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Particle analysis techniques for particulate air pollution
Air particulate matter is a major component of air pollution, posing significant risks to human health and the environment. It is a complex mixture of solid particles and liquid droplets of various sizes and chemical compositions, originating from both natural and anthropogenic sources. Air particulate matter is significant to both researchers and policymakers. The methodologies for its measurement and the role of scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) in its analysis can help with source tracing and effective control.
Impacts of particulate matter in air pollution
Particulate matter is a major atmospheric pollutant. These particles vary in size, shape, and chemical composition. Particulate matter can be primarily categorized by its aerodynamic diameter in micrometers (μm). Particles with a diameter of 10 μm or smaller are known as PM10 or "coarse" particles, while those with a diameter of 2.5 μm or less are known as "fine" particles (PM2.5). In recent years, "ultrafine" particles with a diameter of less than or equal to 0.1 μm (PM0.1) have gained scientific interest since some PM0.1 particles can penetrate the alveolar capillary membrane, crossing from air into the bloodstream, thereby presenting potential health risks for animals and human beings.
The study of particulate matter is crucial due to its profound impact on both human and environmental health. For example, inhalable particulate matter can cause respiratory diseases in both humans and animals. It also affects the climate by influencing the Earth's radiative balance, and it contributes to the formation of photochemical smog, leading to decreased atmospheric visibility. Understanding particulate matter's characteristics, sources, and pathways is vital for developing air quality standards and implementing policies to minimize emissions.
Particulate matter analysis with SEM-EDS
Measuring particulate matter is complex due to its diverse nature. The most known and well-accepted methods involve collecting particles on filters for gravimetric analysis or using instruments like the tapered element oscillating microbalance (TEOM), beta attenuation monitors (BAM), and optical/laser methods. However, these methods are limited by giving only the mass concentration of PM. For instance, it is not possible to differentiate routinely and precisely between the different components of particles.
Scanning electron microscopy (SEM), coupled with energy-dispersive X-ray spectroscopy (EDS), offers an advanced approach to particulate matter analysis. Researchers can collect filters from air samplers and load them into an SEM to acquire high-resolution images of particulate matter morphology. Using EDS, the chemical composition of individual particles can be identified, enabling the determination of PM sources. With the aid of automated software and integrated artificial intelligence and machine learning techniques, this combined information allows for detailed analysis of each PM particle and overall statistics. Researchers can link the results to specific sources, such as car emissions, industrial processes, or natural sources, facilitating targeted pollution control.
Health effects of air pollution
SEM also plays a crucial role in the study of the effects of specific contaminants on cells and tissues under controlled laboratory conditions. This allows for a better understanding of the mechanisms through which particulate matter causes health effects. By utilizing both experimental and simulated data, scientists can conduct risk assessments to quantify our exposure to PM. This involves comparing laboratory-measured risks with those from actual exposure scenarios, providing valuable insights into the potential health risks associated with particulate matter.
Why study particulate air pollution?
The study of air particulate matter is vital due to its multifaceted impact on human health, the environment, and climate. While traditional measuring techniques offer limited information, SEM-EDS provides a reliable approach for the visualization and chemical analysis of each particle. The extended information obtained through SEM-EDS enhances our ability to set effective air quality standards and policies while deepening our understanding of particulate matter's health implications. By making informed decisions, we can mitigate the adverse effects of particulate matter on global health and environmental sustainability.
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