# Temporal Variations of Heavy Metal Sources in Agricultural Soils in Malta
## 3 Results and Discussion
### Chemical Analysis
#### 3.2.3 Multivariate Statistical Analysis
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline  & \multicolumn{3}{c}{**(a) Pre- \& Post-Harvesting Stages**} & \multicolumn{3}{c}{**(b) Pre-Harvesting Stage**} & \multicolumn{3}{c}{**(c) Post-Harvesting Stage**} \\  & \multicolumn{1}{c}{**PC1a**} & \multicolumn{1}{c}{**PC2a**} & \multicolumn{1}{c}{**F1a**} & \multicolumn{1}{c}{**F2a**} & \multicolumn{1}{c}{**PC1b**} & \multicolumn{1}{c}{**PC2b**} & \multicolumn{1}{c}{**F1b**} & \multicolumn{1}{c}{**F2b**} & \multicolumn{1}{c}{**PC1c**} & \multicolumn{1}{c}{**PC2c**} & \multicolumn{1}{c}{**F1c**} & \multicolumn{1}{c}{**F2c**} \\ \hline Co & **0.952** & _0.124_ & **0.967** & _0.100_ & 0.443 & **0.824** & _0.241_ & **0.835** & **0.822** & \(-\)0.343 & **0.709** & **0.410** \\ Cr & **0.919** & _0.134_ & **0.861** & 0.329 & **0.709** & _0.114_ & 0.530 & _0.214_ & **0.843** & _0.111_ & **0.663** & **0.448** \\ Cu & **0.893** & \(-\)_0.125_ & **0.807** & _0.271_ & **0.854** & \(-\)_0.159_ & **0.896** & _0.030_ & **0.712** & _0.284_ & _0.212_ & **0.777** \\ Fe & **0.893** & \(-\)_0.207_ & **0.735** & **0.592** & **0.810** & \(-\)_0.117_ & **0.669** & _0.037_ & _0.229_ & **-0.637** & _0.199_ & _0.072_ \\ Mn & **0.970** & _0.111_ & **0.958** & _0.216_ & **0.864** & _0.170_ & **0.857** & 0.309 & **0.828** & _0.172_ & 0.310 & **0.951** \\ Ni & **0.985** & _0.121_ & **0.961** & _0.265_ & _0.060_ & **0.951** & \(-\)_0.150_ & **0.964** & **0.864** & \(-\)_0.158_ & **0.818** & 0.359 \\ Pb & **0.954** & _0.219_ & **0.995** & _0.053_ & 0.529 & \(-\)0.373 & 0.468 & \(-\)0.172_ & _0.272_ & 0.558 & _0.205_ & _0.031_ \\ Sr & **0.618** & \(-\)_0.281_ & **0.458** & 0.394 & \(\mathbf{-\)0.716} & _0.297_ & \(\mathbf{-\)0.648} & _0.096_ & \(\mathbf{-\)0.684} & 0.351 & \(\mathbf{-\)0.812} & \(-\)_0.066_ \\ Zn & \(-\)0.223 & **0.932** & \(-\)_0.022_ & \(\mathbf{-\)0.446} & 0.458 & \(-\)_0.019_ & 0.550 & _0.094_ & 0.407 & 0.527 & _0.078_ & 0.399 \\ \hline \end{tabular}  
\({}^{2}\) PC1a, PC1b, PC1c—Principal Component 1 for the three results configurations; PC2a, PC2b, PC2c—Principal Component 2 for the three results configurations; FIa, Fib, FIc—Factor 1 for the three results configurations; F2a, F2b, F2c—Factor 2 for the three results configurations.  
\end{table} 
Table 8: PCA initial loading matrix and rotated factor loadings matrix \({}^{2}\). It can be observed that the concentration of the elements has affected considerably the classification of the elements with their respective possible sources. Fertilizer addition and surrounding environmental pollutants have unbalanced the ecosystem, which was possibly at least partly restored after crop growth. Results from the pre-harvesting stage indicate that Cr, Cu, Fe, Mn, Pb, Sr, and Zn are associated to anthropogenic sources available which were present due to the precipitation of pollutants in the rain from the atmosphere, fertilizer addition to prepare the soil for crop cultivation, urban dust, and vehicle and industrial emissions. Post-harvesting results for the same elements suggest a prevalent lithogenic source or mixed with an anthropogenic one in the case of Cr, Fe, and Mn. It also resulted that Fe is only partially affected by the concentration available in the soil matrix. This is due to the high natural Fe content in the soil which was proven in the high loading assigned to Fe in the post-harvesting PCA and rotated factor loadings. These results tie in with studies from [PERSON], et al. (2006) [4] and [PERSON], et al. (2014) [35], who suggest that Cr, Zn, Fe, and Mn are precipitated from the oxides and hydroxides of sedimentary rocks within the Mediterranean region and are present in areas which are of calcareous nature [4; 41]; hence, consolidating a lithogenic nature towards these elements when a low quantity of added nutrients is present in the soil. A similar pattern is observed with Pb which results match perfectly those issued by [PERSON], et al. (2020) [36].