Nitrate vertical transport and simulation in soils of rocky desertification in Karst regions,Southwest China

The characteristics of nitrate vertical transport in soils collected from Libo and Puding in Guizhou Province were studied by simulating soil column in laboratory. The results were as follows: (1) Vertical transport velocity of nitrate decreased, and the breakthrough curves (BTCs) of nitrate were more dispersed, in each horizon from surface layer to bottom layer in every soil profile. As rocky desertification progressed, the BTCs experienced a gentle up and down trend, and tailing was more obvious. (2) An analytical solute transport model (CXTFIT 2.0) was used to estimate nitrate dispersion coefficient (D) and average pore water velocity (V) from the observed BTCs. The results showed that CXTFIT 2.0 model was suitable in fitting the nitrate transport in these soils. The dispersion coefficient was found to be a function of average pore water velocity. (3) The transport of nitrate was mainly affected by the soil structural coefficient. As soil structural coefficient decreased, nitrate outflow was retarded, and the peak concentration was reduced. Soil bulk density, organic matter, and clay also affected the vertical transport of nitrate. Low bulk density, clay content, and high organic matter content were each associated with faster nitrate transport.     

Soil heavy-metal speciation and wheat phytotoxicity in the vicinity of an abandoned lead–zinc mine in Shangyu City,eastern China

Sixteen soil samples were collected from the vicinity of an abandoned lead–zinc mine in Shangyu City, eastern China, and the heavy-metal speciation and wheat phytotoxicity in the soils were studied. The results showed that the concentrations of free Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were highly variable and ranged from <0.01 to 0.32, 0.06 to 10.62, <0.01 to 1.40 and 0.02 to 37.10 μmol l⁻¹, respectively. The concentrations of soluble Cu, Zn, Cd and Pb ranged from 0.38 to 3.24, 0.72 to 78.74, <0.01 to 1.95 and 0.15 to 639.34 μmol l⁻¹, respectively. The general trend of mean solid/liquid partition coefficient and percentage of free metal ion to total soluble metal concentration were Cu > Pb > Zn > Cd and Cd > Zn > Cu > Pb, respectively. Stepwise multiple linear regression with pH, log(total metal) and log(organic matter) showed that log(total metal) was an important factor that controlled log(free metal ion) and log(soluble metal). Of the variability in log(free Cu²⁺), log(free Cd²⁺) and log(free Pb²⁺), 55.2, 58.6 and 64.3% could be explained by log(total Cu), log(total Cd) and log(total Pb) alone, respectively. Of the variability in log(soluble Cu) and log(soluble Cd), 77.1 and 72.5% could be explained by log(total Cu) and log(total Cd) alone, respectively. Wheat root length was controlled by the various metals with different free and soluble concentrations, and 99.2% of the variability in root length could be explained by concentrations of free and soluble Pb, soluble Cu and total Zn in the soils.     

Blasius问题中剪应力函数的分析估计

Blasius问题用来描述稳定不可压缩流体流过平板的情况,常出现在流体力学边界层理论中．主要对Blasius问题中的剪应力进行分析估计．从与Blasius问题等价的积分方程人手,对积分方程的解z（t）进行分析估计,得出z（t）的性质．从而获得Blasius问题中的剪应力的分析估计,其结果如下：∫^＂（0）≥3/√6/β/√-β,9/4√27≤∥∫^＂∥≤3√3√1-3β^2-2β^     

Evaluation and estimation of daily global solar radiation from the estimated direct and diffuse solar radiation

Active layer plays a key role in regulating the dynamics of hydrothermal processes and ecosystems that are sensitive to the changing climate in permafrost regions. However, little is known about the hydrothermal dynamics during freeze-thaw processes in permafrost regions with different vegetation types on the Qinghai-Tibetan Plateau (QTP). In the present study, the freezing and thawing processes at four sites (QT01, 03, 04, and 05) with different vegetation types on the QTP was analyzed. The results indicated that the impact on the soil water and heat during the summer thawing process was markedly greater than that during the autumn freezing process. Furthermore, the thermal-orbit regression slopes for all sites exhibited a homologous variation as the depth increased, with the slowest attenuation for the meadow sites (QT01 and QT03) and a slightly faster attenuation for the desert steppe site (QT05). The air and ground surface temperatures were similar in winter, but the ground surface temperature was significantly higher than the air temperature in summer in the radiation-rich environment at all sites on the QTP. The results also indicated that the n-factors were between 0.36 and 0.55 during the thawing season, and the annual mean temperature near the permafrost table was between − 1.26 and − 1.84 °C. In the alpine desert steppe region, the thermal conditions exhibited to show a warming trend, with a current permafrost table temperature of − 0.22 °C. The annual changing amplitude of the ground temperature at the permafrost table was different for different vegetation types.     

