An investigation into the occurrence and distribution of polycyclic aromatic hydrocarbons in two soil size fractions at a former industrial site in NE England, UK using in situ PFE–GC–MS

Abstract

Polycyclic aromatic hydrocarbon (PAH) concentrations were determined in 16 topsoils (0-10cm) collected across the site of a former tar works in NE England. The soils were prepared in the laboratory to two different particle size fractions: <250μm (fractionA) and >250μm to <2mm (fractionB). Sixteen priority PAHs were analysed in the soils using insitu pressurised fluid extraction (PFE) followed by gas chromatography-mass spectrometry (GC-MS). The average total PAH concentration in the soils ranged from 9.0 to 1,404mg/kg (soil fractionA) and from 6.6 to 872mg/kg (soil fractionB). These concentrations are high compared with other industrially contaminated soils reported in the international literature, indicating that the tar works warrants further investigation/remediation. A predominance of higher-molecular-weight compounds was determined in the samples, suggesting that the PAHs were of pyrogenic (anthropogenic) origin. Statistical comparison (t-test) of the mean total PAH concentrations in soil fractionsA and B indicated that there was a significant difference (95% confidence interval) between the fractions in all but two of the soil samples. Additionally, comparisons of the distributions of individual PAHs (i.e. 16 PAHs×16 soil samples) in soil fractionsA and B demonstrated generally higher PAH concentrations in fractionA (i.e. 65.8% of all individual PAH concentrations were higher in soil fractionA). This is important because fractionA corresponds to the particle size thought to be most important in terms of human contact with soils and potential threats to human health.