Occurrence of Polar Polycyclic Aromatic compounds at contaminated sites
Résumé
Background It has recently been recognized that soils contaminated with polycyclic aromatic hydrocarbons (PAHs) may contain significant amounts of other polycyclic aromatic compounds (PACs) as well. This includes alkylated PAHs, heterocyclic PACs (containing oxygen and sulfur) and more polar compounds such as carbonyl-PAHs (oxy-PAHs), hydroxy-PAHs, nitro-PAHs and nitrogen heterocyclic PACs (N-PACs). Of these, the latter, more polar compounds (polar PACs) have attracted more and more attention in recent years. This is because these compounds are shown to be considerably toxic for both humans and the environment, and because the polar PACs show a different behavior in the environment as compared to less polar PACs, e.g. PAHs. Some polar PACs, e.g. oxy-PAHs and hydroxy-PAHs, can thus be formed as PAHs are degraded, meaning that the levels of these compounds may increase at the same time as the PAH-levels decrease. Furthermore, it has been shown that many polar PACs are more prone to leach than the less polar PACs, which can be attributed to the polar PACs' higher water solubility. These facts make the polar PACs important contributors to the risk at PAC-contaminated sites and thus relevant to consider during risk assessment of the sites. Aim The aim of this study was to investigate the occurrence of polar PACs at various PAC contaminated sites in Sweden and France, including gasworks sites, coke oven sites, wood preservation sites and wood tar production sites. The distribution of polar PACs in soil and groundwater was examined and related to the levels of PAHs. Furthermore, the correlation between the contaminant profile and the site characteristics (i.e. type of site and industry, age of contamination, soil type etc.) was investigated. Conclusion The levels of polar PACs vary considerably between and within sites. The polar PAC levels are to some extent correlated to the PAH levels, but the ratio polar PAC/PAH may still vary considerably. In some cases the polar PACs are even more abundant than the PAHs. Polar PACs are also found in groundwater at contaminated sites, generally with higher polar PAC/PAH ratios than in soil. However, the difference observed in the ratios is smaller than what would have been expected from their differences in water solubility. This is most likely due to colloid facilitated transport of PAHs in particular. The contaminant profiles, of individual polar PACs and PAHs, vary from site to site, but are at least to some extent correlated to the site characteristics.