Effect of aerosol composition on the performance of low-cost optical particle counter correction factors
<p>There is considerable interest in using low-cost optical particle counters (OPCs) to supplement existing routine air quality networks that monitor particle mass concentrations. In order to do this, low-cost OPC data need to be comparable with particle mass reference instrumentation; however...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2020-03-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/13/1181/2020/amt-13-1181-2020.pdf |
| _version_ | 1818034983691878400 |
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| author | L. R. Crilley L. R. Crilley A. Singh L. J. Kramer M. D. Shaw M. S. Alam J. S. Apte W. J. Bloss L. Hildebrandt Ruiz P. Fu P. Fu W. Fu S. Gani M. Gatari E. Ilyinskaya A. C. Lewis D. Ng'ang'a Y. Sun R. C. W. Whitty S. Yue S. Young F. D. Pope |
| author_facet | L. R. Crilley L. R. Crilley A. Singh L. J. Kramer M. D. Shaw M. S. Alam J. S. Apte W. J. Bloss L. Hildebrandt Ruiz P. Fu P. Fu W. Fu S. Gani M. Gatari E. Ilyinskaya A. C. Lewis D. Ng'ang'a Y. Sun R. C. W. Whitty S. Yue S. Young F. D. Pope |
| author_sort | L. R. Crilley |
| collection | DOAJ |
| description | <p>There is considerable interest in using low-cost optical
particle counters (OPCs) to supplement existing routine air quality networks
that monitor particle mass concentrations. In order to do this, low-cost OPC
data need to be comparable with particle mass reference
instrumentation; however, there is currently no widely agreed upon methodology to accomplish this. Aerosol
hygroscopicity is known to be a key parameter to consider when correcting
particle mass concentrations derived from low-cost OPCs, particularly at
high ambient relative humidity (RH). Correction factors have been developed
that apply <span class="inline-formula"><i>κ</i></span>-Köhler theory to correct for the influence of water
uptake by hygroscopic aerosols. We have used datasets of co-located
reference particle measurements and low-cost OPC (OPC-N2, Alphasense) measurements, collected in four cities on three continents, to explore the performance of
this correction factor. We provide evidence that the elevated particle mass
concentrations, reported by the low-cost OPC relative to reference
instrumentation, are due to bulk aerosol hygroscopicity under different RH
conditions, which is determined by aerosol composition and, in particular, the
levels of hygroscopic aerosols (sulfate and nitrate). We exploit
measurements made in volcanic plumes in Nicaragua, which are predominantly
composed of sulfate aerosol, as a natural experiment to demonstrate this
behaviour in the ambient atmosphere; the observed humidogram from these measurements closely
resembles the calculated pure sulfuric acid humidogram. The results
indicate that the particle mass concentrations derived from low-cost OPCs
during periods of high RH (<span class="inline-formula"><i>></i>60</span> %) need to be corrected for
aerosol hygroscopic growth. We employed a correction factor based on <span class="inline-formula"><i>κ</i></span>-Köhler theory and observed that the corrected OPC-N2 PM<span class="inline-formula"><sub>2.5</sub></span> mass
concentrations were within 33 % of reference measurements at all sites.
The results indicated that a <span class="inline-formula"><i>κ</i></span> value derived in situ (using suitable reference
instrumentation) would lead to the most accurate correction relative to
co-located reference instruments. Applying a <span class="inline-formula"><i>κ</i></span> values from the literature in the
correction factor also resulted in improved OPC-N2 performance, with the measurements being within 50 % of the reference values. Therefore, for areas where suitable reference
instrumentation for developing a local correction factor is lacking, using a
literature <span class="inline-formula"><i>κ</i></span> value can result in a reasonable correction. For
locations with low levels of hygroscopic aerosols and low RH values, a simple
calibration against gravimetric measurements (using suitable reference
instrumentation) would likely be sufficient. Whilst this study generated
correction factors specific for the<span id="page1182"/> Alphasense OPC-N2 sensor, the
calibration methodology developed is likely amenable to other low-cost PM
sensors.</p> |
| first_indexed | 2024-12-10T06:47:50Z |
| format | Article |
| id | doaj.art-7cf6aaac278a4a3dbc8f52a20bf61225 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-10T06:47:50Z |
| publishDate | 2020-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-7cf6aaac278a4a3dbc8f52a20bf612252022-12-22T01:58:37ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482020-03-01131181119310.5194/amt-13-1181-2020Effect of aerosol composition on the performance of low-cost optical particle counter correction factorsL. R. Crilley0L. R. Crilley1A. Singh2L. J. Kramer3M. D. Shaw4M. S. Alam5J. S. Apte6W. J. Bloss7L. Hildebrandt Ruiz8P. Fu9P. Fu10W. Fu11S. Gani12M. Gatari13E. Ilyinskaya14A. C. Lewis15D. Ng'ang'a16Y. Sun17R. C. W. Whitty18S. Yue19S. Young20F. D. Pope21School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UKnow at: Department of Chemistry, York University, Toronto, CanadaSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UKSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UKNational Centre for Atmospheric Science, Wolfson Atmospheric Chemistry Laboratories, University of York, York, UKSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UKDepartment