Abstract:Carrier pile is newly developed in recent years. It utilizes a column hammer to tamp the filling in the deep soil, which forms an expanded carried at the pile end. This will greatly increase the vertical pile bearing capacity. Although the carrier pile has been widely used in practice, rare theoretical analysis has been conducted to check the size of the reinforced area and the compaction effect. This greatly restricts the popularization and development of the carrier pile. Under this condition, the process of the tamping through a column hammer is simplified as the spherical cavity expansion model. The soft clay is described by the MCC model. Then, a series of partial differential equations (PDEs) for spherical cavity expansion is constructed. Similarity solution technique is used to transform the PDEs to ordinary differential equations (ODEs), which can be numerically solved through the ODE solver. Subsequently, a series of parametric analyses were conducted to investigate the variation of the soil strength and stiffness after spherical cavity expansion and the size of the compaction zone. This reveals the reinforced mechanism of the formation of the carried part of the pile from the theoretical viewpoint and provides a theoretical basis for constructing the theoretical calculation methods for the vertical bearing capacity of the carrier pile considering the compaction effect.

Abstract:Piles are widely used to reinforce slopes. Uncertainties exist in stability with anti-slide pile reinforced slope due to the uncertainties of soil. Reliability method can be used to quantify the uncertainties. Shear strength reduction method is employed to obtain the factor of safety and slip surfaces with different pile reinforcement locations. A response surface method-based first order reliability method is used to calculate the failure probability. Based on FLAC3D, an automatic programing procedure is proposed for convenient application.Steel pipe piles are adopted for stabilization in the illustrative example. The results show pile location and spacing have significant effect on the reliability of the illustrative example. An optimal location may exist at a certain spacing for the illustrative example. The suggested method can be helpful for the optimal design of pile reinforcement for soil slopes.

Abstract:Variation laws of earth pressure accounting for the displacement of a retaining wall can be well described by mathematical fitting, which is usually based on the earth pressure at rest or the active and passive earth pressures to illustrate the displacement-earth pressure of retaining walls through constructing various mathematical functions. This study subdivides displacement-dependent earth pressure formulations into six categories according to different functional forms, including trigonometric, exponential, hyperbolic, power, sigmoid and other functions. Characteristics and deficiencies of displacement-dependent earth pressure formulations are summarized, and future researches are provided. The findings of this study show that main differences of mathematical fitting are attributed to determination of function forms as well as undetermined parameters as well as their magnitudes, which results in the uncertainty of mathematical fitting and the generallity of research. A reasonable and practical mathematical fitting function has three features:boundary condition and initial value satisfied, parameters with clear meaning and representing the interaction between a retaining wall and soils. In terms of test studies, it is necessary to perform targeted research on different movement modes of a retaining wall, and model tests of earth pressure are conducted on clay, unsaturated soil, collapsible loess, expansive soil, among others. In terms of theoretical calculations, displacement-dependent earth pressure formulations using different mathematical fitting functions are compared to explore their rationality and applicability as well as to reveal intrinsic mechanisms between earth pressure of a retaining wall and its displacement. Displacement-dependent earth pressure of a retaining wall in unsaturated soil needs to be paid more attention. The choice and measurement of different parameters are improved and validated by model tests in order to accelerate the process of engineering applications for mathematical fitting functions.

Abstract:Soil-bentonite mixtures are often used to maintain the stability of the deep mixed pile method for the double round milling wall (Cutter Soil Mixing, CSM). The effect of bentonite content on the unconfined compressive strength and permeability of soil-bentonite mixtures in CSM when the local soil was sand and silt. The properties including the unconfined compressive strength and permeability was measured, and microstructure was investigated using MIP. The relationship between the change of pore ratio and the unconfined compressive strength and permeability coefficient of cement soil samples was investigated. The results show that the expansion of the bentonite and chemical reaction with cement hydration products can change the pore distribution of soil-bentonite mixtures; The variation of bentonite content can significantly reduce the permeability coefficient and improve the unconfined compressive strength; The increase of unconfined compressive strength of sand samples is larger than that of silt samples;The ratio of compressive strength to porosity and cement content is approximately a power function relationship; Bentonite can effectively fill the pores, and at the same time, it reacts with cement hydration products to change the pore distribution in cement soil; A certain amount of bentonite is effective in improving the strength of the cement soil sample, but the marginal effect of improving the dosage is not obvious. The optimum content of bentonite in silt is 5% and in sand is 2.5%~5%.

