Mercury emissions from forest burning in southern Amazon

Several recent studies have indicated that forest fires are likely to re-emit important quantities of atmospherically deposited mercury (Hg) to the atmosphere. Although the Amazon forest accounts for approximately 25% of the world's total rainforest, few data are available about these emissions. The emissions of mercury from prescribed fires of two 4-ha plots of Amazon forest were investigated. Hg concentration and Hg burden were determined for vegetation, litter and soil before and after the fires. The data show that only Hg present in the aboveground vegetation and in the O-horizon was volatilised; no significant soil emission was observed. Before the fire, the Hg stored in the vegetation (logs, branches, leaves and litter) ranged from 3.7 to 4.0 g ha(-1) while 1.8 g ha(-1) was found in the O-horizon. The mass balance calculations of the present work indicate an average Hg emission of 3.5 g ha(-1) due to forest fires, with 1.6 ha(-1) originating from O-horizon and 1.9 from above ground vegetation. On the base of the average annual deforestation rate of the Brazilian Amazon between 2000 and 2008, an annual Hg emission of 6.7 Mg yr(-1) was estimated. Citation: Michelazzo, P. A. M., A. H. Fostier, G. Magarelli, J. C. Santos, and J. A. d. Carvalho Jr. (2010), Mercury emissions from forest burning in southern Amazon, Geophys. Res. Lett., 37, L09809, doi: 10.1029/2009GL042220. (AU)