Characterization,dissolution and solubility of the hydroxypyromorphite–hydroxyapatite solid solution [(Pb<Subscript>x</Subscript>Ca<Subscript>1−x</Subscript>)<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>OH] at 25 °C and pH 2–9     

Yinian Zhu  Bin Huang  Zongqiang Zhu  Huili Liu  Yanhua Huang  Xin Zhao  Meina Liang 《Geochemical transactions》2016,17(1):2

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Iron Reduction Along an Inundation Gradient in a Tidal Sedge (<Emphasis Type="Italic">Cyperus malaccensis</Emphasis>) Marsh: the Rates,Pathways, and Contributions to Anaerobic Organic Matter Mineralization     

Min?Luo  Cong-Sheng?ZengEmail author  Chuan?Tong  Jia-Fang?Huang  Kai?Chen  Feng-Qin?Liu 《Estuaries and Coasts》2016,39(6):1679-1693

Incubation experiments were adopted to characterize the rates and pathways of iron reduction and the contributions to anaerobic organic matter mineralization in the upper 0–5 cm of sediments along a landscape-scale inundation gradient in tidal marsh sediments in the Min River Estuary, Southeast China. Similar sediment characteristics, single-species vegetation, varied biomass and bioturbation, distinct porewater pH, redox potential, and electrical conductivity values have resulted in a unique ecogeochemical zonation along the inundation gradient. Decreases in solid-phase Fe(III) and increases in nonsulfidic Fe(II) and iron sulfide were observed in a seaward direction. Porewater Fe²⁺ was only detected in the upland area. High rates of iron reduction were observed in incubation jars, with significant accumulations of nonsulfidic Fe(II), moderate accumulations of iron sulfides, and negligible accumulations of porewater Fe²⁺. Most of the iron reduction was microbially mediated rather than coupled to reduced sulfides. Microbial iron reduction accounted for 20–89 % of the anaerobic organic matter mineralization along the inundation gradient. The rate and dominance of microbial iron reduction generally decreased in a seaward direction. The contributions of microbial iron reduction to anaerobic organic matter mineralization depended on the concentrations of bioavailable Fe(III), the spatial distribution of which was significantly related to tidal inundation. Our results clearly showed that microbial iron reduction in the upper sediments along the gradient is highly dependent on spatial scales controlled primarily by tidal inundation.  相似文献   

五硼酸铷溶液的物化性质及物种分布          下载免费PDF全文

苗军涛  房艳  房春晖  朱发岩  刘红艳  周永全  戈海文  孙鹏超  赵晓婵 《盐湖研究》2016,24(1)

碳酸铷、硼酸化学计量比混合,蒸发溶液,直至五硼酸铷RbB5O8·4H2O晶体析出。经粉末X射线衍射（XRD）、拉曼光谱（Raman spectroscopy）、热重/微商热重/差示扫描量热（TG/DTG/DSC）、原子吸收光谱等实验方法,确定其化学组成及结构。298.15、333.15K时测量溶液的物理化学性质（密度、电导、pH）,并与经验方程进行拟合,研究五硼酸铷溶液的物化性质随浓度、温度的变化规律。根据文献报道的平衡常数,实验测量的pH数据,采用牛顿迭代法进一步研究五硼酸铷溶液中主要存在的硼酸根离子对类型、含量以及物种的形成。  相似文献   

A late Holocene winter monsoon record inferred from the palaeo-aeolian sand dune in the southeastern Mu Us Desert, northern China     

Bing Liu  HeLing Jin  Fan Yang 《寒旱区科学》2016,8(5):388-399

The variation of the Asian winter monsoonal strength has seriously affected the climate and environmental conditions in the Asian monsoonal region, and even in marginal islands and the ocean in the East Asian region. However, relevant understanding remains unclear due to the lack of suitable geological materials and effective proxies in the key study areas. Here, we present a grain-size record derived from the palaeo-aeolian sand dune in the southeastern Mu Us Desert, together with other proxies and OSL dating, which reflect a relatively detailed history of the winter monsoon and abrupt environmental events during the past 4.2 ka. Our grain-size standard deviation model indicated that >224 μm content can be considered as an indicator of the intensity of Asian winter monsoon, and it shows declined around 4.2-2.1 ka, enhanced but unstable in 2.1-0.9 ka, and obviously stronger since then. In addition, several typical climate events were also documented, forced by the periodic variation of winter monsoonal intensity. These include the cold intervals of 4.2, 2.8, 1.4 ka, and the Little Ice Age (LIA), and relatively warm sub-phases around 3.0, 2.1, 1.8 ka, and the Medieval Warm Period (MWP), which were roughly accordant with the records of the aeolian materials, peat, stalagmites, ice cores, and sea sediments in various latitudes of the Northern Hemisphere. Combined with the previous progresses of the Asian summer monsoon, we preliminarily confirmed a millennial-scale anti-correlation of Asian winter and summer monsoons in the Late Holocene epoch. This study suggests that the evolution of the palaeo-aeolian sand dune has the potential for comprehending the history of Asian monsoon across the desert regions of the modern Asian monsoonal margin in northern China.  相似文献   

