{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/374931"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/374931","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"The application of low-cost sensors to monitor and characterise particulate matter air pollution","abstract":"Particulate matter air pollution is a major threat to health and the environment. Accordingly, monitoring networks have been established to record particle mass concentrations under fixed conditions. However, monitoring sites are sparsely distributed due to the expense, size and calibration requirements of regulatory-grade instruments. Very limited information is available on the particle number, sizes and composition, and how these may vary under typical ambient conditions. Low-cost sensors can improve the spatial resolution and range of deployment sites of particle measurements as they are cheaper to buy and run, and require less space, energy and specialist skills to operate. However, their scope has been mainly limited to measurement of particle mass and number concentrations, the accuracy of which can be variable. The three-channel optical particle counter (3COPC) is a new instrument that uses low-cost sensors to measure the particle number size distribution at different temperatures. This work describes the instrument and demonstrates its use, with the aim of showing how low-cost sensors can provide accurate information including but also beyond the particle mass concentration. It is hoped this will guide and inspire further developments in low-cost particle characterisation. In heated mode, the 3COPC measures particle number size distributions which, after calibration, are equivalent to regulatory-grade instruments in the fine particle size range. These data reveal information about the sources and processes affecting ambient aerosol. For instance, sub-micron particles were associated with aged vehicle and cooking emissions, and secondary inorganic aerosol. At larger diameters, the instrument was sensitive to fog droplets which were not removed by heating. This work describes the first use of low-cost sensors to measure and compare the particle number size distribution at variable temperatures, in order to quantify particle size changes due to both hygroscopic growth and evaporation of semi-volatile components. The 3COPC growth factor provides a marker for higher proportions of hygroscopic and/or volatile components, especially NH<sub>4</sub>NO<sub>3</sub>. The findings from applying a similar measurement technique to a regulatory-grade OPC are also explored. In laboratory experiments, the 3COPC was used to measure the hygroscopicity (via the κ parameter) of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>, NaCl and a 1:1 mixture of the two compounds. The derived values mostly overlapped with the literature range, although with some uncertainty. The instrument also measured the saturation vapour pressure of three dicarboxylic acids (succinic, adipic and pimelic acids) to within an order of magnitude accuracy. In both cases, a kinetic model was developed to simulate the air temperature and gas/particle concentrations inside the 3COPC conditioning system. This is the first such kinetic model to directly use the κ parameter to simulate hygroscopic growth. The 3COPC is a novel prototype instrument. As such, its modes of operation and capabilities are evaluated throughout. Clear recommendations are made for future deployments of the instrument. Learnings to inform the next-phase prototype are also set out. Overall, this work aims to promote more innovative applications of low-cost sensors and to take the first steps towards this.","abstract_html":"Particulate matter air pollution is a major threat to health and the environment. Accordingly, monitoring networks have been established to record particle mass concentrations under fixed conditions. However, monitoring sites are sparsely distributed due to the expense, size and calibration requirements of regulatory-grade instruments. Very limited information is available on the particle number, sizes and composition, and how these may vary under typical ambient conditions. Low-cost sensors can improve the spatial resolution and range of deployment sites of particle measurements as they are cheaper to buy and run, and require less space, energy and specialist skills to operate. However, their scope has been mainly limited to measurement of particle mass and number concentrations, the accuracy of which can be variable. The three-channel optical particle counter (3COPC) is a new instrument that uses low-cost sensors to measure the particle number size distribution at different temperatures. This work describes the instrument and demonstrates its use, with the aim of showing how low-cost sensors can provide accurate information including but also beyond the particle mass concentration. It is hoped this will guide and inspire further developments in low-cost particle characterisation. In heated mode, the 3COPC measures particle number size distributions which, after calibration, are equivalent to regulatory-grade instruments in the fine particle size range. These data reveal information about the sources and processes affecting ambient aerosol. For instance, sub-micron particles were associated with aged vehicle and cooking emissions, and secondary inorganic aerosol. At larger diameters, the instrument was sensitive to fog droplets which were not removed by heating. This work describes the first use of low-cost sensors to measure and compare the particle number size distribution at variable temperatures, in order to quantify particle size changes due to both hygroscopic growth and evaporation of semi-volatile components. The 3COPC growth factor provides a marker for higher proportions of hygroscopic and/or volatile components, especially NH&lt;sub&gt;4&lt;/sub&gt;NO&lt;sub&gt;3&lt;/sub&gt;. The findings from applying a similar measurement technique to a regulatory-grade OPC are also explored. In laboratory experiments, the 3COPC was used to measure the hygroscopicity (via the κ parameter) of (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;, NaCl and a 1:1 mixture of the two compounds. The derived values mostly overlapped with the literature range, although with some uncertainty. The instrument also measured the saturation vapour pressure of three dicarboxylic acids (succinic, adipic and pimelic acids) to within an