Sunday, 06 January 2013

Accurate measurement of VOCs in atmosphere developed

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KwFreeway perthVOCs are hydrocarbons defined by a sufficient vapour pressure to enter the atmosphere and can be emitted through transportation, industry burning, microbial production and plant emissions. Image: Scott Davies AN ANALYSIS of volatile organic compounds (VOCs) in Perth’s atmosphere by scientists from Curtin University has revealed a reliable method of determining the sources of VOCs.

The researchers investigated carbon and hydrogen isotope values of VOCs in various emission sources using a recently developed method involving thermal desorption, gas chromatography and isotope ratio mass spectrometry.

They then compared the results against those taken from the emissions of one of Alcoa Australia’s local aluminium refineries because their sources of organics are different and could therefore act as an emissions fingerprint.

VOCs are hydrocarbons defined by a sufficient vapour pressure to enter the atmosphere and can be emitted through transportation, industry burning, microbial production and plant emissions. 

Curtin University WA-Organic and Isotope Geochemistry Centre director Kliti Grice says the study was meant to establish if 13C/12C (heavy/light carbon ratios) and D/H ratios (natural abundance ratios) of complex mixtures of VOCS can be reliably measured using the thermal desorption technique.

“The paper focuses on the actual values of VOCs emitted from direct source points—diesel sources, combustion of the different vegetation types C3 versus C4 plants, and emissions from an industrial source,” she says.

Professor Grice says the sources of VOCs could be reliably determined by using the thermal desorption method on the emission samples taken.

Existing literature in the field involved research which investigated stable carbon isotopic composition of VOC’s in emissions compared to only a few results on stable hydrogen isotopes.

The study says this was in spite of other research which highlighted that differences between carbon values of VOC’s in an industry emission compared to those from a car exhaust were negligible.

It says a previous dual isotope approach of carbon and hydrogen had effectively distinguished the sources of higher molecular organic compounds and could be a promising tool for establishing VOC sources.

The idea of identifying atmospheric VOCs on a dual stable isotope approach (with hydrogen and carbon) was developed by Curtin PhD student Christiane Vitzthum von Eckstaedt, who was supervised by Professor Grice.

Professor Grice says they are now searching for a researcher to build on their method.

“We are looking at the effects of the combustion of different plant types and their residues to trace back during large burning events or major increases in CO2 where plants would have been subjected to high temperatures and heat stress,” she says.

“These would be associated with some of the largest extinction events on our planet.”

The study also suggests extending the range of emission sources to different car models, other industry fields and bush or forest fires to substantiate the findings.

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