A twenty-year deposition record of elemental carbon in Northern Japan retrieved from archived filters

The black carbon or elemental carbon (EC) content in ice and snow has been a concern in climate change studies, but time-series records have mostly been obtained from glacier ice-core samples in limited geographical locations, such as the Arctic or high mountains. This is the first study to present decade-long records of EC deposition measured at urban (Sapporo) and background (Rishiri Island) sites in Japan, in the mid-latitude zone of the eastern edge of the Asian continent. By using archived membrane filters from an acid rain study, we retrieved monthly EC deposition records of 1993–2012 in Sapporo and intermittent deposition data in Rishiri. Annual EC deposition showed large fluctuations, with a maximum in 2000–2001 and a minor increase in 2010–2011. This interannual change was moderately related to the deposition of non-sea salt SO(4)(2−) and the collected water volume but did not reflect the estimated emission history of China. High depositions in 2000–2001 were probably caused by the transport of Asian Dust accompanied by air pollutants, which were characteristically active in these years. The findings of this study have implications for the use of observational data in validating global aerosol transport models.