THE ATMOSPHERIC PARTITIONING OF DECAMETHYLCYCLOPENTASILOXANE (D5) AND1-HYDROXYNONAMETHYLCYCLOPENTASILOXANE (D4TOH) ON DIFFERENT TYPES OF ATMOSPHERIC PARTICLES
Hk. Latimer et al., THE ATMOSPHERIC PARTITIONING OF DECAMETHYLCYCLOPENTASILOXANE (D5) AND1-HYDROXYNONAMETHYLCYCLOPENTASILOXANE (D4TOH) ON DIFFERENT TYPES OF ATMOSPHERIC PARTICLES, Chemosphere, 36(10), 1998, pp. 2401-2414
A series of outdoor chamber experiments using different types of atmos
pheric particles were conducted to investigate the atmospheric gas-par
ticle partitioning behavior of decamethylcyclopentasiloxane (D5) and i
ts hydroxylated compound, 1-hydroxynonamethylcyclopentasiloxane (D4TOH
). This was undertaken because the phase in which a compound exists di
rectly influences its lifetime in the atmosphere, its deposition to th
e surface of the earth, and ultimately its potential impacts on human
health. To measure the phase distribution, or partitioning, between th
e gas and particle phases, aerosol systems were created in either the
190 m(3) or 25 m(3) outdoor Tenon film chambers at the UNC chamber fac
ility in Pittsboro, NC. Diesel wood, and coal soot were used as organi
c combustion particle sources, while Arizona fine dust was used as an
inorganic particle source. The gas-particle partition coefficient, K-p
, was used as a measure of the phase distribution. K-p can be expresse
d as K-p = (C-p/TSP)/C-g, where C-p(ng/m(3)) and C-g(ng/m(3)) are the
concentrations in the particle and gas phases respectively, and TSP (m
u g/m(3)) is the total suspended particulate matter concentration. The
effect of temperature is considered to be the key parameter that affe
cts the partitioning coefficient. Chamber data showed for both D5 and
D4TOH partitioning, that temperature was very important and could infl
uence partitioning to the particle phase by two orders of magnitude in
going from 25 to 0 degrees C. It was also found that relative humidit
y (RH) was an important parameter affecting D4TOH partitioning especia
lly with mineral dust particles. (C) 1998 Elsevier Science Ltd. All ri
ghts reserved.