An integrated analytical approach has been used to determine the mode of oc
currence of arsenic in samples of four widely used US coals: the Pittsburgh
, Illinois #6, Elkhorn/Hazard, and Wyodak. Results from selective leaching,
X-ray absorption fine structure (XAFS) spectroscopy, and electron micropro
be analysis show that pyrite is the principal source of arsenic in the thre
e bituminous coals, but the concentration of As in pyrite varies widely. Th
e Wyodak sample contains very little pyrite; its arsenic appears to be prim
arily associated with organics, as As3+, or as arsenate. Significant (10-40
%) fractions of arsenate, derived from pyrite oxidation, are also present i
n the three bituminous coal samples. This information is essential in devel
oping predictive models for arsenic behavior during coal combustion and in
other environmental settings. Published by Elsevier Science B.V.