3. Results and discussion
3.1. X-ray fluorescence
In a previous work [27], levels of metal and metal oxides in water hyacinth root and shoot were determined by X-ray fluorescence spectroscopy (XRF) as listed in Table 1. In a general description, the concentration of metal oxides showed higher levels in root samples as compared with shoot samples and the most remarkable difference is noticed for SiO2, Al2O3, Fe2O3 and P2O5. The only exception is that the concentration of K2O in shoot samples is higher than root samples. Also, the concentration of heavy metals showed higher levels in root samples as compared with shoot samples since the remarkable difference is noticed for Sr, Zn and Cu respectively. Such differences are in fact attributed to the differences in biochemistry uptake in both plant parts; the smaller harder cations often bind preferentially to the smaller atoms such as N and O in the roots while when translocated to the shoots, they are bound to more complex compounds such as oxalates or phytochelatins [28]. It is also pointed out that the existence of metal oxides results in high possible hydration of metals that could act like aluminum and accordingly could enhances the uptake of organic acids from the aquatic environment.