Assessment of chemical pollution in water and suspended matter in the Gulf of Skikda (northeastern Algeria)

Abstract

The assessment of marine environmental quality along the Skikda coastline, by analyzing physicochemical parameters (temperature and pH) and concentration of trace metals (Cd, Cu, Pb, and Zn) in both the dissolved phase and suspended particulate matter at five stations, allowed us to establish a preliminary diagnosis of the chemical pollution status of this coastal. The results reveal that the distribution of trace metals between the two compartments is not identical across the five sampling stations. A strong affinity for suspended matter (particulate phase) was observed for all investigated elements during both campaigns, with a partition coefficient (Kd) of approximately 10⁶. According to the LAWA classification, suspended matter at stations 5 (Tedj) and 4 (Oued Safsaf) was contaminated by Zn, Pb, Cu, and Cd, ranking their particles as polluted to highly polluted. The slightly alkaline pH of the waters favored the adsorption of very high concentrations of trace metals in suspended matter (Zn: 2785.16 µg/g⁻¹; Pb: 609.03 µg/g⁻¹; Cu: 79.18 µg/g⁻¹; Cd: 2.60 µg/g⁻¹), mainly at stations 4 and 5. However, these metals also showed significant concentrations in the dissolved phase (Zn: 1093.36 µg/l⁻¹; Pb: 49.91 µg/l⁻¹; Cu: 20.80 µg/l⁻¹; Cd: 2.36 µg/l⁻¹), exceeding the recommended standards (WHO/US-EPA) at station 5 for all studied elements, and at station 4 for Pb. Linear regression test indicates that, except for zinc, temperature exhibits a negative (inverse) correlation with metal distribution, whereas pH shows a positive (proportional) relationship. In conclusion, the Skikda coastline is enriched in trace metals as a result of anthropogenic activities, whether industrial, petrochemical, or domestic. This phenomenon is further amplified by currents, climatic conditions, and especially river inputs. Such contamination represents a potential threat to aquatic life and the balance of the entire coastal ecosystem.