Atmospheric black carbon in PM_2.5 in Indonesian cities

Abstract

Samples of airborne particulate matter were collected at several cities in Indonesia: Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta, from January through December 2011. The samples were collected once a week using a Gent stacked filter unit sampler in two size fractions of 2.5 µm (fine, PM_2.5) and 2.5 to 10 µm (coarse, PM_2.5–10). Black carbon was measured using an EEL smoke stain reflectometer. The average of PM_2.5 during the sampling period for Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta sites was 18.35, 16.50, 7.74, 16.68, and 8.78 µg/m³, respectively. The average of BC for Bandung, Jakarta, Palangka Raya, Serpong and Yogyakarta was 3.05, 3.37, 3.19, 2.51, and 2.20 μg/m³, respectively. The ratio of the 24-hr BC concentration compared to the PM_2.5 concentrations showed that BC comprises about 17–45% of the fine particulate matter collected at all sites. The average percentage of BC in PM_2.5 concentrations in Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta was 18, 22, 45, 17, and 26%, respectively. Bandung and Jakarta compared with Yogyakarta showed higher concentrations of PM_2.5 and BC, which indicated pollution occurring in Bandung and Jakarta is more intense than in Yogyakarta, while the maximum of BC concentration and the percentage of BC in PM_2.5 in Palangka Raya were 6.04 μg/m³ and 75%, respectively. This higher BC concentration than the other cities was due to the forest fires that occurred frequently during the sampling period. The contributions of BC source in these cities were also analyzed to ascertain the local sources of BC.

Implications:

BC in PM_2.5 was monitored over the period of January–December 2011 in several big cities in Indonesia to provide quantitative information on BC concentrations and contributions to PM_2.5 and for comparison among these cities and with other Asian countries. This study supports the national air quality monitoring projects. The results of black carbon concentrations in these areas indicate source contributions from local sources such as forest fire, biomass burning, and vehicle emissions.

Introduction

Atmospheric aerosols are the dominant contributor to the absorption of light in the visible and in the near-infrared spectral region. Black carbon (BC) is almost exclusively responsible for the light absorption by particles (Taha et al., 2007) and is a major contributor to the fine particulate matter in the atmosphere. The most important sources for atmospheric BC are the burning of fossil fuels, forest fires, and biomass burning. Biomass burning may be the dominant BC source over tropical regions and over most of the southern hemisphere (Pakkanen et al., 2000). In Indonesia, the biomass burning factor contributes about 40% of the PM_2.5 mass in the suburban area in Lembang and about 20% in the urban area in Bandung (Santoso et al., 2008). In European cities BC is strongly related to traffic, and BC is among the most important contributors to fine particulate matter of both PM_2.5 and PM₁₀ (Pakkanen et al., 2000).

Pollution caused by airborne particulate matter (APM) in several cities in Indonesia has become worse due to economic activities, rapid population growth, urbanization, and industrialization. It is now being recognized as a national problem with a serious impact on human health. In Indonesia, air quality monitoring for PM_2.5, especially carbonaceous particles, is still limited. There are regions within Indonesia that experience episodes of degraded air quality due to peat forest fires, such as Palangka Raya and Pekanbaru. Recently, the authorities of environmental agencies in these areas have shown a strong motivation to understand the key variables that are responsible for these periods. Several cities have started periodical monitoring of air quality for fine particulate matter as a national project in Indonesia. The Minister of the Environment is aware of this situation, and there is an effort to propose new air pollution regulations to improve the air quality. Regulations related to the anthropogenic emissions have also been made, for example, the banning of open burning in public areas. However, these regulations need scientifically based research, to provide reliable information related to the air pollution degradation and influencing parameters.

In this study, the BC and PM_2.5 concentrations collected in five cities in Indonesia (Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta) were determined by reflectance measurement using a smoke stain reflectometer (Diffusion Systems Ltd. model 43D). A comparison between several cities in Indonesia is presented. The purpose of this study is to provide quantitative information of BC concentrations in several cities in Indonesia, its contributions to PM_2.5, and estimation for the source of BC concentrations.

