Search

Since the first AMS research work was carried out in China, nearly 40 years has past. In this paper, the AMS instrument techniques in world and China were introduced. Particularly, the research works on AMS instrument techniques were introduced in detail which included the super ionization mass spectrometry at the China Institute of Atomic Energy and Qixian Nuclear （Beijing） Science and Technology Company. [ABSTRACT FROM AUTHOR]

According to the characteristics of the LEO space particles radiation environment of China's Fengyun No. 3 (FY-3) polar-orbiting meteorological satellites, in order to monitor the characteristics, and space–time distribution of charged particle radiation in the orbit space, it is proposed to install a three-directional high-energy particle detector (HEPD) in the three vertical orthogonal directions of FY-3E, so as to carry out the energy spectrum and flux observation of high-energy protons and electrons in the three directions of the satellite, namely, −X, +Y, and −Z. The on-orbit detection data acquired by these payloads can be used for space environment modeling and solar-terrestrial physics research, and provide data sources for operational space environment weather warning and forecasting. Through the ground accelerator calibration experiment and simulation analysis of the three-directional HEPDs developed in the flight model phase, the experimental results show that all the HEPDs' measured values meet the requirements for technical indexes, such as the detection energy range (high-energy protons: 3–300 MeV; high-energy electrons: 0.15–5.7 MeV), energy span accuracy (<15%), flux accuracy (<15%), and sensitivity (<5% (ΔN/N)). [ABSTRACT FROM AUTHOR]

Plant materials used in the construction of segments and beacon towers of the ancient Great Wall in northwestern China contain untapped potential for revealing local paleoclimatic and environmental conditions. For the first time, we characterize the molecular preservation and stable carbon and nitrogen isotope compositions of AMS-dated common reeds (Phragmites) collected from ancient Great Wall fascines in today's Gansu and Xinjiang using a combination of chromatographic techniques and isotope analyses. Our molecular data, along with Scanning Electron Microscopy, demonstrate excellent preservation of these ancient reeds, which were harvested from nearby habitats during periods of significant expansion of Imperial China when climate conditions sustained sizeable oases in the region. Stable isotope data capture differential rates of environmental change along the eastern margin of the Tarim Basin since the Han Dynasty (170 BC), implying that significant surface-water hydrological changes occurred only after the Song Dynasty (1160 AD) due to regional climate change. This study reveals the wealth of environmental and climate information obtainable from these site-specific organic building materials and establishes the foundation for further applications of advanced molecular, biochemical, and isotopic technologies to study these common and widely-distributed organic archaeological materials. [ABSTRACT FROM AUTHOR]

Natural and social environment changes have played important roles in social evolution in different times and spaces. Geopolitical change, in particular, might play a decisive role in social evolution during historical periods. The eastern Tienshan Mountains was a transportation hub for communication between the East and the West, where the natural environment is fragile and the social environment has been complex during the historical period. However, geopolitical change and its impact on local social development remain unclear due to fragmented historical records and limited studies. This study investigates the spatiotemporal variations of military facilities in the Hami region, and compares historical documents and archaeological and paleoclimate records to discuss geopolitical changes and social evolution during the historical period in the eastern Tienshan Mountains. A total of 84 visible organic remains from 38 historic beacon towers and 8 dak sites in the Hami region of the eastern Xinjiang Uygur Autonomous Region, northwestern China, were collected and the radiocarbon (14C) dates of these ruins were systematically determined with accelerator mass spectrometry. The dating results show that these sites were mainly built during two major periods: ca. 600–900 cal AD and ca. 1600–1950 cal AD, which roughly correspond to the Tang Dynasty (618–907 AD) and the Qing Dynasty (1636–1912 AD) in ancient China. Human settlement intensity was high during the Han, Tang, and Qing dynasties, and relatively low when the area was controlled by nomadic or local regimes. This suggests that agricultural empires and nomadic/local regimes adopted different strategies for regional management. Climate change might have affected geopolitical patterns, which, in turn, profoundly influenced human activities and social evolution in the eastern Tienshan Mountains over the last two millennia. This study systematically reveals the spatiotemporal variations of beacon towers and dak ruins in the region through a large number of reliable direct 14C dating, it reveals the remarkable differences in human activities in the eastern Tienshan Mountains under different administrations, and it explores the influence of geopolitics and climate change on social evolution in the eastern Tienshan Mountains from a multidisciplinary perspective. [ABSTRACT FROM AUTHOR]

