- Dona Paula, Goa, India.
- +91-0832- 2450327
- iiosc2020[at]nio[dot]org
| Abstract Submission No. | ABS-2022-05-0147 |
| Title of Abstract | Rare earth element Biogeochemistry of Porewater in the Indian Ocean |
| Authors | Tapas Kumar Mishra*, Prof. Sunil Kumar Singh, Chhaya Yadav, Dr. Srinivas Bikkina, Dr. Babasaheb R Thorat |
| Organisation | National Institute Of Oceanography |
| Address | DR-4, Nio Colony , Donapaula Panaji, Goa, India Pincode: 403004 Mobile: 7008626498 E-mail: tapaskumarmishra30@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | The biogeochemical recycling process occurring at the sediment-water interface has a profound influence on the sequestration and release of rare earth elements (REE) in the oceanic sediments. Therefore, the distribution of REEs in the porewater of pelagic sediments can be used as a robust marker for better constraining the post-depositional processes. For instance, the REEs concentrations and their shale-normalized pattern in sediment porewater give critical information regarding the early diagenesis and recycling process at the sediment-water interface. The REE concentration in porewater is helpful for the flux evaluation across the sediment-water interface and establishing an ocean REE budget. We studied here the diagenetic behavior of REE in porewaters of upper 20 cm box core sediments collected from a recent Indian Ocean expedition SSD 079 (March-June 2021). The REE concentrations were rather high in porewater immediately below the sediment-water interface, indicating significant release from the sediments during the early diagenesis process resulting from the remineralization of particulate organic matter. One interesting feature related to the REE data of porewaters obtained from the spade core collected from south of the equator is the prevalence of high concentrations of heavy (HREE: Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) and middle rare earth elements (MREE: Sm, Eu, and Gd) contrary to nearby locations. Such abnormal enrichment of MREE and HREE in the sediment porewater profiles is most likely attributed to the reductive dissolution of iron oxyhydroxides or silicate weathering of ferromagnesian minerals. The shale normalized pattern of the porewater samples reflects a negative Ce anomaly in all these stations. The Ce anomaly is significant and relatively constant (PASS Normalized) throughout the depth profile, indicating that the Ce depleted in seawater was restored in porewater. These results have implications for understanding the distribution of oceanic REEs at the sediment-water interface. |