Evolution of mixing state of black carbon in polluted air from Tokyo

M. Shiraiwa,Y. Miyazaki,N. Takegawa,D. R. Blake,Y. Kondo,N. Moteki

doi:10.1029/2007gl029819

Abstract

The evolution of the mixing state of black carbon aerosol (BC) was investigated using a single‐particle soot photometer (SP2) in polluted air transported from Tokyo. Ground‐based measurements of aerosols and trace gases were conducted at a suburban site (Kisai) 50 km north of Tokyo during July–August 2004. The ratio of 2‐pentyl nitrate (2‐PeONO2) to n‐pentane (n‐C5H12) was used to derive the photochemical age. According to the SP2 measurement, the number fraction of thickly coated BC (Shell/Corel Ratio > ca. 2) with a core diameter of 180 nm increased at the rate of 1.9% h−1, as the photochemical clock proceeded under land‐sea breeze circulation. Positive matrix factorization was applied to investigate the time‐dependent contributions of different coating materials using the mass concentrations of sulfate, nitrate, and organics measured using an aerosol mass spectrometer. The main coating materials found in this study were sulfate and organics.

Highlights

[2] Black carbon aerosol (BC), a by-product of incomplete combustion of fossil fuels and biomass, is an important constituent among atmospheric particles
The light-absorbing property of BC can be enhanced by a factor of about 1.5 if BC is thickly coated with non-refractory compounds [Bond et al, 2006]
[3] In addition, depending on the amount of coating [Kuwata et al, 2007], coated BC particles act as cloud condensation nuclei (CCN), thereby leading to more efficient removal of BC by wet deposition

Summary

[1] The evolution of the mixing state of black carbon aerosol (BC) was investigated using a single-particle soot photometer (SP2) in polluted air transported from Tokyo. Ground-based measurements of aerosols and trace gases were conducted at a suburban site (Kisai) 50 km north of Tokyo during July – August 2004. The ratio of 2-pentyl nitrate (2-PeONO2) to n-pentane (n-C5H12) was used to derive the photochemical age. According to the SP2 measurement, the number fraction of thickly coated BC Positive matrix factorization was applied to investigate the timedependent contributions of different coating materials using the mass concentrations of sulfate, nitrate, and organics measured using an aerosol mass spectrometer. R. Blake (2007), Evolution of mixing state of black carbon in polluted air from Tokyo, Geophys.

Introduction

Results and Discussion

Conclusions