Streets, D.G., Z. Lu, L. Levin, A.F.H. ter Schure, and E.M. Sunderland.
Science of the Total Environment 615:131-140(2018)

Coal combustion is one of the largest contemporary sources of anthropogenic mercury (Hg). It releases geologically sequestered Hg to the atmosphere, and fly ash can contaminate terrestrial and aquatic systems. Coal combustion released an estimated cumulative total of 38.0 (14.8-98.9, 80% C.I.) Gg (gigagrams, 10⁹ g or a thousand tonnes) of Hg to air, land, and water up to the year 2010, most of which (97%) occurred after 1850. The rate of release has grown by two orders of magnitude, from 0.01 Gg/yr in 1850 to 1 Gg/yr in 2010. Geographically, Asia and Europe each account for 32% of cumulative Hg releases and an additional 18% is from North America. About 26.3 (10.2-68.3) Gg or 71% of the total was emitted directly to the atmosphere, mostly from the industrial (45%) and power generation (36%) sectors, while the remainder was disposed of to land and water bodies. While Europe and North America were the major contributing regions until 1950, Asia has surpassed both in recent decades. By 2010, Asia was responsible for 69% of the total releases of Hg from coal combustion to the environment. Control technologies installed on major emitting sources capture mainly particulate and divalent Hg; hence, the fraction of elemental Hg in emissions from coal combustion has increased over time from 0.46 in 1850 to 0.61 in 2010. About 11.8 Gg of Hg or 31% of the total has been transferred to land and water bodies through disposal or utilization of Hg-containing combustion waste and collected fly ash/flue-gas desulfurization sludge; ~8.8 Gg of this Hg has simply been discarded to waste piles or ash ponds or rivers.