• Aromatic Polycyclic Hydrocarbons (PAH)

PAHs result from the coal-tar pitch used for manufacturing anodes. When the anode is pre-baked, as in new technologies, PAH emissions are negligible. The anodes are baked in special dedicated furnaces, equipped with emissions treatment systems. In the Söderberg potrooms, however, the anodes bake during electrolysis in the potrooms. HAP emissions not captured in the scrubbers escape through the vents.

 

 


 

The older technology Söderberg potlines at the Baie-Comeau Smelter were retired in 2013. As a result, Alcoa’s PAH emissions in Québec decreased by 90% overall and by 99% in Baie-Comeau. PAH data is not published here due to the low emission rate.

 

Despite the closure of the Söderberg potlines, monitoring of benzo(a)pyrene (BaP) levels in the City of Baie-Comeau continued in 2015. BaP, a member of the PAH family which is used as an environmental indicator, is measured at three sampling stations located on Bienville Avenue, Bouchette Street and Denonville Street.
 
A significant decrease in PAH has been observed at all stations since the closure of the Söderberg potlines in September 2013.