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Submarine groundwater discharge and seasonal hypoxia off the Changjiang River Estuary
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作者 Tianyi Zhu Bochao Xu +6 位作者 Xiaoyi Guo Qinsheng Wei ergang lian Pengxia Liu William C.Burnett Qingzhen Yao Zhigang Yu 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第8期125-133,共9页
Hypoxia is a common phenomenon in the sea adjacent to the Changjiang River Estuary(CJE),one of the global major estuaries.Submarine groundwater discharge(SGD)is a widely recognized pathway for terrestrial materials en... Hypoxia is a common phenomenon in the sea adjacent to the Changjiang River Estuary(CJE),one of the global major estuaries.Submarine groundwater discharge(SGD)is a widely recognized pathway for terrestrial materials entering the sea,and has been found to be significant off the CJE.We used a^(222)Rn mass balance model to estimate the SGD fluxes off the CJE and showed that it is linked to seasonal dissolved oxygen(DO)variations.Average SGD fluxes were estimated to be(0.012±0.010)m^(3)/(m^(2)·d)in winter,(0.034±0.015)m^(3)/(m^(2)·d)in summer,and(0.020±0.010)m^(3)/(m^(2)·d)in autumn.We found a significant negative correlation between DO concentrations and SGD rates with groundwater discharge being highest in the summer flood season.In addition,distribution patterns of SGD and hypoxia zones in summer are spatially overlapped,indicating that SGD is an important contributor to summer hypoxia in this region. 展开更多
关键词 submarine groundwater discharge ^(222)Rn HYPOXIA ^(226)Ra
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Lake-level records support a mid-Holocene maximum precipitation in northern China 被引量:3
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作者 Jiantao CAO Zhiguo RAO +2 位作者 Fuxi SHI ergang lian Guodong JIA 《Science China Earth Sciences》 SCIE EI CSCD 2021年第12期2161-2171,共11页
Lake level and its inferred East Asian summer monsoon(EASM)evolution in northern boundary of EASM during the Holocene are highly debated.Here,we present a 15-ka record of glycerol dialkyl glycerol tetraethers(GDGTs)in... Lake level and its inferred East Asian summer monsoon(EASM)evolution in northern boundary of EASM during the Holocene are highly debated.Here,we present a 15-ka record of glycerol dialkyl glycerol tetraethers(GDGTs)in a closed lake in northern China to address this issue.Surface and downcore sediment data demonstrate sedimentary GDGT-0 and branched GDGTs(brGDGTs)are of aquatic production.Contents of GDGT-0 and brGDGTs increase but brGDGT-based paleo-temperature proxy decreases with water depth in surface sediments along a nearshore to offshore transect.This trend is likely due to an increasingly hypoxic condition,favored by anaerobic microbes producing these GDGT-0 and brGDGTs,in bottom water.Accordingly,brGDGT-derived water temperature and pH would reflect bottom water conditions that are largely regulated by water depth of the lake.Downcore GDGT data and their derived temperature and pH consistently reveal a gradually increasing lake level from the late Pleistocene to the early Holocene,a high level during 9.5-5 ka BP and a decreasing trend afterward.The lake-level records from independent and robust proxies in this study largely agree with pollen records in the region,supporting a mid-Holocene maximum EASM precipitation. 展开更多
关键词 Lake level membrane lipids East Asian summer monsoon HOLOCENE northern China
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Origin of the springtime South China Sea Warm Current in the southwestern Taiwan Strait: Evidence from seawater oxygen isotope 被引量:2
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作者 Dongyu CHEN ergang lian +5 位作者 Yeqiang SHU Shouye YANG Yalong LI Chao LI Pengfei LIU Ni SU 《Science China Earth Sciences》 SCIE EI CAS CSCD 2020年第10期1564-1576,共13页
Oxygen isotope(δ^18O)of seawater is an excellent proxy for tracing the origins of water masses and their mixing processes.Combining with hydrographic observation,hybrid coordinate ocean model(HYCOM)analysis data,and ... Oxygen isotope(δ^18O)of seawater is an excellent proxy for tracing the origins of water masses and their mixing processes.Combining with hydrographic observation,hybrid coordinate ocean model(HYCOM)analysis data,and seawater oxygen isotope,we investigated the source of the South China Sea Warm Current(SCSWC)in the southwestern Taiwan Strait and its underlying mechanism.Results show that the Kuroshio subsurface water(KSSW)can intrude the continental slope in the southwestern Taiwan Strait,and thereby climb up the continental slope coupled with upwelling.Theδ^18O-salinity relationship further indicates that in spring,the SCSWC in the southwestern Taiwan Strait originates from the upslope deflection of the slope current formed by the KSSW intrusion into the South China Sea,rather than from the west segment of the SCSWC formed to the east of Hainan Island.In addition,the southward flowing Zhe-Min Coastal Current(ZMCC)can reach as far as the Taiwan Bank(TB)and deflects offshore over the western TB at approximately 23.5°N,to some extent affecting the SCSWC.Moreover,this study reveals that seawaterδ^18O is exquisitely sensitive to the determination of the origin and transport of water masses as compared with traditional potential temperature-salinity plot(θ-S)and HYCOM analysis data.In addition,their coupling can more reliably interpret the mixing processes of shelf water masses. 展开更多
