Is sea air really good for you?

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  • Published: Apr 7, 2016
  • Author: Ryan De Vooght-Johnson
  • Channels: Gas Chromatography
thumbnail image: Is sea air really good for you?

The air pollution problem

There are millions of tiny pollutant particles in the air called aerosols, generally less than 1 micrometre in size and invisible to the human eye. In spite of their miniscule size, their impact is vast. Aerosols scatter sunlight back to space, adding to the greenhouse effect.

The air is far more polluted than it may appear. Smoke and smog are clear to see, but there is more going on in the atmosphere than we can see, much of which is of concern for scientists. There are millions of tiny pollutant particles in the air called aerosols, generally less than 1 micrometre in size and invisible to the human eye. In spite of their miniscule size, their impact is vast. Aerosols scatter sunlight back to space, adding to the greenhouse effect. They can also change the size of cloud particles, which affects how clouds reflect and absorb light. Aerosols can also absorb pollutants and distribute them across land and water, damaging the environment. There are also human health implications; very small aerosols can become lodged in the lungs where they may cause respiratory disease.

These tiny particles are found all over the world, including in the air over oceans. These ‘marine aerosols’ can alter crucial geochemical cycles, acidify the ocean and contribute to climate change. However, exactly what happens to these particles in the marine atmosphere remains unclear.

Recent reports have shown high levels of dicarboxylic acids (diacids) in marine aerosols. Despite their prevalence in their environment, some diacids – especially those containing hydroxyl and keto groups – have never been characterised in marine aerosols. This is an important knowledge gap as these compounds likely play critical roles in weather processes, including global warming.

Particles over the Pacific

Identifying hydroxy- and keto-diacids in marine air samples is important for better understanding what makes up organic aerosols, which is in turn important for predicting their effects on air quality, climate and human health. Scientists from Hokkaido University in Japan have moved closer to this goal, by identifying both types of diacid in air samples taken from above the Pacific Ocean.

Particles were collected every week for a year in 2011 at a Japan Aerospace Exploration Agency (JAXA) station on Chichijima Island in the North Pacific, an area that receives dust and polluted air from China. Diacids were extracted before the researchers performed a two-step chemical derivatisation technique, followed by various gas chromatography approaches to identify the acids. Several unknown peaks were detected in the chromatograms, which were found to belong to a homologous series of hydroxydiacids. Although some of these compounds have been detected in the lab, this is the first time they have been reported in marine aerosols.

The compounds were not only identified but also quantified, revealing that malic acid is the most abundant diacid in the sea air, followed by tartronic acid. As well as these hydroxy-diacids, the researchers also identified oxaloacetic acid – a metabolic intermediate in many processes – for the first time in marine aerosols.

Important intermediates

Using a range of GC-based methods, this paper identifies previously unknown intermediates in marine aerosols. “Their structural identification and seasonal variations provide insights into the sources and formation pathways of organic aerosols,” explains Professor Kimitaka Kawamura of Hokkaido University, Japan. The authors say these diacids are likely to be important intermediates in the break-down of organic aerosols, which may be helpful for future research into the climate impacts of aerosols.

Related Links

Rapid Commun Mass Spectrom., 2016, Early View paper. Gowda et al.. Identification of hydroxy- and keto-dicarboxylic acids in remote marine aerosols using gas chromatography/quadruple and time-of-flight mass spectrometry.

Marine aerosols: A review

Aerosols: Tiny Particles, Big Impact

Introduction to marine aerosols

Wiki: Aerosols

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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