In this guest post, we sit down with atmospheric chemist, air quality expert and RADICAL researcher Professor John Wenger to learn more about the Irish Atmospheric Simulation Chamber (IASC). John is a Professor in Physical and Environmental Chemistry, School of Chemistry, UCC.
WHY STUDY RADICALS
The vast expanse of the sky contains thousands of chemical compounds interacting over the course of the day. This is the basis of atmospheric chemistry – a field of research that is increasingly important in the era of climate change.
For decades, air quality legislation has mandated monitoring of pollutants such as nitrogen oxides (NOx), ozone and particulates. The importance of the hydroxyl radical (OH·) on air quality was first realised over 70 years ago during investigations into Los Angeles smog. We now know that hydroxyl radicals are responsible for removing almost all gases emitted into the atmosphere through oxidizing chemical reactions which also produce secondary pollutants such as ozone and fine particulates which cause haze. We also know that a different species, the nitrate radical (NO 3·) takes over from hydroxyl during the night and drives atmospheric oxidation processes through similar types of reactions.
However, many of these radical reactions are poorly understood as they take place over a time scale of multiple days, depending on the temperature and the time of the year. This explains why the effects of pollutants can be felt at a time and space remote from the source. Researchers are still exploring the complex interplay between free radicals in the atmosphere and the chemical compounds found in plumes of pollution from vehicles, chimneys and other sources.
Currently, it is only possible to measure radicals using spectroscopic and mass spectrometric methods that are technically complex and expensive.
The RADICAL project is developing an electronic gas sensor that will enable atmospheric radicals to be detected and monitored in real-time using a low cost sensing platform. This sensor has the potential to transform how researchers study free radicals and contribute to both theoretical advancements in atmospheric chemistry and industry applications for pollution and air quality monitoring.
TESTING THE RADICAL SENSOR
In recent months, consortium partners on the RADICAL project achieved proof-of-principle in developing a new approach to monitor the chemical species that determine indoor and outdoor air quality. To date, first-level experiments have focused on testing the response of different materials to atmospheric gases in a small sensing platform.
Now entering the final phase of the RADICAL project, the focus is moving from the small sensing platform to the large-scale atmospheric simulation chambers based in the Centre for Research in Atmospheric Chemistry (CRAC) at University College Cork (UCC). The facilities in CRAC include the recently commissioned Irish Atmospheric Simulation Chamber (IASC), which is the only one of its kind in Ireland and part of a networked atmospheric research infrastructure in Europe.
This chamber is a vital testing ground for the RADICAL project because it will enable the performance of the sensor devices to be tested under a variety of well-controlled conditions that are close to those in the real-world. We will make use of methods like mass spectrometry and cavity enhanced absorption spectroscopy, developed for NO 3·detection in UCC and now used worldwide for detection of radicals. This will help to assess the sensitivity and selectivity of the RADICAL gas sensor and refine this new technology for radical detection.
ABOUT THE IRISH ATMOSPHERIC SIMULATION CHAMBER
Installed during 2019-2021, the advanced design of IASC required extensive customisation with support from suppliers and building services in UCC to facilitate integration with the air supply and management systems. Bespoke chamber control systems and programming tailored specifically for our project were commissioned during the height of the COVID-19 pandemic. This unfortunately resulted in delays in the complete setup of the IASC, with knock-on effects for research projects such as RADICAL that are dependent on laboratory work.
The IASC facility is larger than an average office and measures 4.5 m long × 3 m wide × 2 m high. The sheer size of this chamber creates potential for new experimental methods. It consists of a Teflon foil cuboid fixed to a frame, enclosed by a super structure with instrumentation, access ports and sensors that enable advanced controls.
Prior to entering the chamber, air undergoes a comprehensive filtering process in the laboratory—cleaned and treated to exacting standards. Fluorescent tubes emit UV light to replicate sunlight, initiating hydroxyl radical production and simulating real-world chemical reactions. The transparent and non-reactive design of the entire structure optimizes conditions for measuring highly sensitive chemical radicals.
Maintaining a fixed volume, the chamber ensures meticulous monitoring of atmospheric pressure and temperature, operating with minimal variability akin to a highly specialised HVAC system. Post-experimental use, the chamber undergoes a thorough cleaning process with air flushing at a rate of 1000 litres per minute. This is done while maintaining vigilant pressure monitoring through predefined set points. Reactive elements are diligently diluted overnight, safeguarding the chamber’s integrity.
The chamber enables researchers to test anything from new devices such as instruments, sensors and marketable products, to new materials and compounds including alternatives to CFCs and other volatile organic compounds (VOCs). This makes the chamber a vital testing ground for the RADICAL project, as well as other research projects underway in CRAC. The IASC is fully equipped with advanced spectroscopy equipment to measure traces gases and radicals. Of the various radicals which influence air quality, the nitrate radical (NO 3·) is easiest to detect as it absorbs red light and is produced in higher concentrations so less sensitivity is required; this can be up to 500 times higher than hydroxyl radicals (OH·).
A game changer for atmospheric research in Ireland, the chamber is incredibly versatile. It is unique to have this amount of controlled space to test such a wide range of gases, particles and the chemical reactions that they undergo.
All involved are excited to test the limits of the IASC, which will come into its own as part of the RADICAL project in 2024.
