The formation mechanisms of the mega-dunes and lakes in the hinterland of Badain Jaran Desert,China,is the focus of extensive academic research in the field of geoscience,and an often debated topic is whether atmosphe...The formation mechanisms of the mega-dunes and lakes in the hinterland of Badain Jaran Desert,China,is the focus of extensive academic research in the field of geoscience,and an often debated topic is whether atmospheric precipitation on the mega-dune can infiltrate to recharge groundwater.In the present study,the probability distribution functions and the return period analysis of extreme daily precipitation based on long-term precipitation records for the southern margin of Badain Jaran Desert and 2-year observation of hinterland precipitation were used to classify precipitation in the desert region.The data of automatic weather station and eddy covariance system in the desert hinterland were used to analyze evaporation on the mega-dune surface after various rain events.The results showed that the rain events in the desert could be divided into three categories.The first is conventional precipitation(CP),which is below 5 mm,accounting for roughly 90%of all rain events in the desert.The second and third categories are ordinary annual maximum(OAM)and extreme precipitation(EP),in which precipitation is roughly 20 mm and more than 40 mm,respectively.The atmospheric precipitation of CP and OAM evaporated from the megadune surface in 1–3 days and 3–4 weeks,respectively.Following an EP event,the mega-dune evaporation was negatively influenced by the upper dry sand layer,and a lengthy period was required for its complete removal.The accumulative evaporation and accumulative precipitation of all three types of rain events indicated that local atmospheric precipitation had no significant contribution to recharging the groundwater system in the hinterland of Badain Jaran Desert.This research will benefit comprehensive elucidation of the formation mechanism of lakes in the hinterland of Badain Jaran Desert.展开更多
A megacrystal zircon occurs in serpentinized dunite veins from North Qaidam, northwestern China. It is red-brown and 3―4 mm long and 2 mm wide in size. BSE imaging shows the presence of micro-grains (30―50 μm) of z...A megacrystal zircon occurs in serpentinized dunite veins from North Qaidam, northwestern China. It is red-brown and 3―4 mm long and 2 mm wide in size. BSE imaging shows the presence of micro-grains (30―50 μm) of zircon between olivine and serpentine, part of them gathering into clusters (100―300 μm). Thus we infer that these zircon crystals were precipitated from hydrothermal fluid. Inclusions of baddeleyite (white) in the shape of isolated island locally occur in the large zircon (grey), implying that the former formed earlier than the latter. The mirco-baddeleyite (50―100 μm) aggregate consists of baddeleyite (3―5 μm) and olivine (<5 μm), indicating the zircon formation through interaction between baddeleyite and silica-bearing fluid. Therefore, we consider a genetic link between the formation of the large zircon and the serpentinization of dunite. SHIRIMP U-Pb dating of the large zircon gave two groups of concordant ages at 414 ± 13 Ma and 371 ± 9 Ma, respectively. This might reflect two episodes of zircon growth in response to two episodes of fluid action.展开更多
The occurrence of the giant jellyfish, Nemopilema nomurai, has been a frequent phenomenon in the Yellow Sea. However, the relationship between the giant jellyfish and protozoa, in particular ciliates, remains largely ...The occurrence of the giant jellyfish, Nemopilema nomurai, has been a frequent phenomenon in the Yellow Sea. However, the relationship between the giant jellyfish and protozoa, in particular ciliates, remains largely unknown. We investigated the distribution of nanoflagellates, ciliates, Noctiluca scintillans, and copepod nauplii along the transect 33~N in the Yellow Sea in June and August, 2012, during an occurrence of the giant jellyfish, and in October of that year when the jellyfish was absent. The organisms studied were mainly concentrated in the surface waters in summer, while in autumn they were evenly distributed in the water column. Nanoflagellate, ciliate, and copepod nauplii biomasses increased from early June to August along with jellyfish growth, the first two decreased in October, while N. scintillans biomass peaked in early June to 3 571 pg C/L and decreased in August and October. In summer, ciliate biomass greatly exceeded that of copepod nauplii （4.61-15.04 ~tg C/L vs. 0.34-0.89 pg C/L）. Ciliate production was even more important than biomass, ranging from 6.59 to 34.19 ~tg C/（L.d） in summer. Our data suggest a tight and positive association among the nano-, micro-, and meso-zooplankton in the study area. Statistical analysis revealed that the abundance and total production of ciliate as well as loricate ciliate biomass were positively correlated with giant jellyfish biomass, indicating a possible predator-prey relationship between ciliates and giant jellyfish. This is in contrast to a previous study, which reported a significant reduction in ciliate standing crops due to the mass occurrence ofN. nomurai in summer. Our study indicates that, with its high biomass and, in particular, high production ciliates might support the mass occurrence of giant jellyfish.展开更多