of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas, USASchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UKDepartment of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas, USAInstitute of Surface-Earth System Science, Tianjin University, Tianjin, ChinaInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaDepartment of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas, USAInstitute of Nuclear Science and Technology, University of Nairobi, Nairobi, KenyaSchool of Earth and Environment, University of Leeds, Leeds, UKNational Centre for Atmospheric Science, Wolfson Atmospheric Chemistry Laboratories, University of York, York, UKInstitute of Nuclear Science and Technology, University of Nairobi, Nairobi, KenyaInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaSchool of Earth and Environment, University of Leeds, Leeds, UKInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaNational Centre for Atmospheric Science, Wolfson Atmospheric Chemistry Laboratories, University of York, York, UKSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK<p>There is considerable interest in using low-cost optical particle counters (OPCs) to supplement existing routine air quality networks that monitor particle mass concentrations. In order to do this, low-cost OPC data need to be comparable with particle mass reference instrumentation; however, there is currently no widely agreed upon methodology to accomplish this. Aerosol hygroscopicity is known to be a key parameter to consider when correcting particle mass concentrations derived from low-cost OPCs, particularly at high ambient relative humidity (RH). Correction factors have been developed that apply <span class="inline-formula"><i>κ</i></span>-Köhler theory to correct for the influence of water uptake by hygroscopic aerosols. We have used datasets of co-located reference particle measurements and low-cost OPC (OPC-N2, Alphasense) measurements, collected in four cities on three continents, to explore the performance of this correction factor. We provide evidence that the elevated particle mass concentrations, reported by the low-cost OPC relative to reference instrumentation, are due to bulk aerosol hygroscopicity under different RH conditions, which is determined by aerosol composition and, in particular, the levels of hygroscopic aerosols (sulfate and nitrate). We exploit measurements made in volcanic plumes in Nicaragua, which are predominantly composed of sulfate aerosol, as a natural experiment to demonstrate this behaviour in the ambient atmosphere; the observed humidogram from these measurements closely resembles the calculated pure sulfuric acid humidogram. The results indicate that the particle mass concentrations derived from low-cost OPCs during periods of high RH (<span class="inline-formula"><i>></i>60</span> %) need to be corrected for aerosol hygroscopic growth. We employed a correction factor based on <span class="inline-formula"><i>κ</i></span>-Köhler theory and observed that the corrected OPC-N2 PM<span class="inline-formula"><sub>2.5</sub></span> mass concentrations were within 33 % of reference measurements at all sites. The results indicated that a <span class="inline-formula"><i>κ</i></span> value derived in situ (using suitable reference instrumentation) would lead to the most accurate correction relative to co-located reference instruments. Applying a <span class="inline-formula"><i>κ</i></span> values from the literature in the correction factor also resulted in improved OPC-N2 performance, with the measurements being within 50 % of the reference values. Therefore, for areas where suitable reference instrumentation for developing a local correction factor is lacking, using a literature <span class="inline-formula"><i>κ</i></span> value can result in a reasonable correction. For locations with low levels of hygroscopic aerosols and low RH values, a simple calibration against gravimetric measurements (using suitable reference instrumentation) would likely be sufficient. Whilst this study generated correction factors specific for the<span id="page1182"/> Alphasense OPC-N2 sensor, the calibration methodology developed is likely amenable to other low-cost PM sensors.</p>https://www.atmos-meas-tech.net/13/1181/2020/amt-13-1181-2020.pdf |
| spellingShingle | L. R. Crilley L. R. Crilley A. Singh L. J. Kramer M. D. Shaw M. S. Alam J. S. Apte W. J. Bloss L. Hildebrandt Ruiz P. Fu P. Fu W. Fu S. Gani M. Gatari E. Ilyinskaya A. C. Lewis D. Ng'ang'a Y. Sun R. C. W. Whitty S. Yue S. Young F. D. Pope Effect of aerosol composition on the performance of low-cost optical particle counter correction factors Atmospheric Measurement Techniques |
| title | Effect of aerosol composition on the performance of low-cost optical particle counter correction factors |
| title_full | Effect of aerosol composition on the performance of low-cost optical particle counter correction factors |
| title_fullStr | Effect of aerosol composition on the performance of low-cost optical particle counter correction factors |
| title_full_unstemmed | Effect of aerosol composition on the performance of low-cost optical particle counter correction factors |
| title_short | Effect of aerosol composition on the performance of low-cost optical particle counter correction factors |
| title_sort | effect of aerosol composition on the performance of low cost optical particle counter correction factors |
| url | https://www.atmos-meas-tech.net/13/1181/2020/amt-13-1181-2020.pdf |
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