Air quality monitoring for harmful particulate

The World Health Organization (WHO) defines air pollution as “contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere”.¹

From an environmental perspective, polluted air can cause acid rain, crop damage, decrease plant growth and productivity, and cause harm to wildlife. For humans, the inhalation of polluted air may lead to respiratory problems, heart disease, cancer, and other severe health issues. This is a concern as 99% of humans worldwide breathe air exceeding the WHO guideline limits on air quality.^1,2

Particulate matter and aerosols are pollutants of particular concern. This article presents the drivers of air pollution and highlights two instruments used for continuous ambient air quality monitoring.

Differences between particulate matter and aerosols

Particulate matter (PM) refers to small solid particles suspended in a gas. In contrast, aerosols are finer liquid droplets or solid particles that remain suspended in gases for prolonged periods of time. PM and aerosols can negatively affect human health, particularly when their diameters are under 2.5 µm (PM_2.5, Figure 1).

Aerosols and PM can originate from natural sources, including volcanic eruptions, but they are often generated from human activities such as industrial operations and transportation. As a result, industrial air quality monitoring is critical in identifying emission sources and the chemical composition of pollutants and in informing strategies to reduce human exposure.

Figure 1. Particulate matter size comparison. Adapted from the US EPA ³. Image Credit: Metrohm Middle East FZC

Analytical methods for PM and aerosol quantification

Analyzing PM and aerosol content typically consists of collecting samples and analyzing them. Representative samples must be collected using appropriate equipment and techniques, and a filtration process must be generally used.

Particles are collected from substrates with filters exposed for a certain duration before being removed with deionized water before the subsequent analysis.⁴ However, this method can only measure particle averages over 24 hours or longer, is cumbersome and imprecise, and cannot support continuous online measurements.

Continually taking samples of aerosol composition is key to understanding and addressing air quality challenges. Specifically, data obtained in real-time provides insights into changes in aerosol composition, thus allowing quicker responses to pollution events and increasing the accuracy of scientific investigations into atmospheric processes.

Modern technologies require continuous aerosol analysis to address these limitations. Devices that collect steam, including the Metrohm AeRosol Sampler (MARS) and the 2060 Monitor for AeRosols and Gases in ambient Air (MARGA) (Figure 2), offer continuous, real-time, monitoring of aerosol composition. The advanced techniques utilized by these instruments provide valuable data for air quality assessment and research.

Figure 2. Inline sample preparation for gaseous samples is made simpler using the 2060 MARGA (left) or MARS (right) systems from Metrohm Process Analytics. Image Credit: Metrohm Middle East FZC

The 2060 MARGA separates gases and aerosols sampled from the same air mass through selective dissolution in water. The resulting solutions, available every hour, are then analyzed using ion chromatography with conductivity detection.

The separation of gases and aerosols enables the detection of crucial precursor gases and ionic species present in the aerosols and provides a more comprehensive understanding of air quality.

In terms of chemical analysis, the MARS device (Figure 3) is specifically designed for aerosol analysis and is typically coupled with external wet chemical analyzers, like ion chromatographs. These are used for cation and/or anion analysis or voltammetric (VA) systems.

The MARS's modular approach offers greater flexibility and adaptability. It accommodates a wider range of analytical requirements than the 2060 MARGA, which integrates anion and cation ICs internally.

Figure 3. MARS enables comprehensive analysis of air samples with IC, VA, or both. Image Credit: Metrohm Middle East FZC

Both instruments (2060 MARGA and MARS) include gas denuders (Wet Rotating Denuder (WRD); Figure 4, left), a condensation particle growth sampler (Steam-Jet Aerosol Collector (SJAC); Figure 4, right), and pumping and control devices.

These instruments convert aerosol particles into droplets in a supersaturated water vapor environment. After being mixed with carrier water, the collected droplets are continuously fed into sample loops or preconcentration columns for analysis.

Figure 4. Left: Wet rotating denuder (WRD) for easy gas removal. Right: Steam-Jet Aerosol Collector (SJAC) incorporated in the MARS and 2060 MARGA. Image Credit: Metrohm Middle East FZC

How to decide between the MARS and the 2060 MARGA

While MARS is designed specifically for sampling aerosols, the 2060 MARGA measures aerosols and water-soluble gases. Unlike classical denuders that remove gases from the air sample before reaching the aerosol collector, the 2060 MARGA captures gaseous species in a Water-Resolving Device (WRD) for online analysis.

In contrast, aerosols with low diffusion speeds pass through the WRD without interference.

The 2060 MARGA is available in two configurations: R (research) or M (monitoring). The R version is intended for research campaigns, such as studying seasonal air quality variability. When the R version is not required, the ion chromatograph can be uncoupled and repurposed for other laboratory applications.

New technologies focus on integrating continuous aerosol analysis to address this caveat in traditional sampling methods. Devices such as the Metrohm AeRosol Sampler (MARS) and the 2060 MARGA (Monitor for AeRosols and Gases in ambient Air) provide real-time, continuous monitoring of aerosol composition.

These instruments employ sophisticated techniques to collect and analyze aerosols, resulting in the measurement of valuable data for air quality assessments.

Table 1. Differences between the analysis capabilities of the 2060 MARGA and MARS systems. Source: Metrohm Middle East FZC

The following compares the correlation between aerosol sampling and measurement using the 2060 MARGA and MARS. Given that the aerosol results from the 2060 MARGA are known to be accurate, a strong correlation between instruments would suggest that MARS also measures aerosols with comparable accuracy.⁵

The graphs illustrate the aerosol results of ambient air in Schiedam, the Netherlands, from June 6-9, 2022, using the 2060 MARGA and MARS systems via ion chromatography. The 2060 MARGA operates with a cycle time of 60 minutes, while MARS has a cycle time of 30 minutes.

