Environmental magnetic and textural characteristics of two estuarine core sediments from Bay of Bengal, India

The present study is aimed to assess the magnetic susceptibility (χlf), frequency-dependent susceptibility (χfd %) and geochemical and textural characteristics of two core samples collected from Adyar estuary and Ennore creek along the Chennai coast, Tamil Nadu. The magnetic susceptibility (χlf) profile of Adyar core sample shows an increasing trend in the upper section (top 20 cm) with values about 57.9 × 10⁻⁸ m³kg⁻¹, compared to its bottom section which has values of 4 × 10⁻⁸ m³kg⁻¹, with an average of 25.09 × 10⁻⁸ m³kg⁻¹.While the magnetic susceptibility values of Ennore core is showing an increasing trend from bottom to top (552.7 to 969.6 × 10⁻⁸ m³kg⁻¹), with an average of 704.11 × 10⁻⁸ m³kg⁻¹, which is higher than that of Adyar estuary, it suggests an increased content of ferromagnetic minerals in the sediments. In both of these core sediments, the silt-sized particles show a good correlation with the low-frequency magnetic susceptibility values (χlf), which indicates that the magnetic minerals mainly belong to these sizes. The textural analysis and magnetic studies indicate that Ennore creek sediments are having high magnetic susceptibility, while Adyar sediments are showing a mixed grain nature. These results suggest anthropogenic origin of the sediments. Also based on the geochemical accumulation index calculated for Ennore core, the sediments are falling in the category of very highly polluted. Thus, the present study indicates that environmental magnetic studies can be used as a rapid tool to monitor and to do qualitative assessment of the level of pollution in urban areas.