This blog post examines how fine dust measurement technology using the beta ray absorption method contributes to environmental management and analyzes its importance in air pollution monitoring and policy formulation.
Fine dust particles with a diameter of 10 micrometers or less can cause various respiratory diseases, making it necessary to know the concentration of fine dust in the air for preventive measures. The impact of fine dust on the human body extends beyond respiratory diseases; long-term exposure can lead to various health problems such as cardiovascular disease, asthma, and reduced lung function. Consequently, international organizations like the World Health Organization (WHO) have designated fine dust as a major public health threat and are continuously strengthening standards for its monitoring and management.
To this end, fine dust measuring devices have been developed, most of which utilize the beta ray absorption method. Fine dust measuring devices using the beta ray absorption method automatically measure the concentration of fine dust at set intervals, regardless of the particle’s composition. This device is broadly composed of a particle separation unit, filter paper, a beta ray light source and detector, and a processing unit.
To accurately measure particulate matter concentration, the collection of the sample material for analysis is first required. The air sample is drawn into the sample intake section by a suction pump, set to ensure a constant volume of air flows in over a fixed time period. The separation device accelerates the particulate matter in the air entering through the sample intake port via an internal nozzle. It then collides the particles with a collision plate, capturing only those larger than 10 μm while allowing smaller particles to pass through.
Ultimately, dust larger than 10 μm in diameter remains on the collision plate, while only the finer dust smaller than this size falls downward and accumulates on the filter paper. The filter paper is in the form of a long tape and collects fine dust over a set period. This collection process is crucial for determining the concentration of fine dust in the atmosphere, providing essential data for environmental management in urban areas and atmospheric pollution research. The fine dust collected on the filter paper has its mass measured by a beta ray source and a beta ray detector before being automatically discharged by a conveyor drive mechanism.
Beta rays are chosen as the radiation source because they exhibit the property of attenuation when passing through materials, with greater attenuation occurring in materials of higher mass. Furthermore, while paper allows rapid passage, thin metal plates or plastics cannot be penetrated, ensuring high safety. Consequently, beta rays are selected as the radiation source for measuring fine dust concentration, offering both reliability and precision. Beta rays emitted from the beta ray light source pass through the fine dust collected on the filter paper and reach the beta ray detector. The intensity of the detected beta rays must be lower than that of beta rays passing through a filter paper without fine dust. This is because, when beta rays pass through the fine dust particles collected on the filter paper, some of them are absorbed or annihilated by the fine dust particles. Therefore, a difference occurs between the intensity of the beta rays passing through the filter paper without fine dust and the intensity of the beta rays passing through the filter paper with fine dust.
The beta ray detector converts the intensities of these two beta rays into data signals and sends them to the processing unit. The processing unit converts these data signals into numerical values and then calculates the mass of the fine dust collected on the filter paper, taking into account the amount of beta rays absorbed by the fine dust. The resulting mass of fine dust is expressed as the concentration of fine dust in the atmosphere in parts per billion (ppb), taking into account the volume of air inhaled during sample collection, as measured by the flow rate measurement unit. This value is essential information for air quality assessment and pollution management, used to evaluate the severity of air pollution and develop appropriate countermeasures.
