skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWAR
Title: High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWAR
Abstract. Observations of the organic components of the natural aerosol are scarce in Antarctica, which limits our understanding of natural aerosols and their connection to seasonal and spatial patterns of cloud albedo in the region. From November 2015 to December 2016, the ARM West Antarctic Radiation Experiment (AWARE) measured submicron aerosol properties near McMurdo Station at the southern tip of Ross Island. Submicron organic mass (OM), particle number, and cloud condensation nuclei concentrations were higher in summer than other seasons. The measurements included a range of compositions and concentrations that likely reflected both local anthropogenic emissions and natural background sources. We isolated the natural organic components by separating a natural factor and a local combustion factor. The natural OM was 150 times higher in summer than in winter. The local anthropogenic emissions were not hygroscopic and had little contribution to the CCN concentrations. Natural sources that included marine sea spray and seabird emissions contributed 56% OM in summer but only 3% in winter. The natural OM had high hydroxyl group fraction (55%), 6% alkane, and 6% amine group mass, consistent with marine organic composition. In addition, the Fourier transform infrared (FTIR) spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions were high in summer and associated with natural sources, likely forming by secondary reactions.  more » « less
Award ID(s):
1659793
PAR ID:
10066418
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Atmospheric chemistry and physics
Volume:
18
Issue:
12
ISSN:
1680-7324
Page Range / eLocation ID:
8571-8587
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Atmospheric Chemistry and Physics)
    Anthropogenic and natural emissions contribute to enhanced concentrations of aerosols in the Arctic winter and early spring, with most attention being paid to anthropogenic aerosols that contribute to so-called Arctic haze. Less-well-studied wintertime sea-spray aerosols (SSAs) under Arctic haze conditions are the focus of this study, since they can make an important contribution to wintertime Arctic aerosol abundances. Analysis of field campaign data shows evidence for enhanced local sources of SSAs, including marine organics at Utqiaġvik (formerly known as Barrow) in northern Alaska, United States, during winter 2014. Models tend to underestimate sub-micron SSAs and overestimate super-micron SSAs in the Arctic during winter, including the base version of the Weather Research Forecast coupled with Chemistry (WRF-Chem) model used here, which includes a widely used SSA source function based on Gong et al. (1997). Quasi-hemispheric simulations for winter 2014 including updated wind speed and sea-surface temperature (SST) SSA emission dependencies and sources of marine sea-salt organics and sea-salt sulfate lead to significantly improved model performance compared to observations at remote Arctic sites, notably for coarse-mode sodium and chloride, which are reduced. The improved model also simulates more realistic contributions of SSAs to inorganic aerosols at different sites, ranging from 20 %–93 % in the observations. Two-thirds of the improved model performance is from the inclusion of the dependence on SSTs. The simulation of nitrate aerosols is also improved due to less heterogeneous uptake of nitric acid on SSAs in the coarse mode and related increases in fine-mode nitrate. This highlights the importance of interactions between natural SSAs and inorganic anthropogenic aerosols that contribute to Arctic haze. Simulation of organic aerosols and the fraction of sea-salt sulfate are also improved compared to observations. However, the model underestimates episodes with elevated observed concentrations of SSA components and sub-micron non-sea-salt sulfate at some Arctic sites, notably at Utqiaġvik. Possible reasons are explored in higher-resolution runs over northern Alaska for periods corresponding to the Utqiaġvik field campaign in January and February 2014. The addition of a local source of sea-salt marine organics, based on the campaign data, increases modelled organic aerosols over northern Alaska. However, comparison with previous available data suggests that local natural sources from open leads, as well as local anthropogenic sources, are underestimated in the model. Missing local anthropogenic sources may also explain the low modelled (sub-micron) non-sea-salt sulfate at Utqiaġvik. The introduction of a higher wind speed dependence for sub-micron SSA emissions, also based on Arctic data, reduces biases in modelled sub-micron SSAs, while sea-ice fractions, including open leads, are shown to be an important factor controlling modelled super-micron, rather than sub-micron, SSAs over the north coast of Alaska. The regional results presented here show that modelled SSAs are more sensitive to wind speed dependence but that realistic modelling of sea-ice distributions is needed for the simulation of local SSAs, including marine organics. This study supports findings from the Utqiaġvik field campaign that open leads are the primary source of fresh and aged SSAs, including marine organic aerosols, during wintertime at Utqiaġvik; these findings do not suggest an influence from blowing snow and frost flowers. To improve model simulations of Arctic wintertime aerosols, new field data on processes that influence wintertime SSA production, in particular for fine-mode aerosols, are needed as is improved understanding about possible local anthropogenic sources. 
    more » « less
  2. (, UC San Diego Electronic Theses and Dissertations)
    Marine boundary layer (MBL) clouds are an important, though uncertain, part of Earth’s radiative budget. Previous studies have shown sources of aerosol particles in the remote MBL consist of primary sea spray, the oxidation of organic and inorganic vapors derived from the ocean, entrainment from the free troposphere, and anthropogenic pollution. The potential for these particles to become cloud condensation nuclei (CCN) varies largely dependent on their hygroscopic properties. Furthermore, when clouds form, physical processes can alter the optical properties of the cloud. This dissertation aims to identify variations in aerosol sources that affect MBL CCN concentrations and physical processes throughout the cloud lifetime that influence cloud optical properties. Ambient measurements of marine particles and clouds were made throughout two campaigns in the north Pacific and four campaigns in the north Atlantic. Both clean marine and polluted clouds were sampled. In addition, dry MBL particles were measured to identify their chemical composition and size distribution, which is necessary to identify their potential to be CCN active. The organic hygroscopicity influenced CCN concentrations and cloud optical properties significantly for particles that were mostly organic, such as ship stack and generated smoke particles. For a typical range of organic hygroscopicity the amount of reflected solar radiation varied by 2-7% for polluted conditions and less than 1% for clean conditions. Simulated droplet spectral width was shown to be more representative of observations when using a weighted distribution of cloud base heights and updraft velocities, and increased the cloud reflectivity up to 2%. Cloud top entrainment and decoupling of the MBL were found to account for a decrease in cloud radiative forcing. Cloud top entrainment was corrected for homogeneous entrainment and accounted for a decrease in radiative forcing of up to 50 Wm-2. Clustering of individual marine aerosol particles resulted in the identification of particle types derived from dimethyl-sulfide (DMS) oxidation. Two particle types were identified to come from DMS oxidation products and accounted for approximately 25% and 65% of CCN at 0.1% supersaturation during the winter and summer, respectively. One of the particle types was found to be entrained from the free troposphere. 
