noise are routinely measured resulting in a lack of understanding of their relationship. We conducted repeated short-term measurements with portable sensors to assess the correlation between noise and UFP number concentrations (PNC) for aircraft and road traffic. Noise and PNC were measured contemporaneously for 30-minutes at 160 sites (repeated three times at a range of site types) in Norwich, a medium size city in the east of England, and repeatedly up to 71 times per site at nine sites (501 in total) around Gatwick airport. In Combining all measurements at Gatwick Airport the correlation was very weak (U = 0.11). Strongest correlations were moderate (|>0.4-0.6|) at a residential site 1.3 km north of the runway and a site 0.6 km south of the runway. The correlation between noise and PNC in Norwich was overall moderate (U = 0.52) and weak (U <0.4) for roadside sites (n = 55) and urban background sites (n = 90) respectively. Results suggest that PNC are unlikely to be a major confounder in epidemiological studies of aircraft or road noise and cardiovascular disease.

Conference paper

Tremper AH, Font A, Priestman M, Hamad SH, Chung T-C, Pribadi A, Brown RJC, Goddard SL, Grassineau N, Petterson K, Kelly FJ, Green DCet al., 2018, Field and laboratory evaluation of a high time resolution x-ray fluorescence instrument for determining the elemental composition of ambient aerosols, Atmospheric Measurement Techniques, Vol: 11, Pages: 3541-3557, ISSN: 1867-1381

Measuring the chemical composition of airborne particulate matter (PM) can provide valuable information on the concentration of regulated toxic metals, support modelling approaches for source detection and assist in the identification and validation of abatement techniques. Undertaking these at a high time resolution (1 h or less) enables receptor modelling techniques to be more robustly linked to emission processes. This study describes a comprehensive laboratory and field evaluation of a high time resolution x-ray fluorescence (XRF) instrument (CES XACT 625) for a range of elements (As, Ba, Ca, Cd, Ce, Cl, Cr, Cu, Fe, K, Mn, Mo, Ni, Pb, Pt, S, Sb, Se, Si, Sr, Ti, V and Zn) against alternative techniques: high time resolution mass measurements, high time resolution ion chromatography, aerosol mass spectrometry, and established filter-based, laboratory analysis using inductively coupled plasma mass spectrometry (ICP-MS).Laboratory evaluation was carried out using a novel mass-based calibration technique to independently assess the accuracy of the XRF against laboratory generated aerosols, which resulted in slopes that were not significantly different from unity. This demonstrated that generated particles can serve as an alternative calibration method for this instrument.The XACT was evaluated in three contrasting field deployments; a heavily trafficked roadside site (PM10 and PM2.5), an industrial location downwind of a nickel refinery (PM10) and an urban background location influenced by nearby industries and motorways (PM10). The XRF technique agreed well with the ICP-MS measurements of daily filter samples in all cases with a median R2 of 0.93 and a median slope of 1.07 for the elements As, Ba, Ca, Cr, Cu, Fe, K, Mn, Ni, Pb, Se, Sr, Ti, V and Zn. Differences in the results were attributed to a combination of inlet location and sampling temperature, variable blank levels in filter paper and recovery rates from acid digestion. The XRF technique also agreed well wit

Journal article

Davy PM, Tremper AH, Nicolosi EMG, Quincey P, Fuller GWet al., 2017, Estimating particulate black carbon concentrations using two offline light absorption methods applied to four types of filter media, ATMOSPHERIC ENVIRONMENT, Vol: 152, Pages: 24-33, ISSN: 1352-2310

Atmospheric particulate black carbon has been linked to adverse health outcomes. Additional black carbon measurements would aid a better understanding of population exposure in epidemiological studies as well as the success, or otherwise, of relevant abatement technologies and policies. Two light absorption measurement methods of particles collected on filters have been applied to four different types of filters to provide estimations of particulate black carbon concentrations. The ratio of transmittance (lnI0/I) to reflectance (lnR0/R) varied by filter type and ranged from close to 0.5 (as expected from simple theory) to 1.35 between the four filter types tested. The relationship between light absorption and black carbon, measured by the thermal EC(TOT) method, was nonlinear and differed between filter type and measurement method. This is particularly relevant to epidemiological studies that use light absorption as an exposure metric. An extensive archive of filters was used to derive loading factors and mass extinction coefficients for each filter type. Particulate black carbon time series were then calculated at locations where such measurements were not previously available. When applied to two roads in London, black carbon concentrations were found to have increased between 2011 and 2013, by 0.3 (CI: −0.1, 0.5) and 0.4 (CI: 0.1, 0.9) μg m−3 year−1, in contrast to the expectation from exhaust abatement policies. New opportunities using archived or bespoke filter collections for studies on the health effects of black carbon and the efficacy of abatement strategies are created.

