## 3 Results and Discussion
### Major and Trace Element Assessment in Crops
#### 3.5.1 Heavy Metals in Plants
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Products** & \multicolumn{6}{c}{**Element Concentrations (mg kg\({}^{-1}\))**} & \multicolumn{3}{c}{**References**} \\ \cline{2-7}  & **Cd** & **Co** & **Cr** & **Cu** & **Ni** & **Pb** & **Zn** & \\ \hline Wheat and corn grains & 0.10 & - & - & - & - & 0.20 & - & [92] \\ Sunflower seeds & 0.50 & - & - & - & - & 0.10 & - & [93] \\ Crops & 0.20 & - & 2.30 & 73.30 & 67.90 & 0.30 & 99.40 & [94] \\ \hline \hline \end{tabular}
\end{table} 
Table 12: The maximum permissible levels (MPLs) of heavy metals in the grains and seeds of wheat, corn, sunflower, and crops according to different authors. In _corn_, the highest concentrations of Cr were found in the leaves, with concentrations ranging from 2.386 \(\pm\) 0.0071 to 2.501 \(\pm\) 0.011 mg kg\({}^{-1}\) d.w., while in caryopsis, the concentration ranged from 0.246 \(\pm\) 0.016 to 0.547 \(\pm\) 0.052 mg kg\({}^{-1}\) d.w. The average value of Cr in leaves and corn grains was 2.077 mg kg\({}^{-1}\) and 0.361 mg kg\({}^{-1}\), respectively, when cultivated on soils fertilized with sewage sludge [101]. The accumulation of chromium in _sunflowers_ demonstrated a distinct pattern, with the achenes containing the highest concentrations (0.711 \(\pm\) 0.033-2.095 \(\pm\) 0.055 mg kg\({}^{-1}\)), whereas in the leaves, it varies between 0.042 \(\pm\) 0.002 and 0.714 \(\pm\) 0.039 mg kg\({}^{-1}\). Reference [101] suggests that both corn and sunflower are good accumulators of Cr, particularly in the root. According to his study, the concentration of Cr decreases in the following order: root \(>\) stem \(>\) leaves \(>\) achenes for sunflower and root \(>\) leaves \(>\) stem \(>\) caryopsis for corn. There are no regulated maximum values allowed for total Cr in the edible sections of crops. However, Table 12 presents the permissible limit of Cr in crops reported by [94]. In _wheat_, the leaves recorded the lowest Cu average values ranging from 5.825 \(\pm\) 0.115 to 25.968 \(\pm\) 1.195 mg kg\({}^{-1}\), while the average level of Cu in caryopsis ranged from 8.218 \(\pm\) 0.177 to 58.397 \(\pm\) 0.467 mg kg\({}^{-1}\). This indicates that the concentration of Cu in wheat is higher in the caryopsis than in the leaves. In _corn_, the concentration of Cu was found to be higher in the leaves, with an average concentration of 20.539 \(\pm\) 0.0270-22.779 \(\pm\) 0.307 mg kg\({}^{-1}\) compared to caryopsis, where the values were between 1.268 \(\pm\) 0.074 and 3.076 \(\pm\) 0.017 mg kg\({}^{-1}\). This demonstrates that the distribution of Cu in corn varies between leaves and caryopsis. In the case of _sunflowers_, in TUL area, the mean concentration of Cu in the leaves ranges between 11.859 \(\pm\) 0.073 and 86.089 \(\pm\) 0.863 mg kg\({}^{-1}\). In seeds, the concentration varies from 28.958 \(\pm\) 0.230 to 54.319 \(\pm\) 0.363 mg kg\({}^{-1}\), with the maximum value recorded at sampling site I-6. In SEN area, the mean content of Cu is 535.348 \(\pm\) 0.535 mg kg\({}^{-1}\) in the leaves, while in VAD area, it varies between 235.947 \(\pm\) 6.842 and 318.245 \(\pm\) 8.911 mg kg\({}^{-1}\). In the seeds, Cu content is between 80.496 \(\pm\) 0.724 and 120.146 \(\pm\) 8.290 mg kg\({}^{-1}\), S-2 registering the maximum concentration. The distribution of Cu in sunflowers varies significantly depending on the location and the agricultural chemical treatments of the plant. The concentration of Cu in _wheat_ and _corn_ was found to be below the maximum limit recommended by [94] for crops, which is 73.30 mg kg\({}^{-1}\). However, in _sunflowers_, the concentration of Cu exceeded the limit in some cases. The maximum permissible limits of Cu content regulated in Europe for sunflower seeds are not defined. Therefore, the results for sunflowers indicate the need for further research to determine the safe limits of Cu content in sunflower seeds. According to [62], the range 20-100 mg kg\({}^{-1}\) can be used to assess the Cu toxicity threshold of plants.