Sains Malaysiana 45(3)(2016): 365–371

Characterization of Hydrocarbons in Smoke Aerosols from Burning of Three Tropical Wood Species

(Pencirian Hidrokarbon dalam Zarah Asap daripada Pembakaran Tiga Spesies Kayu Tropika)

TAN HOCK SENG¹*, MOHD RADZI ABAS² & NORHAYATI MOHD TAHIR^1,2

¹Institute of Oceanography and Environment (INOS), Universiti Malaysia Terengganu

21030 Kuala Terengganu, Terengganu Darul Iman, Malaysia

²Chemistry Department, Universiti Malaya, 50603 Kuala Lumpur, Federal Territory, Malaysia

³School of Marin Science and Environmental, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu Darul Iman, Malaysia

Received: 26 May 2014/Accepted: 8 September 2015

ABSTRACT

A study has been carried out to characterize hydrocarbons emitted from the burning of three tropical wood species. The woods were burned to ember and smoke aerosols emitted were sampled using high volume sampler fitted with a pre-cleaned glass fibre filters. Hydrocarbons were extracted using ultrasonic agitation with dichloromethane-methanol (3:1 v/v) as solvent and the extracts obtained were then fractionated on silica-alumina column. Detection and quantification of aliphatic and polycyclic aromatic hydrocarbons (PAHs) compounds were carried out using GC-MS. The results indicated that the major aliphatic hydrocarbons characterized were straight chain n-alkanes in the range of C₁₂-C₃₅ with Cmax in the range of C₂₇-C₃₃. Rhizophora apiculata and Hevea brasiliensis wood smoke exhibited a weak odd to even carbon number predominance with carbon preference index (CPI) values greater than one whereas Melaleuca cajuputi wood smoke aerosols did not exhibit similar pattern with CPI obtained close to one. The results obtained also indicated that burning of these wood resulted in formation of PAHs compounds in their smoke aerosols with predominance of three to four rings PAHs over the two, five and lesser of six rings PAHs. PAH diagnostic ratios calculated except for Flan/(Flan+Py) and Indeno/(Indeno+BgP) were consistent with the ratios suggested for wood combustion source as reported in literatures. In the case of the latter, two diagnostic ratios, the values were generally lower than the range normally reported for wood combustion.

Keywords: Biomass burning; combustion process; diagnostic ratios; polycyclic aromatic hydrocarbons; smoke aerosols

ABSTRAK

Suatu kajian telah dijalankan untuk mencirikan unsur hidrokarbon yang dibebaskan daripada pembakaran tiga spesies pokok kayu tropika. Sampel kayu dibakar sehingga membara dan zarah asap yang terhasil disampel menggunakan alat persampelan berisi padu tinggi yang dimuatkan dengan penapis gentian kaca. Hidrokarbon telah diekstrak dengan agitasi ultrasonik menggunakan diklorometana-metanol (3:1 v/v) sebagai pelarut dan ekstrak difraksinasi dalam turus silica-alumina. Pengesanan dan kuantifikasi hidrokarbon alifatik dan polisiklik aromatik (PAH) telah dijalankan dengan menggunakan GC-MS. Keputusan menunjukkan hidrokarbon alifatik utama yang diciri adalah sebatian n-alkana rantai lurus dalam julat C₁₂-C₃₅ dengan Cmax dalam julat C₂₅-C₃₃. Zarah asap kayu Rhizophora apiculata dan Hevea brasiliensis menunjukkan lebih banyak karbon bernombor ganjil berbanding karbon genap dengan nilai indeks pemilihan karbon (IPK) melebihi 1 manakala asap kayu Melaleuca cajuputi tidak menunjukkan ciri yang sama dengan nilai IPK yang diperoleh adalah hampir dengan satu. Keputusan juga menunjukkan pembakaran kayu tersebut menghasilkan unsur PAH dalam zarah asap dengan unsur bergelang tiga dan empat mendominasi unsur bergelang dua, lima dan enam. Nisbah diagnostik PAH yang dikira, kecuali nisbah Flan/(Flan+Py) dan Indeno/(Indeno+BgP), adalah konsisten dengan nisbah yang disarankan dalam penulisan untuk sumber pembakaran kayu. Namun dalam kes dua nisbah yang dinyatakan, nilai yang diperoleh pada umumnya lebih rendah daripada julat yang biasa dilaporkan untuk pembakaran kayu.

Kata kunci: Hidrokarbon polisiklik aromatik; nisbah diagnostik; pembakaran biojisim; proses pembakaran

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*Corresponding author; email: hockseng@umt.edu.my