Sujatha, C H; Deepulal, P M; Gireesh Kumar, T R(Indian Academy of Sciences, October , 2012)
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Abstract:
The distribution and accumulation of the rare earth elements (REE) in the sediments of the Cochin
Estuary and adjacent continental shelf were investigated. The rare earth elements like La, Ce, Pr, Nd,
Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the heavy metals like Mg, V, Cr, Mn, Fe, Cu, Zn, U, Th
were analysed by using standard analytical methods. The Post-Archean Australian Shale composition
was used to normalise the rare earth elements. It was found that the sediments were more enriched with
the lighter rare earth elements than the heavier ones. The positive correlation between the concentrations
of REE, Fe and Mn could explain the precipitation of oxyhydroxides in the study area. The factor
analysis and correlation analysis suggest common sources of origin for the REEs. From the Ce-anomalies
calculated, it was found that an oxic environment predominates in all stations except the station No. 2.
The Eu-anomaly gave an idea that the origin of REEs may be from the feldspar. The parameters like
total organic carbon, U/Th ratio, authigenic U, Cu/Zn, V/Cr ratios revealed the oxic environment and
thus the depositional behaviour of REEs in the region
Description:
J. Earth Syst. Sci. 121, No. 5, October 2012, pp. 1215–1227
The fertility of the coastal and estuarine waters is of great concern because of its influence on the
productivity of these waters. Seasonal variations in the distribution of organic carbon, total nitrogen and
total phosphorus in the sediments of Kuttanad Waters, a part of the tropical Cochin Estuary on the south
west coast of India, are examined to identify the contribution of sediments to the fertility of the
aquatic systems. The adjoining region has considerable agricultural activity. The fresh water zones had
higher quantities of silt and clay whereas the estuarine zone was more sandy. Organic carbon, total
phosphorus and total nitrogen were higher in the fresh water zones and lower in the estuarine zones.
Total phosphorus and organic carbon showed the lowest values during monsoon periods. No significant
trends were observed in the seasonal distributions of total nitrogen.
Ratios of C/N, C/P and N/P, and the phosphorus and nitrogen content indicate significant modification
in the character of the organic matter. Substantial amounts of the organic matter can contribute to
reducing conditions and modify diagenetic processes