Urban soils impacted by tailings from coal mining: PAH source identification by 59 PAHs, BPCA and alkylated PAHs

Hindersmann B, Achten C

Zusammenfassung

Urban soils in mining and industrial regions like the Ruhr Area are characterized by admixtures ofanthropogenic substrates, e. g. tailings, coals, ashes, debris or scoria. These soils often show elevatedconcentrations of polycyclic aromatic hydrocarbons (PAHs) which are commonly attributed to non-pointpyrogenic carbon sources like soot and particulate matter. An emission source of PAHs into urban soils inthese regions, that surprisingly is still largely neglected, are the millions of tons of tailings from undergroundcoal mining that have been used as material for road construction, terrain leveling, riverchanneling and support of embankments.Here we classify the PAH sources of 13 urban soils as either petrogenic or pyrogenic. The soils contained(1) tailings, (2) ashes and (3) different anthropogenic substrates. The classification is based on acomprehensive analysis of 59 PAHs and alkylated PAH distributions by GC-MS and BPCA analyses by LCTOF-MS.PAH concentrations (P59 PAHs) of all soils ranged from 60 to 140 mg/kg, except one soil showing559 mg/kg. The PAH source in the urban soils containing tailings was identified as petrogenic carbon dueto (1) the dominance of low molecular weight PAHs, (2) bell shape distribution patterns of the alkylatedPAHs, and (3) comparable BPCA distribution patterns to bituminous coals. In contrast, the PAH source ofthe ash-containing soil was identified as pyrogenic carbon by high molecular weight PAH percentages>80%, slope shape distribution patterns of the alkylated PAHs and a higher degree of aromaticcondensation (B6CA/BPCA) than bituminous coals, coal ashes or charcoal. The urban soils containingdifferent anthropogenic substrates revealed the occurrence of both a petrogenic and a pyrogenic PAHsource. Surprisingly, the separate analyses of isolated coal ash particles revealed typical petrogenic indicatorsshowing that by visual approach coal ashes cannot generally be classified as being of a pyrogenicPAH source.