Emissions of mercury vapor from tree bark

Measurements of the rate of elemental Hg vapor (Hg°) emissions from the bark of red maple (Acer rubrum L.), yellow-poplar (Liriodendron tulipifera L.), chestnut oak (Quercus prinus L.) and white oak (Quercus alba L.) were conducted in a controlled laboratory chamber with a mean air Hg° concentration of 1.6 ng m−3. Measured Hg° emissions for the four bark species studied ranged from a maximum of 10.8 ng m−2 h−1 for white oak to a minimum of 1.2 ng m−2 h−1 for red maple. Chestnut oak, yellow-poplar, and red maple bark all had similar Hg° emission rates with a mean of 1.9 ng m−2 h−1, but the mean emission rates from white oak were up to five times greater. This discrepancy was correlated with higher rates of evaporation from the white oak bark samples. When compared to published values of Hg° emissions from foliage and soils, it was concluded that bark surfaces would contribute less than 10% of all Hg° emissions from a forest landscape.