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The main goal of the study is to establish the spatial and temporal distribution of pyroclastic material from large explosive eruptions of the volcanoes of Kamchatka, the Kuril, and Aleutian Islands to create a generalized tephrochronological model and reveal patterns of explosive activity in this region. This paper presents new data on the composition of volcanic ash (tephra) found in the Pleistocene deposits of the northwestern Pacific from the eastern slope of the Detroit Rise (northwestern part of the Imperial Ridge), 450–550 km east of the Kamchatka Peninsula. Eleven layers and lenses of tephra aged from 28 to 245 ka, which were previously unknown, were studied in the core Lv63-4-2. Their stratigraphic position and age were determined based on age models developed in this study. Based on the geochemical composition of volcanic glass (determined using an electron microprobe), seven layers were correlated with tephra from several cores in the northwestern Pacific and the Bering Sea. The obtained results supplement the information on large explosive eruptions of volcanoes in the region and their periods of activity. They also allow the development of a generalized tephrochronological model of Quaternary deposits, which is necessary for stratigraphic correlation, and of paleooceanological and paleogeographic reconstructions.

Under the background of China’s energy structure optimization, environmental protection, energy conservation, and rising pressure of emission reduction, geothermal, as a potential strategic replacement energy, has ushered in new opportunities and challenges. This paper systematically summarizes the domestic achievements in the exploration and development of geothermal resources, analyzes the endowment, distribution, and accumulation mechanism of geothermal resources in China, and points out the main problems existing in the exploration and development of geothermal resources in China. On this basis, it looks forward to China’s urgent geothermal exploration and development work and key technologies to be urgently developed, providing important guidance for China’s geothermal science and technology innovation and rapid industrialization development.

In the study, we analyzed the hot dry rock geothermal field of the Guide Basin in Qinghai Province, China. We used T2Well software—a coupled wellbore–reservoir simulator—to build a “wellbore–reservoir” coupled model with a “three-spot” well pattern (one injection and two production wells). We simulated several fixed flow rate cases in which water or CO2 is injected. The objectives of our present work are (1) to investigate the fluid flow and thermal processes of water circulating at well bottoms, wellbores, and wellheads; (2) to identify the changing parameters at all physical fields; (3) to understand the influence of injection rates on heat extraction; and (4) to measure the maximum heat extraction capacity of the Guide area. Water extracts more heat than CO2 at the same flow rate. However, water consumes more pressure in reservoir, and its pressure decreases more quickly as the flow rate increases. In contrast, CO2 is in a sense a better working fluid. CO2 consumes less pressure when it flows and can circulate automatically due to the siphon phenomenon. In this way, a lower injection pressure is required in a higher CO2 flow rate case. The density of CO2 is sensitive to both temperature and pressure and vice versa. Inside a wellbore, such interactions are extremely complicated. When the fluid rate is slow, a system could operate for 30 years and remain stable, and there is only a small decrease in temperature. However, with higher flow rate scenarios—namely 50, 75, and 100 kg/s—the reservoir will exhibit greater heat loss. The reservoir’s production temperature and extraction efficiency will drop dramatically. Therefore, for the Guide area, if a “three-spot” well pattern is used for geothermal extraction either with water or CO2 as the working fluid, the most appropriate flow rate is 50 kg/s.

CO2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can achieve the goal of energy exploitation and CO2 geological sequestration. Taking Zhacanggou as research area, a “Three-spot” well pattern (one injection with two production), “wellbore–reservoir” coupled model is built, and a constant injection rate is set up. A fully coupled wellbore–reservoir simulator—T2Well—is introduced to study the flow mechanism of CO2 working as heat transmission fluid, the variance pattern of each physical field, the influence of CO2 injection rate on heat extraction and the potential and sustainability of heat resource in Guide region. The density profile variance resulting from temperature differences of two wells can help the system achieve “self-circulation” by siphon phenomenon, which is more significant in higher injection rate cases. The density of CO2 is under the effect of both pressure and temperature; moreover, it has a counter effect on temperature and pressure. The feedback makes the flow process in wellbore more complex. In low injection rate scenarios, the temperature has a dominating impact on the fluid density, while in high rate scenario, pressure plays a more important role. In most scenarios, it basically keeps stable during 30-year operation. The decline of production temperature is

