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1. Introduction
Polycyclic aromatic hydrocarbons (PAHs) is an overarching term describing hundreds of individual chemical compounds containing two or more fused aromatic rings and are known to persist or accumulate in the environment [1]. Although PAHs occur naturally in the environment (e.g., forest fires, volcanoes, and diagenesis), their natural cycle has been significantly augmented during the past century through anthropogenic processes, such as wood and fossil fuel combustion [2–7]. Combustion is the primary source of long-range atmospheric transport of PAHs into the surrounding environment [8]. However, unlike many legacy persistent organic pollutants (POPs), that typically follow the global distillation model of accumulation in colder regions owing to atmospheric condensation and cold trapping [9], PAHs tend to decrease in concentration further from the initial point source [1]. Atmospheric concentrations of PAHs tend to be higher in temperate regions owing to seasonal heating [10]. In addition, the Arctic still exhibits preindustrial levels of PAHs (e.g., 1–10 ng g−1 per individual PAH [1, 11]) largely owing to the lower atmospheric half-life [12] caused by thermal/photodegradation and propensity for particulate binding [13]. Further, regions receiving high rates of precipitation are particularly vulnerable due to the dominant “washout” of contaminants from the atmosphere [14].
The ubiquitous nature of PAHs in the environment, primarily stored in soils [1], is a major human and ecosystem health concern owing to their known carcinogenicity and potential toxicity to both aquatic and terrestrial organisms [15, 16]. Observations of PAHs in regions remote from direct emission or production provide an understanding of the influence of atmospheric transport on ecosystem integrity. Ireland is a well established background reference region for atmospheric research owing to its location on the western periphery of Europe and dominant prevailing Westerlies [17]. West coast sites are characterised by clean oceanic air while east coast sites show an anthropogenic signal from national and transboundary sources. However, there is limited knowledge on PAHs in the Irish environment; research to date has focused only on lake sediment cores at a few sites [18].
The objective of this research was to provide a comprehensive assessment of...