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- Nath, Bejugam Nagender, et al.
(författare)
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Record of carbonate preservation and the Mid-Brunhes climatic shift from a seamount top with low sedimentation rates in the Central Indian Basin
- 2013
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 42:3, s. 762-778
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation, an age model of carbonate-rich cores from a seamount top in the Central Indian Basin (CIB) was constructed using both isotopic (230Thexcess, AMS 14C, oxygen isotopes) and biostratigraphic methods. The chronologies using the two methods are in good agreement, yielding a record of the late Middle Pleistocene to the Pleistocene-Holocene transition (550 to 11.5ka). The first appearance datum (FAD) of the radiolarian Buccinosphaera invaginata (180ka) and coccolith Emiliania huxleyi (268ka) and the last appearance datum (LAD) of the radiolarian Stylatractus universus (425ka) were used. A monsoon-induced productivity increase was inferred from carbonate, organic carbon and 13C records in response to the Mid-Brunhes Climatic Shift (MBCS), consistent with an increased global productivity. While the coccolith diversity increased, a decrease in coccolith productivity was found during the MBCS. At nearly the same time period, earlier records from the equatorial Indian Ocean, western Indian Ocean and eastern Africa have shown an increased productivity in response to the influence of westerlies and increased monsoon. The influence of easterlies from Australia and the intensification of aridity are evidenced by increased kaolinite content and clay-sized sediments in response to the MBCS. An increased abundance of Globorotalia menardii and other resistant species beginning from marine isotope stage (MIS) 11 and the proliferation of coccolith Gephyrocapsa spp. indicate increased dissolution, which is consistent with the widespread global carbonate dissolution during this period. The relatively high carbonate dissolution during the transition period of MIS 3/2 and glacial to interglacial periods (MIS 6, 7 and 8) may be due to the enhanced flow of corrosive Antarctic Bottom Water (AABW) into the CIB.
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| 2. |
- Yeung, Leo W. Y., 1981-, et al.
(författare)
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A survey of perfluorinated compounds in surface water and biota including dolphins from the Ganges River and in other waterbodies in India
- 2009
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Ingår i: Chemosphere. - Oxford, United Kingdom : Elsevier. - 0045-6535 .- 1879-1298. ; 76:1, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- Despite the reports of the occurrence of perfluorochemicals (PFCs) in industrialized nations, information on PFCs in less industrialized countries is meager. In the present study, concentrations and profiles of PFCs were investigated in surface waters (rivers, lakes, coastal seas and untreated sewage; n = 42) including the Ganges River water, and biota such as shrimp (n = 2), fish (n = 28), and Ganges River dolphin (Platanista gangetica; n = 15). PFOS was the dominant PFC found in most of the samples analyzed including water samples except untreated sewage (water: <0.04–3.91 ng L1; biota: 0.248–27.9 ng g1 ww). Long-chain (C11–C18) perfluorocarboxylates (PFCAs) were not detected in the water samples (<0.2 ng L1), although PFDA (0.061–0.923 ng g1 ww) and PFUnDA (0.072–0.998 ng g1 ww) were found in biological samples The arithmetic mean PFOS concentration found in the liver of Ganges River dolphin was 27.9 ng g1 ww. Bioconcentration and biomagnifications factors of PFCs were estimated in the Ganges River basin food web. The highest concentration of PFOA, 23.1 ng L1, was found in untreated sewage samples. Overall, concentrations of PFCs of water and biological samples from India are lower than the concentrations reported for other countries so far. PFC profiles in Indian waters are dominated by PFOS, followed by PFOA, which is different from the pattern reported for other countries such as Korea, Japan and USA, where PFOA was the predominant compound in waters. The flux estimates for PFOS, PFOA and PFNA from the Ganges River in India to the Bay of Bengal were in the range of several hundreds of kilograms per year.
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