Detection of polycyclic aromatic hydrocarbons, microplastic presence and characterization of microbial communities in the soil of touristic zones at Alqueva’s edges (Alentejo, Portugal)

Environmental pollution is a growing concern. Here, we assessed the occurrence of two groups of persistent organic pollutants (POPs-polycyclic aromatic hydrocarbons (PAHs) and microplastics (MPs)) and bacterial populations in the topsoil of three tourist spots located at the Alqueva's edges during 1 year, once per season. Soil chemical analysis revealed low content of total organic carbon, pH close to neutrality, and nitrogen and phosphorus levels consistent with acquisition of these nutrients only by atmospheric deposition. PAH's concentrations were in the range of ng/kg, being significantly below the "reference values" for contaminated soils. Nevertheless, potentially carcinogenic PAHs, detected at all locations, raise ecotoxicological concerns. Polyamide, polyester, polystyrene, and styrene acrylonitrile resin MPs were found. Six bacterial phyla constitute the core microbiome in the three locations and include genera of bacteria reported as plastic degraders, such as Bacillus, Exiguobacterium, Paenibacillus, and Pseudomonas. The presence of POPs, even at low levels, in the soil at the edges of a water reservoir should be monitored. The identification of bacteria reported as plastic degraders in the soil, and previously in the water, is promising, and their ability to spontaneously ensure the detoxification of the ecosystem should be further investigated.