Lichens as bioindicators of air pollution assessment - a case study from the Upper Silesia region (Poland)

The primary source of air pollution in the Upper Silesia region (Poland) is anthropogenic emissions, including municipal, domestic, and traffic emissions. However, the main problem that arises is to identify the dominating pollution sources and eliminate them. Since lichens absorb even small amounts of anthropogenic organic compounds from the air, they are useful as bioindicators of environmental pollution. For the study, lichen samples were taken from trees growing close to single-family housing estates and near roads with heavy traffic in the Zabrze town, Poland. The lichen samples were analyzed by GC-MS (Agilent gas chromatograph 7890A coupled with a mass spectrometer 5975C XL MDS). Moreover, the concentration of trace elements was determined using an S8 TIGER Series 2 WDXRF spectrometer.

The studied lichen samples are a source of information about air contamination with polycyclic aromatic hydrocarbons (PAHs), which come from fossil fuel combustion and have carcinogenic and mutagenic properties. Identified PAHs include phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, triphenyl, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[j]fluoranthene, benzo[a]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, perylene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene. The phenyl-, and methyl- derivatives of polycyclic aromatic hydrocarbons were also found in the samples. Phenyl derivatives of polycyclic aromatic hydrocarbons (PhPAHs) include phenylnaphtalenes (naphthalene, 1-phenyl-; naphthalene, 2-phenyl-) and terphenyls (o-terphenyl; m-terphenyl; p-terphenyl) as well as phenylphenanthrenes (phenanthrene, 9-phenyl-; phenanthrene, 1-phenyl-; phenanthrene, 3-phenyl-; phenanthrene, 2-phenyl-). Moreover, binaphtyls (1,1’-binaphthyl; 2,2’-binaphtyl) were also found in most of the samples. Among methyl derivatives of polycyclic aromatic hydrocarbons including methylphenanthrenes (3-metyl-; 2-metyl-; 4+9-metyl-; 1-metyl-) and anthracene, 2-methyl- have been identified. Phenols like o-cresol, m-cresol, p-cresol and phenol, 2-nitro- were also determined. It is worth mentioning that exposure to phenol may cause damage to the central nervous system, heart and kidneys.

Heavy metals like lead (av. of 1720 ppm), strontium (av. of 260 ppm), nickel (av. of 30 ppm), and vanadium (av. of 10 ppm) were marked among the elements toxic to human health.

Moreover, the lichens selectively absorb organic compounds like dehydroabietane and simonellite, which are characteristic of immature organic matter and may indicate low-quality coal combustion. Biomarkers investigated comprised pentacyclic triterpenoids (hopanes and moretanes) and steranes. Their distributions show distinctive differences indicating coal combustion in domestic furnaces (steranes absence or very low concentrations and short hopanes distribution) and traffic emission (cholestanes-rich distribution of steranes and long hopanes distribution up to C35). In conclusion, the research points out the usefulness of lichens as bioindicators regarding both organic and inorganic substances of anthropogenic origin.

The authors acknowledge financial support from the Polish National Science Centre 2022/06/X/ST10/00338 grant.