Environmental Engineering Reference
In-Depth Information
3. Results
The partition coefficient was proposed by Pankow (1997) and he defined it as Log
K
p = Log ([F]/[A]) - Log [TSP] (where F represents the particulate concentration
of a given compound, A represents its gaseous concentration, TSP represents the
concentration of the total suspended particles). For field results, we calculated an
approximation to this partition coefficient by using suspended particulate matter
(SPM) instead of TSP (SPM is defined in this work as the particulate matter below
7 μm of aerodynamic diameter, and it is measured by the β-ray attenuation
method) (Takahashi et al., 2007). For chamber experiments, TSP was evaluated by
integration of particle size distributions, assuming an aerosol density of 1.5 g cm
−3
(Kostenidou et al., 2007).
Table 1
shows the results for each compound at all sites
and in the smog chamber, Meguro site (urban), is situated in the center of Tokyo,
all the other sites were situated north of Meguro at different distances, Saitama
site (suburban), at 30 km; Kisai site (rural), at 50 km; and Fukaya site (rural), at
70 km.
In the smog chamber, the Log
K
p values for glyoxal ranged from −1.72 to
−4.88 and for methylglyoxal ranged from −2.96 to −4.87, while in the atmospheric
measurements, Log
K
p value for glyoxal and methylglyoxal ranged from −0.082
to −3.27 and from −0.13 to −3.37, respectively.
Table 1.
Log
K
p average values measured at different sites
Compound
Meguro
Saitama
Kisai
Fukaya
Field
average
Chamber
Glycolaldehyde −1.552 −1.146 −1.696 −2.470
−1.644
−3.479
Hydroxyacetone −1.309 −1.054 −1.584 −2.559
−1.700
−3.514
Glyoxilic acid
−1.231 −1.318 −1.774 −2.571
−1.723
−2.336
Pyruvic acid
−1.442 −1.062 −1.901 −2.668
−1.694
−1.998
Glyoxal
−1.512 −1.184 −1.938 −2.279
−1.630
−2.946
Methylglyoxal
−1.989 −0.999 −1.639 −1.638
−1.467
−3.983
In the field, the highest Log
K
p average values were found at Saitama site, and
the values were decreasing at longer distances from the city. In the chamber
experiments the values found were the lowest. This indicates that the composition
and real atmospheric conditions affect the partitioning of these compounds in
different ways; therefore the compounds tend to be at higher concentrations in the
particulate phase. For example, the presence of salts in the aerosol can make, even
at relatively low acidities, some bifunctional carbonyls (e.g., glyoxal) to increase
their solubility in water (Ervens and Kreidenweis 2007) or perhaps in the more
polar organic compounds. Aerosols undergo a chemical evolution during their
lifetime, including the possibility of being evaporated by oxidation reactions with
radicals. This evolution also seems to affect the partitioning, as seen in the values
on
Table 1.
