283 research outputs found
Falkland School, Grades 1 - 5
No full textLeft to right, back: Carl Taylor, Wilfred Struthers, Len Swift, L. Leaf, H. Bailey, E. Clark, G. Swift. Middle: K. Miller, J. Porrier, G. Tennor, K. Furgason, A. Furgason, C. Bailey, O. Leaf, I. Kent, Miss Mossey. Front: J. Alexander, D. Taylor, O. Swift, E. Smith, G. Bailey, J. Beddows, D. Alexander, G. Furgason, G. Beddows, B. Bailey, B. Matt
Size distribution of airborne particles controls outcome of epidemiological studies
No full textEpidemiological studies typically using wide size range mass metrics (e.g. PM(10)) have demonstrated associations between airborne particulate matter and several adverse health outcomes. This approach ignores the fact that mass concentration may not correlate with regional lung dose, unlike the case of trace gases. When using measured particle size distributions as the basis for calculating regional lung dose, PM(10) mass concentration is found to be a good predictor of the mass dose in all regions of the lung, but is far less predictive of the surface area and particle number dose. On the other hand, measurements of particle number do not well predict mass dose, indicating that the chosen particle metric is likely to determine the health outcomes detectable by an epidemiological study. Consequently, epidemiological studies using mass metrics (PM(2.5) and PM(10)) may fail to recognise important health consequences of particulate matter exposure, leading to an underestimate of the public health consequences of particle exposure
Sources of sub-micrometre particles near a major international airport
No full textThe international airport of Heathrow is a major source of nitrogen oxides, but its contribution to the levels of sub-micrometre
particles is unknown and is the objective of this study. Two sampling campaigns were carried out during warm and cold seasons at
a site close to the airfield (1.2 km). Size spectra were largely dominated by ultrafine particles: nucleation particles ( < 30 nm) were found to be ∼ 10 times higher than those commonly measured in urban background environments of London. Five
clusters and six factors were identified by applying k means cluster analysis and positive matrix factorisation (PMF), respectively, to
particle number size distributions; their interpretation was based on their modal structures, wind directionality, diurnal patterns,
road and airport traffic volumes, and on the relationship with weather and other air pollutants. Airport emissions, fresh and aged
road traffic, urban accumulation mode, and two secondary sources were then identified and apportioned. The fingerprint of Heathrow has
a characteristic modal structure peaking at < 20 nm and accounts for 30–35 % of total particles in both the
seasons. Other main contributors are fresh (24–36 %) and aged (16–21 %) road traffic emissions and urban accumulation from
London (around 10 %). Secondary sources accounted for less than 6 % in number concentrations but for more than 50 % in
volume concentration. The analysis of a strong regional nucleation event showed that both the cluster categorisation and PMF
contributions were affected during the first 6 h of the event. In 2016, the UK government provisionally approved the construction of
a third runway; therefore the direct and indirect impact of Heathrow on local air quality is expected to increase unless mitigation
strategies are applied successfully
Receptor modelling of both particle composition and size distribution from a background site in London, UK – a two-step approach
No full textSome air pollution datasets contain multiple variables with a
range of measurement units, and combined analysis using positive matrix
factorization (PMF) can be problematic but can offer benefits through the
greater information content. In this work, a novel method is devised and the
source apportionment of a mixed unit dataset (PM10 mass and number size
distribution, NSD) is achieved using a novel two-step approach to PMF. In the
first step the PM10 data are PMF-analysed using a source apportionment
approach in order to provide a solution which best describes the environment
and conditions considered. The time series G values (and errors) of the
PM10 solution are then taken forward into the second step, where they are
combined with the NSD data and analysed in a second PMF analysis. This
results in NSD data associated with the apportioned PM10 factors. We
exemplify this approach using data reported in the study of Beddows et
al. (2015), producing one solution which unifies the two separate solutions
for PM10 and NSD data datasets together. We also show how regression of
the NSD size bins and the G time series can be used to elaborate the solution
by identifying NSD factors (such as nucleation) not influencing the
PM10 mass.</p
