Fleischer (1970) compiled literature values for Hg in crustal rocks, worldwide. Average values
for mafic igneous rocks ranged from 0.001 to 0.240 mg/kg, whereas for silicic igneous rock,
averages ranged from 0.005 to 0.190 mg/kg, except for igneous rocks from the Crimea and
Donets Basin, where the average Hg contents ranged from 0.250 to 17.6 mg/kg. Average Hg
contents of sandstones and limestones ranged from 0.018 to 5.70 mg/kg, and in shales from
0.05 to 2.3 mg/kg, with the higher contents typically found in the Russian shales. In metamor‐
phic rocks, contents ranged from 0.060 to 2.50 mg/kg.
Many of the widely used sources of coal contain high concentrations of Hg; these include from
China (Pirrone et al., 2010), Ukraine (Kolker et al., 2009), and Texas, USA (Tewalt et al., 2001).
Coal burning is a major source of Hg release into the atmosphere (Wang et al., 2004); but
potential effects on groundwater are mostly unknown. The Hg content of coals ranges from
0.01 to 1.85 mg/kg, with the highest content found in some Chinese coals (Pirrone et al., 2010
and references therein). Much of the Hg in coals is in associated pyrites, with contents that can
be 10 mg/kg or greater (Yudovich & Ketris, 2005). Direct effects from coal seams on ground‐
water may not be obvious, however. Cravotta (2008) did not find detectable Hg concentrations
in samples of waters discharging from abandoned
coal mines in Pennsylvania, USA.
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