Large dams on the Chinese Huanghe (Yellow River) have altered its water and sediment fluxes, suspended sediment concentration, grain sizes, and inter-annual patterns of water and sediment delivery to the sea. Sediment entrapment by the Sanmenxia and Xiaolangdi reserovirs along with increasing water consumption associated with dam regulation are mainly responsible for curtailed water and sediment discharges. After Xiaolangdi Reservoir was constructed in 1999, peak flows have decreased, with low flow ( 3 /s) now dominating the Huanghe discharge most of the year. Since 2002, a managed water release system through Xiaolangdi Dam, known as Water-Sediment Modulation (WSM), has played a vital role in regulating the delivery of material from Huanghe to the sea. The WSM produces ∼50% of the annual sediment to the sea, of which 60% derives from scoured coarse sediment from the riverbed of the lower reaches. The suspended sediment concentration of Huanghe during operation of the WSM is 17.3 kg/m 3 , compared with just 6.9 kg/m 3 in other times of the year. The WSM also leads to intense riverbed scouring in the lower reaches, which increases transport capacity and reduces flood risk. Sediment infilling in the Xiaolangdi Reservoir remains high, however, and riverbed scouring during the WSM has weakened since 2006. The Huanghe provides an example of management issues when large dams eventually lose their impoundment.

Iodine is an important trace element associated closely with human being, and it will influence human’s normal growth if lacking it. Meanwhile, iodine is an important catalyzer, and is important in atmospheric chemistry study. In nature, iodine is rich mainly in marine organism and sediment, and marine sediment has the largest storage of iodine. The analysis results of sediment samples obtained by the First Chinese National Arctic Research Expedition indicate that iodine contents in sediments in the Chukchi Sea and the Bering Sea are 98.1x10-6 and 73.8x10-6, respec-tively, which are higher than those in sediments of Chinese marginal seas and the southern Pacific Ocean, and show the trend of increase from low latitude to high latitude. This paper proposes a pattern of iodine latitudinal distribution on the basis of the distribution characteristic of iodine and its enrichment mechanism in sediments of the Chukchi Sea and the Bering Sea.

Analyses of rare earth elements (REEs) in 26 surface sediment samples obtained from the Chukchi Sea were conducted using ICP-MS. In general, REEs are relatively rich in fine-grained sediments and deplete in coarse-grained sediments in the Chukchi Sea although REEs have large concentration spans in different types of sediments. Except that a few samples have weak en-richments of light or heavy REEs?most samples exhibit flat shale-normalized REE pattern, indi-cating that surface sediments in the Chukchi Sea are composed dominantly of terrigenous com-ponents experiencing weak chemical weathering. In terms of REE concentrations and other char-acteristic parameters, we inferred that sediments on the eastern and western sides of the Chukchi Sea are derived from landmasses of Alaska and Siberia, respectively; the midsouth sediments are possibly related to northward dispersion of the Yukon River materials. The Herald Shoal in the center of the study area is covered with relict sediment, which has large ratios of light-to-heavy REEs (ΣCe/ΣY ratio) and lacks evident negative Ce anomaly; cerium enrichment is possibly re-lated to manganese transfer under oxidizing conditions in early diagenesis.

By reference of the d 18 O and d 13 C isotopic compositions of G.. sacculifer and accelerator mass spectrometry (AMS) 14 C dates, the , and Pr/Pn in core DGKS9603 have been used to characterize the changes of paleooceanographic environment occurring in the East China Sea (ECS) during the last 35000 years. The stratigraphic records of these proxies have shown that during the last 35 ka the Okinawa Trough has gone through 7 stronger cold-climate events (C 1 —C 7 ) and 9 terrigenous matter-decreasing events (e 1 —e 9 ), of which, the C1 corresponds to the cold episode occurring in the middle late Holocene, C 2 —C 4 and C 7 correspond to the H 1 —H 4 events, respectively. e1 and e 3 —e 8 correspond to the decrease of sea surface temperature (SST), respectively. The terrigenous inputs increased when Heinrich events occurred. Climate colding resulted in the decrease of terrigenous matter transported by rivers, and the increase of that transported by winter monsoon. Heinrich events are closely related to East Asia monsoon. During the Last Glacial Maximum (LGM, 15.5—25.8 Cal ka BP), reduction environment fluctuated strongly, bringing forth three stronger reduction events (R 1 —R 3 ) and one weaker reduction event (O), of which, R 1 —R 3 correspond to the decrease of SST and increase of terrigenous nutrient and O corresponds to the decrease of terrigenous nutrient. The fluctuation of reduction condition must be related to the change of sea surface productivity.