First hit for why does coal have mercurychromeinstantrlz 1 C 1 GGGEUS 547 US 547 ion 1 espv 2 ieUTF 8 # qwhy % 20 does % 20 coal % 20 have % 20 mercuryMERCURY IN COAL WHERE DOES IT COME FROM ? Mercury released from coal during burning for energy production has become an issue of significant concern worldwide . Mercury is a natural component of coal that is released to the flue gas during combustion . Plant species that make up coal have varied over geologic time however , dominant species were vascular plants with some structure that functioned similarly to leaves of today with stomata for gas exchange . Based on our work with present day species it is hypothesized that mercury present in coal was derived by plant assimilation from the atmosphere . This paper summarizes mercury concentrations measured in forest , wetland , desert , and grassland plant species as a function of air and soil mercury exposures and time . Foliage of plants exposed to air mercury concentrations representative of ambient conditions today and low mercury containing soils background exhibited values ranging from 0 . 02 to 0 . 2 ppm based on dry weight . These are within the range reported for coal in the COALQUAL database 0 . 17 0 . 17 ppm . Foliar mercury concentrations were found to vary as function of plant species with deciduous species tending to accumulate more than others . Foliage of plants sampled in the field exhibited lower mercury concentrations than those used in laboratory experiments most likely due to the lower air exposure concentrations over time . At ambient exposure conditions we cannot be certain of the proportion of mercury derived from the soil versus the atmosphere however , based on data derived using multiple soil and air mercury treatments , plant foliage mercury concentrations were more statistically significantly influenced by air concentrations than by soil concentrations . Measurement of the flux of elemental mercury between foliage and the atmosphere for a variety of plant species demonstrated that at low air and soil mercury exposures comparable to ambient conditions exchange consisted of both deposition and emission 3 to 3 ng m 2 h 1 . Deposition of Hg from the atmosphere to plant foliage dominated for grassland , wetland and coniferous species .