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Unexpected arsenic compounds in low-rank coals
Zdenka Slejkovec1, Tjasa Kanduc
1"Josef Stefan" Institute, Jamova 39, 1000 Ljubljana, Slovenia. zdenka.slejkovec@ijs.si
Environmental Science & Technology
|June 15, 2005
Summary
Low-rank coals contain arsenic compounds, with varying organic and inorganic forms found across Slovenian and Czech basins. Biogeochemical processes likely influence arsenic speciation in these coals.
Area of Science:
- Geochemistry
- Environmental Science
- Coal Science
Background:
- Low-rank coals can contain significant concentrations of arsenic.
- Understanding arsenic speciation in coals is crucial for environmental risk assessment and resource management.
Purpose of the Study:
- To analyze the elemental composition and arsenic speciation in low-rank coal samples from Slovenia and the Czech Republic.
- To investigate the factors influencing arsenic distribution and speciation in different coal basins.
Main Methods:
- Elemental analysis of coal samples.
- Extraction of arsenic compounds using a methanol/water mixture.
- Identification and quantification of different arsenic species (e.g., tetramethylarsonium ion, arsenate, monomethyl arsonic acid).
Main Results:
- Total arsenic concentrations varied significantly, with one sample from the Sokolov basin showing exceptionally high levels (142 microg g(-1)).
- Methanol/water extraction efficiency differed between basins, with higher yields from Velenje basin samples.
- Velenje basin extracts were rich in organic arsenic (tetramethylarsonium ion) and arsenate, while Sokolov and Trbovlje basin extracts were dominated by inorganic arsenic (arsenate).
Conclusions:
- Biogeochemical degradation of organic matter is a probable source of organoarsenic compounds in low-rank coals.
- Abiogenic synthesis under high temperature and pressure conditions cannot be ruled out as a contributing factor to arsenic speciation.