Methodology

Samples of airborne particulate matter were collected in five cities located on Java and Borneo islands. The samplers on Java island were placed in Jakarta, Serpong, Bandung and Yogyakarta, while on Borneo the sampler was placed in Palangka Raya. Jakarta (latitude 6˚12’S, longitude 106˚48’E) is the capital and largest city of Indonesia. Located on the northwest coast of Java island, it has an area of 661.52 km² (255 sq mi). Jakarta is the country's economic, cultural, and political center, and it is the most populous city in Indonesia, with many buildings, highways, and small- to large-scale factories located in and around the city. In general, Indonesia has two seasons, dry season (April to September) and wet season (October to March). The rapid growth of industry, population, and motor vehicle usage has strongly affected the city's environmental quality. Motor vehicles contribute nearly 13–44% of suspended particulate matter (SPM) into the air in Jakarta (WALHI, 2007). Meanwhile, the growth rate of motor vehicle numbers in Jakarta is 15% per year, so that for 2015 the estimated number of vehicles in Jakarta is about 15 million (BAPPENAS, 2006). Serpong is a district of South Tangerang, an independent city of Banten province, and categorized as an industrial city with a population of more than 14,000 inhabitants in an area of approximately 24 km². Bandung is the provincial capital of West Java and Yogyakarta is the provincial capital of Yogyakarta special region. Palangka Raya is the provincial capital of central Borneo. The sampling locations are shown in Figure 1.

Map of sampling sites.

The samples were collected once a week using a Gent stacked filter unit sampler in two size fractions of 2.5 µm (fine, PM_2.5) and 2.5 to 10 µm (coarse, PM_2.5–10) (Hopke et al., 1997). The coarse fraction samples were collected on an 8.0-μm-pore Nuclepore filters, whereas the PM_2.5 samples were collected on 0.4-μm-pore Nuclepore filters. Sampling was performed at a flow rate of 15–18 L/min for 24 hr during 2011. In total, 42, 62, 32, 49, and 43 pairs of samples were collected in Jakarta, Serpong, Bandung, Yogyakarta, and Palangka Raya respectively. Sampling in Serpong during April–May 2011 was done twice a week.

The masses of fine and coarse fractions were determined by weighing the filters before and after exposure; then they were divided by the volume of air passing through the filter to obtain the concentrations of PM_2.5 and PM_2.5–10 (μg/m³). The PM₁₀ concentration was obtained by summing these two values. The black carbon concentrations of the samples were determined by reflectance measurement using a smoke stain reflectometer (Diffusion Systems Ltd. model 43D). Secondary standards of known black carbon concentrations are used to calibrate the reflectometer.

Results and Discussion

All samples were collected on weekdays during 2011. Table 1 shows the mean and range of values of the PM_2.5, PM₁₀ and black carbon mass concentrations for the five cities. The mean values of PM_2.5 concentration in Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta sites were 18.35, 16.50, 7.74, 16.68, and 8.78 µgm⁻³, respectively, while the mean values of PM₁₀ concentration were 35.81, 41.58, 17.58, 32.05, and 20.13 µgm⁻³, respectively.

Table 1. The mean and range of PM_2.5, PM₁₀ and BC concentrations

	PM2.5 (µg.m^−3)		PM10 (µg.m^−3)			BC (µg.m^−3)
	Mean	Range	Mean	Range	PM2.5/PM10, mean	Mean	Range	BC/PM2.5, mean
Bandung	18.35	7.72–31.81	35.81	14.41–61.77	51%	3.05	1.67–4.83	18%
Jakarta	16.50	6.92–29.15	41.58	27.19–63.27	40%	3.37	2.14–4.42	22%
Palangkaraya	7.74	2.61–18.83	17.58	8.57–34.42	43%	3.19	1.42–6.04	45%
Serpong	16.68	2.31–34.14	32.05	5.88–62.81	53%	2.51	0.60–4.38	17%
Yogyakarta	8.78	3.93–15.33	20.13	7.21–52.50	48%	2.20	1.00–3.64	26%

