About the 10% of global mercury (Hg) emissions to the atmosphere are due to biomass burning during a wildfire. We calculated the release of Hg by a hypothetical wildfire at two sites (Abbadia San Salvatore, ABS and Vivo d’Orcia, VO) in the Monte Amiata Mining District (MAMD), southern Tuscany (Italy), where past Hg mining affects local Hg concentrations. The two sites are locatedat 1.5 km (ABS) and 3 km (VO) from the mining area. The biomass components of black pine (Pinus nigra Arn.) and chestnut (Castanea sativa Mill), among the most frequent species in the MAMD, were sampled in a woodland area of 630 m2 (VO) and 1066 m2 (ABS). Bark (n=25), wood (n=18), and pine needle (n=3) were collected in February 2020. Chestnut leaves were not collected due to winter sampling. At each site, topsoils (= litterfall, first 7 cm) and subsoils (715 cm) were collected below the trees (n=22). Hg was measured by means of a direct Hg analyzer (DMA). We quantified: i) the Hg content in plant biomass and soil; ii) the involved biomass at each site (allometric equations); iii) the mass of Hg stored in each site. To estimate Hg emissions during a hypothetical wildfire we assumed that: i) barks and needles release 100% Hg (complete burning); ii) only 20% of wood is combusted; ii) topsoil burning releases 100% of Hg; iii) subsoil does not contribute to Hg emissions. At both sites, Hg concentrations vary in the order soil>bark>needles>wood and were higher in pine trees. The calculated Hg storages (tree components + soil) are 1375 g/ha at ABS and 321 g/ha at VO. The topsoil is the major reservoir for Hg (>90-95%). Among biomass, wood is the major reservoir (56%) followed by barks (42%), and lastly needle (2%). These findings should be included in the implementation of existing fire management and prevention activities. Climate change scenario, with the increasing occurrence of wildfires might result in spikes of Hg concentrations in the atmosphere, possibly near to human sensitive sites.
The potential mercury remobilization from soil and biomass in the Mt. Amiata mining district (Italy) during a wildfire
Silvia Fornasaro
Primo
;
2022-01-01
Abstract
About the 10% of global mercury (Hg) emissions to the atmosphere are due to biomass burning during a wildfire. We calculated the release of Hg by a hypothetical wildfire at two sites (Abbadia San Salvatore, ABS and Vivo d’Orcia, VO) in the Monte Amiata Mining District (MAMD), southern Tuscany (Italy), where past Hg mining affects local Hg concentrations. The two sites are locatedat 1.5 km (ABS) and 3 km (VO) from the mining area. The biomass components of black pine (Pinus nigra Arn.) and chestnut (Castanea sativa Mill), among the most frequent species in the MAMD, were sampled in a woodland area of 630 m2 (VO) and 1066 m2 (ABS). Bark (n=25), wood (n=18), and pine needle (n=3) were collected in February 2020. Chestnut leaves were not collected due to winter sampling. At each site, topsoils (= litterfall, first 7 cm) and subsoils (715 cm) were collected below the trees (n=22). Hg was measured by means of a direct Hg analyzer (DMA). We quantified: i) the Hg content in plant biomass and soil; ii) the involved biomass at each site (allometric equations); iii) the mass of Hg stored in each site. To estimate Hg emissions during a hypothetical wildfire we assumed that: i) barks and needles release 100% Hg (complete burning); ii) only 20% of wood is combusted; ii) topsoil burning releases 100% of Hg; iii) subsoil does not contribute to Hg emissions. At both sites, Hg concentrations vary in the order soil>bark>needles>wood and were higher in pine trees. The calculated Hg storages (tree components + soil) are 1375 g/ha at ABS and 321 g/ha at VO. The topsoil is the major reservoir for Hg (>90-95%). Among biomass, wood is the major reservoir (56%) followed by barks (42%), and lastly needle (2%). These findings should be included in the implementation of existing fire management and prevention activities. Climate change scenario, with the increasing occurrence of wildfires might result in spikes of Hg concentrations in the atmosphere, possibly near to human sensitive sites.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
