Hydrocarbons in Smoke Aerosols from Controlled Burning of Mangifera Foetida Litter falls and Panicum repens.

Tay, Joo Huil, and Tan, Hock Sen, and Norhayati Mohd. Tahir (Tahir N.M.), and Mhd. Radzi Abas (Abas M.R.), (2007) Hydrocarbons in Smoke Aerosols from Controlled Burning of Mangifera Foetida Litter falls and Panicum repens. Malaysian Journal of Analytical Sciences, 11 (1). pp. 29-35. ISSN 13942506

Abstract

A study has been carried out to characterize hydrocarbons emitted from the burning of two typical garden wastes, bachang (Mangifera foetida) litter falls and grass (panicum repens). The biomass samples were burned and their respective smoke particulate emitted was sampled using high volume sampler fitted with pre-cleaned glass fibre filters under smouldering and flaming conditions. Hydrocarbons were extracted using dichloromethane-methanol mixture 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 unburnt bachang litter falls and grass were also analyzed for aliphatic and PAHs content. Result indicated that the major components in the aliphatic fraction for all samples were nalkane compounds which exhibited a saw-tooth pattern that is characteristic of a biogenic origin. The major components in this aliphatic fraction for smoke particulate matters were n-alkanes in the range of C12-36, with an odd to even carbon predominance with CPI values ranging from 2.89-4.32 and Cmax generally at C31; total identified n-alkanes for these samples ranged from 221-939 µgg-1. On the other hand, hydrocarbons present in the fresh unburnt bachang litter falls and grass ranged from C12-C36 with C27 and C33 species dominating and CPI value of 4.5 and 23.1, respectively; total identified nalkanes were significantly higher (1530-33000 µgg-1) than those found in smoke aerosols In general, CPI > 1 indicates nalkanes contribution from epicuticular waxes thus it could be concluded that, even though the overall signature of the source of n-alkanes is maintained, burning seems to alter the distribution of aliphatic hydrocarbon emitted accompanied with a decrease in the CPI values and shifting in Cmax. In addition, results also indicated that burning resulted in the formation of many PAHs compounds in all smoke aerosols samples with total PAHs concentration ranging from 187-296 µgg-1. Fresh unburnt bachang litter falls and grass on the other hand did not exhibit any PAHs compound, which clearly indicated that PAHs were generally generated from combustion process.

Satu kajian telah dijalankan bagi mencirikan sebatian hidrokarbon yang dibebaskan daripada pembakaran sampel sisa laman iaitu daun bachang (Mangifera foetida) dan rumput (Panicum repens). Sampel-sampel biojisim ini telah dibakar dalam keadaan membara dan menyala dan zarah asap yang terhasil disampel menggunakan alat pensampelan berisipadu tinggi yang dimuat dengan penapis gentian kaca. Hidrokarbon diekstrak menggunakan campuran diklorometana-ethanol (3:1)sebagai pelarut dan hasil ekstrak yang diperolehi dipisahkan dengan menggunakan turus silika-alumina. Penentuan dan kuantifikasi sebatian hidrokarbon alifatik dan PAHs dijalankan dengan menggunakan GC-MS. Sebagai perbandingan, hidrokarbon daripada daun bachang dan rumput segar yang tidak dibakar juga dikaji bagi menentukan perbezaan di antara profil hidrokarbonnya. Keputusan menunjukkan komponen organik utama dalam pecahan alifatik untuk semua sampel adalah bersebatian n-alkana. Taburan n-alkana ini memberi bentuk gerigi yang mencirikan sumber biogenik. Komponen utama dalam pecahan alifatik adalah daripada sebatian n-alkana dalam julat of C12-C36, dengan kehadiran lebih banyak karbon nombor ganjil berbanding karbon nombor genap. ‘Carbon preference index’ (CPI) adalah dalam julat 2.89-4.32 dan Cmax pada C31; jumlah n-alkana yang dikenalpasti adalah dalam julat 221-939 µgg-1. Sebaliknya, hidrokarbon alifatik yang diperolehi daripada daun bachang dan rumput segar yang tidak dibakar adalah terdiri daripada C12-C36, dengan C27 dan C33 sebagai spesis paling dominan dan nilai CPI masing-masing sebanyak 4.5 dan 23.1; jumlah n-alkana yang dikenalpasti adalah lebih tinggi (1530-33000 µgg-1)berbanding dalam zarah asap. Amnya, CPI > 1 menunjukkan sumbangan n-alkana daripada lilin epikutikular. Kesimpulannya, walaupun keseluruhan penanda n-alkana tidak berubah, pembakaran didapati mengubah taburan hidrokarbon alifatik yang terhasil dengan penurunan nilai CPI. Keputusan juga menunjukkan pembakaran membentuk lebih banyak sebatian PAHs dalam ketiga-tiga sampel asap dengan kepekatan dalam julat diantara 187-296 µgg-1. Daun bachang dan rumput segar yang tidak dibakar pula tidak mempunyai sebatian PAHs dan ini jelas menujukkan PAHs hanya terhasil dari proses pembakaran.

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Abstract