S. M. Nair

Determination and distribution of endosulfan and malathion in an indian estuary

Abstract A field survey was conducted to determine the spatial and seasonal distribution of two very common pesticides, Endosulfan and Malathion, in Cochin estuary, India. Six sampling stations along the estuary were identified and analyses were carried out during premonsoon, monsoon and postmonsoon seasons. Pesticide levels were higher during the premonsoon period than during the postmonsoon season. Throughout the monsoon season, the estuary remained largely free of the pesticides except at the mid-estuarine region which was characterized by prominent agricultural runoff. One of the sampling sites located in the riverine area was designated as “pesticide-loading site” in view of its proximity to the pesticide-manufacturing unit.

Metal concentrations in recently deposited sediments of Cochin backwaters, India

Abstract The concentrations of a number of metals (Cd, Cu, Co, Cr, Fe, Mn, Ni, Pb and Zn) were determined in recently deposited sediments before, during and after flood conditions in the lower reaches of two large tropical rivers and in their adjoining estuarine beds of the Cochin backwater system, southwest India. Markedly elevated concentrations (ppm) of some metals, Cd (0.6–1.8), Cr (20–35), Ni (20–45) and Pb (12–18), were observed near the discharge outlets of industrial units. The results show enrichment of metals during post-flood periods in selected regions of the estuary, indicative of accumulation in sedimentary material. There were pronounced seasonal variations in the distribution of trace metals in the sediments which coincided with the flushing of bottom bed material to nearshore coastal plains. This study reveals that the transport of trace metals associated with bottom sediments occurs predominantly during the monsoonal months (flood conditions). Analyses of dissolved and particulate metals in overlying waters revealed that Cu and Cd concentrations consistently covaried, while Zn, Ni and Pb covaried on a seasonal basis with sediment-associated metals. There was no correlation between trace metal concentrations and organic carbon content of the sediments.

Fractionation of phosphorus in the sediments of a tropical estuary

Fractionation of phosphorus in the sediments of the Cochin estuary situated along the southwest coast of India was studied by applying sequential chemical extraction. The different forms of phosphorus were estimated seasonally (premonsoon, monsoon, and postmonsoon) under eight different schemes. The major forms of phosphorus analyzed were exchangeable P, anion exchangeable P, carbonate-bound P, labile and resistant organic P, Fe and Al P, calcium-bound P, and hydrolyzable surplus P. Quantitatively, the above fractions in isolation or in combination vary in content due to chemoestuarine variability and seasonal fluctuations. Changes in speciation have been noted in association with salinity variations in the waterway, especially following enhanced river runoff during the monsoon. The chemical forms of the sediment-bound phosphorus in the northern parts of this estuary have been shown to be modified by nonpoint sources. Sediment P fractionation defines the role of chemical speciation of phosphates (as nutrients) and is indicative of the processes controlling the pathways of P into the coastal waters. The changes in the exchangeable P, together with marked regional variations in calcium-bound P, exemplify the complex estuarine variability of phosphorus. Enhanced amounts of exchangeable P mark its appearence in high saline waters, signifying the presence of biologically available nutrient phosphorus. The calcium-bound P and hydrolyzable surplus P show significant relation with sediment organic carbon and Fe whereas other forms do not exhibit any marked covariation. The Ca and Na NTA extraction scheme is very specific in its selectivity.

On the determination and distribution of hydroxylated aromatic compounds in estuarine waters

Abstract A modified methodology to determine the hydroxylated aromatic compounds in aquatic waters and sediments has been developed. Interference in seawater samples were overcome by addition of citrate solution permitting the blue colour development on reduction of tungsto‐ and molybdo‐ phosphoric acids by the aromatic hydroxylated groups present in lignins and tannins. The above procedure was adopted to study the fate of tannin and lignin like substances (TALLS) in tropical estuarine and coastal waters and sediments receiving pulp‐paper effluents.

