Effects of pH on ferri-cyanide uptake and assimilation by several plants     

X. Z. Yu  F. Li  K. Li 《International Journal of Environmental Science and Technology》2012,9(2):227-233

This paper presents an investigation of the capacity of four different plants to remove and assimilate ferri-cyanide at different pH conditions. Detached roots of weeping willows (Salix babylonica L.), rice (Oryza sativa L. cv. JY 98), soybean (Glycine max L. cv. WH) and maize (Zea mays L. var. HK) were hydroponically exposed to ferri-cyanide in a closed system at 25?±?0.5°C for 24?h kept under darkness. Almost all applied ferri-cyanide was in the complex form in the hydroponic solution at pH????7.0 in the absence of light, while dissociation of ferri-cyanide to free cyanide and iron in solution was detected at pH????6.5. All plant species used were found to be able to remove and assimilate ferri-cyanide efficiently. The uptake and assimilation rates appeared to be inversely related to the pH, in which positive effects were observed at pH 6.0 and 6.5. Remarkable decreases in the assimilation rates were found at pH 8.0. Results presented here suggest that changes in solution pH have a substantial influence on not only the speciation of ferri-cyanide in the plant growth media, but also the uptake and assimilation mechanisms of ferri-cyanide by plants.  相似文献   

Creep Failure of Roof Stratum Above Mined-Out Area   总被引：1，自引：0，他引：1  

J. -A. Wang  D. Z. Li  X. C. Shang 《Rock Mechanics and Rock Engineering》2012,45(4):533-546

By taking into account the rheological behavior of the rock mass, the creep failure of a roof stratum seated on pillars in mined-out area is analyzed through a newly developed visco-elastic model. The time-dependent deflection of the roof stratum is obtained by numerical inversion of Laplace transform. The study shows that when creep properties of both the pillars and roof stratum are considered, the expected deflection in the roof stratum increases with time. Consequently, the roof would fail when the critical tensile stress is reached as the result of the increased deflection. To demonstrate the present analytical procedure, the failure time of roof stratum of the Xingtai Gypsum Mine in China was estimated, and the results obtained agreed with the observation. The case study indicates that the analytic approach provides a new way to assess the potential impact of the time-dependence of the roof stratum deformation and is useful in predicting its stability above a mined-out area.  相似文献   

Analytical Study of Underground Explosion-Induced Ground Motion   总被引：1，自引：0，他引：1  

J. C. Li  G. W. Ma  Y. X. Zhou 《Rock Mechanics and Rock Engineering》2012,45(6):1037-1046

A theoretical approach is presented to study the ground motion induced by an underground tunnel explosion. The ground motion is caused by two coupled stress waves, i.e., the reflected body wave and the secondary surface wave or Raleigh wave. Based on the principle of conservation of momentum at the wavefronts, the reflected body waves along the ground surface are derived. The interaction of the body wavefront and the ground surface induces the secondary surface wave which transfers outwards on the ground. The particle velocity and particle acceleration on the ground surface are subsequently derived. The analytical results are compared with results from numerical simulations and empirical formulae with different material damping ratios. The effects of the loading density and the material damping on the ground motion are investigated. Finally, the limitations of the proposed theoretical approach for ground motion prediction are discussed.  相似文献   

Influence of redox conditions on iodide migration through a deep clay formation (Toarcian argillaceous rock,Tournemire, France)     

B. Frasca  S. Savoye  C. Wittebroodt  O.X. Leupin  M. Descostes  B. Grenut  J. Etep-Batanken  J.-L. Michelot 《Applied Geochemistry》2012

