Environmental impact of native polycyclic aromatic hydrocarbons from hard coals

Releases of PAHs from hard (bituminous) coals into the environment have not been widely recognized. In hard coals, some hundreds of mg/kg of EPA-PAH and some thousands of mg/kg total PAH concentrations can occur and the concentrations vary significantly depending on hard coal maturity and origin. Highest PAH concentrations are present in the maturity range of the so-called ''oil-window'' (high volatile bituminous coal rank), however there is no general correlation. Only coals from the same origin can be compared. Naphthalene and phenanthrene as well as their alkylated derivatives are the dominant single polyaromatic compounds in hard coals. The PAH distribution patterns change with increasing rank from the low molecular weight, mostly alkylated compounds with linkage to the original organic material to the predominantly higher molecular weight parent compounds. The former are characteristic for coals of petrogenic origin and the latter for those of pyrogenic origin. Currently, PAHs from coals and from crude oil and its products cannot be distinguished by use of common simple diagnostic parameters. In countries holding large coal basins and associated mining activity, coal particles can comprise 10-15% of the sediment or soil. Until today, little has been known about desorption and bioavailability of native PAH from coals. Literature studies so far show slow and very slow desorption and hardly any or no effects on organisms. This shows that there is a lack of systematic studies using heterogeneous coals from different countries. Bioavailability of PAH from coal particles in soils and sediments has an impact on risk assessment and should be included in sediment and soil standards. (orig.)