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Our Air and Ultrafine Aerosol

Written by Quynh Teresa H. Do and Edited by Gauri Ajith

Pollution has been affecting the Earth for decades. The many different types of pollution negatively harm the Earth in varied ways: from land and water pollution destroying natural habitats to air pollution disrupting the atmosphere [​1]. The accumulation of the negative effects of pollution has become a global issue. In the United States alone, the issue of “climate change” has become a major focus in both politics and research. In recent years, researchers have focused on the causes of atmospheric climate change, especially aerosols, due to their extensive contribution to climate change.

Aerosols are a type of atmospheric particle that may negatively affect the climate. Aerosols, also known as particulates, are small particles that float in the air and are released by various sources such as dust, volcano eruptions, and human machinery [​2​]. Aerosols assist in cloud formation by acting as “seeds” for clouds to begin condensing; this has a considerable impact on the climate. A distinct quality of aerosols is that their size affects how long the particulates stay in the atmosphere. Heavier aerosols remain in the atmosphere for several hours before precipitation; however, ultrafine aerosols (that are smaller than one micrometer) can remain in the atmosphere for several weeks [​2]. These particles’ prolonged presence in the atmosphere can be detrimental to both the atmosphere and human health. With an imbalanced amount of aerosols in the air, clouds form abnormally and cause the climate to change. At the University of California, Irvine, Dr. James Smith and his team of researchers are investigating aerosols and the mechanisms by which ultrafine aerosol particles form and grow in the atmosphere. His group is also known as the Ultrafine Aerosol (UA) laboratory. They hope to examine the possible roles of organic compounds in the creation of stable clusters, and how these compounds are responsible for the birth and growth of aerosol particles formed in the atmosphere or within the aerosol particles themselves [​3​].

A previous study in the UA lab attempted to see what effects acid-base clustering and ions (electrically charged molecules) have on atmospheric nanoparticle growth. Acid-base clustering is when the acidic compounds interact with basic compounds in an area to create clusters. In this study, the researchers examined how nanoparticles grow in the atmosphere by observing the relationship between their precursor vapor concentrations and internal gas formation process, also known as the gas-to-particle formation process. These “precursor vapor concentrations” conditions include variations in sulfuric acid concentrations and the allowance of evaporation. The researchers conducted this experiment with sub-3 nm nanoparticles, or particles around the size of 3 nm. Nanoparticles such as these ultrafine aerosols are a source of cloud condensation nuclei [​4​]. Cloud condensation nuclei, or CCNs, are “seeds” where water vapor begins to condense. The amount of CCNs in the atmosphere can affect precipitation, clouds, and ultimately climate change [​5]. The atmospheric concentrations used in the experiment varied in the amounts of sulfuric acid (which is the major focus), water, ammonia, and dimethylamine.

Several instruments were used in the study, including the Cosmics Leaving OUtdoors Droplets (CLOUD) chamber, the atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF), the chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer, the nano-scanning mobility particle sizer (nano-SMPS), and the neutral cluster and air ion spectrometer (NAIS). Each of these machines measured a distinct characteristic of the aerosols. The CLOUD chamber was used to observe the potential influence of galactic cosmic rays on molecular cluster formation. The APi-TOF mass spectrometer was used to measure ion concentration at different mass-to-charge ratios. The CI-APi-TOF mass spectrometer was used to observe sulfuric acid and dimethylamine clusters (acid-base clustering effects). The nano-SMPS was used to measure the mobility of the aerosols in accordance to their size and create a size distribution for analysis. The NAIS was a part of the CLOUD chamber and measured the ion size and concentration distributions. The researchers found that ions and small acid-base clusters are involved in the growth process of nanoparticles. Specifically, they found that the clusters sped up the growth process by stabilizing the sulfuric acid vapors [​4].

Findings such as these highlight the importance of monitoring what is released into the air to prevent inappropriate cloud formations, which affects the climate. Slowly but surely, clouds created from aerosols and other substances create weather that is abnormal. Climate change is quickly killing the Earth and its inhabitants; these changes pose health risks to not only animals, but to humans as well. The World Health Organization predicts that by the year 2030, the risk of various health problems caused by climate change will double due to geological alterations and diseases [​6​]. The issue of ultrafine aerosols, although invisible to the eye, must be considered to save our planet.

References:

  1. Bradford, A. (2018). “Pollution Facts & Types of Pollution.”  Live Science​, https://www.livescience.com/22728-pollution-facts.html.
  2. “Aerosols: Tiny Particulates in the Air.” ​UCAR Center for Science Education​, UCAR, https://scied.ucar.edu/aerosols​.
  3. “SMITH GROUP — Ultrafine Aerosol Laboratory @ UC Irvine.” UA Group, https://sites.uci.edu/uagroup/​.
  4. Lehtipalo, K., Rondo, L., Kontkanen, J., Schobesberger, S., Jokinen, T., Sarnela, N., Kulmala, M.​ (2016). The effect of acid–base clustering and ions on the growth of atmospheric nano-particles. ​Nature Communications,​ ​7​: 11594.
  5. Khain, A. P., Benmoshe, N., & Pokrovsky, A. ​(2008). Factors Determining the Impact of Aerosols on Surface Precipitation from Clouds: An Attempt at Classification. Journal of the Atmospheric Sciences, 65​: 1721-1748.
  6. Patz, J. A., Campbell-Lendrum, D., Holloway, T., & Foley, J. A. ​(2005). Impact of regional climate change on human health. Nature, ​438​: 310-317.
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