Chemical characterization of organic and biogenic atmospheric aerosol particles and their potential to initiate ice crystal formation
EMSL Project ID
44618
Abstract
Atmospheric aerosol particles can affect the environment by changing the global radiative budget, increasing air pollution and impacting air quality with subsequent consequences for health related issues. One of the least understood problems in this regard, is the formation of ice crystals by pre-existing aerosol particles. In particular, the ability of condensed phase organic and biogenic material to serve as ice nuclei (IN) is not known.. Critical for this is a molecular-level understanding of heterogeneous ice nucleation which has been hampered in part by an insufficient description of the complex interfacial particle chemistry. Here we focus on organic and biogenic particles of marine origin and secondary organic aerosol (SOA) as potential IN. Very recently it has been shown that the abundant cosmopolitan marine diatom Thalassiosira pseudonana acts as efficient IN in both deposition and immersion modes under typical tropospheric conditions. However, the underlying chemical and physical processes at this biogenic interface leading to the formation of ice are not known. We also expect that many more marine organic aerosol (MOA) types including phytoplankton cells, bacteria and viruses, organic debris, and a variety of amorphous gel-like organic aggregates can induce the chemical transformation to ice. SOA consist of a large number of species which possess a variety of physical and chemical properties. Until very recently, the phase state and morphology of SOA particles was assumed liquid-like. However, now it is known that these multicomponent organic particles can be solid under ambient temperature conditions adopting an amorphous and possibly a glassy state. This novel finding not only influences the partitioning of semi-volatile compounds, and change heterogeneous chemical reactions, but will significantly influence the interaction of water with these particles. It is therefore expected to transform our understanding of how SOA initiate ice nucleation. Employing an array of ambient pressure ionization mass spectrometry probes, micro-spectroscopy, and microscopy techniques only available at EMSL and LBNL we will investigate the composition, morphology, and state of the ambient organic material and MOA to identify amorphous organic particles and to characterize on a molecular level the biogenic interface. These particle analytical data will then allow molecular interpretation of corresponding ice nucleation experiments using same particles performed at SUNY at Stony Brook, NY. In a truly multi-institutional, multi-disciplinary, and multi-capability effort we will characterize field-collected and laboratory generated organic aerosol and MOA in terms of chemical composition, physical state, and morphology to better understand the interfacial processes which govern the substrate's ability to nucleate ice from a supercooled aqueous or supersaturated gas phase environment. This research is relevant to the Science of Interfacial Phenomena and Biogeochemistry theme and the overarching mission of EMSL. The single particle and surface analytical techniques employed in this proposal will allow us for the first time to assess which (and why) biogenic interfaces allow efficient interaction with water (vapor) to initiate ice formation. In addition, the surface properties of amorphous or glassy SOA and their potential transformation by interaction with the atmospheric environment will be determined.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2011-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Knopf DA, PA Alpert, B Wang, RE O'Brien, ST Kelly, A Laskin, MK Gilles, and RC Moffet. 2014. "Micro-Spectroscopic Imaging and Characterization of Individually Identified Ice Nucleating Particles from a Case Field Study." Journal of Geophysical Research. D. (Atmospheres) 119:10,365-10,381. doi:10.1002/2014JD021866
Wang B, A Laskin, TR Roedel, MK Gilles, RC Moffet, AV Tivanski, and DA Knopf. 2012. "Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K." Journal of Geophysical Research. D. (Atmospheres) 117:Article No. D00V19. doi:10.1029/2012JD017446