Heavy metals pollution in riverine sediments: Distribution, source, and environmental implications.

Area of Science:

• Environmental Science
• Geochemistry
• Ecotoxicology

Background:

• Riverine sediments serve as crucial indicators of heavy metal pollution.
• River Kabul in Pakistan faces potential contamination risks affecting human health and aquatic ecosystems.
• Understanding heavy metal distribution and sources is vital for effective environmental management.

Purpose of the Study:

• To assess the levels and spatial distribution of heavy metals (Cr, Mn, Co, Ni, Cu, Zn, Cd, Hg, Pb, Fe, Al) in River Kabul sediments.
• To identify the pollution status and potential ecological risks associated with these heavy metals.
• To determine the sources and correlations of heavy metal contamination in the riverine environment.

Main Methods:

• Analysis of heavy metal concentrations in riverine sediments using established methods.
• Calculation of contamination factor (CF), pollution load index (PLI), and geo-accumulation index (Igeo) to assess pollution levels.
• Application of correlation statistics, cluster analysis, and principal component analysis (PCA) to determine metal sources and relationships.
• Evaluation of ecological risks using threshold effect concentrations (TECs) and probable effect concentrations (PECs).

Main Results:

• Significant spatial variations in heavy metal concentrations were observed, with Iron (Fe) and Aluminum (Al) being most abundant.
• Cadmium (Cd) and Mercury (Hg) exhibited the highest pollution degrees, with geo-accumulation index (Igeo) values indicating moderate to extreme pollution.
• Contamination factor (CF) and pollution load index (PLI) values highlighted monitoring site S-9 as the most polluted.
• Principal component analysis identified industrial, agrochemical, mining, and domestic wastewater discharges, alongside geogenic inputs, as primary sources.
• Cadmium (Cd) and Mercury (Hg) posed a very high potential ecological risk (PERI), necessitating immediate attention.

Conclusions:

• River Kabul sediments are contaminated with various heavy metals, posing significant ecological risks, particularly from Cd and Hg.
• Multiple anthropogenic and geogenic sources contribute to the heavy metal pollution in the river.
• Urgent pollution control strategies are required to mitigate the adverse biological effects and protect the riverine ecosystem.