Abstract
AbstractBlack carbon (BC) aerosols affect climate, especially in high aerosol loading regions such as South Asia. A key uncertainty for the climate effects of BC is the evolution of light‐absorbing properties in the atmosphere. Here, we present a year‐round comparison of the mass absorption cross section (MAC; 678 nm) of BC in air (PM10) and rain, for samples collected at the Maldives Climate Observatory at Hanimaadhoo. We develop a filter‐loading correction scheme for estimating BC absorption on filters used in high‐volume samplers. The year‐round average MAC678 of BC in the rain is almost twice (13.3 ± 4.2 m2/g) compared to the PM10 aerosol (7.2 ± 2.6 m2/g). A possible explanation is the elevated ratio of organic carbon (OC) to BC observed in rain particulate matter (9.4 ± 6.3) compared to in the aerosols (OC/BC 2.6 ± 1.4 and water‐insoluble organic carbon/BC 1.2 ± 0.8), indicating a coating‐enhancement effect. In addition to BC, we also investigated the MAC365 of water‐soluble brown carbon in PM10 (0.4 ± 0.4 m2/g, at 365 nm). In contrast to BC, MAC365brown carbon relates to air mass history, showing higher values for samples from air originating over the South Asian landmass. Furthermore, calculated washout ratios are much lower for BC compared to OC and inorganic ions such as sulfate, implying a longer atmospheric lifetime for BC. The wet deposition flux for BC during the high loading winter was 3 times higher than during the wet summer, despite much less precipitation in the winter.
Highlights
Sunlight‐absorbing black carbon (BC) and brown carbon (BrC) aerosols may significantly contribute to the warming of the atmosphere
Carbon isotope characterization (δ13C and Δ14C) suggests that water‐insoluble organic carbon (WIOC) at Maldives Climate Observatory at Hanimaadhoo (MCOH) is less affected by atmospheric oxidation, with source signatures that are more similar to Black carbon (BC) than water‐soluble OC (WSOC) (Bosch et al, 2014; Budhavant et al, 2015; Sheesley et al, 2012)
The year‐round average MAC678 of BC in rainwater was almost twice that simultaneously measured for aerosols
Summary
Sunlight‐absorbing black carbon (BC) and brown carbon (BrC) aerosols may significantly contribute to the warming of the atmosphere. Besides contributing to a positive radiative forcing (global average estimates ~ 0.2 to 1.2 W/m2, with higher values over regions such as South Asia), these aerosols have other environmental effects, for example, surface dimming (affecting agriculture fields), glacier melt (affecting fresh water supply), and shifts of the storm frequency and monsoon system (Menon et al, 2010; Ramanathan et al, 2008; Xu et al, 2018). BC is one of the more health‐detrimental components of aerosol pollution that kills more than 1 million people in South Asia per year (World Health Organization, 2016). BC aerosols cause severe perturbations of the regional environmental system
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
