Assessment of ecological risk for heavy metals in surface sediment of an urban river in a developing country

Abstract

The speed of increasing threats to the riverine water resources makes it more critical to protect the health of Old Brahmaputra River ecosystems. The current study was done to investigate the concentrations, distributions, sources, and ecological risk of heavy metals in surface sediment from the Old Brahmaputra River, Bangladesh. Samples were collected from seven sites and analyzed with an inductively coupled plasma-mass spectrometer (ICP-MS). The results showed that mean concentrations (mg/kg) of heavy metals were in the order of nickel (Ni) (44.69) > chromium (Cr) (30.16) > lead (Pb) (19.31) > copper (Cu) (17.84) > cadmium (Cd) (3.94) > arsenic (As) (2.73). The contamination factor (CF), pollution load index (PLI), enrichment factor (EF), and geo-accumulation index (Igeo) indicated low to moderate contamination. Toxic unit analysis revealed that the studied metals from all stations posed low risk. The sediment of the study river was uncontaminated to moderately contaminated, posing a minimal ecological risk. Cd, Cr, Ni, and Pb originated from anthropogenic sources rather than geogenic sources, and caused the severity of contamination. In this regard, pollutant-based intensive monitoring of heavy metals and holistic ecological risk assessments are required to maintain a sound and healthy aquatic environment in the river.