Does Prescribed Burning in Southern Forests Release Significant Amounts of Mercury to the Atmosphere?

Mercury (Hg) emissions from prescribed fire present a potential impact on air quality that could motivate regulators to further restrict prescribed burning. Atmospheric deposition of Hg (originating from industrial sources) to forests is well documented, and the prescribed burning of two to four million acres per year in the South recycles an unknown (but potentially significant) amount of Hg into the atmosphere and surface waters by volatilization and post-fire runoff. This and other environmental concerns present a significant challenge to local land managers who use prescribed fire. Our objectives were (1) to estimate local and South-wide emission of Hg due to prescribed fire, and (2) to test the hypothesis that Hg in ashen fire debris is leached into and subsequently retained in mineral soil. Increased retention of Hg in mineral soils as a result of fire may mitigate the environmental impact of fire-related emissions because Hg volatilization during future fires would be reduced and the retained Hg would be less likely to enter surface waters as runoff. We estimated emissions by measuring Hg amounts in the forest floor and surface mineral soil soon before and immediately after individual prescribed fires. We assessed the influence of fire on Hg storage in mineral soil by determining Hg in the mineral soil and forest floor of paired areas that have been managed with or without prescribed fires for many years