关键词 Oxygen isotope South China Sea Warm Current Zhe-Min Coastal Current KUROSHIO Southwestern Taiwan Strait
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Pacific decadal oscillation impact on East China precipitation and its imprint in new geological documents 被引量:1
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作者 Jiahui YAO Linxiang XIAO +3 位作者 Mengmeng GOU Chao LI ergang lian Shouye YANG 《Science China Earth Sciences》 SCIE EI CAS CSCD 2018年第4期473-482,共10页
This paper briefly introduces the history of the study of the Pacific decadal oscillation(PDO) and explores the relationship between the PDO and sediment grain size from two typical sediment cores from the lower Chang... This paper briefly introduces the history of the study of the Pacific decadal oscillation(PDO) and explores the relationship between the PDO and sediment grain size from two typical sediment cores from the lower Changjiang(Yangtze River) and Huanghe(Yellow River) estuaries. It is found that the median grain sizes of both cores exhibit relatively high correlation with the PDO. This is because the PDO causes interdecadal variability of precipitation in the East Asia Monsoon region, thus changing the hydrodynamics in both the Changjiang and Huanghe catchments, eventually resulting in variation of sediment grain size. Our analysis also revealed that during different phases of the PDO, the sediment grain size of the Changjiang and Huanghe estuaries showed different variations in cold and warm PDO phases. This is related to movement of the precipitation center driven by the shift in different PDO phases. Moreover, we compared more high resolution geological proxies with the PDO, including stalagmites and tree rings, in East China over the past century. The results indicate that variations of studied geological proxies are generally well correlated with the PDO but have some differences. Finally, longer variations of sediment grain sizes in the Changjiang and Huanghe estuaries are compared with a reconstructed PDO over the last 200 years;sediment grain sizes were still correlated with the PDO, implying that sediment grain size may be used as a new proxy for studying the long-term behavior of the PDO. This result supports previous knowledge of the PDO impact on East China climate evolution and offers a new proxy for further PDO study. Our study will improve paleoenvironment reconstruction in East China on a decadal time scale and benefit future climatic predictions. 展开更多
关键词 Sedimentary record δ^18O in stalagmite Precipitation Pacific decadal oscillation(PDO) East Asian Monsoon
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Discovery of the largest natural carbon onions on Earth
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作者 Yilin CHEN Yong QIN +3 位作者 Jiuqing LI Zhuangfu LI Tianyu YANG ergang lian 《Science China Earth Sciences》 SCIE EI CAS CSCD 2022年第9期1736-1750,共15页
The synthesis of carbon onions in the laboratory by various methods is common;however, naturally occurring carbon onions have only been found in a few geological samples on Earth. This study used high-resolution trans... The synthesis of carbon onions in the laboratory by various methods is common;however, naturally occurring carbon onions have only been found in a few geological samples on Earth. This study used high-resolution transmission electron microscopy to identify natural carbon onions in seven intrusion-affected coal samples collected from Permian coal-bearing strata in the Yongan Coalfield, Fujian Province, South China. This study identified the largest natural carbon onions ever recorded on Earth;their outer diameter was ~55 nm. Granite porphyry intrusions and quartz hydrothermal veins are abundant in the Permian coal-bearing strata in this coalfield. All samples collected were tectonically deformed coals with highly developed structural fractures, friction mirror planes, and maximum vitrinite reflectance values of 4.0–9.5%. Natural carbon onions observed in the coal samples had single or multiple cores, with 24–46 graphitic shells characterized by outer diameters of 24–55 nm. The maximum vitrinite reflectance, outer diameter, and graphitic shell number of carbon onions in the intrusion-affected coal were positively correlated, indicating that the carbon onions were secondary products formed during coal metamorphism owing to magmatic intrusion. Our results suggest that carbon onions in intrusion-affected coal are synthesized by chemical vapor deposition. We speculate that natural carbon onions exist mainly in fractures or cavities, similar to vapor-deposited pyrolytic carbon, which is the leading cause of the uneven distribution of carbon onions in intrusion-affected coals in the study area. 展开更多
关键词 Onion-like fullerenes Intrusion-affected coal Chemical vapor deposition HRTEM Coal metamorphism
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