    more » « less
  3. ; (, Journal of Geophysical Research: Atmospheres)
    Abstract Long‐term declines in concentrations of fine particulate matter (PM2.5) in the United States (U.S.) have been disrupted in recent years, with recent trends stagnating or reversing. In this study, we analyze surface observations of PM2.5composition from 2002 to 2022 to identify the chemical components driving this shift. We find that PM2.5concentrations plateau across seasons and regions in the contiguous U.S. since 2016, even after excluding estimated wildfire impacts, suggesting that the rise in wildfire activity alone does not account for these trends. The stagnation is primarily driven by a slowdown in the reduction of sulfate and a non‐significant increase in organic aerosols. In the Eastern and Central U.S., sulfate concentrations generally mirror decreasing anthropogenic SO2emissions, except in winter, where chemical feedbacks related to oxidant limitations weaken the response of sulfate. We find that nitrate and NO2concentrations decrease slower than anthropogenic nitrogen oxides (NOx) emissions, particularly in fall and winter, suggesting a potential overestimate in the decrease of NOxemissions in the U.S. Environmental Protection Agency National Emission Inventory (NEI) and/or an increasing role of natural and non‐U.S. sources. In the Southeast, the decline in organic aerosol concentrations has stalled since 2015, possibly due to weaker decreases in sulfate‐induced secondary organic aerosol (SOA) formation from isoprene, combined with increases in monoterpene‐derived SOA as the climate warms. Despite continued decreases in the NEI black carbon (BC) emissions, BC concentrations have stagnated since 2015, even after removing the estimated influence of wildfire smoke, indicating a possible underestimate in emissions. 
    more » « less
  4. ; ; ; ; ; ; (, Atmospheric Environment)
    Determining the magnitude and origins of nitrogen (N) deposition in the open ocean is vital for understanding how anthropogenic activities influence oceanic biogeochemical cycles. Excess N in the North Pacific Ocean(NPO) is suggested to reflect recent anthropogenic atmospheric deposition from the Asian continent, changes in nutrient dynamics due to marine N-fixation, and/or lateral transport of nutrients. We investigate the impact of anthropogenic and marine sources on reactive N deposition in the NPO, with a focus on ammonium (NH4+), an important bioavailable nutrient, using aerosol samples (n =108) collected off the coast of China (Changdao Island). This study site is used as a proxy for continental emissions that can be exported and subsequently deposited to the ocean. The NH4+concentration of aerosol samples varied seasonally (p < 0.05), with a higher average value in winter (2.8 ±1.1 μg/m3) and spring (1.9 ±0.8 μg/m3) compared to autumn (0.7 ±0.6 μg/m3) and summer (1.4 ±0.4 μg/m3). The isotopic composition of aerosol NH4+ varied seasonally, with higher averages in spring (13.3 ±7.9‰) and summer (15.6 ±6.2‰) compared to autumn (3.2 ±2.5 ‰) and winter (3.8 ±11.4‰). These seasonal patterns in the isotopic composition of NH4+ are investigated based on correlations of aerosol chemical species, seasonal shifts in transport patterns, partitioning of ammonia/ammonium between the gas and particle phase, and continental versus marine sources of ammonia. We find that anthropogenic activities, mainly agricultural practices (e.g., volatilization, fertilizer, animal husbandry), are the primary sources of NH4+ deposited to the NPO. 
    more » « less
  5. ; ; ; ; ; (, Biogeosciences)
    Abstract. Emissions from natural sources are driven by various external stimuli such as sunlight, temperature, and soil moisture. Once biogenic volatile organic compounds (BVOCs) are emitted into the atmosphere, they rapidly react with atmospheric oxidants, which has significant impacts on ozone and aerosol budgets. However, diurnal, seasonal, and interannual variability in these species are poorly captured in emissions models due to a lack of long-term, chemically speciated measurements. Therefore, increasing the monitoring of these emissions will improve the modeling of ozone and secondary organic aerosol concentrations. Using 2 years of speciated hourly BVOC data collected at the Virginia Forest Research Lab (VFRL) in Fluvanna County, Virginia, USA, we examine how minor changes in the composition of monoterpenes between seasons are found to have profound impacts on ozone and OH reactivity. The concentrations of a range of BVOCs in the summer were found to have two different diurnal profiles, which, we demonstrate, appear to be driven by light-dependent versus light-independent emissions. Factor analysis was used to separate the two observed diurnal profiles and determine the contribution from each emission type. Highly reactive BVOCs were found to have a large influence on atmospheric reactivity in the summer, particularly during the daytime. These findings reveal the need to monitor species with high atmospheric reactivity, even though they have low concentrations, to more accurately capture their emission trends in models. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email