Chapter 7
Vapour-Particle Phase Interactions of Some
Selected Persistent Organic Pollutants in the
Marine Atmosphere
M.R. Preston
7.1
Introduction
Unlike the majority of inorganic compounds, many organic chemicals have significant vapour pressures at ambient temperatures. Consequently, organic compounds are
frequently transported within the environment at least partially in the vapour phase.
The nature of the relationship between this vapour, the solid and liquid aerosol and
the dissolved phase is therefore crucial to an understanding of how such chemicals
migrate within the environment. In their major review of atmospheric input of trace
species to the oceans Duce et al. (1991) highlighted both the complexity of the atmospheric transport processes and the general paucity of data. They compiled a summary of the mean concentrations of chlorinated organic contaminants for the major
ocean basins which is reproduced in Table 7.1.
This data represents essentially gas phase material since Duce et al. considered that,
on the basis of the available evidence, >95% of these compounds are measured as a
gas in typical regions of the marine atmosphere. However, within complex chemical
mixtures such as the PCBs, it is clear that there will be a range of gas phase-particle
partitioning behaviour dependent on the individual properties of the PCB congeners.
This paper is intended to review two aspects of partitioning behaviour. First, the
current status of models of gas-particle interactions and second, the conversion of
atmospheric concentration data into air to sea contaminant fluxes. These models derive from early work by Yamasaki et al. (1982) which have been developed to a considerable degree by Terry Bidleman (Atmospheric Environment Service, Canada) and
James Pankow (Oregon Graduate Institute, USA) and which have been utilized by other
workers including the author (Chen and Preston 1998).
7.2
Theory of Gas-Particle Interactions
7.2.1
Gas-Solid Interactions
The mechanism of association between a gas molecule and a particle may be one of
gas-solid adsorption or gas-liquid absorption, so any theory must account for both
aspects of this behaviour. In practice most early theory (e.g. Yamasaki et al. 1982;
Pankow 1987) concentrated on gas-solid adsorption processes and it is only more recently that the role of liquid phase interactions has been considered (see e.g. Finzio
et al. 1997; Pankow 1998). All of the theory below assumes that semivolatile organic
Vapour-Particle Phase Interactions of Some
Selected Persistent Organic Pollutants in the
Marine Atmosphere
M.R. Preston
7.1
Introduction
Unlike the majority of inorganic compounds, many organic chemicals have significant vapour pressures at ambient temperatures. Consequently, organic compounds are
frequently transported within the environment at least partially in the vapour phase.
The nature of the relationship between this vapour, the solid and liquid aerosol and
the dissolved phase is therefore crucial to an understanding of how such chemicals
migrate within the environment. In their major review of atmospheric input of trace
species to the oceans Duce et al. (1991) highlighted both the complexity of the atmospheric transport processes and the general paucity of data. They compiled a summary of the mean concentrations of chlorinated organic contaminants for the major
ocean basins which is reproduced in Table 7.1.
This data represents essentially gas phase material since Duce et al. considered that,
on the basis of the available evidence, >95% of these compounds are measured as a
gas in typical regions of the marine atmosphere. However, within complex chemical
mixtures such as the PCBs, it is clear that there will be a range of gas phase-particle
partitioning behaviour dependent on the individual properties of the PCB congeners.
This paper is intended to review two aspects of partitioning behaviour. First, the
current status of models of gas-particle interactions and second, the conversion of
atmospheric concentration data into air to sea contaminant fluxes. These models derive from early work by Yamasaki et al. (1982) which have been developed to a considerable degree by Terry Bidleman (Atmospheric Environment Service, Canada) and
James Pankow (Oregon Graduate Institute, USA) and which have been utilized by other
workers including the author (Chen and Preston 1998).
7.2
Theory of Gas-Particle Interactions
7.2.1
Gas-Solid Interactions
The mechanism of association between a gas molecule and a particle may be one of
gas-solid adsorption or gas-liquid absorption, so any theory must account for both
aspects of this behaviour. In practice most early theory (e.g. Yamasaki et al. 1982;
Pankow 1987) concentrated on gas-solid adsorption processes and it is only more recently that the role of liquid phase interactions has been considered (see e.g. Finzio
et al. 1997; Pankow 1998). All of the theory below assumes that semivolatile organic