Fractal-like Tar Ball Aggregates from Wildfire Smoke

Journal Article · Tue May 08 04:00:00 EDT 2018 · Environmental Science & Technology Letters (Online)

DOI:https://doi.org/10.1021/acs.estlett.8b00229· OSTI ID:1455269

Girotto, Giulia ^[1]; China, Swarup ^[2]; Bhandari, Janarjan ^[3]; Gorkowski, Kyle ^[4]; Scarnato, Barbara V. ^[5]; Capek, Tyler ^[3]; Marinoni, Angela ^[6]; Veghte, Daniel P. ^[7]; Kulkarni, Gourihar ^[8]; Aiken, Allison C. ^[9]; Dubey, Manvendra ^[9]; Mazzoleni, Claudio ^[3]

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1. Physics Department and Atmospheric Sciences Program, Michigan Technological University, Houghton, Michigan 49931, United States; Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento 38122, Italy
2. Physics Department and Atmospheric Sciences Program, Michigan Technological University, Houghton, Michigan 49931, United States; Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
3. Physics Department and Atmospheric Sciences Program, Michigan Technological University, Houghton, Michigan 49931, United States
4. Physics Department and Atmospheric Sciences Program, Michigan Technological University, Houghton, Michigan 49931, United States; Earth Systems Observations, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
5. Physics Department and Atmospheric Sciences Program, Michigan Technological University, Houghton, Michigan 49931, United States; Det Norske Veritas and Germanischer Lloyd (DNV GL), 1363 Høvik, Norway
6. Institute of atmospheric sciences and climate (ISAC)-National Research Council of Italy, Bologna 40129, Italy
7. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
8. Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
9. Earth Systems Observations, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States

Tar balls are atmospheric particles abundant in slightly aged biomass burning smoke and have a significant, but highly uncertain, role on Earth's radiative balance. Tar balls are typically detected using electron microscopy; they are resistant to the electron beam, and generally, they are observed as individual spheres. Here, we report new observations of a significant fraction of tar ball aggregates (~27% by number) from samples collected in a plume of the Whitewater-Baldy Complex fire in New Mexico. The structure of these aggregates is fractal-like and follows a scale invariant power law similar to that of soot particles, despite the considerably larger size and smaller number of monomers. We also present observations of tar ball aggregates from four other geographical locations, including from a remote high elevation site in the North Atlantic Ocean. Aggregation affects the particle optical properties and therefore, their climatic impact. We performed numerical simulations based on the observed morphology and estimated the effects of aggregation on the tar balls optical properties. We find that aggregation can enhance single scattering albedo by up to 41%.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1455269
• Report Number(s): PNNL-SA-132120; 48856; KP1704020
• Journal Information: Environmental Science & Technology Letters (Online), Journal Name: Environmental Science & Technology Letters (Online) Journal Issue: 6 Vol. 5; ISSN 2328-8930
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory