Lichens as Bioindicators and Bioaccumulators to Assess the Ecological Sustainability of Industrial Pollution: A Distance-Gradient Study Around the Biggest Onshore Oil Extraction Centre of Italy (COVA in Val d’Agri, Basilicata)

Onshore oil extraction is a major source of atmospheric pollution in terrestrial ecosystems, yet its spatial impacts on biological communities and pollutant-deposition gradients remain poorly quantified, particularly in ecologically sensitive landscapes. The Centro Olio Val d’Agri (COVA), located in the municipality of Viggiano (Basilicata, southern Italy), is the largest onshore oil pre-treatment facility in Italy and operates within a landscape of high conservation value encompassing multiple Natura 2000 protected areas and the Pertusillo drinking water reservoir. In this study, we applied an integrated lichen biomonitoring approach, combining biodiversity-based sustainability bioindication with chemical bioaccumulation, to characterise the spatial extent and ecological significance of atmospheric pollution originating from COVA across the Val d’Agri basin. Lichen thalli were collected from oak trees (Quercus spp.) at sampling stations distributed along a gradient of increasing distance from the facility and analysed for the concentrations of 28 heavy metals and 22 polycyclic aromatic hydrocarbons (PAHs). Lichen community composition was simultaneously assessed using the Lichen Biodiversity Index (LBI), calculated separately for total, nitrophilous, and non-nitrophilous species. Pearson correlation analysis revealed significant negative relationships between distance from COVA and the concentrations of manganese (r = −0.656, p < 0.001) and chrysene (r = −0.423, p = 0.006), identifying these compounds as clear chemical fingerprints of industrial pollution associated with the facility. Conversely, aluminium, iron, titanium, vanadium, and selenium showed significant positive correlations with distance (p < 0.05), reflecting the predominance of geogenic crustal dust and agricultural sources in the rural landscape surrounding COVA. No significant correlation was detected between LBI values and distance from COVA for any of the three community metrics examined. This finding is likely attributable to the high ecological background variability generated by coppice forest management, heterogeneity in bark chemistry, and the limited sensitivity of community-based lichen indices to the specific emission profile of the facility. These findings demonstrate that chemical bioaccumulation is a more sensitive diagnostic tool than community-based bioindication for detecting the spatial footprint of oil extraction facilities and highlight the need for integrated, multi-method sustainability biomonitoring frameworks for the environmental surveillance of onshore hydrocarbon production sites.