Although MARS generates twice the data, leading to higher aerosol concentration readings, applying a moving average to correct the data to a 60-minute cycle reveals concentrations were similar in both systems.

Figure 5. Comparison test showing results for various air quality parameters as measured by the 2060 MARGA (top) and MARS (bottom). Image Credit: Metrohm Middle East FZC

Conclusion

Monitoring air pollution is critical for identifying and quantifying the composition and levels of pollutants in the air. Exposure to air pollution can lead to various health issues for humans, including respiratory illnesses, cardiovascular diseases, and cancer. High levels of air pollution also pose environmental risks, contributing to acid rain, ozone depletion, and climate change.

Utilizing tools, including the 2060 MARGA and MARS from Metrohm Process Analytics, will improve air quality measurements and subsequently enhance the assessment of impacts from different pollutants as well as develop effective strategies to minimize exposure. By doing so, research can help inform and drive decisions for a healthier and more sustainable environment for everyone.

References

1. World Health Organization (2019). Air pollution. (online) WHO. Available at: https://www.who.int/health-topics/air-pollution.
2. WHO (2021). WHO global air quality guidelines: particulate matter (‎PM_2.5 and PM₁₀)‎, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. (online) WHO. Available at: https://www.who.int/publications/i/item/9789240034228.
3. EPA (2023). Particulate Matter (PM) Basics. (online) United States Environmental Protection Agency. Available at: https://www.epa.gov/pm-pollution/particulate-matter-pm-basics.
4. Wang, D., et al. (2020). A Sampler for Collecting Fine Particles into Liquid Suspensions. Aerosol and air quality research. https://doi.org/10.4209/aaqr.2019.12.0616.
5. Läubli, M. (2023). Air monitoring with ion chromatography: An overview of the literature references. (online) Available at: https://www.metrohm.com/en/products/a/ir_m/air_monitoring_icv2.html (Accessed 17 Mar. 2025).

About Metrohm Middle East FZC

Metrohm Middle East FZC is a subsidiary of Metrohm AG, Switzerland, located at Sharjah Airport International Free Zone, UAE. Metrohm’s Product range involves both Lab instruments & online Analysers for various industry segments - Water, Petrochemical, Pharmaceutical, Food and Beverages, Environmental Analysis, Chemical analysis, Research and development, Educational Institutions, Sewage Treatment and more.

MME has a team of well trained; knowledgeable and experienced team specialized in Product Management, Service and Application support. Apart from extending our support to distributors, MME also provides direct support and training to our customers on site or at our world class Regional Support Centre.

Your partner for chemical analysis

Metrohm is a leading manufacturer of high precision instruments for chemical analysis. We offer a complete line of analytical laboratory and process systems for titration, ion chromatography, spectroscopy, and electrochemisty. From the beginning, our sales engineers guide you through the instrument purchasing process. Together with our team of application chemists we create unique solutions for your lab's needs

Lab & process solutions

Lab Solutions: Today’s labs are required to produce more results with less resources than ever before. At Metrohm, we partner with you to match the right instrument system to your needs. It begins with a technical discussion to fully understand your measurement requirements. If required, our application chemists test your samples and instrument experts optimize your system configuration.The modularity of our instruments allows us to design sample handling and analysis platforms that deliver precise and reproducible results and increase the productivity of your lab. Process Solutions: Metrohm’s process analyzers take our laboratory solutions a step further. Fully automated, online customizable analyzers facilitate process monitoring across a wide array of applications. Drawing on our core competencies in titration, ion chromatography, spectroscopy, and electrochemistry, we leverage our applications knowledge to create reliable solutions for process analysis that optimize efficiency, decrease chemical consumption and create a safer work environment.

Titration

Ion chromatography

Spectroscopy

Electrochemistry

Autolab Potentiostats & Galvanostats Cyclic voltammetric stripping (CVS) Voltammetry for trace analysis

DNA hybridization and power devices such as fuel cells and batteries are driven by electrochemical processes. Electrochemistry traces the electronic pathways of these natural phenomena and mechanical circuits. Drawing on almost 30 years of experience, Metrohm provides precise measurement solutions for these diverse fields. Our expertise ranges from traditional electro-analysis methods such as polarography to hyphenated modern techniques including spectro-electrochemistry. Metrohm Autolab launched the first computer controlled digital potentiostat/galvanostat and we have gone on to earn a global reputation for innovation, modularity, accuracy, and advanced software. Our products provide you with a variety of measurement tools, from screen-printed electrodes to complete analysis systems.

Quality service

Consulting Installation Application Support Training Preventive Maintenance Repair Service

Metrohm Quality Service begins before you purchase your instrument and continues throughout its entire lifecycle. Instrument experts help you make the right decisions to satisfy your analytical and environmental requirements. Application chemists assist you in every technical aspect, from support in method development to troubleshooting and process optimization. Our certified service engineers are always on alert to provide emergency service in the shortest possible time – wherever you are. Metrohm provides the same high standard of service all over the world by trained and certified service engineers based at local Metrohm offices. After all, who is better qualified to care for your instruments than the people who built them?

Sponsored Content Policy: News-Medical.net publishes articles and related content that may be derived from sources where we have existing commercial relationships, provided such content adds value to the core editorial ethos of News-Medical.Net which is to educate and inform site visitors interested in medical research, science, medical devices and treatments.