| Summary: | 碩士 === 國立臺灣大學 === 環境衛生研究所 === 86 === ABSTRACT The objective of this study is to determine the bulk characteristics
of n-alkanes in the carbon number range of C15∼C36 in urban air and two-stro
ke motorcycle exhaust. The vapor/particle distribution of n-alkanes in urban
air was also examined. The bulk characteristics of n-alkanes were used in ide
ntifying various sources of fine particles. We used a Model 310 Universal Air
Sampler (MSP Corporation) to collect fine particulate matter (≦2.5 micromete
r) on quartz fiber filters and to adsorb vapor-phase compounds on solid sorben
ts placed downstream of the filter. The sorbents consisted of XAD-2 sandwiche
d between two layers of polyurethane foam（PUF）. The sampler was placed on t
he rooftop, 15.7m above the street level, at Chung Shan Elementary School in t
he Taipei City. Samples were collected once every 10 days. The sampler ran 1
0 minutes in each quarter of an hour at a flow rate of 285 L/min during Septem
ber 10, 1997 to March 24, 1998. A two-stroke 50c.c. motorcycle engine was tes
ted under constant speeds on a dynamometer. Motorcycle exhaust samples were c
ollected downstream of a dilution tunnel by using quartz filter follwed by XAD
-16 solid sorbent. The n-alkanes collected on filters and solid sorbent were
extracted with CH2Cl2 in a Soxhlet extraction apparatus. Qualitative and quan
titative analysis of the n-alkanes were carried out by GC/FID. The results sh
ow that the ambient concentrations of total particulate and vapor n-alkanes ra
nged from 67 ~ 586 ng/m3 and 401 ~ 1003 ng/m3, respectively. The Carbon Prefe
rence Index ( CPI ) of n-alkanes obtained from the motorcycle exhaust samples
were around 1 and the Carbon number maximum ( CMAX ) at C19、C24 or C25. The
data on CPI and CMAX of ambient samples indicate that emssions from fossil fue
l combustions are the major sources of n-alkanes in the Taipei aerosol.Keyword
s：fine particle, two-stroke motorcycle exhaust, semivolatile organic matter,
n-alkanes, vapor / particle distribution
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