The Relationship Between pH, Organic Matter and Heavy Metal Concentrations in Surface Sediment of Ganga River, India

This study investigates the influence of pH and organic matter (OM) on the concentrations of potential toxic elements, that is, Fe, Mn, Cd, Cu, Cr, Ni, Pb, and Zn metals in the surface sediments of the Ganga River. The research explores the interaction between sediment properties and metal contamination in a 225-km stretch of the river in Uttar Pradesh, India, where industrial, agricultural, and domestic pollution contribute to heavy metal accumulation. Surface sediments act as reservoirs for these metals, influencing their mobility, bioavailability, and toxicity. Sediment samples from 10 sites were analyzed using Atomic Absorption Spectroscopy (AAS), revealing metal concentrations in the decreasing order: Fe > Mn > Cr > Zn > Ni > Pb > Cu > Cd. OM content ranged from 4.73% to 6.57% (mean: 5.79% ± 0.60%), whereas pH values (7.31-7.63) indicated slightly alkaline conditions. Correlation analysis identified significant relationships between metals and sediment properties. Strong positive correlations were observed for Mn-Pb and Fe-Cr, suggesting similar sources or geochemical behavior. Mn, Pb, Ni, and Cd correlated positively with OM, indicating its role in metal binding, whereas Fe, Cr, Zn, and Cu showed negative correlations. Furthermore, Mn, Zn, Pb, Ni, Cu, and Cd correlated positively with pH, suggesting reduced mobility in alkaline conditions, whereas Fe and Cr exhibited increased solubility. These findings underscore the importance of sediment characteristics in assessing heavy metal contamination and ecological risks. Understanding these interactions is vital for targeted pollution mitigation and sustainable river health management.