Jianguo Liu

Continental margins regulate land‐ocean carbon transfer, but the mechanisms linking monsoon variability, sediment routing, and organic carbon (OC) burial remain incompletely resolved. We present a high‐resolution ∼37 kyr multi‐proxy reconstruction from sediment core E87‐32B in the middle Bengal Fan, integrating pollen assemblages, bulk geochemistry, stable isotopes, mass accumulation rates, redox‐sensitive proxies (Th/U), and Monte Carlo source apportionment to resolve the relative roles of source, transport, and preservation controls. Marine OC constitutes ∼50%–70% of sedimentary carbon, while terrestrial inputs account for ∼30%–50%. Within the terrestrial fraction, C ₄ ‐derived carbon comprises 55%–70% during MIS 3–2 and exceeds C ₃ ‐derived carbon despite pollen evidence for expanded C ₃ vegetation, indicating preferential export of C ₄ ‐rich grassland and floodplain carbon. Bulk δ ¹³ C values (−20.5‰ to −18.0‰) further demonstrate a persistent decoupling between vegetation composition and exported OC, while burial flux does not correlate with vegetation composition. Terrestrial OC mass accumulation was 150%–230% higher during glacial lowstands than during the Holocene, coincident with higher sedimentation rates and more reducing depositional conditions inferred from Th/U. During transgression, total OC accumulation declined by ∼53% despite a ∼60% increase in marine organic matter, while higher Th/U values indicate enhanced oxygen exposure associated with shelf trapping and sediment reworking. These results demonstrate that sea‐level‐controlled sediment connectivity and oxygen exposure time, rather than monsoon‐driven productivity or vegetation shifts alone, govern carbon burial efficiency. Preservation efficiency therefore emerges as a dominant control on tropical margin carbon sequestration, and provides a framework for understanding natural carbon‐cycle dynamics across glacial‐interglacial sea‐level changes.

Among various climate drivers, direct evidence for the Intertropical Convergence Zone (ITCZ) control of sediment supply on the millennial scale is lacking, and the changes in ITCZ migration demonstrated in paleoclimate records need to be better investigated. Here, we use clay minerals and Sr–Nd isotopes obtained from a gravity core on the Ninetyeast Ridge to track the corresponding source variations and analyze the relationship between terrestrial material supply and climatic changes. On the glacial–interglacial scale, chemical weathering weakened during the North Atlantic cold-climate periods and falling sea level hindered the transport of smectite into the study area due to the exposure of Andaman and Nicobar Islands. However, the influence of the South Asian monsoon on the sediment supply was not obvious on the millennial scale. We suggest that the north–south migration of the ITCZ controlled the rainfall in Myanmar and further directly determined the supply of clay minerals on the millennium scale because the transport of smectite was highly connected with the ITCZ location; thus, the regional shift of the ITCZ induced an abnormal increase in the smectite percentage during the late Last Glacial Maximum (LGM) in our records. The smectite percentage in the studied core is similar to distinct ITCZ records but different in some periods, revealing that regional changes in the ITCZ were significantly obvious, the ITCZ is not a simple north–south displacement, and closer connections occurred between the Northern–Southern Hemisphere in the eastern Indian Ocean during the late LGM.

Among various climate drivers, direct evidence for the Intertropical Convergence Zone (ITCZ) control of sediment supply on the millennium scale is lacking, and the changes in ITCZ migration demonstrated in paleoclimate records need to be better investigated. Here, we use clay minerals and Sr-Nd isotopes obtained from a gravity core on the Ninetyeast Ridge to track the corresponding source variations and analyze the relationship between terrestrial material supplementation and climatic changes. On the glacial-interglacial scale, chemical weathering weakened during the North Atlantic cold climate periods, and falling sea level hindered the transport of smectite into the study area due to the exposure of islands. However, the influence of the South Asian monsoon on the sediment supply was not obvious on the millennium scale. We suggest that the north-south migration of the ITCZ controlled the rainfall in Myanmar and further directly determined the supply of clay minerals on the millennium scale because the transport of smectite was highly connected with ITCZ location. Furthermore, the regional shift of the ITCZ induced an abnormal increase in the smectite percentage during the late Last Glacial Maximum (LGM) in our records. The smectite percentage in the studied core is similar to distinct ITCZ records in different time periods, revealing that regional changes in the ITCZ were significantly obvious, and that the ITCZ is not a simple N-S displacement and closer connections occurred between the Northern-Southern Hemispheres in the eastern Indian Ocean during the late Last Glacial Maximum (LGM).

Astaxanthin (AST) is a xanthophyll carotenoid widely distributed in aquatic animals, which has many physiological functions such as antioxidant, anti-inflammatory, anti-hypertensive and anti-diabetic activities. Astaxanthin has three optical isomers, including a pair of enantiomers (3 S ,3 ‘ S and 3 R ,3 ‘ R ) and a meso form (3 R ,3 ‘ S ). Different optical isomers have differences in a variety of physiological functions. Traditionally, High Performance Liquid Chromatography (HPLC) can be used to distinguish these isomers. In this work, it’s found that Raman spectroscopy can be employed to distinguish the three optical isomers. Because the intensities of two Raman bands at 1190 cm ^-1 and 1215 cm ^-1 of three isomers are different. DFT calculations are performed and used to analyze the spectral differences. The calculation results show that the structures of these chiral isomers are not strictly mirror-symmetrical to each other, which leads to the difference in their Raman spectra. Highlights: Raman spectroscopy can be utilized to distinguish three optical isomers of all- trans astaxanthin. The DFT-calculated spectrum is used to explain why the Raman bands of optical isomers at 1190 and 1215 cm ^-1 are different. The structural parameters of the three optical isomers have been identified.

Heavy metals (Sc, Cr, Co, Ni, Cu, Ga, Ge, Nb, Mo, Cd, In, Hf, Ta, W, Tl, Pb, Bi, Th, and U) in the surface sediments of the Ganges-Brahmaputra-Meghna (GBM) river system of the Bengal Basin (BB) were measured to evaluate the heavy metal contamination and anthropogenic influence. The average concentration levels of most of the heavy metals (except Mo and Tl) were above the average crustal and shale values. Contamination indices, including the contamination factor, pollution load index, enrichment factor, and geo-accumulation index, and multivariate statistical analyses indicated that the GBM is slightly polluted by heavy metals with some considerable pollution from Bi, Th, Ta, Cd, Nb, Pb, In, and U. Among the four individual rivers, the Brahmaputra River and Ganges-Brahmaputra (GB) confluence river sediments contain higher heavy metal concentrations than do the Ganges and Meghna Rivers, which may be caused by the effects of local municipal discharge, industrial or urban wastes, and ferry crossing activities.

Climate change, sea level fluctuations, and tectonic uplift play key roles in the evolution of sedimentary systems on continental margins. In the Arabian Sea, the Makran continental margin is suitable for studying these processes during the Holocene due to its high sedimentation rate and continuous sequence of Holocene sediments. Here, high‐resolution clay mineral and grain size analyses have been conducted to better understand the sedimentary process and controlling factors over the past 13,000 yr. The results show that the influence of Indus‐derived sediments on the Makran continent margin is negligible. Holocene relative sea level fluctuations can strongly control the shelf accommodation space due to the narrow shelf, which in turn affects the deposition process at the Makran continental margin. The sediment records at the central Makran continental margin are more suitable for studying ancient earthquakes or tsunamis.