Sujan Shrestha 1,2, Siva Praveen Puppala 1, Bhupesh Adhikary1, Kundan Lal Shrestha2, Arnico K. Panday1 1 International Centre for Integrated Mountain Development (ICIMOD), Khumaltar, Lalitpur, Nepal
2 Department of Environmental Science and Engineering, Kathmandu University, Dhulikhel, Kavre, Nepal
Received:
December 3, 2017
Revised:
December 30, 2017
Accepted:
December 31, 2017
Download Citation:
||https://doi.org/10.4209/aaqr.2017.11.0492
Cite this article:
Shrestha, S., Puppala, S.P., Adhikary, B., Shrestha, K.L. and Panday, A.K. (2018). Field Measurements for Quantifying Semi-Volatile Aerosol Influence on Physical and Optical Properties of Ambient Aerosols in the Kathmandu Valley, Nepal.
Aerosol Air Qual. Res.
18: 1617-1630. https://doi.org/10.4209/aaqr.2017.11.0492
HIGHLIGHTS
ABSTRACT
An intensive field campaign was conducted during the pre-monsoon season of 2015 in the urban atmosphere of the Kathmandu Valley to study the influence of the semi-volatile aerosol fraction on physical and optical properties of aerosols. Ambient air was siphoned through a specific ambient air inlet and then split into two parts. The first part connected directly with an ambient air sample while the second received the air sample through a thermodenuder (TDD). The aerosol properties, such as the aerosol number, size distribution, absorption, and scattering, were studied using Condensation Particle Counters (CPCs), Scanning Mobility Particle Sizers (SMPSs), Aethalometers (AE33) and Nephelometers, respectively. The differences in the properties of the aerosol fraction at room temperature and other TDD set temperatures (50°C, 100°C, 150°C, 200°C, 250°C, and 300°C) were calculated to study the influence of the semi-volatile aerosol fraction on ambient aerosols. The evaporated fraction of the semi-volatile aerosols increased with the TDD set temperature. The semi-volatile fraction of the aerosol number increased from 16% to 49% of ambient aerosol, while the peak mobility diameter of particles shifted from around 60 nm to 40 nm as the temperature increased from 50°C to 300°C. However, increasing the TDD set temperature had no influence on the effective diameter of the aerosol size distribution. Larger aerosol size bins of the SMPS experienced a significantly stronger influence (~70%) from temperature increments compared to smaller size bins (~20%). The semi-volatile aerosol fraction amplified BC absorption by up to 28%, while scattering by the semi-volatile aerosol fraction contributed up to 71% of the total.ABSTRACT
Keywords:
Aerosol number concentration; Absorption; Scattering; Black carbon.