基金supported by the National Natural Science Foundation of China(41371114)the Public Industry Scientific Research Foundation of Ministry of Environmental Protection of China(201209034)+1 种基金the National Basic Science Talents Foundation of China(J1210065)Higher Specialized Research Foundation for Doctoral Program(20100211120006)
文摘The formation mechanisms of the mega-dunes and lakes in the hinterland of Badain Jaran Desert,China,is the focus of extensive academic research in the field of geoscience,and an often debated topic is whether atmospheric precipitation on the mega-dune can infiltrate to recharge groundwater.In the present study,the probability distribution functions and the return period analysis of extreme daily precipitation based on long-term precipitation records for the southern margin of Badain Jaran Desert and 2-year observation of hinterland precipitation were used to classify precipitation in the desert region.The data of automatic weather station and eddy covariance system in the desert hinterland were used to analyze evaporation on the mega-dune surface after various rain events.The results showed that the rain events in the desert could be divided into three categories.The first is conventional precipitation(CP),which is below 5 mm,accounting for roughly 90%of all rain events in the desert.The second and third categories are ordinary annual maximum(OAM)and extreme precipitation(EP),in which precipitation is roughly 20 mm and more than 40 mm,respectively.The atmospheric precipitation of CP and OAM evaporated from the megadune surface in 1–3 days and 3–4 weeks,respectively.Following an EP event,the mega-dune evaporation was negatively influenced by the upper dry sand layer,and a lengthy period was required for its complete removal.The accumulative evaporation and accumulative precipitation of all three types of rain events indicated that local atmospheric precipitation had no significant contribution to recharging the groundwater system in the hinterland of Badain Jaran Desert.This research will benefit comprehensive elucidation of the formation mechanism of lakes in the hinterland of Badain Jaran Desert.
基金Supported by the Basic Outlay of Scientific Research Work from Ministry of Science and Technology of the People's Republic of China (Grant No. J0710)China Geological Survey Project (Grant No. 1212010611811)
文摘A megacrystal zircon occurs in serpentinized dunite veins from North Qaidam, northwestern China. It is red-brown and 3―4 mm long and 2 mm wide in size. BSE imaging shows the presence of micro-grains (30―50 μm) of zircon between olivine and serpentine, part of them gathering into clusters (100―300 μm). Thus we infer that these zircon crystals were precipitated from hydrothermal fluid. Inclusions of baddeleyite (white) in the shape of isolated island locally occur in the large zircon (grey), implying that the former formed earlier than the latter. The mirco-baddeleyite (50―100 μm) aggregate consists of baddeleyite (3―5 μm) and olivine (<5 μm), indicating the zircon formation through interaction between baddeleyite and silica-bearing fluid. Therefore, we consider a genetic link between the formation of the large zircon and the serpentinization of dunite. SHIRIMP U-Pb dating of the large zircon gave two groups of concordant ages at 414 ± 13 Ma and 371 ± 9 Ma, respectively. This might reflect two episodes of zircon growth in response to two episodes of fluid action.
基金Supported by the National Basic Research Program of China(973 Program)(No.2011CB403604)
文摘The occurrence of the giant jellyfish, Nemopilema nomurai, has been a frequent phenomenon in the Yellow Sea. However, the relationship between the giant jellyfish and protozoa, in particular ciliates, remains largely unknown. We investigated the distribution of nanoflagellates, ciliates, Noctiluca scintillans, and copepod nauplii along the transect 33~N in the Yellow Sea in June and August, 2012, during an occurrence of the giant jellyfish, and in October of that year when the jellyfish was absent. The organisms studied were mainly concentrated in the surface waters in summer, while in autumn they were evenly distributed in the water column. Nanoflagellate, ciliate, and copepod nauplii biomasses increased from early June to August along with jellyfish growth, the first two decreased in October, while N. scintillans biomass peaked in early June to 3 571 pg C/L and decreased in August and October. In summer, ciliate biomass greatly exceeded that of copepod nauplii （4.61-15.04 ~tg C/L vs. 0.34-0.89 pg C/L）. Ciliate production was even more important than biomass, ranging from 6.59 to 34.19 ~tg C/（L.d） in summer. Our data suggest a tight and positive association among the nano-, micro-, and meso-zooplankton in the study area. Statistical analysis revealed that the abundance and total production of ciliate as well as loricate ciliate biomass were positively correlated with giant jellyfish biomass, indicating a possible predator-prey relationship between ciliates and giant jellyfish. This is in contrast to a previous study, which reported a significant reduction in ciliate standing crops due to the mass occurrence ofN. nomurai in summer. Our study indicates that, with its high biomass and, in particular, high production ciliates might support the mass occurrence of giant jellyfish.