Phosphate fractionation in mud bank sediments from the southwest coast of India

Mud banks are unique, occurring along the southwest coast of India. They are known as ‘Zones of Bio-rhythm’, providing shelter to abundant aquatic life. The cyclic variation of nutrients in this region provides a clue to the continued and enriched presence of a variety of fish.This study reports on the different forms of phosphate in the resuspended sediments collected during the seasons with and without mud banks from the above mentioned coastal zones. Applying sequential and parallel chemical extractions using eight different schemes, the major forms of phosphate namely exchangeable P, anion exchangeable P, carbonate bound P, labile and resistant organic P, Fe-, Al- and Ca bound P and hydrolysable P have been determined.Quantitatively, these fractions vary and exhibit seasonal fluctuations. The concentration of potentially available anion exchange P, together with resistant organic and hydrolysable surplus P, provide an explanation to the existing organic food web supporting the aquatic life. Sediment phosphate fractionation reflects the role of chemical speciation of nutrients in the propagation of mud banks and is indicative of the biogenic processes controlling the pathways of phosphate in these coastal waters.

Distribution of organochlorine pesticides in a tropical waterway: HCH isomers

Pesticide residue levels in the aquatic systems are scattered and fragmentory in India. A systematic analysis of the distribution pattern of the common organochlorine pesticide Hexachlorocyclohexane (HCH) and its isomers in the waters of the tropical positive estuarine system (the Cochin Estuarine System) has been carried out for the first time. The average concentrations of HCH ranged between 0.013 and 1.125 μg 1−1. α‐HCH was found to be at an appreciable concentrations throughout the study area and formed the highest percentage (90%) of all isomers of the HCH family

Spatial diversity of trace metals in recent sediments of Cochin estuary (India)

The concentration levels of Fe, Mn, Cu, Cr, Pb, Sr, Zn, Co, Cd and Ni in the recent surficial sediments of Cochin estuary are reviewed. The significance of bottom water salinity and pH and sediment grain size and P content in the distribution of these metals is discussed. In general, most of these metals are found to be enriched in the middle estuarine sediments. Significant correlations were observed between the metals Cu, Zn, Cd, Co, Ni and Fe and Mn.

A survey of the protein content in estuarine waters

A survey of the protein content in a tropical estuary and its nearshore regions are reported for two seasons—postmonsoon (November 1987) and monsoon (June 1988)—using a modified dye binding method. The content of protein varied from 0.05 to 8.0μgl‐1 in the fresh and estuarine waters with little variability between surface and bottom values. The enhanced biological production during postmonsoon months causes a higher level of protein in the lower estuary compared to low values in the freshwater, riverine end. Increased terrestrial runoff and discharge of industrial waste mainly from seafood processing units are linked to the higher concentrations of protein in monsoon, more than double the content during postmonsoon. Auxiliary data on chlorophylla, organic NO3 ‐—N, PO3 4—P, urea and dissolved organic carbon support the above contention. Interparametric relationships suggest seasonally varying correlation between protein and chlorophylla, urea and DOC, signifying the role of biological control.

Phosphate‐phosphorus (AD‐) sorption characteristics of sediments from a very high productive coastal zone

Sorption characteristics are reported for sediments from the west coast of India, where annual mudbank phenomena occur. Experimental studies were performed on a combination involving water and sediments from the mudbank region at different phosphate concentrations. Synthetic seawater as well as kaolin were also incorporated in these studies to understand the sorption characteristics. Field and laboratory studies were conducted under varying ionic concentrations to elucidate information on the phosphate desorption features. A biphasic or two‐slope sorption pattern helped to describe the kinetics of phosphate‐phosphorus mechanism in the high productive coastal waters.

Aliphatic and polycyclic aromatic hydrocarbon contamination in surface sediment of the Chitrapuzha River, South West India

ABSTRACT Distribution (seasonal and spatial) of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of the Chitrapuzha River, Cochin, India, was investigated using gas chromatography. Significantly high concentrations prevailed during the pre-monsoon season with the industrial zones of the river appearing to be hot spots with particularly elevated levels of the hydrocarbons. AHCs ranged between 7754 and 41,173 ng/g with an average of 25,256 ng/g, while total PAHs varied from 5046 to 33,087 ng/g. n-Alkane indices and PAH diagnostic ratios point to petroleum contamination in the sediments. The significance of PAHs in the sediments was explored using universally accepted interpretation tools. Observed levels of PAHs in sediments of Chitrapuzha are likely to cause adverse effects on biota.