[AAS07-P18] Chemical composition of atmospheric aerosols over Jakarta megacity
Keywords:atmospheric aerosols, PM2.5, chemical composition, urban monitoring, Indonesia
In addition to the continuous monitoring systems of NOx, SO2, O3, CO, CO2, CH4, and meteorological parameters, we installed three continuous dichotomous aerosol chemical speciation analyzers (ACSA-14, Kimoto) at Bogor (center of Bogor city) in 2016, Cibeureum (mountainous area, background-like site) in 2017, and Serpong (Jakarta suburb) in 2019. The ACSA-14 can automatically measure not only the mass concentrations of PM2.5 and PM10-2.5 and optically measured black carbon (OBC), but also the chemical composition of PM2.5 and PM10-2.5 (nitrate ion (NO3-), sulfate ion (SO42-), water soluble organic compounds (WSOC), ammonium ion (NH4+)), simultaneously. The measurement interval is 3 hours to extend the replacement interval of filter tapes and chemical reagents for the chemical composition analysis of PM2.5 and PM10-2.5.
The averages of PM2.5 from November 2017 to October 2019 are 23.9 μg/m3 at Bogor and 18.3 μg/m3 at Cibeureum. The seasonal averages of PM2.5 observed at Bogor and Cibeureum in the dry season (May to October in 2018/2019) are 34.2 and 28.0 μg/m3, which are 2.4 and 3.2 times higher than those of rainy season (November 2017/2018 to April 2018/2019), respectively. While the long-term trends of PM2.5 observed at Bogor are similar to Cibeureum, the averaged PM2.5 concentrations at Bogor in the dry and rainy seasons are 1.2 and 1.6 times larger than Cibeureum, respectively.
We compared the chemical composition of PM2.5 observed at three sites in February 2020. The amount of SO42- (20.9%) is almost same as WSOC (20.8%) at Bogor. The dominant components at Cibeureum are SO42- (27.4%) and WSOC (13.4%). While the most dominant component at Serpong is WSOC (22%), the percentage of NO3- (13.2%) at Serpong is larger than Bogor (11.8%) and Cibeureum (8.7%). The NO3-/SO42- ratio at Serpong (1.76) is higher than Bogor (0.82) and Cibeureum (0.43). These results suggest that the urban pollution caused by NOx in automobile exhausts is significant at Serpong compared to Bogor and Cibeureum.
In our presentation, we will also present the result of PM10-2.5, OBC, and the other species.