Evaluation of PM1 Size-selective Samplers

1665 

Student Poster 

J MAO¹, C Chen²

¹NTU, TAIPEI, TAIPEI, ²National Taiwan University, Taipei, Taiwan

JIA-YI MAO  
NTU

Chih-Chieh Chen  
National Taiwan University

Particulate matter (PM) is an important atmospheric pollutant, impacting on air quality and human health. In the past years, we pay a lot attention to PM2.5. However, PM1 is also easier to enter human respiratory tract. The sources of aerosols are very diverse, and can be roughly divided into coarse mode and fine mode, which have different sources, health effects, and chemical components. In fact, PM1 is more suitable as a cut-point of separation between coarse and fine particles, and also enable to be used as a criterion for source differentiation, comparing to PM2.5, PM1 can more accurately estimate the artificially generated particles. For atmospheric sampling and stack sampling, installing a PM1 size-selective sampler at the front of the sampling instrument can reduce the deposition of large particles in the pipeline and avoid the PM1 monitoring bias.This study aims to evaluate the PM1 size-selective sampler and develop better design parameters. As there is currently no international convention of PM1 size-selective samplers to refer, so we consider the 50% cut-size, sharpness of the separation curve and particle loading effect as a reference to evaluate the efficiency.

PM1 is defined as aerodynamic particle size of less than 1 micron. Compared with PM2.5, PM1 has a higher lung deposition rate and is easier to enter the human circulatory system. From the perspective of health effects, exposing PM1 for a long time make the risk of developing cardiovascular disease higher than exposing to PM2.5, and its cytotoxicity and genotoxicity are more significant than PM2.5. In addition, during the sampling process of the atmosphere and the stack, large particles are easily deposited in the pipeline, causing sampling deviations. After installing the PM1 size-selective device at the front of the instrument, the problem of large particles deposited in the sampling pipeline can be solved. Improve the monitoring accuracy of PM1 and clarify the source of its generation. The distribution of atmospheric particles is very complicated, because the aerosol mixture source is very diverse, and can be roughly divided into coarse particle size (Coarse Mode) and fine particle size (Fine Mode). PM1 can more accurately distinguish the two mode than PM2.5. As the results, evaluating the PM1 size-selective samplers.

In addition to the TSI-FMPS, all the size-selective samplers tested in the experiment are made with PLA by 3D printing technology, including HM-a, HM-b, HM-APEX, HM-SCC and Virtual Cyclone. The experiment system was divided into two part, first part is particle generation, use a syringe pump to deliver the sodium chloride solution to the ultrasonic atomizer. The particles will pass through a radioactive source, which neutralizes the particles to the Boltzmann charge equilibrium, and dilution air with 80 L/min was mixed with particles and ventilated into the chamber, and the second part is particle measurement, using an aerodynamic particle sizer to measure the particle size distributions and number concentrations upstream and downstream of the PM1 size-selective samplers, to obtain the separation efficiency curve.Using the original system to perform a long-term penetration test and observe the deviation of the separation curve for the loading effect test.

The experimental data shows that when the five different size-selective samplers sampling with 3.1, 11.7, 7.76, 8.5, and 16.67 L / min as the operating flow rate, the cut-size falls at 1 μm (± 0.02 μm); the slopes of the separation efficiency curves are 1.43, 1.28, 1.4, 1.25, and 1.34, respectively. Except for HM-a and HM-b, the rest are traditional cyclones. In addition, the results of the loading effect test show that with the exception of the virtual cyclone sampler, all the other size-selective samplers have a significant deviation (10-20%) within 10 to 20 minutes.
According to the results above, the separation efficiency curve of TSI-FMPS is the sharpest, and it can distinguish particles from different sources more clearly than other size-selective samplers. For the problem that HM-a and HM-b cannot make the 50% cut-point fall to 1 μm with the expected flow rate, the design parameter model needs to be modified and verified, and the experimental deviation that may be caused by 3D printing need to be considered. Finally, comprehensive experimental results of loading effect test, the virtual cyclone should be more suitable for long-term sampling as a monitoring equipment.

Aerosols

Sampling and Analysis