FINGERPRINTING BAYER REFINERY AIR EMISSIONS USING δ13C COMPOSITIONS OF SELECTED VOCS BY COMPOUND SPECIFIC ISOTOPE ANALYSIS (CSIA)

Determining the contribution of alumina Bayer refining to VOCs in ambient air is complex mainly due to the fact that many of the organic compounds are ubiquitous. Organic molecules from different sources have been differentiated in solid and liquid samples using the stable carbon isotope compositions (δ¹³C). This has been particularly useful for petroleum samples when traditional petroleum biomarkers have been unsuccessful at determining the source of hydrocarbons.

The current work describes the use of a novel method to measure the δ¹³C compositions of VOCs in an alumina refinery stack and a car exhaust gas sample for the first time. The method involves using a sorbent tube trap and then analysing by direct thermal desorption/CSIA. The δ¹³C values of several VOCs in an Alcoa World Alumina refinery calciner stack and a car exhaust air samples were measured and showed that the δ¹³C of several common organic compounds (e.g. benzene and toluene) in the two sample types were similar. Interestingly the isotopic ratios of other compounds (e.g. Ethylhexanol) in the refinery stack were significantly different to the other VOCs and may be a useful marker.