The mass concentrations of PM_2.5 and PM₁₀ at the five sites are compared in Figure 2 and 3. The box represents 25 to 75% of the value. The horizontal bar in the box indicates the median and the plus symbol (+) denotes the mean data. The points lying outside the range defined by the whiskers are plotted as outlier dots. It can be seen that the annual averages of PM_2.5 mass in Bandung, Jakarta, and Serpong during the collection periods were higher than the Indonesian ambient air quality standard (15 µg/m³) (Government Regulation, 1999) and the U.S. Environmental Protection Agency-recommended standard, which is also set at 12 µg/m³, while in Yogyakarta and Palangka Raya sites, the values were lower than the standard. The concentration distributions of PM_2.5 in 14 countries in the Asian region during 2002–2005 also indicate that the air quality in many urban areas fail to meet the standards (Hopke et al., 2008). The PM_2.5 concentrations for Bandung and Jakarta are higher compared with Yogyakarta, which indicated that Bandung and Jakarta are more polluted than Yogyakarta. The PM₁₀ concentrations in Bandung, Jakarta, and Serpong sites were also higher than for Yogyakarta and Palangka Raya. It should be noted that the numbers of industrial activities in Yogyakarta and Palangka Raya were less than in Jakarta, Bandung, and Serpong. The rapid growth of industry, population, and motor vehicle usage in Bandung, Jakarta, and Serpong has strongly affected the city's environmental quality. The imbalance between the number of motor vehicles and available roads has created traffic problems in almost every section of these cities, and has caused the air quality deterioration.

Box and whisker plot of the distribution of PM_2.5.

Box and whisker plot of the distribution of PM₁₀.

The average concentrations of BC in Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta were 3.05, 3.37, 3.19, 2.51, and 2.20 μg/m³, respectively, while the average percentages of BC in PM_2.5 concentration at these sampling sites were 18, 22, 45, 17, and 26%, respectively. These concentrations are operationally defined based on the amount of reflected light that is absorbed by the filter sample and an assumed mass absorption coefficient (7 m²/g, with exposed area 12.57 cm²) to convert reflectance measurement to micrograms per cubic meter. A linear response of absorption (BC) against elemental carbon (EC) even in high concentrations is still obtained (Salako et al., 2012). The average BC concentrations at these sites were lower than other sites in Asian countries, such as Bangladesh, Philippines, and Sri Lanka (Hopke et al., 2008). The concentrations of BC from the same sites in Bandung in the period of 2002–2005 were reported by Hopke et al. (2008). BC sources in Bandung have been studied previously by Santoso et al. (2008) and showed that the important BC source was biomass burning. In Serpong, Santoso et al. (2011) showed that BC originates from diesel vehicles and biomass burning mixed with road dust. For Jakarta, the BC sources were attributed to motor vehicles since the sampling site in Jakarta was located near one of the busiest arterial roads in Jakarta. For Yogyakarta, the contributions of the various sources to BC concentrations are poorly known and further study related source apportionment and source identification is needed.

Figure 4 shows that the concentrations of BC at these sampling sites are in a similar range of values, except for Palangka Raya where a high concentration of BC was observed. The maximum BC concentration and percentage of BC in PM_2.5 in Palangka Raya were 6.04 μg/m³ and 75%, respectively. The BC concentration in Palangka Raya was higher than in the other cities due to forest fires during the dry season of the sampling periods. During August to November 2011, thick haze from forest fires blanketed much of Borneo, affecting major cities like Palangka Raya ( Jakarta Globe, 2012). Studies have shown that the “blackness” of the deposit depends on location with respect to the distance to traffic and the sources of particles (Jeong et al., 2004).

Box and whisker plot of the distribution of black carbon.

Conclusion

This study has quantified the PM_2.5, PM₁₀, and black carbon concentration at five cities in Indonesia during 2011. The mean PM_2.5 mass concentration ranged from 7.74 to 18.35 μg/m³. The annual averages of PM_2.5 mass in Bandung, Jakarta, and Serpong during the collection periods were higher than the Indonesian ambient air quality standard. The average percentage of BC in PM_2.5 concentration in these sampling sites ranged from 17 to 45%. The maximum BC concentration in Palangka Raya was higher than in the other cities, due to forest fires.

Acknowledgment

The authors extend their thanks to all the staff members in Radiometry Analytical Techniques group in BATAN Bandung and PUSARPEDAL Environmental Management Center, Ministry of Environment for their technical assistance. This work is financially supported by National Nuclear Energy Agency of Indonesia (BATAN) and the International Atomic Energy Agency.