Abstract:Hydrodynamic effect will enhance the shear effect of sediment and water interface, and the physical and chemical properties of the overlying water and sediment (dissolved oxygen, pH, redox potential, etc. ) will be changed. Thus, the release law of pollutants will be affected or even changed. The advances in the past decade are reviewed and summarized to reveal the release mechanism of nutrients, heavy metals and persistent organic matters as well as the main factors affecting the release process under hydrodynamic forces in this paper. It is proposed that some issues should be improved in the further study, including the mechanism of sediment resuspension and redistribution behavior under multiple hydrodynamic disturbances, the synergistic or antagonistic coupling mechanism between the hydrodynamic action and the release of various pollutants in sediments, microscopic mechanism of pollutant release under the combined action of hydrodynamic forces and aquatic plants, and the model construction of sediment release dynamics based on complex conditions.

Abstract:There are a large number of persistent organic pollutants(polycyclic aromatic hydrocarbons)in the stormwater runoff, and many researchers have studied the removal of polycyclic aromatic hydrocarbons in bioretention cells. However, as the construction of the China’s sponge city has just started, the relevant research has not yet been reported. Herein, the authors present a review of the main removal mechanism of polycyclic aromatic hydrocarbons and the influencing factors in bioretention cells. Firstly, the origin, transfer and source of polycyclic aromatic hydrocarbons are briefly introduced. Secondly, main removal mechanisms in the rhizosphere are elaborated including the soil media adsorption, degradation, plant uptake and stimulation of microbiological activity. Besides, main factors affecting the removal of the polycyclic aromatic hydrocarbons, such as the content of carbon, environmental factors and the composition of organic matter are concluded as well. Finally, current gaps for future research are discussed. In this paper, the research progress on the removal of polycyclic aromatic hydrocarbons in bioretention cells abroad can provide scientific support for the optimization of bioretention cells and the efficiency improvement of persistent organic pollutants in our country.

Abstract:To explore the stress effect of naphthalene on the cyanobacteria of different cell size, Microcystis aeruginosa and Synechococcus sp. were exposed to different concentration of naphthalene(0, 0. 01, 0. 1, 1, and 10 mg/L)for seven days. Changes of cell concentration, the content of chlorophyll a, and the chlorophyll fluorescence of algae in these groups were determined to investigate effects of naphthalene on the growth and physiological parameters of two species. Results showed that the growth of Synechococcus sp. was significantly inhibited by the naphthalene during the whole experimental. The chlorophyll a content of Synechococcus sp. declined by 3. 9%-40. 4%(compared with the control). The photosynthetic activity and the potential maximum photosynthetic rate of Synechococcus sp. both depressed due to the naphthalene stress, while its tolerance to strong light was improved. This indicates that Synechococcus sp. has a high sensitivity to naphthalene. On the contrary, the growth and the photosynthetic activity of Microcystis aeruginosa were significantly promoted. However, the synthesis of chlorophyll a in the cells of Microcystis aeruginosa was inhibited.

Abstract:In the southern tidal area, it is indispensable to fully unearth and develop the potentialities of a reservoir for the flood detention and storage, which can make the reservoir fully display the functions of the flood detention and thefresh water storage, effectively relieving severe waterlogging disasters and the problem of insufficient water supply due to the influence of saline. Take the Tianxin reservoir located in the Zhong-Zhu union catchment of Guandong province as an example, these were described in detail including the train of thought about exploiting reservoirs potentialities and methods of making a regulation for the reservoir operation and parsing process. To make a regulation for the reservoir operation is a difficult point, because it must take some factors into account, such as changing rules of outer water level and regional drainage situation. An reservoir revamping is studied at the original catchment area first. By setting 4-meter-high gate on the spillway and using the rational operation regulation, it is possible to reserve a maximum flood of 6 h for the peak shifting and increase the beneficial reservoir capacity by 1. 21 million m³ without increasing the dam height. Then, combining the terrain around reservoir region, the flood of the west shoulder is led to the Tianxin Reservoir. The revamping research with increasing catchment area indicates that by setting 6-meter-high gate on the spillway, increasing dam height by 2 m and using the rational operation regulation, it is possible to reserve a maximum flood of 6 h for the peak shifting as well and increase the beneficial reservoir capacity by 1. 93 million m³.