Secondary inorganic aerosol (especially SNA: sulfate, nitrate, and ammonium) formed from different pathways, account for significant proportions of ambient particulate matter during haze events. For the first time, we quantitatively explored contributions from different SNA formation pathways by an online monitoring AMS instrument and 3‐dimension factor analysis PMF3 model, which is called "SNA formation pathway apportionment". Three formation process were identified: NH4NO3 heterogeneous phase reactions (NH4NO3‐heter), (NH4)2SO4 gas phase reactions ((NH4)2SO4‐gas), and mixed NH4NO3 and (NH4)2SO4 aqueous phase processes (S&N‐aque). Their overall contributions to SNA were 25.7%, 22.1%, and 52.2%, respectively. Moreover, (NH4)2SO4‐gas contributed mainly in clean (52.1%); S&N‐aque got the highest contribution in haze episode (69.6%); while sulfate gas phase formations were also found in haze stage (10.3%). The quantitative findings from this work provide hard evidence that aqueous phase processes (including sulfate aqueous phase reactions and nitrate gas‐particle partition) were major drivers for SNA increasing. Plain Language Summary: Secondary inorganic aerosol (particularly SNA: sulfate, nitrate and ammonium) was found to be the main component of particulate matter in northern China. SNA can be formed through different reaction pathways, such as gas phase, aqueous phase, and heterogeneous reactions pathways. However, quantitative assessments of different pathways are still lacking, especially during different pollution processes. In this work, AMS data with high time resolution and three‐dimension receptor model (PMF3) were used to study the characteristics of secondary aerosols in winter in Beijing and make SNA formation pathway contribution apportionment. Three possible formation pathways were identified by PMF3: Heterogeneous reactions pathway of NH4NO3, gas phase reactions pathway of (NH4)2SO4, and aqueous phase processes of mixed NH4NO3 & (NH4)2SO4, respectively. We found that the main dominant factors were diverse during different periods: (NH4)2SO4 gas phase reactions pathway contributed mainly to SNA in clean period; mixed NH4NO3 and (NH4)2SO4 aqueous phase processes contributed mostly in haze episode. The methods and findings of this work enable and further our understandings on the formations of secondary inorganic aerosol in haze. Key Points: Mixed NH4NO3 and (NH4)2SO4 (aqueous phase process) had the highest contribution during winter haze period (69.6%)(NH4)2SO4 (gas phase formation pathway) contributed mainly in clean (52.1%)(NH4)2SO4 (gas phase formation pathway) was also found during haze pollution stage (10.3%) [ABSTRACT FROM AUTHOR]

Detailed organic carbon isotope (δ13Corg) measurements were conducted on two peat sequences recovered from the north bank of the Yangtze River, East China. Seven radiocarbon dates provided firm age control of this δ13Corg record and reveal palaeoclimatic changes since the Late Glacial period. The results show that the Holocene Megathermal Maximum occurred between 8385 and 7040 cal. yr BP. The Late Glacial climate was generally cold but fluctuated frequently between 12940 and 11815 cal. yr BP. The Older Dryas (from 12940 to 12810 cal. yr BP) and the Younger Dryas (from 12645 to 12170 cal. yr BP) were characterised by cold climate conditions. In contrast, 12810 to 12645 cal. yr BP (corresponding to the Allerød Warm Period) and 12170 to 11815 cal. yr BP (corresponding to a rapid warming period after the Younger Dryas, marking the beginning of the Holocene) were relatively warm phases. In contrast to other high-resolution records, it shows that the δ13Corg records of our study peats are largely controlled by a common forcing mechanism of solar insolation changes in the Northern Hemisphere, and exhibit similar variability to δ18O records obtained from stalagmites and GISP2 during the Late Glacial and early-mid Holocene. [ABSTRACT FROM AUTHOR]