ENVIRONMENTAL IMPACT OF PHOSPHATE FERTILIZERS AND BY-PRODUCTS ON AGRICULTURAL SOILS - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 52

was just applied on the study parcels; the corresponding metal concentrations at the different
depths represent the soil background concentrations (Figure 3 and Figure 4).
Figure 3. Time-variation of TEs concentrations in the soil profile - Reference parcel R (T=0);
PG-amended parcels P1 (T1 = 5 months); P2 (T2 = 12 months); and P3 (T3 = 16 months).
Figure 4. Time-variation of TEs concentrations in the soil profile - Reference parcel R (T=0);
PF-amended parcels P1 (T1 = 4 months); P2 (T2 = 11 months); and P3 (T3 = 15 months).
It could be seen from PG application Figure 3, for the overall depth, that TEs showed
different periods for reaching their peak concentration values. Peaks for TEs occurred in PG1
for Cd (in September) and PG2 for Zn and Pb (in April) before it decreased gradually with
time (Spring-Summer) to reach a minimum value in PG3 (in August) within the initial