Pinpointing sources of pollution using citizen science and hyperlocal low-cost mobile source apportionment
No full textCurrently, methodologies for the identification and apportionment of air pollution sources are not widely applied due to their high cost. We present a new approach, combining mobile measurements from multiple sensors collected from the daily walks of citizen scientists, in a high population density area of Birmingham, UK. The methodology successfully pinpoints the different sources affecting the local air quality in the area using only a handful of measurements. It was found that regional sources of pollution were mostly responsible for the PM2.5 and PM1 concentrations. In contrast, PM10 was mostly associated with local sources. The total particle number and the lung deposited surface area of PM were almost solely associated with traffic, while black carbon was associated with both the sources from the urban background and local traffic. Our analysis showed that while the effect of the hyperlocal sources, such as emissions from construction works or traffic, do not exceed the distance of a couple of hundred meters, they can influence the health of thousands of people in densely populated areas. Thus, using this novel approach we illustrate the limitations of the present measurement network paradigm and offer an alternative and versatile approach to understanding the hyperlocal factors that affect urban air quality. Mobile monitoring by citizen scientists is shown to have huge potential to enhance spatiotemporal resolution of air quality data without the need of extensive and expensive campaigns
Comparative signal-to-noise analysis of fibre-optic based optical coherence tomography systems
No full textSeveral optical coherence tomography ( OCT) systems are proposed using optical.
fibre components and based around Fizeau sensing interferometers. The
theoretical signal- to- noise ratio ( SNR) is calculated for each of the
proposed configurations, using a constant set of assumed values for illumination
and detection parameters. The SNR values obtained are compared with values
calculated for typical existing configurations based around Michelson
interferometers. Fizeau- based systems incorporating a secondary processing
interferometer offer the advantage over current interferometer configurations of
down- lead insensitivity, which prevents signal fading and reduces thermal
fringe drift. The most basic form of the Fizeau system makes inefficient use of
optical power, and has a low SNR compared with the widely used Michelson
configuration. However, the results of the analysis described in this paper show
that the SNR for more sophisticated Fizeau configurations, incorporating optical
circulators and balanced detection systems, can be as high as the value for the
most sensitive existing fibre- based OCT systems. Fizeau configurations
therefore offer the combined advantages of optimized SNR and down- lead
insensitivity, indicating their suitability for use in relatively poorly
controlled environments such as in- vivo measurements
Variations in tropospheric submicron particle size distributions across the European continent 2008-2009
No full textBeddows, D. C. S. ... et. al.-- 22 pages, 11 figures, 1 table, supplementary material related to this article is available online at http://www.atmos-chem-phys.net/14/4327/2014/acp-14-4327-2014-supplement.pdfClusteranalysis of particle number size distributions frombackground sites across Europeis presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was identified as most frequently being detected inside and around northern Germany and neighbouring countries, showing clear evidence of local afternoon nucleation and growth events that could be linked to movement of air masses from south to north arriving ultimately at the Arctic contributing to Arctic haze.The second group of particle size spectra proved to have narrower size distributions and collectively showed a dependence of modal diameter upon the longitude of the site (west to east) at which they were most frequently detected.These clusters indicated regional nucleation (at the coastal sites) growing to larger modes further inland. The apparent growth rate of the modal diameter was around 0.6-0.9 nm h-1. Four specific air mass back-trajectories were successively taken as case studies to examine in real time the evolution of aerosol size distributions across Europe. While aerosol growth processes can be observed as aerosol traverses Europe, the processes are often obscured by the addition of aerosol by emissions en route. This study revealed that some of the 24 stations exhibit more complex behaviour than others, especially when impacted by local sources or a variety of different air masses. Overall, the aerosol size distribution clustering analysis greatly simplifies the complex data set and allows a description of aerosol aging processes, which reflects the longer-term average development of particle number size distributions as air masses advect across Europe. © 2014 Author(s)The National Centre for Atmospheric Science is funded by the UK Natural Environment Research Council. This work was also supported by the European Union EUCAARI (Contract Ref. 036833) and EUSAAR (Contract Ref. 026140) research projectsPeer Reviewe
