Seasonal variability of metallic trace elements in surface water and Chelon ramada (Risso, 1827) tissues from the...

This study investigates the contamination levels of MTE in the surface waters of the Moulouya Estuary during both dry and wet seasons, as well as their bioaccumulation in the tissues (liver, gills, and muscles) of two size-based groups of Chelon ramada. The mean concentrations of MTEs in water followed the order: Al (191.68 μg/L) > Pb (125.18 μg/L) > As (91.4 μg/L) > Zn (52.52 μg/L) > Cu (8.91 μg/L) > Cd (5.41 μg/L). Pb, Cd, and As levels exceeded the guidelines for water quality, and most analyzed MTE surpassed thresholds for aquatic life, suggesting potential ecological risks. Pollution Index (PI) highlighted significant Pb and As contamination, while the Heavy Metal Evaluation Index (HEI) indicated a low contamination. Metal Pollution Index (MPI) showed that S2 and S4 were the most contaminated stations, likely due to anthropogenic activities. In fish tissues, metal accumulation demonstrated organotropism; the liver accumulated the highest levels of MTE (78.06 μg/g for Zn, 15.96 μg/g for Cu, 11.98 μg/g for As, 0.058 μg/g for Cd, and 0.016 μg/g for Hg), gills showed predominant of Al (36.83 μg/g), and muscles had the lowest levels of MTE, except for As(tot) (11.26 μg/g). Human health risk revealed that HQ and HI values for MTE in muscle were below safety thresholds, indicating no non-carcinogenic risk for adults or children. However, the TCR for iAs and Cd indicates a potential long term cancer risk for children. These findings highlight the need for continuous monitoring and risk management strategies to protect vulnerable populations.