New study reveals chemical transformations of ambient organic aerosols

June 17, 2013
Changes in the chemical composition of OA throughout the day indicate the potential role of ammonium-carbonyl reaction chemistry in forming the nitrogen-containing organic constituents of aerosols.

Deciphering the molecular composition of organic aerosols, or OA, in the atmosphere is essential for understanding how these complex aerosols transform and impact the environment and climate forcing. The chemical composition of OA influences how atmospheric radiation is absorbed. For example, the presence of nitrogen-containing organic compounds (NOC) in OA may have a profound effect on its light-absorption properties, affecting how OA influences regional haze and Earth's climate. OA sources, their atmospheric transformation, and radiative effects are core sources of uncertainty in today's atmospheric climate models. At present, the understanding of OA composition is limited to the extent that their impact cannot be accurately predicted and mitigated.

To probe the chemical compositional changes that occur in OA during a diurnal cycle and study the distribution of unique OA species across multiple scales, scientists employed EMSL's nanospray desorption electrospray ionization (nano-DESI) coupled with high-resolution mass spectrometry (HR-MS) capabilities to characterize more than 850 unique molecular species in the study area. Nano-DESI/HR-MS enables fast, sensitive direct analysis of minute amounts of the OA samples deposited on substrates and affords an accurate assessment of the transforming reactions and their plausible causes. The analyses revealed patterns, such as increased NOC in samples taken at night with more OA containing only carbon, hydrogen, and oxygen (CHO) in the afternoon. High correlated with the predominant CHO compounds, indicating they were secondary products of daytime oxidation, including ozonolysis and/or photochemical reactions.

Meanwhile, the observed nighttime enhancement of NOC showed evidence of being formed by reactions that transform carbonyls into imines, which require aqueous-phase chemistry of ammonium and organic compounds in liquid-phase particles. Thus, the scientists hypothesized ammonium chemistry may be an important pathway for NOC formation in OA. In addition to providing an alternate technique for investigating OA, and potentially more precise models, this work is another step toward clarifying environmental and climate change ramifications that stem from the chemical transformations that determine OA composition.

Explore further: Dietary PA/OA fat ratio may affect T2DM risk in women only

More information: O'Brien, R. et al. 2013. Molecular characterization of organic aerosol using nanospray desorption/electrospray ionization mass spectrometry: CalNex 2010 field study, Atmospheric Environment 68:265-272. DOI: 10.1016/j.atmosenv.2012.11.056.

Related Stories

Dietary PA/OA fat ratio may affect T2DM risk in women only

December 28, 2012

(HealthDay)—A diet low in palmitic acid (PA) and high in oleic acid (OA) improves insulin sensitivity and is associated with lower levels of markers of metabolic and oxidative stress in women only, according to a study ...

Study finds genetic risk factor for knee osteoarthritis

May 14, 2013

(Medical Xpress)—A newly published paper reports that individuals with radiographic knee osteoarthritis (OA) who had a specific pattern of gene variations in the interleukin-1 receptor antagonist gene (IL1RN), which is ...

Characterization of winter organic aerosols in Beijing, China

March 5, 2012

Organic aerosol (OA) is a crucial component of atmospheric fine particles. To achieve a better understanding of the sources of OA is very significant for air pollution control. In the 2012, Vol 57(7) of Chinese Science Bulletin, ...

Multifactorial mechanisms underlie leg weakness in hip OA

August 9, 2012

(HealthDay) -- Multiple factors contribute to leg weakness in people with hip osteoarthritis (OA), with muscle atrophy being the strongest contributor, according to the results of a systematic review published online July ...

BMI, post-exercise knee laxity change tied to OA progression

August 21, 2012

(HealthDay) -- In patients with osteoarthritis (OA) of the knee, changes in knee joint laxity during stair climbing or other repetitive physical activity and baseline body mass index (BMI) are associated with disease progression, ...

Recommended for you

Multinationals act on ocean-clogging plastics

January 16, 2017

Forty of the world's biggest companies assembled in Davos agreed on Monday to come up with cleaner ways to make and consume plastic as waste threatens the global eco-system, especially in oceans.

Tracking Antarctic adaptations in diatoms

January 16, 2017

Diatoms are a common type of photosynthetic microorganism, found in many environments from marine to soil; in the oceans, they are responsible for more than a third of the global ocean carbon captured during photosynthesis. ...

Study tracks 'memory' of soil moisture

January 16, 2017

The top 2 inches of topsoil on all of Earth's landmasses contains an infinitesimal fraction of the planet's water—less than one-thousandth of a percent. Yet because of its position at the interface between the land and ...

How the darkness and the cold killed the dinosaurs

January 16, 2017

66 million years ago, the sudden extinction of the dinosaurs started the ascent of the mammals, ultimately resulting in humankind's reign on Earth. Climate scientists have now reconstructed how tiny droplets of sulfuric acid ...

Soil pores, carbon stores, and breathing microbes

January 16, 2017

Researchers at the Pacific Northwest National Laboratory (PNNL) recently studied how moisture influences soil heterotrophic respiration. That's the breathing-like process by which microbes convert dead organic carbon in the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.