## 2 Materials and Methods
### Soil and Plant Analysis  
The soil samples were cleaned of roots, stones, and other debris, air-dried, crushed in a porcelain mortar, and sieved through a 150 \(\upmu\)m nylon mesh according to [17]. The crop samples were first sorted into leaves and grains and then washed with tap water and rinsed with distilled water to remove any dust and pesticides that might have been present. The washing process was quick to prevent any chemical elements from being lost. The plants were air-dried in a room without contamination and with good ventilation before being further dried in an oven at 80 \({}^{\circ}\)C until they reached a constant weight (Figure 3). Once dried, the samples were then crushed in a porcelain mortar, sifted through a 150 \(\upmu\)m nylon mesh, and stored in plastic bags in a desicator until the analysis. For various analyses, the soil and plant samples were pelletized using the Specac Ltd. (Orpington, UK) hydraulic press (5 tf were applied for soil samples and 4 tf for  
Figure 3: Samples of crop grains/seeds and leaves after cleaning and drying. Figure 2: Soil sampling pits from crop allotments: (**a**) wheat, (**b**) sunflower (**c**) corn. plant samples). However, the sunflower seeds, which contain oil, could not be pelletized. Therefore, they were analyzed at the surface and in section. Several methods were employed to determine the chemical properties of soil and plants [1]. The pH was measured according to [18], and organic matter (OM) and organic carbon (OC) levels were determined using [19]. The CaCO\({}_{3}\) content was measured by the volumetric method according to [20], while the other properties (SEBs = Sum of Exchange Bases, HA = Hydolytic Acidity, and DBS = Degree of **B**ase **S**aturation) were examined as per [21]. To determine the soil EC (**E**lectrical **C**onductivity) and TDS (**T**otal **D**issolved **S**alts), [22; 23] were used. The soil granulometric fractions were employed according to [24]. Moreover, advanced complementary methods were applied at INPOLDE research center of Dunarea de Jose University of Galati and \"Horia Hulubei\" National Institute for R&D in Physics and Nuclear Engineering (NIPNE) at Magurele, Romania, to study the soil and plant. The mineralogical and elemental analyses were conducted by Scanning Electron Microscopy combined with Energy-Dispersive X-ray analysis (SEM-EDX) and the Attenuated Total Reflectance-Fourier Transform Infrared technique (ATR-FTIR). The High-Resolution Continuum Source Atomic Absorption Spectrometry (HR-CS AAS) method was employed to determine toxic and potential toxic metals, such as Cd, Co, Cr, Cu, Ni, Pb, Zn, and Mn. The non-destructive Particle-Induced Gamma-ray Emission (PIGE) nuclear technique was useful to identify medium atomic mass and light elements (LEs) like Ca, Ti, Fe, as well as Na, Mg, Al, Si, P, and F.  
For the determination of the total contents of HMs in soil and plant, the following protocols were applied: _for soil_. Soil samples were prepared as described above and oven-dried at 105 \({}^{\circ}\)C until a constant mass was achieved, as per [25]. Around 1 g of each sample was treated with modified aqua regia, which is a mixture of 2.5 mL HNO\({}_{3}\) (69%), 7.5 mL HCl (37%), and 1 mL HF (48%). A control sample was also prepared using the same reagent mixture. The prepared samples were placed in a Berghof microwave oven and digested as follows: Step 1--180 \({}^{\circ}\)C, time 15\({}^{\prime}\), power 90%; Step 2--150 \({}^{\circ}\)C, time 15\({}^{\prime}\), power 90%; and Step 3--100 \({}^{\circ}\)C, time 10\({}^{\prime}\), power 90%. After cooling to room temperature for about 30 min, the digestate was filtered, transferred to 50 mL volumetric flasks, and diluted with 0.5% HNO\({}_{3}\). _For plant_: Approximately 0.3 g of finely ground and dried plant samples was placed in reaction vessels. Then, 6 mL of HNO\({}_{3}\) (69%) was added to the vessels and left overnight under a fume hood. The following day, 3 mL of H\({}_{2}\)O\({}_{2}\) (35%) was added to the teflon vessels.