Number size distribution and chemical compositions of indoor and outdoor aerosols

Abstract

The vast majority of individuals spend a significant portion of their time indoors, engaged in various daily activities. Consequently, it is crucial for the general public to have an awareness of the detrimental impact that indoor air pollution can have on their health. One significant contributor to indoor particulate matter (PM), in addition to indoor activity, is infiltration from the outdoor environment. Persistent free radicals (PFRs) present in PM can arise from transportation and combustion pollutants. Different particle sizes of PM in the atmosphere pose different health risks to human health, depending on the particle accumulation efficiency and the chemical composition and concentrations of harmful substances contained. The study area was inside and outside the main library, Chia Nan University of Pharmacy and Science, Taiwan. To measure and illustrate the size distribution of number of aerosols in the library by using Optical Particle Sizer (OPS) and Scanning Mobility Particle Sizer (SMPS). Furthermore, to measure the water-soluble ions, carboxylates, and saccharides in PM, an ion chromatograph was utilized. On the other hand, the determination of persistent free radicals involved the use of an ESR spectrometer. Particle number (PN) properties of indoor environments, Aitken mode (50-100 nm) was the highest size mode of particle number concentration followed by accumulation I mode (100-200 nm) in both spring and early winter. The average of PN concentrations during close time was higher than during open time, indicating that high temperature when without air-conditioning and no ventilation caused the nanoparticle formation. However, the average PN (0.3-10 µm) concentration during open time is higher than during close time suggesting that number of students, their activities, ventilation, penetration from outdoors and the resuspension of carpet dust by occupants result from the increase in the average PN concentration. In addition, the size distribution of number during open time was found particle diameter at 70.8 nm. It can be suggested that the same activities in the library during open time are associated with printed matter. Moreover, chemical compositions including water-soluble ions, carboxylates, saccharides, and PFRs, are found outdoor more than in indoor buildings. Levoglucosan, nss-potassium, nss-sulfate, ammonium, maleate, malate and oxalate were specific chemical compositions that have a strong correlation with the concentrations of PFRs in PM in both indoor and outdoor . The source of PFRs in PM is constituted of precursor compounds released from primary and secondary aerosols which are related to the result of numerous natural and anthropogenic activities such as biomass burning, industrial activities, traffic emission, photochemical processes and plasticizers. This finding suggested that the penetration of outdoor PM is one source of indoor PFRs but the outdoor aerosol is not the main contributor affecting the indoor air quality in the library. Due to the complexity of PFRs in PM formation and its relationship with multiple chemical components, a comprehensive examination of the sources and production pathways is essential. However, the public should be concerned about the impacts of PFRs-containing PM indoors, which can enter the body by inhalation and pose a negative health risk.