Fate and Transport of Polycyclic Aromatic Hydrocarbons in Upland Irish Headwater Lake Catchments

Heidi E. M. Scott,Julian Aherne,Chris D. Metcalfe

doi:10.1100/2012/828343

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a concern due to their carcinogenicity and propensity for transboundary atmospheric transport. Ireland is located on the western periphery of Europe and assumed to receive clean Atlantic air. As such, it has been used as an atmospheric reference for comparison to other regions. Nonetheless, few studies have evaluated concentrations of PAHs within the Irish environment. In the current study, PAHs were measured at five upland (500–800 masl) headwater lake catchments in coastal regions around Ireland, remote from industrial point source emissions. Semipermeable membrane devices were deployed in lakes for a 6-month period in July 2009, and topsoils were sampled from each catchment during October 2010. The concentrations of PAHs were low at most study sites with respect to other temperate regions. Homologue groups partitioned between lake and soil compartments based on their molecular weight were: “lighter” substances, such as Phenanthrene and Fluorene, were found in higher proportions in lakes, whereas “heavier” compounds, such as Chrysene and Benz[a]anthracene, were more prominent in soils. Concentrations of PAHs were highest at the east coast sites, potentially due to contributions from historical transboundary and regional combustion sources.

Highlights

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]
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]
The study sites were located in acid-sensitive moorland regions [20]; the catchments were dominated by organic soils and the vegetation was primarily Calluna vulgaris along with various graminoid and bryophyte species

Summary

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]. Combustion is the primary source of long-range atmospheric transport of PAHs into the surrounding environment [8]. 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]. Regions receiving high rates of precipitation are vulnerable due to the dominant “washout” of contaminants from the atmosphere [14]

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