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| Abstract Submission No. | ABS-2022-05-0222 |
| Title of Abstract | Processes controlling the distributions and cycling of dissolved aluminium and manganese in the northeastern Indian Ocean |
| Authors | Yichao Yang*, Lei Li, Shuo Jiang, Jingling Ren, Jing Zhang |
| Organisation | Ocean University of China |
| Address | 238 Songling Road Qingdao, Shandong Province, China Pincode: 266100 Mobile: 8617854202825 E-mail: yyc@stu.ouc.edu.cn |
| Country | China |
| Presentation | Oral |
| Abstract | Data on dissolved aluminium (dAl) and dissolved manganese (dMn) relative to their geochemical behavior remains limited in the northeastern Indian Ocean (IO, including Bay of Bengal (BoB) and equatorial Indian Ocean (Eq. IO)). Seawater samples collected in the BoB and Eq. IO during the spring inter-monsoon period (7th March to 9th April) of 2017 were analyzed to investigate the behavior and main processes controlling the distribution of dAl and dMn in the northeastern IO. The average concentrations of dAl and dMn in the mixed layer of BoB were 16.6 nM and 6.7 nM, respectively. A modified version of 1-D box-model equation was utilized to estimate the contributions of different sources to dAl and dMn in the mixed layer of northeastern IO. Al released from the desorption of and/ or dissolution of the lithogenic sediments discharged by the Ganga-Brahmaputra (G-B) river system, predominantly controlled the dAl distributions in the mixed layer of BoB. While lithogenic sediments release supported about 13~21% dMn. Additional dMn input from the advection of Andaman Sea water and photo-reduction-dissolution of particulate Mn (IV) contributed more than 60% dMn in the mixed layer of BoB. dAl and dMn in the surface mixed layer of Eq. IO were mainly affected by the mixing of BoB surface water and southern Arabian Sea surface water through the relationship between dAl, dMn, and salinity. dMn had an obvious regeneration under the low oxygen in the subsurface and intermediate water body of BoB. The T-S diagram and dAl distributions indicated that the intermediate water (750~1500 m) of study area resulted from mixing of Red Sea Intermediate Water (RSIW), Indonesian Intermediate Water (IIW), and intermediate water of BoB. Relatively high dAl and dMn than original water masses supported remineralization and/ or regeneration under low oxygen environment during water transporting. The influence of Indonesian Throughflow (ITF) on dAl and dMn distribution was also observed at the southernmost area in the study. |