Journal article

Helfter C, Tremper AH, Halios CH, Kotthaus S, Bjorkegren A, Grimmond CSB, Barlow JF, Nemitz Eet al., 2016, Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK, Atmospheric Chemistry and Physics, Vol: 16, Pages: 10543-10557, ISSN: 1680-7316

We report on more than 3 years of measurements of fluxes of methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) taken by eddy-covariance in central London, UK. Mean annual emissions of CO2 in the period 2012-2014 (39.1 ± 2.4ktonskm-2yr-1) and CO (89±16tonskm-2yr-1) were consistent (within 1 and 5% respectively) with values from the London Atmospheric Emissions Inventory, but measured CH4 emissions (72±3tonskm-2yr-1) were over two-fold larger than the inventory value. Seasonal variability was large for CO with a winter to summer reduction of 69%, and monthly fluxes were strongly anti-correlated with mean air temperature. The winter increment in CO emissions was attributed mainly to vehicle cold starts and reduced fuel combustion efficiency. CO2 fluxes were 33% higher in winter than in summer and anti-correlated with mean air temperature, albeit to a lesser extent than for CO. This was attributed to an increased demand for natural gas for heating during the winter. CH4 fluxes exhibited moderate seasonality (21% larger in winter), and a spatially variable linear anti-correlation with air temperature. Differences in resident population within the flux footprint explained up to 90% of the spatial variability of the annual CO2 fluxes and up to 99% for CH4. Furthermore, we suggest that biogenic sources of CH4, such as wastewater, which is unaccounted for by the atmospheric emissions inventories, make a substantial contribution to the overall budget and that commuting dynamics in and out of central business districts could explain some of the spatial and temporal variability of CO2 and CH4 emissions. To our knowledge, this study is unique given the length of the data sets presented, especially for CO and CH4 fluxes. This study offers an independent assessment of "bottom-up" emissions inventories and demonstrates that the urban sources of CO and CO2 are well characterized in London. This is however not the case for CH4 emissions which

Journal article

Lee JD, Helfter C, Purvis RM, Beevers SD, Carslaw DC, Lewis AC, Moller SJ, Tremper A, Vaughan A, Nemitz EGet al., 2015, Measurement of NO<i><sub>x</sub></i> Fluxes from a Tall Tower in Central London, UK and Comparison with Emissions Inventories, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 49, Pages: 1025-1034, ISSN: 0013-936X

Journal article

Bohnenstengel SI, Belcher SE, Aiken A, Allan JD, Allen G, Bacak A, Bannan TJ, Barlow JF, Beddddows DCS, Blossss WJ, Booth AM, Chemel C, Coceal O, Di Marco CF, Dubey MK, Faloon KH, Flemiming ZL, Furger M, Gietl JK, Graves RR, Green DC, Grimmimmimmond CSB, Halios CH, Hamiamiamilton JF, Harrisison RM, Heal MR, Heard DE, Helfter C, Herndon SC, Holmes RE, Hopkins JR, Jones AM, Kelly FJ, Kotthaus S, Langford B, Lee JD, Leigh RJ, Lewisis AC, Lidsidsidster RT, Lopez-Hilfiker FD, McQuaidaid JB, Mohr C, Monks PS, Nemimitz E, Ng NL, Percival CJ, Prévôt ASH, Ricketts HMA, Sokhi R, Stone D, Thornton JA, Tremper A, Valach AC, Vissississer S, Whalley LK, Williamsiamsiamsiams LR, Xu L, Young DE, Zotter Pet al., 2015, Meteorology, air quality, and health in London, The ClearfLo project, Vol: 96, Pages: 779-804, ISSN: 0003-0007

The Clean Air for London (ClearfLo) project provides integrated measurements of the meteorology, composition, and particulate loading of the urban atmosphere in London, United Kingdom, to improve predictive capability for air quality.

Journal article

Visser S, Slowik JG, Furger M, Zotter P, Bukowiecki N, Dressler R, Flechsig U, Appel K, Green DC, Tremper AH, Young DE, Williams PI, Allan JD, Herndon SC, Williams LR, Mohr C, Xu L, Ng NL, Detournay A, Barlow JF, Halios CH, Fleming ZL, Baltensperger U, Prevot ASHet al., 2015, Kerb and urban increment of highly time-resolved trace elements in PM<sub>10</sub>, PM<sub>2.5</sub> and PM<sub>1.0</sub> winter aerosol in London during ClearfLo 2012, ATMOSPHERIC CHEMISTRY AND PHYSICS, Vol: 15, Pages: 2367-2386, ISSN: 1680-7316

Journal article

Visser S, Slowik JG, Furger M, Zotter P, Bukowiecki N, Canonaco F, Flechsig U, Appel K, Green DC, Tremper AH, Young DE, Williams PI, Allan JD, Coe H, Williams LR, Mohr C, Xu L, Ng NL, Nemitz E, Barlow JF, Halios CH, Fleming ZL, Baltensperger U, Prevot ASHet al., 2015, Advanced source apportionment of size-resolved trace elements at multiple sites in London during winter, ATMOSPHERIC CHEMISTRY AND PHYSICS, Vol: 15, Pages: 11291-11309, ISSN: 1680-7316

