• Modes of occurrence
• Behaviour during combustion
• Health and environmental effects
• 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 lead in Australian export coals, other internationally traded coals, the Earth's crust and shales.

Concentration of lead in:	mg/kg
Australian export coals	2 - 14 (6) #
Other internationally traded coals	<1 - 22 (6) #
Earth's crust	12
Earth's shales	20
# values in parentheses are averages

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

Modes of occurrence

Lead is present predominantly in pyrite and other sulfide minerals in bituminous coals. Occurrences of lead selenide have been reported.

Behaviour during combustion

Lead is volatile and condenses on the fly ash particles. It is enriched in the finer particles. A small percentage of these fine particles are emitted to the atmosphere from modern power stations.

Health and environmental effects

On the spectrums:

• for the NPI health hazard of 0-3, lead and compounds registers 1.7
• for the NPI environmental of 0-3, lead and compounds registers 1.5.

Lead is generally low in coal and coal ash. There are apparently no reports of adverse health or environmental impacts from lead in coal.

Analytical methods

It is not possible to accurately determine the low concentrations of lead in most product coals using flame atomic absorption spectrometry (AAS) or inductively coupled plasma atomic emission spectrometry (ICP-AES). Analytical methods based on the use of graphite furnace atomic absorption spectrometry or inductively coupled plasma mass spectrometry are required.

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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