Mercury Emission from Prescribed Open Grassland Burning in the Aso Region, Japan

Abstract

In every Spring, prescribed grassland burning, so-called Noyaki in Japanese, has been conducted for over a 1000 years by local residents in the Aso region, Japan, for the purpose of grassland conservation because Noyaki prevents invasion of woody plants in the grassland and helps the growth of grasses, which were an important resource of primary industry for roofing materials of houses and livestock feed. Meanwhile, biomass burning is known to be one of the most significant sources of airborne substances including mercury. Taking advantage of the characteristics and resources of the place we live in, we here describe our on-going study for the emission of gaseous mercury from the traditional Noyaki in the Aso region and other grasslands of western Japan. During Noyaki, we sampled and measured gaseous mercury from the Noyaki plumes to better understand mercury emissions and cycles in the local environment. Results showed, on average, 3.8 times higher atmospheric mercury concentrations, demonstrating the emission of gaseous mercury from the Noyaki. The possible origins, novel information the results inferred, and future research direction are discussed in this chapter.