NSF-BSF: Understanding Evolution of Atmospheric Brown Carbon

Brown carbon (BrC) particles are emitted from the incomplete combustion of fuels affecting global climate and human health, yet their optical properties and chemical composition remain ill-defined. The laboratory-based project seeks to investigate key properties of BrC aerosols produced specifically from biomass burning (BB). Access to a unique array of advanced instruments and complementary expertise is secured through the international collaboration between U.S. and Israeli institutions of higher education.

Funding is provided via the NSF-BSF Lead Agency Agreement in which the U.S. component is funded by NSF and the Israeli component by the U.S.-Israel Binational Science Foundation (BSF). Novel results will be used in climate models and help better understand reactivity of BrC particles toward ecological and human health. Students and an early career scientist are slated to play essential roles in every aspect of the work thus contributing to the development of a well-prepared globally aware workforce.

Specific emphasis is on the least-studied subgroup of moderately (M) and strongly (S) absorbing BrC (M/S-BrC). The laboratory component to be carried out at the Israeli institution Weizmann Institute of Science (WIS) consists of (i) generation of M-BrC and S-BrC proxies in laboratory-controlled biomass/pyrolysis burning tests, (ii) particle ageing while mimicking day- and night-time processes, and (iii) real-time analysis of wavelength-dependent optical measurements of airborne size-fractionated ensembles of particles.

Generated particles are collected and sent to the U.S. counterpart, Purdue University (PU), for off-line analyses of molecular characterization and light-absorbing properties of individual BrC chromophores from extracts of filter samples. In addition, chemical imaging is carried out to characterize particle composition, size, mixing state and morphology (PU).

Tasks between the two institutions are intended to complement each other and provide fundamental information on the composition, aging chemistry and light-absorption properties of M/S-BrC with the ultimate goal of improving predictive understanding of BrC impacts on atmospheric environment and climate.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.