Spatio-temporal evolution of urban innovation structure based on zip code geodatabase: An empirical study from Shanghai and Beijing     

Dezhong Duan  Debin Du  Chengliang Liu  Seamus Grimes 《地理学报(英文版)》2016,26(12):1707-1724

In today’s world, the innovation of science and technology has become the key support for improving comprehensive national strength and changing the mode of social production and lifestyle. The country that possesses world-class scientific and technological innovation cities maximizes the attraction of global innovation factors and wins a strategic initiative in international competition. Based on the urban zip code geodatabase, an evaluation system of urban innovation with the perspective of innovation outputs, and the spatial evolutionary mode, concerning the structure of innovation space of Shanghai and Beijing from 1991 to 2014, was developed. The results of the research indicated that the zip code geodatabase provided a new perspective for studying the evolving spatial structure of urban innovation. The resulting evaluation of the spatial structure of urban innovation using the urban zip code geodatabase established by connecting random edge points, was relatively effective. The study illustrates the value of this methodology. During the study period, the spatial structure of innovation of Shanghai and Beijing demonstrated many common features: with the increase in urban space units participating in innovation year by year, the overall gap of regional innovation outputs has narrowed, and the trend towards spatial agglomeration has strengthened. The evolving spatial structure of innovation of Shanghai and Beijing demonstrated differences between the common features during the 25 years as well: in the trend towards the suburbanization of innovation resources, the spatial structure of innovation of Shanghai evolved from a single-core to a multi-core structure. A radiation effect related to traffic arteries as spatial diffusion corridors was prominent. Accordingly, a spatial correlation effect of its innovation outputs also indicated a hollowness in the city center; the spatial structure of innovation of Beijing had a single-core oriented structure all the way. Together with the tendency for innovation resources to be agglomerated in the city center, the spatial correlation effect of innovation outputs reflected the characteristics of the evolutionary feature where “rural area encircles cities”. The innovation spatial structure of Shanghai and Beijing have intrinsic consistency with the spatial structure of their respective regions (Yangtze River Delta urban agglomeration and Beijing-Tianjin-Hebei metropolitan region), which suggested that the principle of proportional and disproportional distribution of a city-scale pattern of technological and innovational activities is closely related to its regional innovation pattern.  相似文献   

Progress in China’s sustainable development research: Contribution of Chinese geographers   总被引：2，自引：0，他引：2  

Yu Yang  Yi Liu 《地理学报(英文版)》2016,26(8):1176-1196

Sustainable development has always been a hotspot in Chinese geographical research. Herein, we conduct a systematic statistical analysis of the contribution of Chinese geographers to sustainable development research using bibliometric methods. Based on the review of a vast amount of literature, we identify the main research teams, research funding sources, journals, and key research fields. The findings are as follows: (1) the resources and environmental institutes of the Chinese Academy of Sciences have a significant influence on sustainable development research; (2) China’s central government foundations (the National Natural Science Foundation of China and National Social Sciences Fund) are the main research funding sources; (3) most of the highly cited articles are published in journals sponsored by the Geographical Society of China; and (4) sustainable development theory and its research areas are being constantly enriched and perfected. Based on the statistics of keywords, the theory, research methods, research regional scales, and key research areas are summarized and expounded.  相似文献   

Degrading river network due to urbanization in Yangtze River Delta   总被引：1，自引：0，他引：1  

Longfei Han  Youpeng Xu  Chaogui Lei  Liu Yang  Xiaojun Deng  Chunsheng Hu  Guanglai Xu 《地理学报(英文版)》2016,26(6):694-706

Evolution of river systems under the background of human activities has been a heated topic among geographers and hydrologists. Spatial and temporal variations of river systems during the 1960s–2010s in the Yangtze River Delta (YRD) were investigated based on streams derived from the topographic maps in the 1960s, 1980s and 2010s. A list of indices, drainage density (Dd), water surface ratio (WSR), ratio of area to length of main streams (R), evolution coefficient of tributaries (K) and box dimension (D), were classified into three types (quantitative, structural, and complex indices) and used to quantify the variations of stream structure. Results showed that: (1) quantitative indices (Dd, WSR) presented decreasing trend in the past 50 years, and Dd in Wuchengxiyu, Hangjiahu and Yindongnan have decreased most, about 20%. Structurally, the Qinhuai River basin was characterized by significant upward R, and K value in Hangjiahu went down dramatically by 46.8% during the 1960s–2010s. Decreasing tendency in D was found dominating across the YRD, and decreasing magnitude in Wuchengxiyu and Hangjiahu peaks for 7.8% and 6.5%, respectively in the YRD. (2) Urbanization affected the spatial pattern of river system, and areas with high level of urbanization exhibited least Dd (2.18 km/km²), WSR (6.52%), K (2.64) and D (1.42), compared to moderate and low levels of urbanization. (3) Urbanization also affected the evolution of stream system. In the past 50 years, areas with high level of urbanization showed compelling decreasing tendency in quantitative (27.2% and 19.3%) and complex indices (4.9%) and trend of enlarging of main rivers (4.5% and 7.9% in periods of the 1960s–1980s and the 1980s–2010s). In the recent 30 years, areas with low level of urbanization were detected with significant downward trend in Dd and K. (4) Expanding of urban land, construction of hydraulic engineering and irrigation and water conservancy activities were the main means which degraded the river system in the YRD.  相似文献   

