Hydrocarbons in Smoke Aerosols from Controlled Burning of Selected Tallgrass and Litterfall Samples: A Preliminary Study

Norhayati Mohd. Tahir, and Tan, Hock Sen and Marinah Ariffin, and Suhaimi Suratman, (2006) Hydrocarbons in Smoke Aerosols from Controlled Burning of Selected Tallgrass and Litterfall Samples: A Preliminary Study. Malaysian Journal of Analytical Sciences, 10 (1). pp. 121-128. ISSN 13942506

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Affiliations

Kolej Universiti Sains dan Teknologi Malaysia, Faculty of Science & Technology, Dept. of Chemical Sciences, Environmental Research Group

Abstract

A study has been carried out to characterize hydrocarbons emitted from the burning of selected tall grass and litter fall samples. The biomass samples were burned under smouldering and flaming conditions and their respective smoke particulate emitted was sampled by high volume filtration on a pre-cleaned (solvent extracted) glass fibre filters. Hydrocarbons were extracted from the filters using dichloromethane as solvent and the extracts fractionated on silica-alumina column. Detection and quantification of aliphatic hydrocarbons and PAHs compounds were carried out using GC-MS. For comparison, hydrocarbons in fresh tall grass sample were also characterized to determine differences in hydrocarbon profiles. Result indicated that the major organic component characterized from the smoke particles were straight chain aliphatic compound in the range of C18-C36, with an odd to even carbon number predominance and carbon preference index (CPI) ranging from 1.21- 2.47. On the other hand, hydrocarbons present in the fresh tall grass ranged from C25-C34 with C31 species dominating and CPI value of 10.31. In general, CPI > 1 indicates n-alkanes contribution from epitucular waxes. It could be concluded that, even though the overall signature of the source of n-alkanes is maintained, burning seems to increase the range of aliphatic hydrocarbon emitted accompanied with a decrease in the CPI values. In addition, results also indicate that burning resulted in the formation of many PAHs compounds in all the three samples with concentration ranging from 731 - 3380 μg g-1. Fresh tall grass on the hand did not exhibit any PAHs compound, which clearly indicated that PAHs were generally generated from combustion process.

ABSTRAK Satu kajian telah dijalankan bagi mencirikan sebatian hidrokarbon yang dibebaskan daripada pembakaran sampel lalang dan dedaun hutan. Sampel-sampel biojisim ini telah dibakar dibawah keadaan membara dan menyala dan zarah asap yang terhasil disampel menggunakan pensampel berisipadu tinggi diatas penapis gentian kaca. Hidrokarbon diekstark menggunakan diklorometana sebagai pelarut dan ekstrak yang diperolehi dipisahkan dengan menggunakan turus silika-alumina. Penentuan dan kuantifikasi unsur hidrokarbon alifatik dan PAHs dijalankan dengan menggunakan GC-MS. Sebagai perbandingan, hidrokarbon dari daun lalang segar yang tidak dibakar juga dikaji bagi menentukan perbezaan dalam profil hidrokarbonnya. Keputusan menunjukkan komponen organik utama yang dikelaskan dari zarah asap adalah unsur alifatik rantai lurus dalam julat of C18-C36, dengan lebih banyak karbon nombor ganjil berbanding karbon genap dan ‘carbon preference index’ (CPI) dalam julat 1.21 - 2.47. Dalam pada itu, hidrokarbon alifatik yang diperolehi dari daun lalang segar yang tidak dibakar adalah sebatian C25 hingga C34, dengan spesies C31 sebagai spesis paling dominan dan nilai CPI sebanyak 10.31. Amnya, CPI > 1 menunjukkan sumbangan n-alkana daripada lilin epitukular. Kesimpulannya, walaupun keseluruhan penanda n-alkana tidak berubah, pembakaran seakan-akan meningkatkan julat hidrokarbon alifatik yang terhasil dengan penurunan nilai CPI. Keputusan juga menunjukkan pembakaran membentuk lebih banyak unsur PAHs dalam ketiga-tiga sampel asap dengan kepekatan berjulat dari 731 - 3380 μg g-1. Daun lalang segar pula tidak mempunayai unsur PAHs dan ini jelas menunjukkan PAHs hanya terhasil dari proses pembakaran.

Item Type:

Journal

Additional Information:

Financial supports from the Department of Chemical Sciences, KUSTEM through a grant for final year project students is kindly acknowledged. The use of GC-MS from Institute of Oceanography (INOS) is also acknowledged.

Keywords:

Smoke aerosols, biomass, controlled burning, hydrocarbons, polycyclic aromatic hydrocarbons.

Subjects:

Q Science

ID Code:

1084