Geostatistical Analysis of Suspended Particulate Matter Along the North-Western Coastal Waters of Bay of Bengal

A geostatistical approach was used to envisage the spatial variability of the suspended particulate matter (SPM) concentration in the coastal waters of the Bay of Bengal. The study was conducted in-between Subarnarekha and Rasulpur estuary. Semivariogram analysis followed by ordinary kriging unfolded the environmental factors influencing spatial variation of the SPM concentration. An alongshore increasing trend of SPM concentration was observed toward the eastern sector of the study area (67–168 mg/l), with maximum concentration observed in the Junput–Rasulpur belt. While the western sector, from the Subarnarekha estuary mouth to Tajpur, showed relatively low SPM concentration (≤16–46 mg/l). The high-energy regime of the Hugli estuarine flow was found to be the dominant factor behind the high SPM concentration in the eastern sector. The fluvial activity of the tidal inlets and subsurface topography resulted in the intermittent occurrence of high SPM concentration in the alongshore direction. This was explained by the observed cyclicity and nugget effect in the semivariogram. The in situ analysis revealed a dominancy and uniform distribution of muddy suspended sediments in the eastern sector compared to the sandy nature of suspended sediments in the western sector. The eastern zone was marked by deposition and pollution-prone regime, whereas the western zone was found to be in a predominant erosional regime. The geostatistical approach provided an advantage over the classical statistical method, as it included the aspect of spatial distribution, with the production of near accurate cartography of SPM concentration and its associated uncertainty.