Soil and biomass mercury emissions during a prescribed fire in the Amazonian rain forest

Mercury stored in forests can be volatilized to the atmosphere during fires. Many factors influence this process such as mercury concentration, vegetation loading and the soil temperature reached during the fire. We quantified mercury emissions from biomass and soil during a prescribed fire in Brazil using the difference in mercury burden in vegetation and soil before and after burning, and data were critically compared with those previously obtained in a similar experiment in another part of the Amazonia. The calculated mercury emission factor was 4.1 ± 1.4 g Hg ha−1, with the main part (78%) originating from litterfall and O-horizon, and only 14% associated with live biomass. When considering the fuel burned loading, the emission factor ranged from 40 to 53 μg Hg kg−1. Data were also obtained on soil temperature profile and on Hg speciation in soil in an effort to relate these parameters to Hg emissions.