• Modes of occurrence
• Behaviour during combustion 
• Analytical methods 

Trace elements in coals may be associated with specific minerals or with organic 'coaly' matter.

The sources of trace elements include biological material (plants, algae and bacteria) that is the precursor of the coaly material, water in the peat swamp and mineralogical material washed or blown into the swamp.

Table representation of uranium in Australian export coals, other internationally traded coals, the Earth's crust and shales.

Concentration of uranium in:	mg/kg
Australian export coals	0.3 - 2.5 (0.9) #
Other internationally traded coals	<0.1 - 7.0 (1.3) #
Earth's crust	2.7
Earth's shales	4.0
# values in parentheses are averages

Uranium has been identified as a Hazardous Air Pollutant (HAP) by environmental authorities.

Modes of occurrence

Uranium is associated with clays, zircon and phosphates and may also be organically bound in coal.

Behaviour during combustion

Uranium exhibits some volatility during combustion. It is slightly enriched on the finer ash particles.

Analytical methods

There are a number of standard methods for determining uranium in coal.

AS 1038.10.0, Australian Standard, Coal and coke - Analysis and testing - Part 10.0: Determination of trace elements – Guide to the determination of trace elements.

ASTM D6357-00a Test Methods for Determination of Trace Elements in Coal, Coke, & Combustion Residues from Coal Utilization Processes by Inductively Coupled Plasma Atomic Emission, Inductively Coupled Plasma Mass, & Graphite Furnace Atomic Absorption Spectrometries.

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