Impact of the Controlled Dump of Fez City (Morocco): Evaluation of Metallic Trace Elements Contamination in the Sediments

Abstract

In order to qualify and quantify the impact of sediment contamination in hydric settings by metallic trace elements (MTE) emanating from the controlled dump of Fez city (northern Morocco), leachate and sediment sample analyses were carried out. The leachates collected from the 24 sites are characterised by a pH between 6.91 and 8, a COD varying between 430.7 and 7962 mg/L, an NTK content up to 1955 mg/L, with an average of 1514 mg/L, and a nitrate concentration reaching 46 mg/L in some samples, which exceeds the standards for discharges into the natural environment. The chromium content emanating mainly from household waste varies between 1.69 and 4.90 mg/L. The MTE content (As, Cd, Co, Cr, Cu, Ni, Pb, Zn and Fe) of the different leachates varies from one basin to another. The sediments downstream of the dump along the sampling profile show pH values between 7.34 and 8.21 (compared to 7.96–8.82 for the reference samples), and electrical conductivity values fluctuate between 1.21 ms/cm and 5.37 ms/cm for the contaminated sediments (compared to 0.8 ms/cm for the reference sediment). The analysis of metallic trace elements in the sediments by ICP-AES shows that their content varies slightly from one sampling point to another. Furthermore, they do not vary considerably from the surface (0 cm) to the depth (20 cm). The average values of metallic element concentrations are 45.83 ± 2.14 mg/Kg for Cu, 4.40 ± 0.07 mg/Kg for Cd, 43.76 ± 3.40 mg/Kg for Cr, 72.99 ± 1.85 mg/Kg for Ni, 21.71 ± 6.55 mg/Kg for Pb and 102.02 ± 7.28 mg/kg for Zn. In effect, the negative environmental impact of Fez controlled dumping site is ostensibly underlined both by (i) the pollution load index values, which indicate a strong and progressive deterioration along the thalweg, and (ii) the statistical analysis (PCA), which reveals a common origin of the deduced pollutants through the strong correlation between the majority of the analysed elements.