Stable isotopes in surface snow along a traverse route from Zhongshan station to Dome A, East Antarctica

Samples of surface snow were collected for stable isotope analysis along the traverse route from Zhongshan to Dome A (East Antarctica) from Dec 28th, 2007 to Feb. 8th, 2008. The local relationship between δD and surface temperature is established to be 6.4 ± 0.2 ‰ per °C, very similar to the average for East Antarctic. The deuterium excess shows a pattern of high values over Antarctica, particularly at Dome A. We compare our data with an atmospheric general circulation model which includes stable water isotopes (ECHAM5-wiso). The model simulation captures the right levels of δD, but overestimates δ¹⁸O. This study provides support for the ongoing deep ice core project at Dome A.     

北京城市边缘区典型乡镇发展有序协调度研究

大城市边缘区是人口、用地、经济、社会和生态等发展最无序的区域。基于城市边缘区有序协调发展的机理,综合运用影响程度法、层次分析法和专家评判法等方法,从时间、空间、数量和功能4个维度上评价并分析北京城市边缘区3个典型乡镇(旧宫镇、长陵镇和永清镇)发展的有序协调程度。研究结果表明,旧宫镇的有序协调程度最高,其次是长陵镇,永清镇最低。     

Morphology and molecular identification of Ulva forming green tides in Qingdao, China

Green tides are caused by the proliferation of chlorophytes under suitable hydrographic conditions.These blooms lead to environmental degradation and negatively impact the waters and seagrass beds,as well as fishing and other recreational activities in the bay.A comprehensive ecological understanding of the bloom dynamics,including the origin and persistence,is needed to foster management decisions.The algae in the great majority of green tide blooms usually belong to two genera of Ulvophyceae,Ulva and Enteromorpha.Ulva has been observed more often in recent years.In China,green tides occurred for the first time in the middle area of the Yellow Sea in 2007,and a large-scale algae blooming broke out in the middle and southern areas of the Yellow Sea in late May 2008.We identified them as Ulva prolifera by comparative analysis of the rDNA internal transcribed spacer 1 (ITS1),5.8S and ITS2 sequences in combination with microscopic observation.Morphological differences were found between the free-floating algae and the attached thalli.Various reproduction patterns of the free-floating algae include sexual,asexual and vegetative propagations,which played important roles in the long-term green tide persistence in China.The ITS sequences of the blooming algae were identical to those of the samples from the Lianyungang sea area but were different from the attached samples from the Qingdao sea area.The results infer that the blooms are originated from other sea areas rather than from the local attached populations.     

Two-dimensional numerical model for debris flows in the Jiangjia Gully, Yunnan Province

Debris flows are recurrent natural hazards in many mountainous regions.This paper presents a numerical study on the propagation of debris flows in natural erodible open channels,in which the bed erosion and sedimentation processes are important.Based on the Bingham fluid theory,a mathematical model of the two-dimensional non-constant debris flow is developed.The governing equations include the continuity and momentum conservation equations of debris flow,the sediment convection-diffusion equation,the bed erosion-deposition equation and the bed-sediment size gradation adjustment equation.The yield stress and shear stress components are included to describe the dynamic rheological properties.The upwind control-volume Finite Volume Method (FVM) is applied to discretize the convection terms.The improved SIMPLE algorithm with velocity-free-surface coupled correction is developed to solve the equations on non-orthogonal,quadrilateral grids.The model is applied to simulate a debris flow event in Jiangjia Gully,Yunnan Province and to predict the flow pattern and bed erosion-deposition processes.The results show the effectiveness of the proposed numercial model in debris flow simulation and potential hazard analysis.     

Monitoring and warning of landslides and debris flows using an optical fiber sensor technology

Landslides and debris flows are typical geo-hazards which occur in hilly or mountainous regions. Debris flows may result from landslides. Geotechnical instrumentation plays an important role in monitoring and warning of landslides and resulted debris flows. Traditional technologies for monitoring landslides and debris flows have certain limitations. The new optical fiber sensors presented in this paper can overcome those limitations. This paper presents two new optical fiber sensor systems: one is the Fiber Bragg Grating (FBG)-based in-place inclinometer for monitoring landslides and the other is the FBG-based column-net system for monitoring debris flows. This paper presents the calibration results of FBG-based in-place inclinometers in laboratory. It is found that the calibration results are in good agreement with theoretical results. Both the FBG-based in-place inclinometers and the FBG-based column-net system have been installed at a site in Weijiagou valley, Beichuan County, Sichuan Province of China. Some preliminary results have been obtained and reported in the paper. The advantages of the FBG monitoring systems and their potential applications are also presented.     

The research of sea-land breeze (SLB) on the west coast of Bohai Bay based on field observation

Four automatic meteorological stations were set up in a line from beach to inland perpendicular to the west coast of Bohai Bay. Wind direction and velocity at altitudes of 2 m, 4 m and 12 m were surveyed with 10 minute intervals. On "Sea-Land Breeze" (SLB) days, the transition from sea breeze to land breeze was very evident in the study area. Direction of sea breeze was basically perpendicular to the coast and mainly from the ENE and E. Duration of sea breeze varied by the stations’ distance to the coastline, and the near-coast wind velocity was larger than that of the inland and decreases as it reaches inland. There was increased development of SLB on sunny days than on overcast days. The term "Climatic Coastal Zone" can be defined for the area influenced by SLB, which reaches more than 74 km inland on a typical SLB day but less than 10 km on a non-typical SLB day.