Preprints
https://doi.org/10.5194/egusphere-2026-3224
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2026-3224
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
22 Jun 2026
| 22 Jun 2026
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).
Gravimetrically Measured Water Content of Filter Sampled Fine Particulate Matter at Low Relative Humidity: Insight from the Surface Particulate Matter Network (SPARTAN)
Abstract. Accurate measurements of the composition of fine particulate matter (PM2.5) are important for understanding its sources and health impacts. Water, a portion of PM2.5 mass, is difficult to measure. We describe developments to the Surface PARTiculate mAtter Network (SPARTAN) to better characterize the chemical composition of PM2.5 on polytetrafluoroethylene filters. A robotic weighing facility is used to estimate water content of PM2.5 sampled at three sites (Fajardo, Puerto Rico; Bujumbura, Burundi; Abu Dhabi, United Arab Emirates), and the chemical composition is used to attribute water content to three hygroscopic categories: high growth (sodium chloride), medium growth (ammonium-nitrate-sulfate-potassium), and low growth (organics). The growth rates are tested using two additional sites (Beijing, China; Halifax, Canada). The water content at 35 % relative humidity (RH) is estimated to be 16.5 % (11.6 %–26.5 %, 95 % confidence) for the high growth category, 3.9 % (3.0 %–4.2 %, 95 % confidence) for medium growth, and 1.0 % (0.6–1.3 %, 95 % confidence) for low growth. We calculate the average water content at 35 % RH for 2442 filters from 24 globally distributed sites from December 2019 to September 2024 to be 2.06 % (0.85 %–5.47 %, range), where 58 % of the aerosol water is associated with the medium growth category (22 % low growth, 19 % high growth).
How to cite. Oxford, C. R., Zhu, H., Mehrotra, M., Liu, X., Ren, Y., Arnott, M., Adimula, I. A., Ajibolataiye, T. B., Akoshile, C., Amador-Munoz, O., Asfaw, A., Chang, R. Y.-W., Dey, S., Dillner, A. M., Diner, D. J., Flynn, C. J., Francis, D., Gahungu, P., Garland, R. M., Grutter, M., Hasheminassab, S., Imam, F., Kim, J., Langerman, K., Lee, P.-C., Lestari, P., Lin, P.-H., Loria-Salazar, S. M., Mamo, T., Mayol-Bracero, O. L., Naidoo, M., Nelli, N., Park, S. S., Salam, A., Sarangi, B., Saud, T., Schofield, R., Schechner, Y., Tripathi, S. N., West, E. K., Windwer, E., Wu, M.-T., Zhang, Q., Brauer, M., Rudich, Y., Turner, J. R., and Martin, R. V.: Gravimetrically Measured Water Content of Filter Sampled Fine Particulate Matter at Low Relative Humidity: Insight from the Surface Particulate Matter Network (SPARTAN), EGUsphere [preprint], https://doi.org/10.5194/egusphere-2026-3224, 2026.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Measurement Techniques.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.Download & links
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Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Haihui Zhu
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80521, United States
Maya Mehrotra
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Xuan Liu
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Scripps Institution of Oceanography, University of California San Diego, San Diego, California 92093, United States
Yuxuan Ren
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Maya Arnott
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Isaac Abionum Adimula
Department of Physics, University of Ilorin, Ilorin, 240003, Nigeria
Taiye Benjamin Ajibolataiye
Department of Physics, University of Ilorin, Ilorin, 240003, Nigeria
Clement Akoshile
Department of Physics, University of Ilorin, Ilorin, 240003, Nigeria
Omar Amador-Munoz
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico
Araya Asfaw
Institute of Geophysics and Space Science, Addis Ababa University, Addis Ababa,1176, Ethiopia
Rachel Ying-Wen Chang
Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
Sagnik Dey
Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India 110016
Adjunct Faculty, Department of Health, Management and Policy, Korea University, Seoul, South Korea
Ann M. Dillner
Air Quality Research Center, University of California Davis, Davis, CA, USA
David J. Diner
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, United States
Connor J. Flynn
School of Meteorology, University of Oklahoma, Norman, Oklahoma, United States
Diana Francis
Environmental and Geophysical Sciences Lab, Earth Science Department, Khalifa University, Abu Dhabi, 127788, United Arab Emirates
Paterne Gahungu
Institute of Applied Statistics, University of Burundi, Bujumbura, BP1550, Burundi
Rebecca M. Garland
Council for Scientific and Industrial Research, Pretoria, 0001, South Africa
Department of Geography, Geo-Informatics and Meteorology, University of Pretoria, Pretoria, 0002, South Africa
Michel Grutter
Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico
Sina Hasheminassab
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, United States
Fahad Imam
Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India 110016
Jhoon Kim
Department of Atmospheric Sciences, Yonsei University, Seoul, 03722, Republic of Korea
Kristy Langerman
Department of Geography, Environmental Management and Energy Studies, University of Johannesburg, Johannesburg, 2006, South Africa
Pei-Chen Lee
Department of Public Health, National Cheng Kung University, Tainan, 701, Taiwan
Puji Lestari
Faculty of Civil and Environmental Engineering, Bandung Institute of Technology, Bandung, 40132, Indonesia
Po-Hsiung Lin
Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan
S. Marcela Loria-Salazar
School of Meteorology, University of Oklahoma, Norman, Oklahoma, United States
Tesfaye Mamo
Department of Physics, Addis Ababa University, Addis Ababa, Ethiopia
Olga L. Mayol-Bracero
Department of Environmental Science, University of Puerto Rico, Puerto Rico, 00931, United States
Mogesh Naidoo
Council for Scientific and Industrial Research, Pretoria, 0001, South Africa
Narendra Nelli
Environmental and Geophysical Sciences Lab, Earth Science Department, Khalifa University, Abu Dhabi, 127788, United Arab Emirates
Sang Seo Park
Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
Abdus Salam
Department of Chemistry, University of Dhaka, Dhaka, 1000, Bangladesh
Bighnaraj Sarangi
Department of Environmental Science, University of Puerto Rico, Puerto Rico, 00931, United States
Trailokya Saud
National Aerosol Facility, Indian Institute of Technology Kanpur, Kanpur, 208016, India
Robyn Schofield
School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Melbourne, 3010, Australia
Yoav Schechner
Department of Electrical Engineering, Technion Israel Institute of Technology, Haifa, 3200003, Israel
Sachchida N. Tripathi
Kotak School of Sustainability, Indian Institute of Technology Kanpur, Kanpur, 208016, India
Emily K. West
School of Meteorology, University of Oklahoma, Norman, Oklahoma, United States
Eli Windwer
Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
Ming-Tsang Wu
Department of Family Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, 807, Taiwan
PhD Program in Environmental and Occupational Medicine, Kaohsiung Medical University, Kaohsiung, 807, Taiwan
Qiang Zhang
School of Environment, Tsinghua University, Beijing, 100084, China
Michael Brauer
School of Population and Public Health, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
Yinon Rudich
Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
Jay R. Turner
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Randall V. Martin
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
Short summary
A high-sensitivity balance, controlled temperature and relative humidity chamber, and filter samples collected around the world were used to develop a mass as a function of relative humidity relationship. We subsequently measured the chemical composition of these same samples. A relationship between the chemical composition and water mass was created and used to calculate aerosol water content showing how composition and water content varies worldwide.
A high-sensitivity balance, controlled temperature and relative humidity chamber, and filter...