comparative analytical study of the cadmium and humic acids contents of two lentic water bodies in tamil nadu, India

Humic acids, which are derived mainly from decaying organic matter, are considered as complex macromolecules having various functional groups and are very effective in the binding and removal of different cations including heavy metals. Two lentic water bodies selected for the comparative analysis of humic acids and cadmium content in this study are the Devarajan lake [polluted lake] and Srinivasapuram lake [reference lake] located in the Denkanikottai taluk of Krishnagiri district, Tamil Nadu, India. Water and soil samples were collected on every alternate month for one year from Feb. 2008 to Feb. 2009 from five fixed sites in both the lakes. While water samples were collected in polyethylene bottles, sediment samples were collected using a core sampler. In addition to the determination of cadmium in the water and sediment samples using atomic absorption spectrophotometer, the humic acids contents in the sediment samples were also quantified on a bimonthly interval. The dissolved oxygen [DO] content and biochemical oxygen demand [BOD] of the two water bodies were also monitored. BOD and DO showed considerable variations between the two lakes indicating the pollution load of the Devarajan lake. Both the lakes exhibited significant differences between their humic acids contents as well as cadmium contents. In both the lakes, the amount of cadmium in the sediments was positively correlated to the respective humic acids contents indicating the possible interaction and complex formation between humic acids and cadmium. Such interactions may be responsible for the reduction of the bioavailability of toxicants including cadmium especially in the polluted lake leading to the survival of the aquatic fauna in it

Toxicopathological impact of cadmium chloride on the accessory respiratory organ of the air-breathing catfish heteropneustes fossilis

Sublethal cadmium chloride [0.3 ppm] toxicity induced stress related morphopathological alterations in the accessory respiratory organ of the air-breathing catfish Heteropneustes fossilis [Siluriformes; Heteropneustidae] have been investigated at various intervals of exposure. The histopathological manifestation of the cadmium toxicity includes bulging of the hyperemic secondary lamellae into the lumen of the accessory respiratory organ, necrosis and sloughing of the respiratory epithelium leading to haemorrhage and fusion of SL at various stages of the exposure. Periodic alterations in the densities of epithelial cells and mucous cells along with the development of non-tissue spaces have also been noticed at different exposure periods leading to alterations in the thickness of the respiratory epithelia. The heavy metal salt exposure has affected the mucogenic activity of the respiratory epithelium not only quantitatively but qualitatively also, indicating the probable ameliorative role fish mucus in cadmium toxicity