Evaluation of Population Exposures to PM_2.5 before and after the Outbreak of COVID-19

Abstract

Background:The coronavirus disease (COVID-19) has caused changes in human activity, and these changes may possibly increase or decrease exposure to fine dust (PM 2.5 ). Therefore, it is necessary to evaluate the exposure to PM 2.5 in relation to the outbreak of COVID-19. Objectives:The purpose of this study was to compare and evaluate the exposure to PM 2.5 concentrations by the variation of dynamic populations before and after the outbreak of COVID-19.Methods: This study evaluated exposure to PM 2.5 concentrations by changes in the dynamic population distribution in Guro-gu, Seoul, before and after the outbreak of COVID-19 between Jan and Feb, 2020. Gurogu was divided into 2,204 scale standard grids of 100 m×100 m. Hourly PM 2.5 concentrations were modeled by the inverse distance weight method using 24 sensor-based air monitoring instruments. Hourly dynamic population distribution was evaluated according to gender and age using mobile phone network data and time-activity patterns.Results: Compared to before, the population exposure to PM 2.5 decreased after the outbreak of COVID-19.The concentration of PM 2.5 after the outbreak of COVID-19 decreased by about 41% on average. The variation of dynamic population before and after the outbreak of COVID-19 decreased by about 18% on average. Conclusions:Comparing before and after the outbreak of COVID-19, the population exposures to PM 2.5 decreased by about 40%. This can be explained to suggest that changes in people's activity patterns due to the outbreak of COVID-19 resulted in a decrease in exposure to PM 2.5 .

Mini‐Review: Progress on the Controllable Synthesis of Micro/Nanoscale Bi2S3 Functional Materials

“…[ 146 ] In addition, aiming at nonmagnetic/metal‐free materials, there are some valid approaches to separate, including membrane separation, [ 147 ] biological separation, [ 148 ] and chemical separation. [ 149 ] However, the above ways possess their own advantages and disadvantages, which are required further research on the operating parameters of Bi 2 S 3 micro/nanomaterials.…”