Lichen transplants for high spatial resolution biomonitoring of Persistent Organic Pollutants (POPs) in a multi-source polluted area of Central Italy

The ability of lichen transplant Evernia prunastri (L.) Ach. to reflect air concentration and spatial distribution of 7 polychlorinated dibenzodioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), and 23 polychlorinated biphenyls (PCBs) was evaluated through the construction of a wide and dense biomonitoring network. For this purpose, 23 lichen transplants were placed in a highly polluted area in Central Italy, characterized by the presence of different local emission sources such as a power plant, a steel plant, vehicular traffic, and domestic heating. The high spatial resolution data obtained from lichens were used to map the spatial distribution of the studied compounds, useful to identify the location and strength of target compounds sources over the territory. The maps showed that the highest concentrations of the pollutants were detected, as expected, in the sites close to the power plant and to the steel plant, confirming their important role as persistent pollutants emission sources. The statistical analysis performed on the spatially resolved data allowed us to identify the steel plant as the main source of PCDD/Fs, while PCBs were emitted by both the steel plant and the power plant. Finally, the efficiency of lichen transplants to reflect PCDD/Fs and PCBs atmospheric concentrations was assessed by comparing lichen data with POPs deposition measured by bulk deposition samplers at sites impacted by intensive emission sources; good results were achieved from the comparison (R2 > 0.79). Lichen transplants have demonstrated to be suitable biomonitors of POPs, allowing to obtain a high spatial monitoring network. The low-cost biomonitoring and experimental approach described in this study can be applied to other monitoring campaigns for identifying localizing emission sources of POPs in areas contaminated by several disaggregated sources.