Assessment of Hydrogeochemical Characteristic in an Urbanized Estuary using Environmental Techniques

Assessment of spatial variation in hydrogeochemical characteristics was studied in a tropical estuary, Cochin India. Noticeable spatial variations was observed in transparency, turbidity, salinity, PO43--P, NH4+-N, dissolved Cd and Hg. Light limitation due to high turbidity reduced the primary production, even under high nutrient conditions. An enrichment of both dissolved and sediment Cd, Pb and Hg were noticed in the harbour region associated with high organic carbon and silty-clay fraction. The multivariate statistical methods such as factor analysis (FA), cluster analysis (CA), canonical correspondence analysis (CCA) and analysis of variance (ANOVA) were employed to appraise and interpret complex hydrogeochemical data, to categorize pollution sources for better understanding about various biogeochemical processes. CA and CCA showed a meaningful classification of estuarine samples based on spatial criteria. Statistical analysis revealed that Secchi disk depth (SD), water salinity, NO2--N, NO3--N, dissolved oxygen (DO), total phosphorus (TP), total nitrogen (TN), petroleum hydrocarbon (PHC), sediment pH, organic carbon (SOC) and Pb were the most crucial parameters influencing the hydrogeochemistry of the estuary.