The Characteristics of Black Carbon of Seoul

서울의 블랙카본 특성 연구

Abstract

The concentration and coating thickness of black carbon (BC) were measured along with fine dust in the fall of 2018, at the Seoul Metropolitan Area Intensive Monitoring Station (SIMS). In fall, the concentration of $PM_{10}$ and $PM_{2.5}$ was $23{\pm}12.6{\mu}g/m^3$ and $12{\pm}5.8{\mu}g/m^3$, respectively, lower than that in other seasons. The BC level, measured using an Aethalometer, was $0.73{\pm}0.43{\mu}g/m^3$, while the levels of elemental carbon (EC) and refractory-BC (rBC), measured by semi-continuous carbon analyzer (SOCEC) and single particle soot photometer (SP2), were $0.34{\pm}0.18{\mu}g/m^3$ and $0.32{\pm}0.18{\mu}g/m^3$, respectively. As such, the concentration level differed according to the measurement method, but its time-series distribution and diurnal variation showed the same trends. The BC concentration at SIMS was primarily affected by automobiles with higher levels of BC during morning and evening commuting times due to increased traffic congestion. rBC, measured by SP2, had a peak concentration and coating thickness of 84 nm and 43 nm, respectively. Notably, the coating thickness had an inverse relationship with particle size.

2018년 가을철(9월 5일~10일, 6일간) 수도권대기오염집중측정소에서 미세먼지와 함께 블랙카본(BC, black carbon)의 농도 및 코팅두께를 파악하였다. 가을철 $PM_{10}$은 $23{\pm}12.6{\mu}g/m^3$, $PM_{2.5}$는 $12{\pm}5.8{\mu}g/m^3$으로 다른 계절보다 낮은 수준이었다. Aethalometer로 측정한 BC는 $0.73{\pm}0.43{\mu}g/m^3$, SOCEC로 측정한 EC(elemental carbon)는 $0.34{\pm}0.18{\mu}g/m^3$, SP2로 측정한 rBC(refractory-BC)는 $0.32{\pm}0.18{\mu}g/m^3$으로 측정방법에 따른 농도차이를 보여주었으나, 시계열 분포와 일 변동은 동일한 경향을 나타내었다. 수도권대기오염집중측정소에서 측정된 블랙카본은 자동차와 같은 일차오염원의 영향을 강하게 받았고, 주간과 야간의 출퇴근으로 인한 교통 혼잡 시간대에 높은 특징을 보였다. SP2로 측정한 $PM_{1.0}$ 단일입자에 대한 블랙카본의 개수농도는 84 nm에서 최고치로 관측되었으며, 코팅두께는 43 nm로 산정되었다. 특히 블랙카본 입자의 직경이 작을수록 코팅두께는 증가하였고, 입자의 직경이 증가할수록 코팅두께는 작아지는 특성을 나타내었다.

Figure 1. Image of SIMS location map (Google Earth Pro, Ver 7.3.2.5491, Aug. 2018).

Figure 2. Plot of the Wind rose of study period at SIMS.

Figure 3. Time variation of PM concentrations (left) and scatter plot (right) at SIMS.

Figure 4. Pollution rose of PM₁₀ (left) and PM_2.5 (right) at SIMS.

Figure 5. Time variation of carbon compounds (EC, BC and rBC) and its scattered plots at SIMS.

Figure 6. Pollution rose of EC (left), BC (middle) and rBC (right) at SIMS.

Figure 7. Diurnal variation of PM (PM₁₀, PM_2.5) (left) and carbon compounds (EC, BC, rBC) (right)

Figure 8. The rBC size distribution spectrum and number concentrations by SP2 at SIMS.

Figure 9. The rBC averaged size distribution (left) and coating thickness (right) at SIMS.

Table 1. Daily weather conditions during the study period at SIMS.

Table 2. Instrumentation of the BC and PM_2.5 Measurement at SIMS.

Table 3. Summary on concentrations of PM₁₀ and PM_2.5.

Table 4. Summary on the carbon compounds as EC, BC and rBC

Table 5. Summary on the PM_2.5, EC, BC and rBC in case of the rush-hour and non rush-hour