With a half-life of 15.7 Ma, a high mobility and the potential to accumulate in the biosphere, ¹²⁹I is considered, in safety assessment calculations for radioactive waste repositories, to be one of the main contributors to the radiological dose. Several authors have reported that, at low concentration, I⁻ is weakly retained on argillaceous rocks. This process is not yet well-understood and different hypotheses have been put forward as to whether reactive phases or experimental artifacts (e.g. pyrite oxidation) could be the reason for the retention of I⁻ observed at low concentration. The aim of this study was to investigate the effect on I⁻ mobility of (i) the redox conditions and (ii) the amount of pyrite and natural organic matter (NOM) contents of the rock. These questions were addressed by performing batch sorption, through-diffusion and out-diffusion experiments on rock samples of Toarcian argillaceous rock from Tournemire (Aveyron, France). One of the challenges faced during this study was to distinguish actual transport properties from experimental artifacts. A especially elaborate experimental set-up allowed limiting the (i) oxidation of both argillaceous rock and I⁻, and (ii) carbonate precipitation. A comparison of the batch sorption results obtained for two Toarcian clay specimens, that differed in their amount of pyrite and NOM, allowed relating I⁻ sorption to pyrite oxidation. However, no evidence was found to associate the I⁻ behavior to the NOM amounts. While the through-diffusion experiments showed a very slight sorption (distribution ratio (R_d) = 0.016 mL g⁻¹) for the lowest I⁻ concentration under oxic conditions, the out-diffusion tests performed after the through-diffusion experiments on the same cells showed significant sorption under both oxic and anoxic conditions, resulting in R_d ranging from 0.02 mL g⁻¹ to 1.25 mL g⁻¹. The range of R_d values was higher for the upstream reservoir under oxic conditions. The discrepancies observed between the through-diffusion and the out-diffusion experiments suggest a kinetic control of the I⁻ uptake by argillaceous rocks under oxic and anoxic conditions.  相似文献   

Formation and characteristics of post-earthquake debris flow: a case study from Wenjia gully in Mianzhu, Sichuan, SW China   总被引：3，自引：0，他引：3  

H. Y. Ni  W. M. Zheng  Y. B. Tie  P. C. Su  Y. Q. Tang  R. G. Xu  D. W. Wang  X. Y. Chen 《Natural Hazards》2012,61(2):317-335

During the three flood seasons following the Wenchuan earthquake in 2008, two catastrophic groups of debris flow events occurred in the earthquake-affected area: the 2008-9-24 debris flow events, which had a serious impact on rebuilding; and the 2010-8-13/14 debris flow events, which destroyed much of the progress made in rebuilding. The Wenjia gully is a typical post-earthquake debris flow gully and at least five debris flows have occurred there. As far as the 2010-8-13 debris flow is concerned, the deposits of the Wenjia gully debris flow reached a volume of 3.1 × 10⁶ m³ in volume and hundreds of newly built houses were buried. This study took the Wenjia gully debris flow as an example and discussed the formation and characteristics of post-earthquake debris flow on the basis of field investigations and a remote sensing interpretation. The conclusions drawn from the investigation and analysis were as follows: (1) Post-earthquake debris flows were a joint result of both the earthquake and heavy rainfall. (2) Gully incision and loose material provision are key processes in the initiation and occurrence of debris flows and a cycle can be presented as the following process: runoff—erosion—collapse—engulfment—debris flow—further erosion—further collapse—further engulfment—debris flow enlargement. (3) The amount of rainfall that triggered debris flows from the Wenjia gully was significantly less than the average daily rainfall, while the intraday rainfall threshold decreased by at least 23.3%. (4) The occurrence mechanism of Wenjia gully debris flow was an erosion type and there was a positive relationship between debris flow magnitude and rainfall, which fitted an exponential model. (5) There were five representative characteristics of Wenjia gully debris flow: the long duration of the occurring process; the long distance of deposition chain conversion during the process of damage; magnification in the scale of debris flow; and the high frequency of debris flow events.  相似文献   

Experimental and numerical analysis on the responses of slope under rainfall   总被引：1，自引：0，他引：1  

X. B. Lu  T. L. Ye  X. H. Zhang  P. Cui  K. H. Hu 《Natural Hazards》2012,64(1):887-902

Rainfall is an important factor to trigger the slope failure such as landslides and debris flows. First, the relationship between rainfall duration with the initiation of debris flow and rainfall intensity was mainly studied by the series tests in a box model. Then, the rainfall induced responses of slopes and the initiation of slope failure were simulated by using the software FLAC2D based on the soil parameters in Weijia Gully, Beichuan County, Sichuan Province. The effects of the slope angle, rainfall intensity, soil parameters on the development of the stress, and pore pressure in the soil of the slope were analyzed. It indicates that largest displacements in the slope are mainly located near the toe. With the increase of the rainfall intensity, the effective stress in the slope decreases and the displacement increases.  相似文献   

