The spatiotemporal variation of reference evapotranspiration and the contribution of its climatic factors in the Loess Plateau,China     

Yanzhong Li  Kang Liang  Peng Bai  Aiqing Feng  Lifang Liu  Guotao Dong 《Environmental Earth Sciences》2016,75(4):354

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An experimental and theoretical study of the seepage migration of suspended particles with different sizes     

Bing Bai  Tao Xu  Zhiguang Guo 《Hydrogeology Journal》2016,24(8):2063-2078

This study experimentally investigates the effect of particle size, particle concentration and flow velocity on the migration of suspended particles of size 1.02–47 μm in porous media. The results show that at the same flow velocity, the peak values of the breakthrough curves decrease and corresponding pore volumes increase slightly with increasing particles size. The migration velocity of smaller suspended particles is even greater than water flow velocity, which is attributed to the size exclusion effect. With increase of the injected particle concentration, the deposition coefficients of small single particles increase at first and then tend to a steady state or even decrease slightly, explained by the maximum retention concentration. The dispersivity of small particles decreases with increasing velocity. However, at a high flow velocity, the hydrodynamic dispersivity becomes increasingly dominant with the increase of particle size. The deposition coefficients for large-sized particles are higher than those for small-sized particles, which is attributed to considerable mass removal due to straining. An analytical solution, considering the release effect of sorbed particles, is developed to account for the one-dimensional flow and dispersive effect using a source function method, and then three transport parameters—dispersivity, deposition coefficient and release coefficient—are fitted using the experimental results. Finally, suspended-particle migration is predicted by the proposed model for short-time constant-concentration injection and repeated three-pulse injection. Overall, particle size has a significant effect on the seepage migration parameters of suspended particles in porous media such as the particle velocity, dispersivity and deposition coefficient.  相似文献   

Effects of aluminum toxicity induced by acid deposition on pine forest ecosystem in Longli of Guizhou Province,Southwestern China     

ZHANG Jing  LYU Zhipeng  SHAO Siya  LI Fangfang  YANG Shengtian  SONG Wenlong  LI Wei  LI Shun-jiang 《中国地理科学(英文版)》2016,26(4):495-507

The effects of acid deposition on pine forest ecosystems in Longli of Guizhou Province, southwestern China are studied using indoor experiments and model simulations. Indoor experiments are designed to explore the aluminum toxicity on pine seedlings, and the long-term soil acidification model（LTSAM） and a terrestrial biogeochemistry model（CENTURY） are used to simulate the influences of acid deposition on pine forest ecosystems. The indoor experiment results of aluminum toxicity show that aluminum ions in solution limit plant growth and acid deposition enhances this effect by facilitating the release of aluminum ions from the soil. Pine seedling biomass and root elongation decrease as the aluminum concentration increases. The results of model simulations show that the soil chemistry varies significantly with different changes in acid deposition. When the acid deposition increases, the pH value in the soil solution decreases and the soil Al³⁺ concentration increases. The increased acid deposition also has negative impacts on the forest ecosystem, i.e., decreases plant biomass, net primary productivity（NPP） and net CO₂ uptake. As a result, the soil organic carbon（SOC） decreases because of the limited supply of decomposition material. Thus acid deposition need be reduced to help protect the forest ecosystems.  相似文献   

Modelling the upwelling offthe east Hainan Island coast in summer 2010     

白鹏  顾艳镇  李培良  吴克俭 《中国海洋湖沼学报》2016,34(6):1358-1373

A synoptic-scale upwelling event that developed off the east coast of the Hainan Island(EHIU) in the summer of 2010 is defi ned well via processing the Moderate Resolution Imaging Spectroradiometer(MODIS) sea surface temperature(SST) data. The Regional Ocean Modeling System(ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo fl oat profi les and MODIS SST, it is confi rmed that the ROMS reproduces the EHIU well. The cooler-water core(CWC) distinguished by waters(27) 27.5°C in the EHIU, which occurred in the east Qiongzhou Strait mouth area and was bounded by a high temperature gradient, was the focus of this paper. Vertical structure of the CWC suggests that interaction between the westward fl ow and the bathymetry slope played a signifi cant role in the formation of CWC. Numerical experiments indicated that the westward fl ow in the Qiongzhou Strait was the result of tidal rectifi cation over variable topography(Shi et al., 2002), thus tides played a critical role on the development of the CWC. The negative wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2–0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefi t the development of the CWC.  相似文献   

