Experimental Investigation of the Particle-Phase Products and Reaction Mechanism of Δ-3-Carene with NO₃ Radicals

Marla DeVault,
ANYL 3rd year, Ziemann Group

"Oxidation products of monoterpenes have been shown to contribute to secondary organic aerosol (SOA) formation in the atmosphere. However, the nighttime oxidative processes, which are dominated by nitrate radical (NO₃) addition to alkenes, are not well understood. In order to fill this gap, I am working to quantify the yields of particle-phase products of the nitrate radical-initiated oxidation of Δ-3-carene, a monoterpene that is primarily emitted by coniferous plants. Using functional groups analysis methods, liquid chromatography with UV-Vis detection, and electrospray and electron ionization mass spectrometry to characterize SOA formed in environmental chamber reactions, I have identified a series of acetal dimers. The mechanism derived from these measured particle-phase products will help to inform chemical transport models on the contribution of nighttime oxidation of monoterpenes to SOA. In addition, these acetal dimers are analogous to those that have been identified and quantified in the β-pinene + NO₃ radical system, and appear to form from reactions of a variety of monoterpenes."

Bering Strait Oceanic Volume and Heat Transports and Links to Atmospheric Circulation, Ocean Temperature and Sea Ice Conditions by Dr. Mark Serreze

The Arctic’s Chukchi Sea is a focus of resource exploration, and all vessels transiting the Arctic Ocean must pass through it.   However, operations in this area are strongly influenced by variability in sea ice conditions.  Our recent work shows that the Bering Strait oceanic heat inflow is a key predictor of seasonal sea ice retreat and advance dates in the Chukchi Sea.  But what are the divers of this variability?  This inflow represents an interplay between water temperature in the strait and factors controlling the volume transport, namely, local winds in the strait and a pressure head difference between the Pacific and Arctic.  Variability in the pressure head difference, especially during summer, relates to the strength of the zonal (west to east) wind in the East Siberian Sea that raises or drops sea surface height in this area.  Variability in the zonal wind in the East Siberian Sea during summer relates to a tendency for winds over the Arctic Ocean to vary between clockwise and anticlockwise, linking the Bering Strait transports to processes influencing September sea ice extent for the Arctic Ocean as a whole.  Some of the most recent large heat transports are associated with high water temperatures, consistent with recent persistence of open water in the Chukchi Sea into winter and early ice retreat in spring.  The highest inflow recorded, for October 2016, resulted from high water temperatures in the strait and ideal wind conditions yielding a record-high volume transport.

Mark Serreze, Director of the National Snow and Ice Data Center and Professor of Geography at the University of Colorado Boulder, has published widely on issues of Arctic environmental change and has played a prominent role in science communication. His widely acclaimed popular science book, “Brave New Arctic”, was published in April 2018.  https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JC015422

Revisiting dry deposition of trace gases and particles in the atmosphere

Delphine K. Farmer
Associate Professor, Department of Chemistry, Colorado State University

"Dry deposition is a key process that removes trace gases and particles from the atmosphere, and thus one factor that controls the atmospheric lifetime of pollutants and short-lived climate forcers. In fact, dry deposition is the single largest component of uncertainty in our understanding of aerosol effects on climate. Despite its importance, dry deposition of trace gases and particles is poorly constrained by observations due to the instrumental challenge in measuring surface-atmosphere exchange. Instruments must be adequately fast, sensitive and selective to measure low concentrations on the rapid (<1 s) timescale of turbulence. We have developed several measurement techniques that use the eddy covariance approach to flux measurements over terrestrial surfaces incorporating both spectroscopy and mass spectrometry. This talk will be divided into two parts – the first considering the mechanisms that control forest-atmosphere exchange of acidic organic molecules, and the second revisiting our understanding of size-resolved particle deposition in the atmosphere. We contrast these observations with previous measurements in the literature, and with commonly used resistance models, highlighting several model-measurement discrepancies. To further investigate the mechanisms of particle deposition, we use black carbon deposition as an inert tracer for particle wet and dry deposition. We show that wet deposition dominates in an agricultural environment in Oklahoma, and provide observational constraints on black carbon lifetime in this region. Our suite of observations inform a revised model parameterization, which we incorporate in a global chemical transport model to investigate how dry deposition can impact particle loading and the radiative balance of the atmosphere. Together, these new measurements highlight the importance of observational constraints in developing, validating, and revising models of fundamental chemical and physical processes in the atmosphere – and in reducing uncertainties in our understanding of climate."

CU Boulder joined The Conversation  last year, and the results have been impressive: Experts in sea ice and nanotechnology, the history of mathematics and groundwater have penned dozens of essays that have been read by tens of thousands of people on theconversation.com and reprinted in >100 other outlets.

How can you work with The Conversation, and how does it work? What are the benefits of writing short articles on timely topics related to your research?

Please join a lunchtime conversation with chief innovation officer Bruce Wilson and environment & energy editor Jenny Weeks and several CU Boulder researchers who have worked already with The Conversation—Mark Serreze (NSIDC Director), Lupita Montoya (researcher, Engineering) and Matthew Coggon and Aaron Lamplugh (CIRES researchers in NOAA).

Space is limited to 40 people so RSVP is required (eventbrite). Lunch is provided.

