## 3 Results and Discussion
### Sorghum Metal Transfer on the TE-Contaminated Site and Biomass Quality
#### 3.3.2. TE Transfer in the Aerial Biomass of the Sorghum  
In general, Trudan HL had higher TE content than Biomass 133, even though this varied between areas and specific TEs (Figure 3). In addition, according to Figure 3, area 2 resulted in the lowest TE accumulation, regardless of the cultivar and the TE, which correlates well with its lowest level of contamination. A positive correlation between TE extractable concentrations and biomass accumulation was also observed (\(p<0.05\)). However, this is not true for area 1, which had the lowest extractable TE concentrations but high TE contents in the biomass. The link between dry weight and TE concentrations, especially Zn and Cd, might suggest that the lowest TE contents were obtained at the end of the growth period, where the biomass was the highest. To confirm this assumption, additional experiments should be performed to follow the composition of different cultivars at different times of growth, in order to investigate this dilution effect.  
When comparing with other studies, the average Zn concentrations in the biomass of the two cultivars were between 2.6 and 6 times higher than concentrations found in sorghum grown in a culture chamber with artificially contaminated soil (50 \(\mathrm{\SIUnitSymbolMicro g}^{-1}\)) [56]. This can be possibly related to the different levels of contamination between our study and [PERSON] et al., as their maximum Zn concentration was six to nine times lower than the ones found in the sediments of the present study. Regarding Cd, a field plot experiment on TE-contaminated soil [13] found concentrations in sweet sorghum of the same order as in  
Figure 3. Concentrations of Zn, Cd, Pb, and Cu in the sorghum Biomass 133 (blue) and the sorghum Trudan Headless (orange) in the three areas (1 = area 1, 2 = area 2, 3 = area 3). The box plots indicate the median and the 25 and 75 percentiles; red diamond = mean. Significant differences between conditions are indicated by different letters at the level of \(\alpha=0.05\).  
our study. Conversely, [33] measured 10 to 20 times lower Cd concentrations in sorghum biomass (0.2 ug g\({}^{-1}\)) after 40 days of growth. The different concentrations reported in these studies could be explained by the use of different cultivars, the different growth duration before harvest, or a different extractable fraction in sediment. Pb concentration in the leaves of three sweet sorghum cultivated on a contaminated site ranged from 37 to 42 ug g\({}^{-1}\) of DM [13]. In our study, Pb concentrations (<2 ug g\({}^{-1}\), Figure 3) were much lower than those reported in [13] and in other Poaceae, such as barley (8 ug g\({}^{-1}\)), cultivated on uncontaminated site [50]. Regarding Cu, [34] showed, for different cultivars of sorghum, that concentrations in the leaves were of 3 and 4.5 ug g\({}^{-1}\) on uncontaminated and contaminated soil, respectively. Concentrations found in our study were similar, indicating that Cu concentrations could be considered normal for the two cultivars.  
The bioconcentration factors (BCF) were calculated for the two cultivars for the different areas and TEs (Supplementary Table S2). The highest BCFs were found for Cd, irrespective of cultivar or area, varying from 0.26 to 0.43 for Biomass 133 and 0.53 to 0.76 for Trudan HL. All factors were below 1, characterizing an excluder behavior, which is one trend required in a phytostabilization strategy.