CHAPTER 7 . Vapour-Particle Phase Interactions of Organic Pollutants in the Marine Atmosphere
~
"0
2l ..
. g
III
III
..
~
·f
~
80.-----------------------------------,
70
60
50
40
30
20
10
125
135
•
145
Congener
155
•
•.......
165
Fig. 7.2. The relationship between partitioning behaviour and aerosol characteristics for urban (+),
average continental (x) and clean continental (A) aerosols for PCB congeners 128, 145, 149, 156 and 169
at 298 K
7.3.4
Wet Deposition
To calculate wet depositional fluxes it is necessary to know the scavenging ratio (i.e. the
concentration ratio between a chemical in aerosol and its concentration in rain). There
are considerable uncertainties in estimates of the most appropriate scavenging ratios
for organic compounds with estimates lying between 13 and 1600. A value of 500 is
commonly accepted as reasonable (Duce et al. 1991; Preston 1992).
A further problem in calculating wet depositional fluxes at sea is that rainfall data
is very sparse. Anyone with experience of work at sea will know firstly that rain fall is
very patchy and secondly that any attempts to measure rain fall from a ship are almost certainly doomed to failure because of the influence of sea spray.
~
"0
2l ..
. g
III
III
..
~
·f
~
80.-----------------------------------,
70
60
50
40
30
20
10
125
135
•
145
Congener
155
•
•.......
165
Fig. 7.2. The relationship between partitioning behaviour and aerosol characteristics for urban (+),
average continental (x) and clean continental (A) aerosols for PCB congeners 128, 145, 149, 156 and 169
at 298 K
7.3.4
Wet Deposition
To calculate wet depositional fluxes it is necessary to know the scavenging ratio (i.e. the
concentration ratio between a chemical in aerosol and its concentration in rain). There
are considerable uncertainties in estimates of the most appropriate scavenging ratios
for organic compounds with estimates lying between 13 and 1600. A value of 500 is
commonly accepted as reasonable (Duce et al. 1991; Preston 1992).
A further problem in calculating wet depositional fluxes at sea is that rainfall data
is very sparse. Anyone with experience of work at sea will know firstly that rain fall is
very patchy and secondly that any attempts to measure rain fall from a ship are almost certainly doomed to failure because of the influence of sea spray.