Temporal Variation of Mass Absorption Efficiency of Black Carbon at Urban and Suburban Locations

Abstract

The mass absorption efficiency (MAE) of black carbon (BC) was measured for the ambient aerosols in urban and suburban areas and exhaust plumes from motor vehicles from September 2010 to September 2011 in Xiamen, China. Ambient aerosols, collected on quartz fiber filters, were analyzed for BC loadings using an OC/EC Carbon Aerosol Analyzer and measured for optical attenuations with a laser/LED transmissometer. The MAE of BC in Xiamen shows a large temporal and spatial variability, varying from 0.47 to 5.15 m 2 /g. In the same month (May 2011), the average MAE of BC in suburban area (0.50 m 2 /g) was one third that in urban area (1.50 m 2 /g), suggesting that the variance of MAE was related to the specific emission sources of BC. Here we report the large variation in MAE of BC measured during different sampling times and for different sources in Xiamen. The average MAE was 1.69 m 2 /g and the coefficient of variance was 52%. Factors contributing to the variability were also discussed, as well as the uncertainties caused by different carbon analysis methods, working wavelengths for optical attenuation measurements, and relative humidity when measuring the optical attenuation of the aerosol filters. The results suggest that if a constant value of MAE within the range of 0.47-5.15 m 2 /g is used to quantify the BC concentration, then this would bias the results with a maximum factor of 11. Site-specific values of MAE are recommended for long-term stationary monitoring of ambient BC in air quality monitoring stations.

Seasonal Variation of Mass Absorption Efficiency of Elemental Carbon in the Four Major Emission Areas in China

“…Factors contributing to the uncertainty of MAE EC measurement were investigated in our previous work (Wang et al, 2013). The results showed that measurement uncertainty of MAE EC using an 880 nm LED transmissometer and a Semi-Continuous OC/EC Carbon Aerosol Analyzer (Sunset Laboratory Inc.) was 6.9%.…”

“…Statistics of MAE EC were then obtained using MAE EC for each data point. Details of the determination of MAE EC can be found in our previous work (Wang et al, 2013).…”

“…Lan et al (2013) reported a MAE EC with 6.5 ± 0.5 m 2 /g at 532 nm in South China. According to a study conducted in Xiamen, MAE EC in suburban areas was only one third of that in urban areas (Wang et al, 2013). In Beijing, the MAE EC measured at the wavelength of 632 nm was 8.45 ± 1.71 m 2 /g and 9.41 ± 1.92 m 2 /g during winter and summer respectively (Cheng et al, 2011).…”

The spatio-temporal evolution of black carbon in the North-West European ‘air pollution hotspot’

“…Residential biomass burning, another contributor in urban areas, has also been targeted with schemes such as the Clean Air Strategy in the UK (DEFRA, 2019) and the EPA's New Source Performance Standards for residential wood heaters as part of the Clean Air Act in the US (EPA, 2020). Owing to the emerging evidence of BC as pollutant of concern here have been a number of short-term studies investigating the role of BC in the Earth's atmosphere and its impact on air quality across the world including in Europe (Becerril-Valle et al, 2017;Reche et al, 2011), Asia (Chen et al, 2014;Wang et al, 2013), and the Americas (Healy et al, 2017;Peralta et al, 2019;Shirmohammadi et al, 2017). However, in order to better understand its spatio-temporal evolution and to ultimately help elucidate and legislate for its impacts on the environment and on human health, it is necessary to establish integrated permanent measuring networks for the production of long-term data sets.…”