order of magnitude accuracy. In both cases, a kinetic model was developed to simulate the air temperature and gas/particle concentrations inside the 3COPC conditioning system. This is the first such kinetic model to directly use the κ parameter to simulate hygroscopic growth. The 3COPC is a novel prototype instrument. As such, its modes of operation and capabilities are evaluated throughout. Clear recommendations are made for future deployments of the instrument. Learnings to inform the next-phase prototype are also set out. Overall, this work aims to promote more innovative applications of low-cost sensors and to take the first steps towards this.","abstract_has_math":false,"creators":["Fleming, Jessica"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Jones, Roderic"],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-05-09","date_published":"2024-05-09","updated_at":"2026-07-22T22:24:20Z","subjects":["Air pollution","Air quality","Atmospheric chemistry","Chemistry","Low cost sensors","Optical particle counter","Particulate matter","PM10","PM2.5"],"languages":["eng"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/9132c797-7e2c-4270-8ae5-c85665801868/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.112804","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Jones, Roderic"]},{"key":"dc:creator","label":"Author","values":["Fleming, Jessica"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2024-05-09"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/374931"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Air pollution","Air quality","Atmospheric chemistry","Chemistry","Low cost sensors","Optical particle counter","Particulate matter","PM10","PM2.5"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/9132c797-7e2c-4270-8ae5-c85665801868/download","https://www.rioxx.net/licenses/all-rights-reserved/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.112804"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/3d243e96-9d9e-4ece-8969-4ddb0cad743e/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Particulate matter air pollution is a major threat to health and the environment. 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This work describes the instrument and demonstrates its use, with the aim of showing how low-cost sensors can provide accurate information including but also beyond the particle mass concentration. It is hoped this will guide and inspire further developments in low-cost particle characterisation. In heated mode, the 3COPC measures particle number size distributions which, after calibration, are equivalent to regulatory-grade instruments in the fine particle size range. These data reveal information about the sources and processes affecting ambient aerosol. For instance, sub-micron particles were associated with aged vehicle and cooking emissions, and secondary inorganic aerosol. At larger diameters, the instrument was sensitive to fog droplets which were not removed by heating. This work describes the first use of low-cost sensors to measure and compare the particle number size distribution at variable temperatures, in order to quantify particle size changes due to both hygroscopic growth and evaporation of semi-volatile components. The 3COPC growth factor provides a marker for higher proportions of hygroscopic and/or volatile components, especially NH<sub>4</sub>NO<sub>3</sub>. The findings from applying a similar measurement technique to a regulatory-grade OPC are also explored. In laboratory experiments, the 3COPC was used to measure the hygroscopicity (via the κ parameter) of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>, NaCl and a 1:1 mixture of the two compounds. The derived values mostly overlapped with the literature range, although with some uncertainty. The instrument also measured the saturation vapour pressure of three dicarboxylic acids (succinic, adipic and pimelic acids) to within an order of magnitude accuracy. In both cases, a kinetic model was developed to simulate the air temperature and gas/particle concentrations inside the 3COPC conditioning system. This is the first such kinetic model to directly use the κ parameter to simulate hygroscopic growth. The 3COPC is a novel prototype instrument. As such, its modes of operation and capabilities are evaluated throughout. Clear recommendations are made for future deployments of the instrument. Learnings to inform the next-phase prototype are also set out. 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In heated mode, the 3COPC measures particle number size distributions which, after calibration, are equivalent to regulatory-grade instruments in the fine particle size range. These data reveal information about the sources and processes affecting ambient aerosol. For instance, sub-micron particles were associated with aged vehicle and cooking emissions, and secondary inorganic aerosol. At larger diameters, the instrument was sensitive to fog droplets which were not removed by heating. This work describes the first use of low-cost sensors to measure and compare the particle number size distribution at variable temperatures, in order to quantify particle size changes due to both hygroscopic growth and evaporation of semi-volatile components. The 3COPC growth factor provides a marker for higher proportions of hygroscopic and/or volatile components, especially NH<sub>4</sub>NO<sub>3</sub>. The findings from applying a similar measurement technique to a regulatory-grade OPC are also explored. In laboratory experiments, the 3COPC was used to measure the hygroscopicity (via the κ parameter) of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>, NaCl and a 1:1 mixture of the two compounds. The derived values mostly overlapped with the literature range, although with some uncertainty. The instrument also measured the saturation vapour pressure of three dicarboxylic acids (succinic, adipic and pimelic acids) to within an order of magnitude accuracy. In both cases, a kinetic model was developed to simulate the air temperature and gas/particle concentrations inside the 3COPC conditioning system. This is the first such kinetic model to directly use the κ parameter to simulate hygroscopic growth. The 3COPC is a novel prototype instrument. As such, its modes of operation and capabilities are evaluated throughout. Clear recommendations are made for future deployments of the instrument. 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