Sediment boron and its relation to sediment properties in a tropical estuary

Abstract

Boron in the sediments of Mandovi estuary varied from 8.0 to 258.0 ppm with an average of 118 ppm. It showed an inverse relation to the texture of sediments and was found to be concentrated in silt and clay fraction with generally decreasing concentrations from mouth towards upstream. Seasonal variations of boron indicate all higher values during pre-monsoon (50.8 to 216.0 ppm; av. 128 ppm) while very low to very high concentrations during post-monsoon (8.0 to 258.0 ppm; av. 108 ppm). During monsoon itself narrow range was observed with moderate concentrations (87.0 to 148.0 ppm; av. 118 ppm). Clay minerals by x-ray diffractometry of sediments showed the presence of Kaolinite + chlorite (av. 60%), Illite (av. 15%) and Montmorillonite (av. 6.5%) while the non-clay minerals like Feldspar (av. 4.84%) and Quartz (av. 8.67%) were found all along the estuary and the Gibbsite (av. 9.84%) was found only in the upstream