Are industrial footprints driving potentially toxic element contamination in the Karnaphuli River Estuary?

Abstract

Background

The contamination of estuarine sediments with potentially toxic elements (PTEs) is a growing concern in industrialized regions. The Karnaphuli River estuary, a critical ecosystem in Bangladesh, is exposed to untreated industrial, agricultural, and urban effluents, posing ecological and health risks.

Objective

This study aimed to assess the levels and spatial distribution of chromium (Cr), cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), and nickel (Ni) in sediments of the estuary, along with potential contamination sources and the associated ecological risks.

Methods

Sediment samples were collected from six key discharge points and analyzed using atomic absorption spectrophotometry. The data were examined to identify contamination patterns using geostatistical techniques, element correlations, and possible pollution sources. Results were compared with international sediment quality guidelines and findings from global estuarine systems to assess ecological risks.

Results

The concentrations of Cr (77.13–165.29 mg kg^-1), Zn (67.86–83.29 mg kg^-1), and Cu (53.28–73.66 mg kg^-1) were highest near industrial zones. Strong correlations were observed among Cr, Zn, and Pb, indicating overlapping anthropogenic sources such as industrial discharges and urban runoff. When compared to global estuarine systems, the contamination levels of PTEs in the Karnaphuli estuary were found to be moderate to high, reflecting similar patterns observed in other industrialized regions. Several PTEs exceeded permissible limits, raising significant ecological concerns.

Conclusions

The findings underscore the need for stricter wastewater management, advanced remediation technologies, and robust monitoring frameworks to mitigate contamination risks. The study provides a baseline for policymaking to protect estuarine ecosystems in rapidly industrializing regions.