Size distributions of elemental carbon and its contribution to light extinction in urban and rural locations in the pearl river delta region, China

Abstract

Abstract. Elemental carbon (EC) in size-segregated aerosol samples were determined at five urban, one suburban, and one rural locations in the Pearl River Delta region in South China during 2006-2008 period. The size modal characteristics of EC were different at the urban and suburban/rural locations. The urban EC had a dominant condensation mode with a mass median aerodynamic diameter (MMAD) in the 0.36-0.43 µm range and a slightly less abundant mode in the droplet mode size (MMAD: 0.8-1.1 µm), while the suburban/rural EC had a prominent mode in the droplet mode size (MMAD: 0.7-1.1 µm) and a minor condensation mode (MMAD: 0.22-0.33 µm). Calculations using Mie theory and the measured size distributions of EC, organic carbon, and major inorganic ions indicate that EC-containing particles contributed 76±20% of the observed light extinction at the urban sites. Among the EC-containing particles, EC mass alone contributed 21±11% of the observed light extinction while non-EC materials on the EC particles (i.e., organic matter, ammonium sulfate, and water) contributed 55±15%. At the suburban/rural locations, EC-containing particles contributed 37-48% of the measured light extinction, with EC mass contributing 4-10% and non-EC coating materials contributing the remaining light extinction. Our results suggest that EC-containing particles were important to the overall light extinction in the urban atmospheres due to their more abundant presence from vehicular emissions. The ECcontaining particles in the suburban/rural locations had a reduced but still significant contribution to light extinction budget.

Variation of secondary coatings associated with elemental carbon by single particle analysis

“…Previous studies demonstrated an important role of EC in atmospheric light extinction in the PRD region (e.g., Yu et al, 2010). However, the aerosol measurements of EC in China reported so far have been primarily based on bulk techniques (Wu et al, 2012) that could not provide sufficient information on compositions of EC-containing particles, including the coating materials at single particle level.…”

“…Study in this region also revealed that urban EC had a dominant condensation mode and a less abundant droplet mode, while the suburban/rural EC had a prominent mode in the droplet mode, due to the growth of smaller particles when the air mass moved from the urban source regions to the suburban/rural site (Yu et al, 2010). In Paris, Healy et al (2012) showed that EC in the droplet mode, Fig.…”

Quantifying black carbon light absorption enhancement with a novel statistical approach

“…Considering that the LII technique is specific to BC mass determination which is independent of BC mixing state, the size distribution reported using LII is able to represent the size distribution of the BC core. A study using a micro-orifice uniform deposit impactor (MOUDI) found a EC mass size distribution in the PRD exhibiting three modes peaking at ∼ 300, ∼ 900 and ∼ 5000 nm (Yu et al, 2010), implying a substantial coating of BC particles, and a diameter amplification of 3. BC sizing from LII is based on volume-equivalent diameter (VED), while MOUDI is based on aerodynamic diameter.…”

The single-particle mixing state and cloud scavenging of black carbon: a case study at a high-altitude mountain site in southern China

“…S9). A detailed discussion on the comparison of these two measurements can be found in the Supplement (Yu et al, 2010;Huang et al, 2011Huang et al, , 2012. The size-resolved scavenged/activated fractions (Nf scav ) of the BC-containing particles and all the detected particles were further investigated as a function of their size (Fig.…”