Infrared-absorbing carbonaceous tar can dominate light absorption by marine-engine exhaust ...

• Main Authors: Corbin, Joel C., Czech, H., Massabò, Dario, Buatier de Mongeot, Francesco, Jakobi, Gert, Liu, Fengshan, Lobo, Prem, Mennucci, Carlo, Mensah, Amewu Antoinette, Orasche, Jürgen, Pieber, Simone M., Prévôt, André S.H., Stengel, Benjamin, Tay, Li-Lin, Zanatta, Marco, Zimmermann, Ralf, El Haddad, Imad, Gysel, Martin
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2019
• Subjects: Arctic; black carbon
• Online Access: https://dx.doi.org/10.3929/ethz-b-000390543; http://hdl.handle.net/20.500.11850/390543

Ship engines in the open ocean and Arctic typically combust heavy fuel oil (HFO), resulting in light-absorbing particulate matter (PM) emissions that have been attributed to black carbon (BC) and conventional, soluble brown carbon (brC). We show here that neither BC nor soluble brC is the major light-absorbing carbon (LAC) species in HFO-combustion PM. Instead, “tar brC” dominates. This tar brC, previously identified only in open-biomass-burning emissions, shares key defining properties with BC: it is insoluble, refractory, and substantially absorbs visible and near-infrared light. Relative to BC, tar brC has a higher Angstrom absorption exponent (AAE) (2.5–6, depending on the considered wavelengths), a moderately-high mass absorption efficiency (up to 50% of that of BC), and a lower ratio of sp2- to sp3-bonded carbon. Based on our results, we present a refined classification of atmospheric LAC into two sub-types of BC and two sub-types of brC. We apply this refined classification to demonstrate that common ... : npj Climate and Atmospheric Science, 2 ...