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Spatial and temporal distributions of water quality using multivariate statistical techniques for the evaluation of nutrients (NO(2)-N, NO(3)-N, NH(4)-N, PO(4)-P, SiO(4)-Si, total N, total P) in relation to some physico-chemical features (DO, BOD, TSS, TDS, SO (4) (2-) , Cl(-)) were studied for 31 different stations of the Mahanadi river-estuarine system in the eastern part of India. The seasonal nutrient variations (except SiO(4)-Si) exhibit higher values during monsoon season in unpolluted stations and the reverse trends for polluted stations, which are related to agricultural run-off and regional anthropogenic activities respectively. Silicate shows a well defined pattern of distribution with a higher concentration during the monsoon, which is slightly removed from the estuarine water of Mahanadi during the pre-monsoon season. The results of R-mode factor analyses revealed that anthropogenic contributions are responsible for the increase in nutrients and the decrease in DO and pH levels of the water. The magnitude of BOD with respect to total N and P demonstrates the intensity of organic pollution in the system. The removal of silicate in the saline system is clearly visible through factor analysis and the different mode of association of TSS is reflected seasonally. The relationships among the stations are highlighted by cluster analysis, represented in dendograms to categorize different levels of contamination.

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In order to establish the natural processes and geochemical factors responsible for enrichment of trace metal ions (Cu, Co, Ni, Zn and Cr) with respect to textural parameters (sand, silt and clay weight percentages) along with depth, multivariate statistical approach has been carried out for sediments in different water zones of Chilika lake, the largest brackish water lagoon in Asia. The rotated varimax factor results reveal that Cobalt enrichment is controlled by both textural parameters as well as adsorption mechanism. In fresh and saline water region, textural parameters and in mixed water, adsorption phenomenon predominates. Zn in fresh water is related to clay, whereas it is in adsorbed state in mixed water. Cu in fresh water sediments is in absorbed state and in mixed water it is related to depth and Co concentration. Cr does not show any specific association in fresh water, but in both mixed and saline water it is associated with clay minerals. Although both textural parameters and adsorption mechanism play an important role for the enrichment of trace metal ions in these lagoonal sediments, their relative importance varies with specific metal ions as well as the water quality. Sequential extraction technique was used to characterize the various forms of metals in the < 63 micro size sediments of Chilika lake. The concentrations determined indicated selective accumulation of the various metals in the different phases with spatial variability in different water zones. Slightly higher availability of Co and Zn near Balugaon township in exchangeable phase may be related to anthropogenic activities. Among the non-lithogenous (NL) phases, reducible phase associated with higher concentration of Ni, Cu and Cr. Organic bound Zn and Co contributed highest percentages among NL fractions. Residual fraction contributed more than 50% in most of the cases, reflected the predominance of physical weathering, high erosion rate along the drainage basin.