Thermal stability of inorganic and organic compounds in atmospheric particulate matter

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• 作者：Cinzia Perrino^a ; ^{perrino@iia.cnr.it} ; Elisabetta Marconi^b ; Luca Tofful^a ; Carmela Farao^b ; Stefano Materazzi^b ; Silvia Canepari^b ; ^{silvia.canepari@uniroma1.it}
• 关键词：Atmospheric particulate matter ; Thermogravimetric analysis ; Ammonium salts ; Thermo-optical analysis ; Water ; Sampling artefact
• 刊名：Atmospheric Environment
• 出版年：2012
• 期刊代码：11_13522310
• 类别：env
• 出版时间：July, 2012
• 卷：54
• 期：Complete
• 页码：36-43
• 文件大小：792 K

摘要

The thermal behaviour of atmospheric particulate matter (PM) has been investigated by using different analytical approaches to explore the added value offered by these technique in environmental studies. The thermogravimetric analysis (TGA), carried out on both certified material and real PM samples, has shown that several mass losses can be detected starting from 80聽掳C up to above 500聽掳C, when pyrolysis occur.

Thermo-optical analysis of PM and ion chromatographic analysis of the residual have shown that the mass losses in the temperature range 80-180聽掳C are not justified by the release of either organic or inorganic compounds; it can be thus attributed to the release of weakly and strongly bound water. Release of water has also been evidenced in the temperature range 225-275聽掳C.

The release of ammonium chloride and nitrate has been detected only above 80聽掳C. This indicates that the release of nitric acid, hydrochloric acid and ammonia, which is observed downstream of the filters during the sampling of atmospheric PM at ambient temperature, cannot be reproduced off-line, after the end of the sampling. We successfully explored one of the possible explanations, that is the desorption of HNO₃, HCl and NH₃ adsorbed on collected particles.

NH₄NO₃ and NH₄Cl, which can be thermally released by the filter, exhibit a different thermal behaviour from NaNO₃ and NaCl, which are thermally stable up to 370聽掳C. This different behaviour can be used to discriminate between natural and secondary sources of atmospheric inorganic salts, as the interconversion that is observed when heating mixtures of pure salts resulted to be not relevant when heating real PM samples.