## 3 Results and Discussion
### Bioremediation of Polluted Soil  
The polluted soil was transported to the bioremediation station and subjected to bioremediation techniques and procedures. In the first step, it was transported to the perimeter of the bioremediation site and sorted according to grammage and degree of pollution so that the shales created have similar characteristics (Figure 2A). An important objective is given by the aeration of the soil, which is carried out mechanically using the BACKUS A50 system (Figure 2B), with a very important role in determining the starting temperature value for bioremediation. Placing the bioremediation soil in prisms also involves the introduction of straw manure, which allows the temperature inside the sieve to rise and the development of microorganisms that will break down pollutants to achieve the bioremediation objectives (Figure 2C,D). After the bioremediation soil prisms were made, the soil was left to rest without being aerated. The objective was to increase the soil temperature to 30-35 degrees Celsius at a moisture value of 50%, after which an NPK addition of 1/1000 was applied. Bioremediation technologies must be chosen according to their efficiency depending on the nature of the contaminant, its concentration, and the physical and chemical characteristics of the soils. Thus, two main categories of bioremediation are differentiated: in situ through the use of indigenous microorganisms and the addition of phosphorus and nitrogen, specific enzymes with biodegradation effect [36], and ex-situ performed on bioremediation platforms that involve additional transport costs but reduced energy costs [37] but the effects of bioremediation maintain the ecological balance. The literature draws attention to the influence of soil clay content on soil hydrocarbon retention, for soils with higher permissivity runoff can reach depths of 80 cm, with clay soils being those that will hinder their bioremediation techniques [38; 39]. There are studies indicating that in the presence of glycolipids, hydrocarbons can be removed even in periods shorter than one month [40]. Inoculation with Acinetobacter haemolyticus and Pseudomonas ML2 (biosurfactant-producing strains) resulted in a 71% reduction of hydrocarbons after two months [41]. The time required to reduce the concentration of hydrocarbons differs depending on the pollutant and the agent used for biodegradation. For example, using Pseudomonas aeruginosa in the case of TPH (Total Hydrocarbon Concentration), its concentration was reduced to 42% in five weeks [42]. In the case of the soil taken from well 251 Scarisoara Noua, 21 straw bales, 1600 kg of manure, 300 kg of NPK and three aerations with the Backus were added. Thus, in about four months, the soil reached TPH concentration values of 1761 and a soil temperature of 29.5 degrees Celsius (Figure 3, Supplementary Files Table S1). In the case of the soil taken from well 560 Mihai Bravu, an initial concentration of 8638 TPH was estimated, requiring the addition of 40 straw bales, 300 kg NPK and three aeration stages and a long period of more than three months to reach the bioremediation targets (Figure 3, Supplementary Files Table S2). Figure 3: The evolution of the TPH concentration during the bioremediation of the soil from the area of well 251 Scárisoara Noua (**left**) and the soil from the area of well 560 Mihai Bravu (**right**). Figure 2: Technological stages of bioremediation of polluted soil. Similarly, for the soil taken from well 561 Mihai Bravu, 50 straw bales and 300 kg NPK were needed to achieve a soil temperature of 25.9 degrees Celsius and a TPH concentration of 1821 (Figure 3, Supplementary Files Table S3). For the soil taken from the well area of well 682 Suplac, despite the application of 20 straw bales and 250 kg of NPL after a bioremediation period of 3 and a half months, it was necessary to resume bioremediation because the objectives were not achieved. Thus, this soil was re-treated by adding a further 100 kg NPK, and ten more bales and two more rounds of aeration were required.