Journal article

Fuller GW, Tremper AH, Baker TD, Yttri KE, Butterfield Det al., 2014, Contribution of wood burning to PM10 in London, ATMOSPHERIC ENVIRONMENT, Vol: 87, Pages: 87-94, ISSN: 1352-2310

Ahead of measures to incentivise wood heating, the current level of wood burning in London was assessed by two tracer methods; i) a six week campaign of daily measurements of levoglucosan along a 38 km transect across the city during winter 2010, ii) a three year (2009–2011) measurement programme of black carbon and particulate matter from wood burning using differential IR and UV absorption by Aethalometer. Mean winter levoglucosan concentrations were 160 ± 17 ng m−3 in central London and 30 ± 26 ng m−3 greater in the suburbs, with good temporal correlation (r2 = 0.68–0.98) between sampling sites. Sensitivity testing found that the aethalometer wood burning tracer method was more sensitive to the assumed value of the Ångström coefficient for fossil fuel black carbon than it was to the Ångström coefficient for wood burning PM, and that the model was optimised with Ångström coefficient for fossil fuel black carbon of 0.96. The aethalometer and levoglucosan estimates of mean PM from wood burning were in good agreement during the winter campaign; 1.8 μg m−3 (levoglucosan) and 2.0 μg m−3 (aethalometer); i.e. between 7% and 9% of mean PM10 across the London transect. Analysis of wood burning tracers with respect to wind speed suggested that wood burning PM was dominated by sources within the city. Concentrations of aethalometer and levoglucosan wood burning tracers were a greatest at weekends suggesting discretionary or secondary domestic wood burning rather than wood being used as a main heating source. Aethalometer wood burning tracers suggests that the annual mean concentration of PM10 from wood burning was 1.1 μg m−3. To put this in a policy context, this PM10 from wood burning is considerably greater than the city-wide mean PM10 reduction of 0.17 μg m−3 predicted from the first two phases of the London Low Emission Zone which was introduced to reduce PM from tr

Journal article

Larsen RS, Bell JNB, James PW, Chimonides PJ, Rumsey FJ, Tremper A, Purvis OWet al., 2007, Lichen and bryophyte distribution on oak in London in relation to air pollution and bark acidity, ENVIRONMENTAL POLLUTION, Vol: 146, Pages: 332-340, ISSN: 0269-7491

Journal article

Tremper AH, Agneta M, Burton S, Higgs DEBet al., 2004, Field and laboratory exposures of two moss species to low level metal pollution, Journal of Atmospheric Chemistry, Vol: 49, Pages: 111-120, ISSN: 0167-7764

Moss transplants of the species Rhytidiadelphus squarrosus and Pleurozium schreberi were used as active biomonitoring organisms as a part of a monitoring study to assess the impact of metals associated with ambient particles on mosses at roadsides. The moss samples were exposed at a semi-urban and roadside site for 3 months for subsequent analysis of metal concentration (Cu, Pb and Zn). This field experiment was carried out to investigate the accumulation of the metals over a period of 0, 4, 8 and 12 weeks at the two sites. The metal concentration in the moss samples generally increased with the length of exposure and was higher at the roadside site. The two species, however, showed slightly different accumulation patterns. In addition to the metal analysis chlorophyll concentrations were analysed as a measure of stress response in the moss samples of the above mentioned field exposures. The chlorophyll concentrations of exposed mosses showed no or only weak correlations to the concentration of the three metals measured in the moss, which suggests that other conditions have a greater influence on the chlorophyll concentration. The effect of a single metal on the moss was studied in laboratory experiments exposing R. squarrosus to the metals copper, lead and zinc at concentrations based on the above field data. At the concentrations used there was a significant reduction in the chlorophyll a concentration after exposure to copper. © 2004 Kluwer Academic Publishers.

Journal article

Sokhi RS, Bualert S, Luhana L, Tremper A, Burton MAet al., 2000, Monitoring and modelling of NO<inf>2</inf> and fine particles for urban air quality management, Systems Analysis Modelling Simulation, Vol: 37, Pages: 329-343, ISSN: 0232-9298

Atmospheric nitrogen dioxide and fine particles in urban areas are a major cause for concern especially with regard to health effects. This paper employs measured data for NO2, PM2.5 and PM10 to investigate temporal trends and correlations between various sites particularly for episodic conditions. Comparisons of the data with the UK air quality standards indicate numerous exceedances for NO2 and particularly for PM10. Good correlation is observed between PM2.5 and PM10 at two sites within London where PM2.5 contributes around 70% to the total PM10 mass. Strong correlation is also observed for PM2.5 and PM10 between the two sites at London Bloomsbury (urban centre) and the Marylebone Road indicating consistent concentrations for fine particles in urban areas. The use of an urban scale Box model. PEARL, and a roadside model, CALINE4, for predicting concentrations of NO2 and PM10 in and around urban sites is discussed and comparisons made with the air quality standards.

Journal article

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