*On Feb 12th ESOC Coffee Hour will be held in the Aerospace building, 4th Floor Atrium. 

ESOC coffee hour occurs weekly from 9-10am in the ESOC Reading Room (Ekeley W230). ESOC researchers, post-docs and graduate students gather for conversation and to discuss research. Occasional guest speakers are invited to give short presentations on topics of interest.

The Role of H₂S in Photochemical Methane Haze Experiments

Nathan Reed,
ANYL 3rd year student, Browne / Tolbert Groups), CU Boulder

"Although sulfur gases and organic haze from methane photochemistry are thought to be present in numerous planetary atmospheres, including the atmosphere of the Archean Earth (2.5-3.5 bya), direct interactions between their chemistries have historically been neglected. This assumption may limit the understanding of atmospheric sulfur and organic haze chemistry, and it would therefore be beneficial to examine photochemical haze production with sulfur gases present. Organic haze laboratory studies including H₂S, an atmospheric sulfur gas with both biogenic and abiogenic (e.g. volcanic) sources, have until now been non-existent. To better understand the role of H₂S in organic haze chemistry, I have conducted UV photochemistry experiments of CH4 gas mixtures in N2 with the inclusion of trace amounts of H₂S. I investigated the product aerosol composition, number, and size distribution as a function of H₂S mixing ratio. It was found that increasing the H2S mixing ratio increased the organic aerosol effective density, number, and mass loading. Further, organic sulfur compounds were found to form in the aerosol phase. I will discuss the importance of these findings in the context of organic haze and sulfur chemistry, possible mechanisms, and future steps for the project."

Biogeochemical, Ecological, and Societal Impacts of Thermokarst in Permafrost soils by Merritt R. Turetsky, Director of INSTAAR and Associate Professor of Ecology and Evolutionary Biology 

Permafrost thaw is altering northern ecosystems and the services they provide at scales ranging from local subsidence to global climate feedbacks. In organic-rich peatlands, thermokarst initiation and spread rates are increasing with rising mean annual air temperatures, changes in wildfire, and human land use. This presentation will outline empirical and modeling approaches to better understand the consequences of thermokarst in peatlands on carbon cycling, wildlife, and other aspects of ecosystem services.  We are using fine scale datasets and remote sensing to map thermoakarst coverage and expansion in both the Northwest Territories, Canada and interior Alaska. Using chronosequences and regional gradients, we are studying thermokarst impacts along gradients of time-since-thaw. Through a Permafrost Carbon Network synthesis, we developed conceptual and numerical models to understand how thermokarst development (formation, stabilization, re-accumulation of permafrost in some conditions) affects carbon storage and release. We are using a combination of empirical and modelled data to test hypotheses about climatic, ecological, and Quaternary controls on thermokarst rates and subsequent impacts on ecosystem services. We demonstrate that thermokarst in peat-rich landscapes are hotspots for permafrost carbon release primarily through methane emissions, have the potential to impact hunter movement and safety, and affect caribou habitat quality.

Dr. Urs Baltensperger,
Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland

Physics and chemistry of new particle formation in the atmosphere

"Globally, a significant source of cloud condensation nuclei for cloud formation is thought to originate from new particle formation (aerosol nucleation). Despite extensive research, many questions remain about the dominant nucleation mechanisms. Specifically, a quantitative understanding of the dependence of the nucleation rate on the concentration of the nucleating substances such as gaseous sulfuric acid, ammonia, water vapor and others has not been reached. This is of relevance for climate as the atmospheric concentrations of sulfuric acid, ammonia and other nucleating agents are strongly influenced by anthropogenic emissions. Ions, produced e.g. by galactic cosmic rays, are also known to influence nucleation rates, however their importance is still debated. By providing extremely well controlled and essentially contaminant free conditions in the CLOUD chamber, we were able to show that indeed sulfuric acid is often an important component for such new particle formation, however, for the typical temperatures encountered in the planetary boundary layer the concentrations of sulfuric acid are not high enough to explain the atmospheric observations [1]. Under these conditions, ammonia [1], amines [2] or oxidized organic molecules [3] are needed for nucleation with sulfuric acid to occur. The relevant organic molecules are highly oxygenated molecules (HOMs). HOMs produced by the oxidation of biogenic precursors are able to trigger new particle formation on their own, even in the absence of sulfuric acid [4,5]. We confirmed that this mechanism does occur in today’s lower free troposphere [6]. Moreover, the latest CLOUD results from new particle formation in urban environments, a topic of extensive current research, will be presented."

References: [1] Kirkby, J. et al., Nature, 476, 42-433, 2011 [2] Almeida, J. et al., Nature, 502, 359-363, 2013. [3] Riccobono F. et al., Science, 344, 717-721, 2014. [4] Kirkby, J. et al., Nature, 533, 521-526, 2016. [5] Tröstl, J. et al., Nature, 533, 527-531, 2016. [6] Bianchi, F. et al., Science, 352, 1109-1112, 2016.

ESOC coffee hour occurs weekly from 9-10am in the ESOC Reading Room (Ekeley W230). ESOC researchers, post-docs and graduate students gather for conversation and to discuss research. Occasional guest speakers are invited to give short presentations on topics of interest.