Abstract:To improve the operational safety of earth rockfill dam, a longitudinal reinforcement is proposed. This rigid structure has triple functions as the seepage controlling, stress resistance and deformation resistance. Based on the classical mechanics, its anti-seepage effect, anti-deformation ability and the capacity to withstand external force is quantitatively analyzed. In addition, the quantitative relationships between the reinforcement thickness and the downstream water level, as well as the material properties of the rockfill dam are derived. For the theoretical derivation, the reinforced body is regarded as a fixed-end beam, loaded by water pressures from upstream and downstream, the active earth pressure from rockfill and the vertical drag force due to the differential settlement between core walls and rockfill. The top displacement together with the rotation angle and the bottom stress of the fixed end are derived from the deformation differential equation and validated through designing reviews. Subsequently, the construction method of buried steel pipe, which is adopted to perform the base grouting and also to meet the strength requirements, is put forward. The proposed method plays an important guiding role in rehabilitating and reinforcing the dangerous earth rockfill dams, as well as the design and construction of new dams.

Abstract:A three-dimensional hydrodynamic numerical model was used to study the hydrodynamic characteristics of the excavated basin built in the convex side of a bend river and the influence of the project on the river. The results showed the project’s influence on the water level and velocity distribution of the river section. It showed that after the wharf built, the backwater in the main channel occurred mainly in the narrow river before the bend end, indicating that the narrowed section of a meandering channel had great influence on the backwater. The range of the water level and velocity near the wharf apron was larger than other regions, perhaps resulting in scouring in this area. The wharf construction influenced the bend exit more than the entrance and middle. In the wharf working condition, there was obvious backflow in the basin, while the velocity was small. It may cause the depositing that will obstruct the wharf operating. The results were useful for studying the hydrodynamic characteristics of excavated harbor basins and its influence on flood control in the meandering river. The results could also provide the basis for the wharf management.

Abstract:The hydraulic gradient at the bottom of cutoff wall in a deep overburden foundation is large, and may cause the local seepage failure near the bottom of cutoff wall, which may induce the differential settlement and crack of anti-seepage structure threatening the dam safety. In order to reduce the hydraulic gradient at the bottom of cutoff wall, a new cutoff wall of expanded base type was proposed to change the local structure type of the cutoff wall tip. The distributions of the hydraulic gradient at the bottom of cutoff wall were compared and analyzed with different types of local structure. The results show that the expanded base structure could significantly reduce the maximum hydraulic gradient at the bottom of cutoff wall and the maximum hydraulic gradient at the downstream side; the larger the radius of expanded base structure was, the smaller the maximum hydraulic gradient was. For the generalized model, when the penetration depth of cutoff wall with the conventional type was 35 m, the maximum hydraulic gradient at the bottom of cutoff wall was 0. 85, and the maximum hydraulic gradient at the downstream side was 0. 27. For the cutoff wall of expanded base type with a radius of 1. 5 m, in order to achieve the same anti-seepage effect, the penetration depth was only 23 m. It can be seen that the type of a expanded base structure was significantly superior to the conventional type. It can significantly reduce the construction quantity, the investment, and the construction period of cutoff wall.

Abstract:For the two-dimensional simulation of transversal seepage of the lock chamber, in order to take the effect of the width of lock chamber into account, the resistance coefficient model of inner section has been built based on the improved resistance coefficient method. By the local model of the ABAQUS software, this study changed the ratio of the foundation depth to the impervious depth and the ratio of the foundation depth to the outflow width, to calculate the discharge coefficient, the resistance coefficient and partition coefficient, based on the infiltration capacity, and then charts of different coefficients have been drawn. The result shows that the narrower the chamber width is, the larger the impervious depth will be, and the effect on the lateral outflow width will be more pronounced. For the lock of a lower level, narrower chamber width and larger water head, the impact of the chamber width should be taken full account to prevent the under estimation of the exit section slope, which is not conducive to the seepage stability. In this paper, the accuracy of the conventional resistance coefficient method has been improved, and the principle can be applied to similar projects, e. g. the effect of outlet width on the infiltration of a foundation pit.

