The National Center for Atmospheric Research (NCAR) and the University of Washington conducted the study that showed that large amounts of mercury are emitted from forest fires. This new knowledge could result in increased regulation and cost impacts for anybody dealing with forest products.
Mercury in the atmosphere is a concern because it is toxic and eventually is deposited on land and water bodies, where it enters the food chain. Scientists estimate that about half of the mercury in the atmosphere comes from natural causes (erosion or other soil processes, volcanic eruptions, etc.) and half from human activity. As an example, NCAR estimates that about 25 percent of the mercury emitted in the United States each year comes from coal-fired power plants.
Since a large part of the earth is forested, a significant amount of mercury from the atmosphere is deposited onto forests. In a sense, this forestry-deposited carbon is sequestered until something happens-such as a storm-to release it again. The main mechanism causing this release is forest fires.
Laboratory tests conducted by the U.S. Forest Service burned samples of leaves and forestry litter. These tests found that nearly all the mercury contained in these materials was emitted as either gaseous or elemental mercury. Actual measurements from wildfires found higher emission levels than from the laboratory tests. One theory as to why the higher emissions occur is that soils heated by the fires are also emitting mercury.
NCAR scientists have calculated that more than 800 tons of mercury may be re-entering the atmosphere as a result of forest fires. Since this level is 19 times the mercury emitted annually from US power plants, it is extremely significant in the overall world mercury budget.
Source: http://www.bioenergyupdate.com