Environmental geochemistry of the Pichavaram mangrove ecosystem (tropical), southeast coast of India |
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Authors: | A L Ramanathan V Subramanian R Ramesh S Chidambaram A James |
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Institution: | (1) Department of Geology, Annamalai University, Annamalainagar 608 002, India, IN;(2) School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067, India, IN;(3) Ocean Data Centre, Centre for Water Resources, Anna University, Chennai 600 018, India, IN |
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Abstract: | Spatial and temporal geochemical variations of various parameters in the water and sediment of a relatively small mangrove
situated on the southeast coast of India were examined in detail for the first time. The water quality generally reflects
the impact of seawater and the Vellar estuary (mixing effect) aided by evaporation and in situ biological productivity. The
depletion and fluctuation of dissolved silica are controlled by biological processes. Nitrate and phosphate are contributed
by fertilizer input from adjoining agriculture fields. Total suspended matter (TSM) shows an erratic range and trend due to
deforestation and resuspension processes. Sand and silt constitute 70–90% of the sediments. Statistical analysis of the sediments
shows the prevalence of a moderately high-energy environment with very effective winnowing activity. Organic matter content
is higher in the mangrove sediments in comparison to adjacent estuaries. Water and sediment show fluctuations in their chemical
concentration, but no specific trends could be identified. Heavy metals are also enriched in the mangrove sediments, indicating
their unique chemical behavior and the existence of trapping mechanisms. Factor analysis and correlation analysis of water
and sediments show the complexity of the system and the multitude of contributing sources. The core sediment chemistry suggests
the depletion of metal input due to the damming of the detrital inputs. The Pichavaram mangrove seems to be relatively unpolluted,
since the anthropogenic signal observed is small and acts as a sink for heavy metals contributed from a multitude of sources
without an adverse effect.
Received: 5 November 1997 · Accepted: 30 March 1998 |
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Keywords: | Mangrove Geochemistry Biological productivity Anthropogenic impacts Heavy metal sink |
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