- 期刊
- OpenAccess
Analysis of Surface Level PM_(2.5) Measured by Low-Cost Sensor and Satellite-Based Column Aerosol Optical Depth (AOD) over Kathmandu
摘要
A low-cost PurpleAir PA-II sensor was installed, in 2020 at the Institute of Engineering (IOE) Pulchowk Campus, TU located in Kathmandu valley, Nepal, to measure particulate matter with an aerodynamic diameter equal to or smaller than 2.5 μm (PM_(2.5)). The observation shows that hourly averaged PM_(2.5) fluctuates bimodally in four seasons (Winter: December, January, and February; Spring: March-May; Summer: June-September; and Autumn: October-November), with the highest levels occurring during morning and evening rush hours. PurpleAir records PM_(2.5) with a maximum average of 101 ± 26.31 μg m^(-3), in winter, 55.58 ± 11.42 μg m^(-3), in spring, 45.46 ± 12.16 μg m^(-3), in autumn, and a minimum of 22.78 ± 3.23 μg m^(-3), in the summer. Due to rain and diffusion in the vertical atmosphere, PM_(2.5) levels are lowest during the summer. The ± number for each season represents the standard deviation from the hourly average. AOD_(550nm) data collected by MODIS (Moderate Resolution Imaging Spectroradiometer) onboard two NASA satellites, Terra and Aqua, are compared with simultaneously observed PM_(2.5). With humidity correction factor f(RH), R^2 increases from 0.413 to 0.608 (in winter), 0.426 to 0.508 (in spring), and 0.083 to 0.293 (in autumn). The summer AOD data and PM_(2.5) are not compared due to a lack of AOD observations. By comparing the column-integrated aerosol data with the surface-level aerosol concentration, this study illustrates the relevance of atmospheric parameters while investigating the reliability of PurpleAir measurements. A cluster analysis of five-day back trajectories of air masses arriving at different altitudes in different seasons indicates that long-range transport of air pollution contributes to MODIS's column integrated AOD by adding aerosol population.
延伸閱讀
- Krishna, R. K., Ghude, S. D., Kumar, R., Beig, G., Kulkarni, R., Nivdange, S., & Chate, D. (2019). Surface PM_(2.5) Estimate Using Satellite-Derived Aerosol Optical Depth over India. Aerosol and Air Quality Research, 19(1), 25-37. https://doi.org/10.4209/aaqr.2017.12.0568
- Kiros, F., Shakya, K. M., Rupakheti, M., Regmi, R. P., Maharjan, R., Byanju, R. M., Naja, M., Mahata, K., Kathayat, B., & Peltier, R. E. (2016). Variability of Anthropogenic Gases: Nitrogen Oxides, Sulfur Dioxide, Ozone and Ammonia in Kathmandu Valley, Nepal. Aerosol and Air Quality Research, 16(12), 3088-3101. https://doi.org/10.4209/aaqr.2015.07.0445
- Misra, A., Jayaraman, A., & Ganguly, D. (2015). Validation of Version 5.1 MODIS Aerosol Optical Depth (Deep Blue Algorithm and Dark Target Approach) over a Semi-Arid Location in Western India. Aerosol and Air Quality Research, 15(1), 252-262. https://doi.org/10.4209/aaqr.2014.01.0004
- Agnihotri, R., Mishra, S. K., Yadav, P., Singh, S., Rashmi, Prasad, M., Sharma, C., & Arya, B. C. (2015). Bulk Level to Individual Particle Level Chemical Composition of Atmospheric Dust Aerosols (PM5) over a Semi-Arid Urban Zone of Western India (Rajasthan). Aerosol and Air Quality Research, 15(1), 58-71. https://doi.org/10.4209/aaqr.2013.08.0270
- Dumka, U., Sagar, R., & Pant, P. (2009). Retrieval of Columnar Aerosol Size Distributions from Spectral Attenuation Measurements over Central Himalayas. Aerosol and Air Quality Research, 9(3), 343-351. https://www.airitilibrary.com/Article/Detail?DocID=16808584-200909-9-3-343-351-a