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Geochemical and statistical approach for evaluation of heavy metal pollution in core sediments in southeast coast of India
Seshan, B. R. R.; Natesan, U. & Deepthi, K.
Abstract
Industrialization coupled with urbanizaton has led to stress in the Buckingham Canal which runs
parallel to Bay of Bengal at a distance of around 1 km from the coastline. 4 sediment cores were collected along
Ennore - Pulicat stretch to determine acid leachable trace metal concentration. Core samples were collected using
gravity corer. The cores were sliced horizontally at 2.5 cm to determine the grain size, sediment composition, pH,
organic matter, calcium carbonate, acid leachable trace metals; cadmium, chromium, copper, lead, zinc. The trace
metals were extracted using acid mixture containing hydro fluoric acid, nitric acid and sulphuric acid and analysed by
atomic emission spectrophotometer. In an attempt to infer anthropogenic input from geogenic input, several approaches
including comparison with sediment quality guidelines - ecotoxicological sense of heavy metal contamination and
classification by quantitative indexes such as geoaccumalation index, anthropogenic factor, enrichment factor,
contamination factor and degree and pollution load index was attempted. Grain size analysis and sediment composition
of core samples shows Ennore is sandy in nature having a neutral pH. Organic matter enrichment is observed to a
higher extent in core 3. Core 2 at a depth of 5 cm shows organic matter of 9.4 %. calcium carbonate is totally absent
at the surface sediments in core 2. Cores collected within the canal showed a higher heavy metal concentration than
the cores collected from Pulicat lagoon and 2 km into the Ennore Sea. The trace metal concentration for cadmium, lead
and zinc in Ennore does not pose a threat to the sediment dwelling fauna whereas chromium and copper are likely to
pose a threat. Quantitative indexes place Ennore under moderately polluted. Ennore is likely to face a serious threat
of metal pollution with the present deposition rates unless stringent pollution control norms are adopted.
Keywords
Core; Depth; Ennore; Pollution; Sediment; Trace metals
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