Detection of nitroaromatic compounds on coal combustion particles

Area of Science:

• Environmental Chemistry
• Toxicology
• Combustion Science

Background:

• Fly ash from fluidized bed combustion (FBC) contains potentially mutagenic compounds.
• Direct-acting mutagens in environmental samples are of significant toxicological concern.
• Polycyclic aromatic hydrocarbons (PAHs) are known combustion byproducts and can be converted to mutagens.

Purpose of the Study:

• To identify compounds responsible for direct mutagenic activity in FBC fly ash extracts.
• To investigate the role of nitroaromatic compounds and PAHs in fly ash mutagenicity.
• To explore the formation pathways of direct-acting mutagens in FBC fly ash.

Main Methods:

• Analysis of mutagenic and nonmutagenic FBC fly ash extracts using Salmonella mutagenicity assay (Ames test) with Salmonella typhimurium strain TA98.
• Detection and identification of nitro derivatives of polycyclic aromatic hydrocarbons (nitro-PAHs) using tandem triple quadrupole mass spectrometry.
• Quantification of polycyclic aromatic compounds (PACs) using gas chromatography-mass spectrometry (GC-MS).
• Chemical treatment of extracts with dinitrogen tetroxide (N2O4) to assess mutagenicity enhancement.

Main Results:

• Nitro derivatives of PAHs, identified as direct-acting mutagens, were detected in FBC fly ash extracts.
• Treatment with N2O4 significantly increased direct mutagenicity in both mutagenic (28-fold) and nonmutagenic (3200-fold) extracts.
• N2O4 treatment also increased the relative abundance of nitroaromatic compounds, correlating with increased mutagenicity.
• PACs were detected and tentatively identified, suggesting their presence as precursors.

Conclusions:

• Direct-acting mutagens in FBC fly ash extracts are likely nitroaromatic compounds.
• The formation of these mutagens appears to involve the reaction of PAHs with nitrogen oxides (NOx) present in combustion gases.
• Fly ash from FBC processes poses a potential mutagenic risk due to the presence of these reaction products.