Vertically and Size-Resolved Chemical Speciation of Aqueously Processed Organic Aerosols
EMSL Project ID
60289
Abstract
This proposal focuses on improving process-level understanding and model representation of 1) aerosol-cloud interactions and 2) aerosol processes affecting cloud lifecycle, properties, and/or processes observed during current and future Atmospheric Radiation Measurement (ARM) deployments. Respectively, we seek to investigate the influence of aqueous processing on aerosol chemical composition and elucidate the effects of the resulting aerosol composition on growth, aging, and removal processes that may impact the ability of aerosol particles to form clouds. Specifically, we propose to address three key science questions: 1) What percentage of ground level organic aerosol (OA) is aqueously processed in the atmosphere? 2) Which specific chemical markers indicate ground level secondary OA (SOA) produced through aqueous processing? 3) To what extent do anthropogenic emissions impact SOA formation and its interactions with water?
To answer these questions, we seek to obtain and analyze representative filter samples collected using EMSL’s Size and Time-Resolved Aerosol Collector (STAC) onboard ARM’s tethered balloon system (TBS) of OA in highly convective environments with varying anthropogenic influence. We intend to characterize compounds at the molecular-level and incorporate these markers into our growing DOE Biological and Environmental Research-sponsored database of OA compounds observed in previous field and laboratory measurements to connect chemical tracers with known sources, chemistry, and atmospheric processes. To date, we have observed a very surprising result in analysis of tens of thousands of organic chemicals: laboratory oxidation datasets are far more chemically diverse than ambient atmospheric datasets. Furthermore, a broad array of chemicals we observe in ambient atmosphere are so far not produced by the laboratory experiments—with at most ~30% of ambient compounds observed in laboratory measurements. This demonstrates that previous laboratory simulations of SOA formation, despite starting from some of the known major atmospheric SOA sources, do not effectively simulate most of the underlying processes governing SOA formation.
We hypothesize that this gap exists because lab simulations are performed primarily under room temperature and dry conditions, and we are missing compounds that result from cloud processing of OA (aqueous phase chemistry, temperature cycles, photolysis, etc.) that lead to the true chemical diversity we are observing in field. Moreover, laboratory simulations to date are insufficient for deriving the mechanistic-led parameterizations required for accurate representation of SOA in models. Further research is needed to probe the spectrum of chemical and environmental spaces as observed across ARM deployments (e.g. we propose analysis of OA from SGP and TRACER) to better understand the magnitudes and sources of OA chemical diversity and thereby adequately represent OA in global models. We will elucidate important chemical families and functionalities associated with aqueous pathways that lead to aerosol growth and cloud formation across a wide range of environments. We will work with scientists at DOE/Pacific Northwest National Laboratory simulating in laboratory and implementing aerosol schemes into earth system models, to identify knowledge gaps for representation of SOA features that are missing, develop new SOA parameterizations, and test them. This will advance integration of global OA modeling with harmonized field and laboratory measurements improving predictability of Earth’s radiative balance and hydrologic cycle.
Project Details
Project type
FICUS Research
Start Date
2022-10-01
End Date
N/A
Status
Active
Released Data Link
Team
Principal Investigator
Co-Investigator(s)