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A fossil diatom-based reconstruction of sea-level changes for the Late Pleistocene and Holocene period in the NW South China Sea

Zhang Jinpeng, Tomczak Michał, Witkowski Andrzej, Zhen Xia, Li Chao

Oceanologia

2023

Vol. 65 (1)

211-229

Marine transgressions-regressions have profoundly shaped marginal seas following global sea-level fluctuations driven by climate change. This study on a sedimentary core profile SO219/31-4 from the Beibu Gulf, northwestern South China Sea (SCS), reveals information about paleoenvironment, paleoceanography and paleoclimate changes through fossil diatom assemblages and grain size distributions during the last ca. 12900 cal. yr. BP. Eight local diatom assemblage zones were distinguished and assigned to paleoenvironmental fluctuations recording sea-level and depositional environment changes in eight stages, ca. 12900–11700 (stage 1), ca. 11700–9500 (stage 2), ca. 9500–7200 (stage 3), ca. 7200–5800 (stage 4), ca. 5800–3800 (stage 5), ca. 3800–2400 (stage 6), ca. 2400–800 (stage 7) and ca. 800–0 (stage 8), cal. yr. BP. After the low sea level of stage 1 within the last deglaciation, rapid increases in sea level in stages 2 and 3 were recorded as meltwater events pulse-1B and pulse-1C resulting in marine transgression rates of ca. 16 m/kyr and 8 m/kyr, respectively. The high sea level, above the present level, in stages 4 and 5, in the Middle Holocene Climatic Optimum period, was clearly documented by more significant open sea/tropical diatom species and coastal planktonic species percentages, respectively. The late Holocene regression of sea levels was marked by a pronounced reversion of diatom taphocoenosis, responding to neoglacial climate. Fossil diatom assemblages outlined responded to paleoclimate of global warming in the deglacial and early Holocene. This study provides additional insights into the late Pleistocene and Post-glacial history of a tropical-subtropical shallow water gulf, in the NW-SCS.

Effect of elevated pressure on gas-solid flow properties in a powder feeding system

Ren Guanlong, Sun Haijun, Xu Yihua, Li Chao

Polish Journal of Chemical Technology

2022

Vol. 24, nr 3

41--52

In view of the powder feeding system, a multi-physical coupling model of the gas-powder-piston was established based on the Euler-Euler two-fluid model. The numerical simulation method was applied to explore the effects of dense gas-solid flow characteristics under different operating pressures. The results show that gas-solid pulsations at different operating pressures are mainly concentrated in the upper part of the powder tank. An elevated operating pressure efficiently decreases the powder layer area (εp = 0.1) fluctuation. As the operating pressure increases from 0.5 MPa to 3.0 MPa, the rising time and fluctuation rate of pressure are reduced by 71.4% and 62.3%, respectively, and the pressure in the tank has a long stabilization period. Meanwhile, the variation of the instantaneous powder flow rate is more stable and its average value is closer to the theoretical. A high-pressure environment is more conducive to the stable transportation of powder.

Enhanced effect of fine magnetite on the flotation performance of fine hematite in sodium oleate system

Pei Bin, Luo Ximei, Yang Wen, Wei Dayong, Li Chao, Wang Yunfan

Physicochemical Problems of Mineral Processing

2022

Vol. 58, iss. 4

art. no. 149673

In this work, the effect of magnetite with different particle sizes on the flotation performance of both coarse and fine hematite particles were investigated by using sodium oleate as a collector. The results showed that the magnetite particles with different particle sizes showed a negative effect on hematite (-106+45 μm) recovery, but the addition of magnetite with the same particle sizes as hematite during the direct flotation of -45 μm hematite was beneficial to improve the recovery of micro-fine hematite and the Fe grade of concentrate. The finer the magnetite particle was, the more obvious the agglomeration effect of hematite was. Therefore, the beneficial effect could be achieved by adjusting the particle sizes of particles. Moreover, sodium oleate was beneficial to promote the agglomeration of micro-fine magnetite and hematite. The results from the microscopic analysis, laser particle size analysis, and EDLVO calculation proved that there was an effective aggregation between fine magnetite and fine hematite particles, which increased the apparent size of hematite particles and the probability of the mineral particles adhering to bubbles, thus improving the hematite recovery.