Semivolatile organic compounds (SOCs) include pollutants such as polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). These compounds usually occur at trace concentrations in the atmosphere (ng m-3 to fg m-3) and many of them are potentially harmful to human and environmental health. High volume air samplers are the conventional means for environmental monitoring of SOCs but these systems are limited by financial and practical issues. Passive samplers have the potential to augment active sampling systems because they are relatively inexpensive, and because they do not require electricity or a high level of maintenance to operate. In addition, passive samplers are suitable for deployment at many sites for extended periods. Semipermeable membrane devices (SPMDs) and polyurethane foam (PUF) samplers are the most commonly used passive air samplers for SOCs. These samplers have been used b identify sources of pollutants and assess the transport of these compounds in the atmosphere. With appropriate modelling and calibration, passive samplers can also be used to measure time-integrated atmospheric concentrations of pollutants. However wide-scale use of passive air samplers is still inhibited by certain limitations. For example, only limited work has been done developing performance reference compounds (PRCs) for use in passive air samplers. However PRCs are required to account for the influence of environmental factors such as wind on sampler performance. Furthermore, passive air samplers have not been validated using active sampling systems. Validation data is required to show how accurately passive samplers can measure the air concentration of SOCs.
The aim of this thesis was to address these key developmental issues associated with SPMDs and PUF samplers and also to evaluate the usefulness of PSDs as a passive air sampler. Specifically, this work evaluated the use of simple PSDs as passive air samplers of SOCs, determined whether PRCs could be used in single phase passive samplers (PSDs and PUF), to determine calibration data for SPMDs and undertake a field evaluation of SPMD performance with respect to reproducibility and accuracy in measuring air concentrations.
The evaluation of PSDs showed that deploying samplers with the same surface area but different thickness was sufficient to determine whether uptake was in the linear phase or approaching equilibrium for specific compounds. Important calibration data (sampling rates and sampler/air partition coefficients) for PAHs were also determined. This approach may have significant advantages in time and cost when compared with alternative approaches to characterising uptake kinetics. Experimentation trialling the use of PRCs in PSDs and PUF samplers confirmed that an increase in wind speed did affect sampler performance. Results revealed that PRCs could be loaded into these single phase samplers with good reproducibility and air resistance dominated chemical exchange for a range of PCBs and PAHs. Loss rate constants and sampling rates for PAHs and PCBs increased proportionally in PSDs exposed to increasing wind speeds. However in the case of PUF samplers, sampling rates increased to a greater degree than loss rate constants, when the samplers were exposed to increasing wind speed. When loss rate constants measured in PSDs were used with sampler/air partition coefficients, to estimate the concentration of certain PAHs in the vapour phase, results agreed closely with measurements made using active samplers. The reproducibility and accuracy of SPMDs were evaluated in the field. Results showed 1hat these samplers can be used to estimate air concentrations of PAHs with reasonable accuracy. Interestingly, this included PAHs predominantly associated with particles, such as benzo[a]pyrene. Importantly, the use of PRCs in SPMDs showed that when deploying passive air samplers to collect photosensitive compounds, such as PAHs, samplers must be adequately shielded from sunlight.
The results from this study provided new data for a better understanding of the potential and limitations of passive samplers for measuring atmospheric concentrations of semivolatile organic pollutants. Overall, this work showed that passive air samplers can be used effectively to augment conventional active sampling systems for the monitoring of SOCs, However further work is required to thoroughly understand how these samplers accumulate SOCs predominantly associated with particles and whether certain PRCs can be used to account for photodegradation.