Dissolved Heavy Metals in the Rupsha River Near Khulna Shipyard, Bangladesh: Spatial and Seasonal Variation in the Surface Waters

Abstract

Shipyard activities can introduce dissolved metals to adjacent waterways through hull maintenance, painting, sanding, fuel handling, and waste discharge. This study assessed spatial and seasonal variation in dissolved heavy metals in surface water of the Rupsha River near Khulna Shipyard, Bangladesh. Twelve river-water samples were collected during the pre-monsoon and post-monsoon periods of 2023. Samples were collected at approximately 0.30-0.61 m depth, filtered through 0.45 µm membrane filters, acid-preserved, and analyzed for Cr, Mn, Ni, Cu, Zn, As, Hg, and Pb using EDXRF. Descriptive statistics, station-level exceedance analysis, contamination factor (CF), Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), Metal Index (MI), and GIS-based IDW interpolation were used to evaluate contamination patterns. Mean pre-monsoon concentrations were Cr 3.67, Mn 26.84, Ni 16.03, Cu 22.96, Zn 13.96, As 1.22, Hg 6.86, and Pb 3.41 mg/L. Mean post-monsoon concentrations were Cr 1.32, Mn 1.99, Ni 0.56, Cu 3.25, Zn 5.76, As 1.99, Hg 9.67, and Pb 1.58 mg/L. Most metals decreased during the post-monsoon period, whereas As and Hg increased. CF and pollution-index results indicated severe station-level contamination, particularly for Hg, Pb, As, Cr, Mn, and Ni. Spatial patterns showed localized hotspots near shipyard-influenced sections of the river. The findings indicate substantial dissolved metal contamination in the Rupsha River near Khulna Shipyard and highlight the need for regular monitoring, source-control measures, and future sediment, biota, and human-exposure assessments.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 15(1), 2026, P 107-121