<p>The accumulation of heavy metals in soils, often resulting from socio-economic development, poses a significant environmental challenge. Metallic elements can be adsorbed by organic matter and minerals in the soil, eventually accumulating in river sediments. This study aims to assess the extent of metal contamination in the sediments of the El Maleh River and its estuary in the Mohammedia region of Morocco and identify potential sources of pollution. A total of 27 sediment samples were collected along the river, covering the estuary, urban areas, industrial zones, and agricultural areas. Samples were analyzed for physicochemical properties (pH, electrical conductivity, organic matter, CaCO3, and texture) and heavy metal concentrations (Cd, Cr, Cu, Fe, Pb, and Zn). Multiple pollution indices, including the geoaccumulation index (Igeo), contamination factor (CF), enrichment factor (EF), pollution load index (PLI), and ecological risk index (RI), were calculated to evaluate the level of contamination and ecological risks. The results indicate that the sediments have a pH ranging from slightly acidic to slightly alkaline (6 to 7.4) and exhibit low to moderate salinity (0.31–9.20 µS/cm). In addition, the organic matter content is predominantly high, with an average of 15.83%. Also, the sediments are characterized by moderate to high levels of CaCO3 (averaging 22.88%) and a predominantly silty to loamy texture. Notably, the analysis revealed that the concentrations of five metals (Pb, As, Cr, Cu, and Zn) exceed the recommended threshold standards, indicating significant environmental risks. In contrast, the concentrations of Fe and Ni in the samples remain within acceptable limits. The Igeo index for Pb, As, Cu, Ni, and Cr indicates that these sediments are moderately contaminated to contaminated. Arsenic displays moderately high contamination factor (CF) values, indicating moderate to considerable contamination; chromium shows significant contamination, and nickel indicates low contamination. The enrichment factor (EF) calculations reveal enrichment in chromium and zinc, with low contamination for lead, nickel, copper, and arsenic. The integrated pollution assessment using the pollution load index (PLI) indicates that lead, copper, zinc, arsenic, and chromium are the most significant pollutants. The ecological risk index (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="42990_2025_162_Article_IEq1.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">${E}_{r}^{i}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>E</mi> <mrow> <mi>r</mi> </mrow> <mi>i</mi> </msubsup> </math></EquationSource> </InlineEquation>) suggests that lead, arsenic, chromium, and zinc pose medium ecological risks, while copper presents a substantial risk to aquatic fauna and flora. The risk index (RI) indicates moderate ecological risk for zinc, copper, and chromium and considerable risk for Pb and As. These findings highlight the urgent need for targeted remediation strategies and enhanced monitoring protocols in the Mohammedia region, focusing on industrial discharge management. Implementing stricter environmental regulations and further investigating potential bioaccumulation in the aquatic food chain is recommended to mitigate long-term ecological and public health impacts.</p>

Assessing trace metal pollution and ecological risks in the sediments of the El Maleh river estuary (Mohammedia, Morocco)

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发表日期：

2025年4月22日

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Samir Nadem,
Ahmed Barakat,
Mohamed El Baghdadi,
Hassan Mosaid,
El Houssaine Bouras,
Oussama Nait-taleb,
Sana Elomari,
Lahcen Eddahbi

摘要

The accumulation of heavy metals in soils, often resulting from socio-economic development, poses a significant environmental challenge. Metallic elements can be adsorbed by organic matter and minerals in the soil, eventually accumulating in river sediments. This study aims to assess the extent of metal contamination in the sediments of the El Maleh River and its estuary in the Mohammedia region of Morocco and identify potential sources of pollution. A total of 27 sediment samples were collected along the river, covering the estuary, urban areas, industrial zones, and agricultural areas. Samples were analyzed for physicochemical properties (pH, electrical conductivity, organic matter, CaCO3, and texture) and heavy metal concentrations (Cd, Cr, Cu, Fe, Pb, and Zn). Multiple pollution indices, including the geoaccumulation index (Igeo), contamination factor (CF), enrichment factor (EF), pollution load index (PLI), and ecological risk index (RI), were calculated to evaluate the level of contamination and ecological risks. The results indicate that the sediments have a pH ranging from slightly acidic to slightly alkaline (6 to 7.4) and exhibit low to moderate salinity (0.31–9.20 µS/cm). In addition, the organic matter content is predominantly high, with an average of 15.83%. Also, the sediments are characterized by moderate to high levels of CaCO3 (averaging 22.88%) and a predominantly silty to loamy texture. Notably, the analysis revealed that the concentrations of five metals (Pb, As, Cr, Cu, and Zn) exceed the recommended threshold standards, indicating significant environmental risks. In contrast, the concentrations of Fe and Ni in the samples remain within acceptable limits. The Igeo index for Pb, As, Cu, Ni, and Cr indicates that these sediments are moderately contaminated to contaminated. Arsenic displays moderately high contamination factor (CF) values, indicating moderate to considerable contamination; chromium shows significant contamination, and nickel indicates low contamination. The enrichment factor (EF) calculations reveal enrichment in chromium and zinc, with low contamination for lead, nickel, copper, and arsenic. The integrated pollution assessment using the pollution load index (PLI) indicates that lead, copper, zinc, arsenic, and chromium are the most significant pollutants. The ecological risk index ( ${E}_{r}^{i}$ $E_{r}^{i}$ ) suggests that lead, arsenic, chromium, and zinc pose medium ecological risks, while copper presents a substantial risk to aquatic fauna and flora. The risk index (RI) indicates moderate ecological risk for zinc, copper, and chromium and considerable risk for Pb and As. These findings highlight the urgent need for targeted remediation strategies and enhanced monitoring protocols in the Mohammedia region, focusing on industrial discharge management. Implementing stricter environmental regulations and further investigating potential bioaccumulation in the aquatic food chain is recommended to mitigate long-term ecological and public health impacts.