RESEARCH ARTICLE Assessment of contaminants in the northwestern Bay of Bengal Romi Nambiar 1,2 & Chinmay Shah 1 & Jitender Kumar 1 & Pranav S. Shrivastav 2 & Ravi Bhushan 1 Received: 9 September 2019 /Accepted: 2 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract The coastal sediments in the northern Bay of Bengal has undergone contamination due to the heavy metal contribution from rivers. To evaluate the status of contamination in the inner shelf region of the Bay of Bengal, a sediment core chronologically constrained using 210 Pb dating technique from the northwest Bay of Bengal was investigated for several trace elements. To assess sediment quality, enrichment factor (EF), geo-accumulation index (Igeo), and Modified Nemerow Pollution Index (MPI) were derived. The influence on ecology by individual contaminants and combined contaminants was evaluated using the potential ecological risk factor (Er i ) and modified ecological risk index (MRI). The single-element pollution indices indicated that the sediment has no significant pollution by individual elements. However, the multi-elemental approach shows slight pollution in the sediment core. The ecology is at low risk by contaminants present in the sediment. Comparison of the elemental values of shelf sediment with adjacent riverine and estuarine samples demonstrates the role of estuarine environment and/or high riverine flux of sediments causing either removal or dilution of trace elements during its transport from the river to the sea. Keywords Bay of Bengal . 210 Pb dating . Trace elements . Pollution indices . Estuarine environment Introduction The last few decades have seen increasing concern of metal pollution due to rising anthropogenic contributions, especially in the aquatic ecosystem. Worldwide deterioration in water quality arises from both natural and anthropogenic processes, including soil erosion, mining, agricultural, industrial, trans- portation, and energy production–related activities (Duodu et al. 2016). Heavy metals in the marine environment have received much attention because they are toxic, non- biodegradable in the environment, easy to accumulate in or- ganisms, and increases considerably due to the inputs of in- dustrial waste, sewage, runoff, and agricultural wastes (Ebah et al. 2016). Heavy metals discharged into the marine envi- ronment by either natural or anthropogenic sources are distrib- uted between the aqueous phase and sediments through adsorption to clay, metal oxide/hydroxide, organic matter, hy- drolysis, and co-precipitation or via biological uptake (Konhauser et al. 1997; Delshab et al. 2017). Pollutants get easily bound to marine sediment particles due to their relative- ly higher surface area and mineralogical characteristic (Herut and Sandler 2006). Sediments can also be a secondary source of pollution by releasing bound metals and other pollutants to overlying water and affect the marine environment (Goher et al. 2014). Sea receives more than 90% of sediments from the rivers, which include many anthropogenic contaminants (Liu 2018). The rising inputs of metal contaminants may cause significant risk to the marine ecosystem. Several investigators have contributed towards estimation of the trace element contaminants in sea sediments (Loring et al. 1995; Rubio et al. 2000; Khan and Khan 2003; Selvaraj et al. 2004; Santos et al. 2005; Raj and Jayaprakash 2008; Fang et al. 2009). The study from the northeast coast of Bay of Bengal sediments reported Cd contamination from the untreated waste release from ship breaking industries (Khan and Khan 2003). Surface sediments from the southwest Bay of Bengal investigated to study the geochemical processes showed that the region is contaminated by Pb, Cd, Zn, and Cr, off Kalpakkam (Selvaraj et al. 2004). Raj and Jayaprakash (2008) who assessed sediments from the southwest Bay of Bengal (off Ennore) observed contamination by Cd, Cr, and Cu due to nearby heavily industrialised area. Studies on spatial Responsible editor: Vedula VSS Sarma * Ravi Bhushan bhushan@prl.res.in 1 Geosciences Division, Physical Research Laboratory, Ahmedabad 380 009, India 2 Department of Chemistry, School of Sciences, Gujarat University, Ahmedabad 380 009, India Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-09576-5