## 3 Results and Discussion
### Characterization of the Inputs and Output Products of the Phosphate Laundries
#### 3.1.3 Geochemistry
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Elements (\%)**} & \multicolumn{8}{c}{**Sample**} \\ \cline{2-10}  & **RP-ZL** & **MP-ZL** & **CW-ZL** & **FW-ZL** & **RP-R** & **MP-R** & **CW-R** & **FW-R** \\ \hline OM & 1.36 & 0.60 & 0.58 & 1.51 & 1.22 & 1.56 & 1.72 & 3.89 \\ CaCO\({}_{5}\) & 16.87 & 14.81 & 27.16 & 17.47 & 15.85 & 14.63 & 24.19 & 8.46 \\ N & 0.004 & 0.004 & 0.003 & 0.003 & 0.005 & 0.005 & 0.005 & 0.01 \\ CaO & 41.7 & 47.93 & 39.6 & 38.3 & 45.3 & 49.51 & 36.8 & 21.5 \\ Fe\({}_{2}\)O\({}_{3}\) & 1.44 & 0.21 & 1.64 & 2.34 & 1.48 & 0.34 & 2.25 & 5.97 \\ Na\({}_{2}\)O & 0.08 & 0.01 & n.a 1 & 0.21 & 0.02 & 0.3 & n.a & n.a \\ K\({}_{2}\)O & 0.17 & 0.02 & 0.16 & 0.31 & 0.21 & 0.04 & 0.15 & 0.66 \\ Al\({}_{2}\)O\({}_{3}\) & 1.96 & 0.51 & 2.4 & 3.26 & 2.13 & 0.82 & 2.95 & 7.34 \\ MgO & 1.15 & 0.46 & 1.44 & 1.96 & 0.89 & 0.6 & 1.5 & 2.25 \\ P\({}_{2}\)O\({}_{5}\) & 25.05 & 29.37 & 18.38 & 18.81 & 23.28 & 28.45 & 15.1 & 8.45 \\ SiO\({}_{2}\) & 10.3 & 3.84 & 12.73 & 14.84 & 10.03 & 5.73 & 20.68 & 32.29 \\ LOI * & 15.1 & 15.8 & 22.65 & 18.8 & 14.44 & 13.23 & 19.47 & 20.20 \\ CaO/P\({}_{2}\)O\({}_{5}\) & 1.66 & 1.63 & 2.15 & 2.03 & 1.94 & 1.74 & 2.43 & 2.54 \\ Elements(mg/kg) & & & & & & & & & \\ Cd & 19.7 & 17.61 & 1.34 & 26 & 28.8 & 22 & n.d & 30.6 \\ Cr & 164 & 122.2 & 130 & 302.5 & 187 & 147 & 144.7 & 466.5 \\ Pb & 5.15 & 1.44 & n.d 2 & 4.37 & 3.9 & 3.4 & n.d & 8.9 \\ Sr & 1307 & 1583 & 1096 & 1240 & 1392 & 1507 & 1007 & 705  
The oxides SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), and Fe\({}_{2}\)O\({}_{3}\) characterize mainly the fine wastes (Table 3), which is indicative of the abundance of alumino-silicates in the sludge in both laundries and in particular those of Redeyef (32.29%, 7.34%, and 5.97%, respectively). Likewise, MgO (1.96% for ZL and 2.25% for Redeyef) is generally known as a component deriving from magnesium clay and dolomite. Most studies conducted on sedimentary phosphate-rocks have shown outstanding enrichment in some trace elements in the apatite [9; 26; 29; 32; 33; 34; 37; 38; 39; 40]. Furthermore, the majority of Cd, Zn, Cr, and U are characterized by their affinity to substitute for Ca in the apatite structure [41]. Strontium content ranged between 705 mg/kg and 1583 mg/kg. The highest levels characterize mainly the marketable and raw phosphates (1583 mg/kg and 1307 mg/kg for M'Dhilla-Zone L, respectively, and 1507 mg/kg and 1392 mg/kg for Redeyef, respectively). High Sr contents (1240 mg/kg) characterize also the fine wastes from M'Dhilla-Zone L (Table 3). Such high Sr contents were reported in the literature [29; 30; 32; 33; 34; 38]. Zinc contents ranged between 151.6 mg/kg and 292 mg/kg, with the highest levels detected in fine wastes (271.6 mg/kg for FW-ZL and 292 mg/kg for FW-R), whereas in all other fractions, the contents ranged between 151.6 mg/kg and 220 mg/kg. Although Zn may easily permeate the apatite structure, the high contents observed in the fine wastes, especially in Redeyef, may be attributed to the high content in OM. The distribution of Cd was different, with the highest concentrations being recorded in both fine wastes (30.6 mg/kg for FW-R and 25.9 mg/kg for FW-ZL) and raw phosphates (19.7 mg/kg for RP-ZL and 28.8 mg/kg for RP-R) (Table 3). With its bivalent state and the ionic radius of 0.97A\({}^{\circ}\)[42] being close to that of Ca (0.99A\({}^{\circ}\)), Cd can replace Ca in the apatite structure. Therefore, cadmium has been associated with the apatite structure, even though in very small quantities [29; 32; 34; 43]. Equally, cadmium can be also adsorbed by apatite crystals [44]. Chromium content ranged between 122.2 mg/kg and 466.5 mg/kg (Table 3). Fine wastes from the two laundries contained the highest amounts (302.3 mg/kg for FW-ZL and 466.5 mg/kg for FW-R), making up to three times the Cr contents in the other fractions (182 mg/kg to 187 mg/kg).