Bias estimation and correction for triangle-based surface area calculations     

Shuqiang Xue  Jiping Liu  Jinzhong Mi  Chun Dong  Yingyan Cheng 《International journal of geographical information science》2016,30(11):2155-2170

The calculation of surface area is meaningful for a variety of space-filling phenomena, e.g., the packing of plants or animals within an area of land. With Digital Elevation Model (DEM) data we can calculate the surface area by using a continuous surface model, such as by the Triangulated Irregular Network (TIN). However, just as the triangle-based surface area discussed in this paper, the surface area is generally biased because it is a nonlinear mapping about the DEM data which contain measurement errors. To reduce the bias in the surface area, we propose a second-order bias correction by applying nonlinear error propagation to the triangle-based surface area. This process reveals that the random errors in the DEM data result in a bias in the triangle-based surface area while the systematic errors in the DEM data can be reduced by using the height differences. The bias is theoretically given by a probability integral which can be approximated by numerical approaches including the numerical integral and the Monte Carlo method; but these approaches need a theoretical distribution assumption about the DEM measurement errors, and have a very high computational cost. In most cases, we only have variance information on the measurement errors; thus, a bias estimation based on nonlinear error propagation is proposed. Based on the second-order bias estimation proposed, the variance of the surface area can be improved immediately by removing the bias from the original variance estimation. The main results are verified by the Monte Carlo method and by the numerical integral. They show that an unbiased surface area can be obtained by removing the proposed bias estimation from the triangle-based surface area originally calculated from the DEM data.  相似文献   

Effects of experimental warming on soil microbial communities in two contrasting subalpine forest ecosystems,eastern Tibetan Plateau,China     

Di-di Sun  Yue-jiao Li  Wen-qiang Zhao  Zi-liang Zhang  Dan-dan Li  Chun-zhang Zhao  Qing Liu 《山地科学学报》2016,13(8):1442-1452

Soil microbial communities are primarily regulated by environmental temperature. Our study investigated the effects of global warming on soil microbial community composition as measured via phospholipid fatty acid (PLFA) analysis and soil chemical characteristics in relation to soil depth in a dragon spruce plantation and a spruce-fir-dominated natural forestin the Eastern Tibetan Plateau. Open-top chambers were utilized to increase the soil and air temperature. Soil samples were collected from the 0-10 cm, 10-20 cm, and 20-30 cm layers after a 4-year warming. Our results showed that the soil microbial community and the contents of TC (Total carbon), TN (Total nitrogen), NO ₃ ^- , and NH ₄ ⁺ responded differently to warming in the two contrasting forests, especially at the 0-10 cm soil depth. Warming increased soil microbial biomass at the 0-20 cm depth of soil in natural forest but reduced it at the 0-10 cm depth ofsoil in the plantation. In contrast, the TC and TN contents were reduced in most soil layers of a natural forest but increased in all of the soil layers of the plantation under warming conditions. This result suggested that the effects of warming on soil microbial community and soil C and N pools would differ according to soil depth and forest types; thus, the two contrasting forests would under go differing changes following the future climate warming in this region.  相似文献   

Dynamic process simulation with a Savage-Hutter type model for the intrusion of landslide into river   总被引：1，自引：0，他引：1  

Wei Liu  Si-ming He  Chao-jun OnYang 《山地科学学报》2016,13(7):1265-1274

Natural damming of rivers by mass movements is a very common and potentially dangerous phenomena which has been documented all over the world. In this paper, a two-layer model of Savage-Hutter type is presented to simulate the dynamic procedure for the intrusion of landslide into rivers. The two-layer shallow water system is derived by depth averaging the incompressible Navier-Stokes equations with the hydrostatic assumption. A high order accuracy scheme based on the finite volume method is proposed to solve the presented model equations. Several numerical tests are performed to verify the realiability and feasibility of the proposed model. The numerical results indicate that the proposed method can be competent for simulating the dynamic process of landslide intrusion into the river. The interaction effect between both layers has a significant impact on the landslide movement, water fluctuation and wave propagation.  相似文献