Abstract:To investigate the influence of bio-organic fertilizer on the water-salt dynamics and crop yield of different saline soils(greenhouse secondary saline soil(NS)and coastal saline soil(S)), the pot experiment was adopted to study the effects of fertilization regimes on the soil moisture content, soil electric conductivity(EC), soil salt composition, crop yield and water use efficiency of irrigation. The following treatments were applied: controlling without fertilization(CK), chemical fertilizer(C), bio-organic fertilizer(O), bio-organic fertilizer combined with chemical fertilizer(CO, bio-organic fertilizer: chemical fertilizer=1∶1). The results showed that: (a)Compared to C, O and CO can improve the soil water content inboth types of saline soils. (b)Soil salt, indicated by the soil electric conductivity, was controlled well by O and CO treatment. (c)Compared with NS-C, the total amount of soil salt ions in NS-O and NS-CO decreased by 23. 63% and 15. 60%, respectively. (d)Compared with S-C, the total amount of soil salt ions in S-O and S-CO decreased by 22. 34% and 10. 32%, respectively. (e)After the tomato harvesting, the proportion of NO^-₃ and SO^2-₄ in the soil salinity decreased in NS, while the proportion of Na⁺, K⁺ and Cl^- decreased in S. (f)O was the most favorable for soil microbial growth, followed by CO. The yield of tomato treated with CO in the secondary saline soil was the highest, and the yield increased by 165. 5% compared with O. (g)The application of bio-organic fertilizer could improve the crop yield and irrigation water use efficiency of S, and the chemical fertilizer will result in the crop failure. (h)The application of chemical fertilizer can improve the crop yield on saline soil, and irrigation water use efficiency of the bio-organic fertilizer treatment is higher than other treatments.

Abstract:There are many influencing factors of irrigation quality in the border irrigation, and it is important to analysis the quality sensitivity of these factors. Based on the results of field experiments, the grey correlation analysis was combined with the WinSRFR model and uniform design to study the factor sensitivity on the irrigation quality of border irrigation. The analysis shows that the sensitivity of the factors for border irrigation can be listed according to the order from large to small as: inflow cutoff G, unit discharge q, surface roughness n, border length L, infiltration coefficient K, infiltration index α, and longitudinal slope of border field Z. The irrigation quality is more affected by the irrigation technology than the natural elements. During the design and management of border irrigation, it should be taken more attention on the controlling accuracy of irrigation technology.

Abstract:For saturated quasi-brittle rocks containing randomly distributed microcracks, the interstitial water pressure has an important impact on the internal deformation and strength. Fully considering the microscopic characteristics and evolution of material, a multiscale damage constitutive model with the hydro-mechanical coupling under undrained condition was established to study the damage behaviors of quasi-brittle rocks. This model is based on the linear homogenization method of Mori-Tanaka and the irreversible thermodynamics theory. For the small perturbation, an analytical expression of the strength, suitable for the conventional triaxial test under undrained condition, was derived through the remarkable hydro-mechanical coupling analysis. The proposed multiscale model was finally applied to simulate a series of undrained triaxial compression tests of sandstone, where the laws of stress-strain curves and interstitial water pressure in the mechanical loading process were reasonably demonstrated.

Abstract:By the plate colon-counting method and scanning electron microscopy, the influence of culture mediums on the marine microbe adhesion of hardened cement paste surface was discussed through immersing the hardened cement paste in three different culture mediums simulating sea water for 3 h, 10 h and 24 h. Results show that the main marine microbe adhered on hardened cement paste surface is the gram-negative bacteria with rodlike shape, and adhesion amounts are different depending on the culture medium. Meanwhile, the 10 h adhesion amount is the lowest among three time points of each culture medium. For hardened cement paste immersed in each culture medium for 24 h, there are reversible adhesion stage and irreversible adhesion stage.

Abstract:Northwest and east wind events are two major types of strong winds that dominate waters off Mackenzie delta during open water summer seasons. A storm from the northwest during the Oct. 2008 storm is selected, and the SWAN model is applied to simulate the generated storm waves in waters off the delta during this storm. Also, the coastal hydrodynamic phenomena caused by east wind events are analyzed based on the observed wind, current data and MODIS data. The results show that, northwest storms generate strong waves that impact the delta waves and strong currents in the upper and middle layers of ocean, inducing the obvious wave set-up and wave dissipation. East storm winds cause the strong currents from the surface to the bottom of ocean, and even mild sustaining east winds can cause the upwelling and mixing in waters off the delta. In addition, both the northwest and east winds can lift the fine sediment at the bottom.

Abstract:Through the field investigation of 30 sections and profile characteristics of the sedimentat of the Xiamen Bay Beach, as well as numerical simulations of the tidal current field and the wave field, the beach type of Xiamen Bay is divided from the perspective of dynamics. It was figured out that there is “sandy-muddy hybrid beach” in addition to the sandy beach and muddy beach, and in the environment of the muddy coast, strong coastal waves and supply of the coarse-particle sedimentmay produce sandy-muddy hybrid beach. The concept of “sand-silt demarcation point” is proposed and applied in artificial beach problems. It can be found that the elevation of sand-silt demarcation point mainly depends on the local wave condition.