Graf, Carola and Sweetman, Andrew and Jones, Kevin (2023) Persistent organic pollutants in ambient air – sources, patterns, and environmental behaviour. PhD thesis, Lancaster University.
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Abstract
Long-term air monitoring datasets are needed for persistent organic pollutants (POPs) to assess the effectiveness of source abatement measures and the factors controlling ambient levels, and to provide governments, regulators, and researchers with valuable information on emission/source controls and on the effectiveness of international chemicals regulation such as the Stockholm Convention and UN/ECE Protocol on POPs. These data can be provided by active or passive air sampling. The UK Toxic Organic Micro Pollutants (TOMPs) Network, using high-volume active air samplers, has demonstrated the constant decline in UK air concentrations for polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polybrominated diphenyl ethers (PBDEs) since 1991, in accordance with emission estimates. For a latitudinal passive ambient air sampling transect from the south of England to the north of Norway established in 1994, which had reported several years of decreasing PCB air concentrations previously, increased levels were observed between 2008 and 2016. The reasons for this could include local sources, effects of climate change, and impact of polluted air masses from Eastern Europe. In contrast, PBDE concentrations have decreased since 2000 in line with expectations. Furthermore, seasonal patterns for PCB and PBDE concentrations in UK ambient air are discussed. PCBs generally showed a summer > winter pattern, while ƩPBDE concentrations were distributed over a range of congeners with more uniform concentrations but greater differences in seasonal patterns, thus their overall seasonality was characterized by these contrasting patterns. In addition to long-term trends and regular seasonal variations, short-term emission events like the UK ‘Bonfire Night’, where increased PBDE concentrations possibly stemming from ‘backyard burning’ were observed, were shown to impact POPs concentrations in ambient air. In order to overcome some limitations of current air sampling methods, two potential improvements were evaluated and recommended: the addition of XAD® pods in standard active air samplers, and the addition of monofluorinated PCBs to the range of performance reference compounds for passive air sampling.