Characteristics of Urban Aerosol Nanoparticles in Southeast Asia: A Case Study of Medan City, Indonesia

In this study, to evaluate the particulate matter pollution in Southeast Asia (SEA), a typical Metropolitan city in Indonesia has been selected, i.e., Medan city.As similar with other big cities in developing region, agriculture and municipal solid waste are two expected emission sources along with the transportation.Two approaches for the evaluation were based on estimation of emission inventory of those sources and field sampling in 3 sites in urban area (roadside, school environment, and industrial area).A location in the rural area nearby volcano (inactive) was selected as the background sites to the urban location.To estimate the emission inventory, we conducted the laboratory-scale experiment for the identification of emission factor of plastic burning, while the other two sources or biomass and vehicles, we used the emission factor from previous studies which used by the GAINS.Ambient nano sampler (ANS) was used to collect the six-different sizes of particles.For the laboratory scale experiment of plastic burning, not only its mass and carbonaceous components evaluated in this study, but also the real-time particle number concentration during the plastic combustion which provided more information about its characteristic.Most of the particle emitted from plastic combustion in the laboratory scale experiment was in the UFPs size.The highest emission factor was founded in the PS types while the most resistant one was PET types.Similar to the mass concentration, particle number concentration (PNC) recorded by using OPC suggested smaller particle (0.3-0.5 m) was the highest fraction among the other sizes.This finding indicated that the open waste/plastic combustion commonly occurred in the SEA as Indonesia could emit a lot of UFPs.The average emission factor of plastic burning was 2.2 and 4.2 mg/g for UFPs and PM2.5, respectively.The emission inventory of PMs emitted from plastic burning, vehicles, and biomass were 46.7; 15.4; and 583.3 ton/year for PM2.5 respectively, while for TSP, it was contributed around 69.0; 20.7, and 619.3 ton/year.In term of transportation types, heavy vehicles (truck) were the highest contribution of PMs to atmosphere even the number of trucks is lower than cars and motorcycles.The UFPs monitored in four-different characteristic sites in Medan city indicated that it was higher than previously studies in Sumatra Island (Indonesia), Hanoi (Vietnam), and Kuala Lumpur (Malaysia), while it was comparable with the concentration founded in Bangkok, Thailand, and much lower than recorded in Chiang Mai, Thailand during forest fires.UFPs in Indonesia has different characteristic with the East Asian (EA) countries or Japan and Korea.Carbon and organic compounds suggested that urban environment was much polluted by vehicles, open plastic burning and even biomass burning compared to the rural area in VA.Day and nighttime of chemical composition have different characteristic with PMs mass concentration.Higher carbon and organic compound fraction in PMs during nighttime, indicated the influence of sources other than vehicles.