Effects of climatic changes and anthropogenic activities on lake eutrophication in different ecoregions   总被引：1，自引：0，他引：1  

X. Chuai  X. Chen  L. Yang  J. Zeng  A. Miao  H. Zhao 《International Journal of Environmental Science and Technology》2012,9(3):503-514

Climatic changes and anthropogenic activities could affect nutrients?? status significantly in the different lake ecosystems. Nutrients in Lake Hulun and Lake Taihu, two largest shallow cyanobacteria-blooming lakes in northern and southern China, respectively, were at eutrophicated levels in 2009. The concentrations of total nitrogen and total phosphorus were 3.346 and 2.250?mg/L as well as 0.435 and 0.062?mg/L, respectively, in these two lakes with different causes of eutrophication. For Lake Hulun, it was the decreased amount of water as a result of the warming and drying climate that accounted for the abrupt increase of total nitrogen and total phosphorus levels through inspissation. In addition, the icebound effects, no outflows, low nutrients sequestration by the sediment and the reduction of aquatic productivity made the situation even worse. On the contrary, high population densities, the rapid development of agriculture and industry as well as urbanization have increased the nitrogen and phosphorus loads on Lake Taihu. Therefore, higher criteria of total nitrogen and total phosphorus should be applied in Lake Hulun given the difficulties in controlling climatic changes while much more rigorous standards should be established for Lake Taihu since the anthropogenic impacts on nutrient status are relatively easy to control.  相似文献   

Semivolatile organic compounds removal and health risk reduction in drinking water treatment biofilters applying different backwashing strategies     

Y. Chen  X. X. Zhang  B. Wu  B. Liu  L. Xiao  A. Li  S. Cheng 《International Journal of Environmental Science and Technology》2012,9(4):661-670

This study aimed to investigate the removal of 24 semivolatile organic compounds in Yangtze River (China) source water treated by six biofilters using different backwashing methods. Health risks induced by the pollutants in the influent and effluent water were also assessed based on the chemical detections. Comparatively, the biofilter backwashed with both air (15?m/h, 3?min) and water (8?m/h, 5?min) was most efficient in removing semivolatile organic compounds and reducing health risk. PCR-denatured gradient gel electrophoresis showed that backwashing alterations posed considerable influences on microbial community structure in the six biofilters. About 72.4?% of di-n-butyl phthalate and 81.8?% of bis(2-ethylhexyl)phthalate (two main semivolatile organic compounds in the river water) were removed under the optimal backwashing conditions. However, in the effluent of each biofilter, non-carcinogenetic risks of 2,6-dinitrotoluene and bis[2-ethylhexyl]phthalate and carcinogenetic risks of dibenz[a,h]anthracene and benzo[a]pyrene did not reach safety levels, revealing that these pollutants in the source water deserve more public health concerns. This study might serve as a basis for biofiltration process optimization and also as a benchmark for the authorities to reduce the health risk induced by exposure to the hazardous pollutants.  相似文献   

A Cross Section from the Pre-Sinian to Triassic Along the Three Gorges of Yangtze River, Central China: a Pre-Symposium Field Trip of IGCP-368/411/440 in 1999     

S. Sengupta  M. Yoshida  X. Wang 《Gondwana Research》2000,3(4):564-566

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Comparisons of u ‐, g ‐, r ‐, i ‐, and z ‐band luminosity distributions between galaxy members of compact groups and isolated galaxies     

X.‐F. Deng  S.‐Y. Zou 《Astronomische Nachrichten》2011,332(2):202-207

To investigate the environmental dependence of u ‐, g ‐, r ‐, i ‐, and z ‐band luminosities, we perform comparative studies of luminosity distributions between galaxy members of compact groups (CGs) and isolated galaxies. It is found that for the r, i, and z bands isolated galaxies have a higher proportion of faint galaxies and a lower proportion of luminous galaxies than galaxy members of CGs, but for the u band an opposite trend is observed. The correlation between the g ‐band luminosity and the environment has different trends in different luminosity regions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献