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- Kumar Ranjan, Rajesh, et al.
(författare)
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Elemental and stable isotope records of organic matter input and its fate in the Pichavaram mangrove–estuarine sediments (Tamil Nadu, India)
- 2011
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Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 126:1-4, s. 163-172
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Tidskriftsartikel (refereegranskat)abstract
- In order to evaluate the sources and fate of organic matter (OM) in the Pichavaram mangrove–estuarine ecosystem, Corg, Ntot, C/Natm, and stable isotopes (δ13Corg and δ15Norg) of five 210Pb dated sediment cores were investigated. Core A was collected from the Vellar Estuary, cores B, C, and D from mangrove forests, and core E was from the Coleroon Estuary. In mangrove sediments, Corg, Ntot, and C/Natm concentration varied from 1.2 ± 0.52%, 0.08 ± 0.03%, and 16.6 ± 4.1%, respectively. In the estuaries, Corg, Ntot, and C/Natm varied from 0.37 ± 0.19%, 0.03 ± 0.01%, and 12.3 ± 2.9%, respectively. In mangrove forests the δ13Corg and δ15Norg values varied from − 24.3 ± 1.8‰ and 4.2 ± 0.86‰, whereas in estuaries these values were − 23.2 ± 1.6‰ and 5.1 ± 1.3‰, respectively. The variation represents variable inputs of marine and terrestrial OM in these area, OM degradation, replacement of native vegetation due to increasing salinity, and early diagenetic changes. Some of these changes could be attributed to anthropogenic activities that have been happening in the Pichavaram complex over the last few decades. OM once deposited in the sediments is rapidly decomposed or remineralized in both mangrove and estuarine sites. The rate of Corg burial is more in mangrove forests than estuaries. Early diagenetic changes are modeled in the cores based on C/N stoichiometry. This was most applicable in mangrove sediments (core C) where ~ 56% C was remineralized representing a first order diagenetic model.
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| 2. |
- Ranjan, Rajesh Kumar, et al.
(författare)
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Polycyclic aromatic hydrocarbons fingerprints in the Pichavaram mangrove-estuarine sediments, southeastern India
- 2012
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Ingår i: Organic Geochemistry. - : Elsevier BV. - 0146-6380 .- 1873-5290. ; 53, s. 88-94
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Tidskriftsartikel (refereegranskat)abstract
- The sources and historical deposition of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated in dated sediment cores from the Pichavaram mangrove–estuarine complex. The ΣPAH flux in mangrove and estuarine sediments was 0.064 ± 0.031 μg/cm2/yr and 0.043 ± 0.020 μg/cm2/yr, respectively. The PAH flux in sediments increased up-core, coinciding with rapid urbanization since the 1970s. The flux showed a decrease in recent years (since 1990), coinciding with less riverine discharge, and perhaps more effective implementation of environmental regulations. The sediments were dominated by low molecular weight PAHs, suggesting anthropogenic input. Ratios of specific PAH isomer pairs suggested a greater input of petrogenic vs. pyrogenic derived PAHs. Notably, the deposition of high molecular weight PAHs increase in mangrove surface sediments was due to lignite and firewood combustion. Because of their overall low concentration in sediments it is unlikely these PAHs pose an immediate ecological hazard.
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