Distribution and sources of organic carbon, nitrogen and their isotopic signatures in sediments from the Ayeyarwady (Irrawaddy) continental shelf, northern Andaman Sea

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dc.contributor.author Ramaswamy, V.
dc.contributor.author Gaye, B.
dc.contributor.author Shirodkar, P.V.
dc.contributor.author Rao, P.S.
dc.contributor.author Chivas, A.R.
dc.contributor.author Wheeler, D.
dc.contributor.author Thwin, S.
dc.date.accessioned 2008-11-26T07:19:45Z
dc.date.available 2008-11-26T07:19:45Z
dc.date.issued 2008
dc.identifier.citation Marine Chemistry, Vol.111; 137-150p.
dc.identifier.uri http://drs.nio.org/drs/handle/2264/1510
dc.description.abstract Total organic carbon (TOC), total nitrogen (TN) and their delta sup(13) C and delta sup (15) N values were determined from 110 sediment samples from the Ayeyarwady (Irrawaddy) continental shelf, northern Andaman Sea to decipher the concentration and source of organic matter. Comparatively higher TOC and TN concentrations are found in the inner-shelf mud belt, and on the continental slope sediments, whereas the outer-shelf sediments, composed mostly of relict sands, are low in TOC. The TOC contents are positively correlated with the abundance of fine-grained sediments. The TOC:TN ratios and delta sup(13) C and delta sup(15) N values show low variability within the modern inner-shelf mud belt and Gulf of Martaban, indicating similar source. The TOC:TN ratios are mostly between 6 and 8 in the inner-shelf mud belt and these values are similar to the suspended sediments in the Ayeyarwady and Salween rivers. The delta sup(13) C values of organic matter increase from – 25 ppt in the Gulf of Martaban to about – 22 ppt in the slope regions indicating decreasing terrestrial input away from the coast. The sup (15) N values on the Ayeyarwady shelf are rather low (+ 3.3 to + 4.8 ppt), especially off the mouths of the Ayeyarwady River mouths, reflecting greater influence of freshwater and terrigenous sediment discharge. A simple two end-member carbon mixing model applied to the Ayeyarwady shelf region indicates that terrigenous sources contribute more than 70 % of the organic carbon in the modern mud belt in the inner shelf and Gulf of Martaban. Terrigenous organic carbon percentages reduce gradually offshore, reducing to less than 60 % near the continental shelf edge. A strong terrigenous signal is preserved in the inner shelf and Gulf of Martaban sediments probably because organic matter from the source region is not subject to intensive processing and replacement in the floodplains and deltaic regions as well as rapid burial at sea.
dc.language.iso en
dc.publisher Elsevier
dc.rights Copyright [2008]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
dc.subject continental shelf
dc.subject Organic carbon
dc.subject Total nitrogen
dc.subject Stable isotopes
dc.subject North Andaman Sea
dc.subject organic matter
dc.title Distribution and sources of organic carbon, nitrogen and their isotopic signatures in sediments from the Ayeyarwady (Irrawaddy) continental shelf, northern Andaman Sea
dc.type Journal Article

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