Vitamin D supplementation and breast cancer prevention : a systematic review and meta-analysis of randomized clinical trials
No full textIn recent years, the scientific evidence linking vitamin D status or supplementation to breast cancer has grown notably. To investigate the role of vitamin D supplementation on breast cancer incidence, we conducted a systematic review and meta-analysis of randomized controlled trials comparing vitamin D with placebo or no treatment. We used OVID to search MEDLINE (R), EMBASE and CENTRAL until April 2012. We screened the reference lists of included studies and used the “Related Article” feature in PubMed to identify additional articles. No language restrictions were applied. Two reviewers independently extracted data on methodological quality, participants, intervention, comparison and outcomes. Risk Ratios and 95% Confident Intervals for breast cancer were pooled using a random-effects model. Heterogeneity was assessed using the I2 test. In sensitivity analysis, we assessed the impact of vitamin D dosage and mode of administration on treatment effects. Only two randomized controlled trials fulfilled the pre-set inclusion criteria. The pooled analysis included 5372 postmenopausal women. Overall, Risk Ratios and 95% Confident Intervals were 1.11 and 0.74–1.68. We found no evidence of heterogeneity. Neither vitamin D dosage nor mode of administration significantly affected breast cancer risk. However, treatment efficacy was somewhat greater when vitamin D was administered at the highest dosage and in combination with calcium (Risk Ratio 0.58, 95% Confident Interval 0.23–1.47 and Risk Ratio 0.93, 95% Confident Interval 0.54–1.60, respectively). In conclusions, vitamin D use seems not to be associated with a reduced risk of breast cancer development in postmenopausal women. However, the available evidence is still limited and inadequate to draw firm conclusions. Study protocol code: FARM8L2B5L
Low cost source apportionment of urban air pollution
No full textOver the last 10 years, there has been a revolution in the use of low cost sensors to measure air pollution concentrations. These sensors are not without problems, but it is now possible to get high quality measurements of air pollutants. In particular, the use of low cost optical particle counters (OPCs) for the measurement of particulate matter (PM) in regulatory size ranges has been successfully achieved in many urban areas worldwide, with an associated cost that is far less than regulatory instruments.Successful air quality management and control not only requires measurement of air pollution levels, but it also requires information on the sources and their relative importance. Without this critical, targeted information on pollution sources, it is difficult to plan and enact control measures with which to reduce air pollution.This talk will present new work on using low cost PM sensors to achieve low cost source identification and apportionment. The measured PM size distribution obtained from OPCs is used to identify sources. Typically, source apportionment that uses particle size distributions as input relies on particle size information in the sub 300 nm size range to obtain information about sources. However, OPCs typically only provide size information above approximately 300 nm. Initial work used k-means clustering to obtain source information (Bousiotis et al. 2021). Subsequent work has used other algorithms including positive matrix factorization (PMF). Comparison between source information obtained between low cost and regulatory grade instruments is remarkably promising.This presentation will highlight the methodological approaches undertaken. It will then use a series of urban case studies showing how low cost source apportionment can be used to identify different sources of PM pollution in urban areas, both in the ambient air and indoor air. Finally, the presentation will discuss the prospects for low cost urban source apportionment and hyperlocal air pollution management.Bousiotis, D., Singh, A., Haugen, M., Beddows, D., Diez, S., Murphy, K.L., Edwards, P.M., Boies, A., Harrison, R.M. and Pope, F.D., 2021. Assessing the sources of particles at an urban background site using both regulatory instruments and low-cost sensors–a comparative study. Atmospheric Measurement Techniques, 14(6), pp.4139-4155. https://doi.org/10.5194/amt-14-4139-202
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