1980-2017年中国碳强度关键影响因子变化特征     

唐志鹏  梅子傲  刘卫东  夏炎 《地理学报(英文版)》2020,30(5):743-756

The Chinese government ratified the Paris Climate Agreement in 2016.Accordingly,China aims to reduce carbon dioxide emissions per unit of gross domestic product(carbon intensity)to 60%–65%of 2005 levels by 2030.However,since numerous factors influence carbon intensity in China,it is critical to assess their relative importance to determine the most important factors.As traditional methods are inadequate for identifying key factors from a range of factors acting in concert,machine learning was applied in this study.Specifically,random forest algorithm,which is based on decision tree theory,was employed because it is insensitive to multicollinearity,is robust to missing and unbalanced data,and provides reasonable predictive results.We identified the key factors affecting carbon intensity in China using random forest algorithm and analyzed the evolution in the key factors from 1980 to 2017.The dominant factors affecting carbon intensity in China from 1980 to 1991 included the scale and proportion of energy-intensive industry,the proportion of fossil fuel-based energy,and technological progress.The Chinese economy developed rapidly between 1992 and 2007;during this time,the effects of the proportion of service industry,price of fossil fuel,and traditional residential consumption on carbon intensity increased.Subsequently,the Chinese economy entered a period of structural adjustment after the 2008 global financial crisis;during this period,reductions in emissions and the availability of new energy types began to have effects on carbon intensity,and the importance of residential consumption increased.The results suggest that optimizing the energy and industrial structures,promoting technological advancement,increasing green consumption,and reducing emissions are keys to decreasing carbon intensity within China in the future.These approaches will help achieve the goal of reducing carbon intensity to 60%–65%of the 2005 level by 2030.  相似文献   

东北松嫩平原生态系统服务价值损失的的估算   总被引：2，自引：0，他引：2  

王宗明  张柏  张树清  SONG Kaishan  Duan Hongtao 《地理学报(英文版)》2005,15(1):80-86

1IntroductionEcosystems around the globe create and maintain an environment suitable for the continuation of human life. Ecosystems supply goods such as timber, pharmaceuticals, and seafood, and so provide services including purification of air and water,…  相似文献   

依据海洋法对海警涉外案件管辖的分析          下载免费PDF全文

白俊丰 《海洋开发与管理》2005,22(5):64-68

依据海洋法确定的管辖海域对沿海国的管理有着法律意义.海警在我国管辖海域内执法,尤其是处理涉外案件,不仅要依照国内法律、法规、规章,而且必然受到海洋法的影响.  相似文献   

江西省横迳温泉区地热气体地球化学   总被引：2，自引：0，他引：2  

孙占学  高柏  刘金辉 《现代地质》2004,18(1):116-120

从赣南横迳温泉区采集10个水样并分析了温泉及冷泉的水化学成分,认为热水起源于大气降水补给。在此基础上,还在温泉区采集了4个气样,测定了气体组分的含量及氦同位素．以及CO₂和CH₄的碳同位素。研究结果表明：横迳地区温泉气中CO₂的含量很高(>96％),δC_CO2较重(-4.43‰～-5.50‰),属幔源CO₂;He同位素特征值(R/Ra)变化于1.36～2.11之问．均大于1,有幔源He的加入;本区温泉气的的组合类型为二氧化碳幔源温泉气,从整体上来说属于幔源无机成因气,是地幔脱气的产物。  相似文献   

黑河上游生态建设的模式与效益   总被引：8，自引：6，他引：2  

张耀生  赵新全  李春喜  薛白  代建聪 《中国沙漠》2004,24(4):456-460

在黑河上游实施的以牛羊育肥、退化草原的植被恢复、人工草地建设为主要内容的生态建设, 通过技术集成和试验示范, 效果显著。混播一年生草地平均产干草9.6t·hm², 每公顷约可为400只羊提供冬春季节补饲用草, 补饲措施可降低牲畜越冬死亡率50%以上, 提高仔畜成活率10%; 围栏封育增加草地水源涵养功能, 可使土壤含水量提高20%左右。绵羊育肥可使示范区农牧民人均增加收入300元。农业结构已经呈现明显的"山地河谷绿洲"一体化发展的系统耦合新结构, 系统耦合的效应对植被的保护起到了很好的作用。  相似文献   

吉林省耕地变化对粮食生产的影响     

何艳芬  张柏  马超群 《地理学报(英文版)》2004,14(1):56-62

1IntroductionThe quantity and quality of cropland guarantees the grain production (Feng, 2000), and the essence of cropland security is food security. Cropland security means the stability of total quantity of cropland, which also means stable quality, potential productivity and regional balance (Feng, 2000). With the development of urbanization and industrialization, more and more cropland is encroached, especially the cropland with great market-value (Cai, 2000; Ge, 2002; Richard, 2002), w…  相似文献