## 1 Introduction
PAHs, in particular, are of great concern both for the environment and human health, mainly due to the strong toxic properties they possess and the possibility of bioaccumulation [33; 34], to the point that some of them are considered \"priority pollutants\" due to their carcinogenicity by the U.S. Environmental Protection Agency [35]. In general, the natural attenuation process takes place, that is, biodegradation mediated mainly by the native soil microbial community, which rapidly changes in both the type and quality of species through selective pressure operated by the specific contaminants [36]. However, each soil microorganism does not express all the required enzymes needed to oxidize hydrocarbons entirely, so only symbiotic relationships with other microorganisms (consortia) allow their effective potential to be fully exploited [37; 38]. Unfortunately, PAHs are not easily degraded naturally and persist for long periods in soil, especially when they have a high molecular weight. Because most PAHs stay in the surface layers of soil explored by plant roots [39], these compounds pose a considerable threat to human health due to uptake from the soil by plant roots, compounded by atmospheric deposition through leaf stomata [40]. In addition to soil characteristics and plant species, plants uptake depends on PAHs' properties, such as the octanol-water partition coefficient (Kow) [41]. Highly lipophilic substances with log Kow \(>5\) can adsorb tightly on root surfaces. In contrast, hydrophilic substances with log Kow \(<5\) may be taken up by roots and translocated into other areasof the plant, such as the shoots. This especially concerns water-soluble chemicals such as pyrene (log Kow = 4.88) [42]. The risk of contaminants entering the food chain makes contamination in agricultural areas of particular concern. At the same time, it is also necessary to reduce the soil degradation resulting from the remediation of this ecosystem as much as possible. In this context, phytoremediation technologies play an essential role. The use of plants is particularly suitable for remediating soils aimed at agricultural production [43]. In addition to the attractive remediation features already mentioned, from low cost to a reduced environmental impact [12], these technologies do not interfere with other activities occurring outside of contaminated areas. After an oil spill, plants provide optimal conditions for the proliferation of microorganisms capable of oxidizing hydrocarbons. This results in a greater drop in hydrocarbon concentration in vegetated soils compared to non-vegetated soils, confirming that rhizodegradation (oxidizing activity provided by rhizosphere microorganisms) is the main factor in the decomposition of hydrocarbon compounds [44; 45]. Depending on soil characteristics, further contributions in reducing contamination may come from uptake by certain plant species, resulting in the degradation of contaminants into harmless substances or their immobilization through accumulation by roots [46]. Considering the above, while the release of root exudates by the plant is crucial in decreasing the concentration of PAHs--through increased populations of hydrocarbon-oxidizing microorganisms--for biodegradation to actually occur, it is important to exploit appropriate rhizodegradation processes [44]. However, PGPB are very specific in their action and their efficacy, which are influenced by many factors related to complex soil and plant interactions, making the selection of potentially effective consortia nontrivial [47]. This study deals with an extensive laboratory-scale experimental campaign conducted on soil from an agricultural area contaminated by a diesel oil spill due to the break-in of a pipeline near the field. The purpose was to evaluate the feasibility of phytoremediation by assessing the effectiveness of three plant species: _Zea mays_, _Lupinus albus_ and _Medicago sativa_.