Emissions of black carbon in East Asia estimated from observations at a remote site in the East China Sea

Abstract

[1] East Asia, including China, is the largest source of anthropogenic black carbon (BC). In estimating the BC emissions from this region, it is advantageous to use BC mass concentrations measured at remote locations on the ocean appropriately distant from the large sources because of spatially uniform distributions through mixing during transport. We made continuous measurements of the BC mass concentration with an accuracy of about 10% at Cape Hedo on Okinawa Island, Japan, in the East China Sea, from February 2008 to May 2009, simultaneously with carbon monoxide (CO). The seasonal median BC concentrations at Hedo were highest (0.23–0.31 μg m−3 at standard temperature and pressure) in winter and spring when plumes from China, predominantly northern China north of 33°N, were often transported to the site. A three-dimensional chemical transport model is used to calculate the mass concentration of BC using the annual mean emission inventory of Zhang et al. (2009) for the base year 2006. The model results and the observed BC-CO correlation are used to exclude the BC data substantially influenced by wet deposition. The calculated BC mass concentrations agree with those observed to within about 30% in air strongly affected by emissions in China for winter and spring on average. We estimate the annually averaged BC emission flux over the whole of China to be 1.92 Tg yr−1 with an uncertainty of about 40%. This value is very close to the value of 1.81 Tg yr−1 estimated by Zhang et al. (2009). The overall uncertainty of 40% of the present estimate is a substantial improvement in the uncertainty (208%) of the bottom-up inventory.