Abstract:For the design of a piled raft foundation that considering the pile-soil interaction, one of the key factors is to evaluate the load sharing characteristics of the raft reasonably. In order to determine the load sharing ratio of the raft accurately, a nonlinear elastic-plasticanalysis method for the rigid piled raft foundations under verticalloading is developed based on the pile-soil-raft interactions theory. On that basis, the influences of soil parameters, pile number, pile spacing, pile length and pile diameter on the pile-raft load sharing ratio of rigid piled raft are analyzed further, and a normalized calculation method of raft load sharing ratio is proposed based on a series of calculation results of piled raft under different working conditions. The results show that:the overall safety factor of the piled raft has a remarkable influence on the load sharing behavior of raft, i.e., the raft load sharing decreases with the increaseof foundation safety factor.Pile number, pile length and pile spacing have a direct influenceon the raft load sharing ratio,but the influence degreesare different. Pile spacing has the most significant influence, followed by pile length, and pile number has the least influence degree. The normalized calculation model can unify the influences of the aboveparameters on the raft load sharing behavior. Finally, the proposed normalized calculation model is verified preliminarily by the collected project examples.

Abstract:Determining the potential failure surface plays an important role in basal stability analysis of braced excavations in soft clay by upper bound method. For traditional upper bound method, it is assumed that failure surfaces are only related with excavation width. However, for progressive search method, the critical failure surfaces can be evaluated by multi-iterations without assuming detailed shape of failure surfaces. And this method was successfully applied to slope stability analysis. Firstly, this paper introduced the step of basal stability analysis of excavation via multi-block upper bound method. Secondly, this paper illustrated the framework of progressive search method. Considering the characteristic of basal stability analysis of excavation, the generation of initial failure surfaces, the search boundary and the convergence criteria are reset. And some solutions are proposed to deal with the problems during search process. Moreover, this paper verifies the performance of progressive search method by case studies, and proposes conclusions about search length, number of pointsat the failure surface and number of searches. At last, this paper concludes that progressive search method is applied in basal stability analysis successfully. And compared to other upper bound method, progressive search method without assuming detailed shape of surfaces is easier to calculate.

Abstract:The two-stage method is used for analyzing the pipeline deformation caused by the underneath shield tunneling. In the first stage, the Loganathan formula is modified for studying the ground loss when the tunnel axis intersection with the pipeline axis is not orthogonal. The soil-pipeline interaction is studied based on the Vlasov model in the second stage, and the pipeline deformation is also obtained. Then, through comparison with the finite element results, the proposed method was verified to be correct. The influences of pipeline diameter; tunnel depth and intersection between the tunnel and pipeline on pipeline deformation have been further studied. The parametric study shows that the intersection angle of the tunnel and the pipeline significantly influences the pipeline horizontal displacement, and the pipeline deformation increases remarkably as the intersection angle decreasing. The parametric study indicates:a. the pipeline horizontal displacement can't be ignored compared to the pipeline vertical displacement when the intersection angle of the tunnel and the pipeline is relatively small; b. the pipeline deformation is weakening as the pipeline diameter and tunnel depth increasing.

Abstract:The commonly used destructive testing of traditional railways ballast track is not suitable for high-speed railway ballast-less track. At present, high-speed railway subgrade status detection mostly depends on the non-destructive method of track inspection car, but the weakness is that the track quality index (TQI) only represents the geometric state of the track, which can't directly reflect the subgrade service status or the severity of the subgrade defects. In view of this, with the Shanghai-Nanjing intercity high-speed railway as the study object, the rail inspection car detection and post-construction settlement observation were conducted to carry out the study on the service status monitoring of high-speed railway subgrade. On the basis of TQI statistical diagram and post-construction settlement curve of the whole line, the correlation analysis of TQI and settlement overruns was carried out, combined with the exploration of under structures such as geo-radar and wave velocity survey, a new service status monitoring method of the high-speed railway subgrade based on the comparison screen of "TQI + settlement value + under-scan" was proposed, while the condition of the subgrade defects was also verified. The results showed that there was no mutual inclusion relation between the overruns of TQI and settlement, and the maximum value didn't correspond to each other. By comparing the frequency and value of TQI overruns, the settlement overruns were more correlated to the frequency. Compared with the previous TQI oriented assessment method, the non-defected conditions with TQI overruns were reduced, and the defected conditions without TQI overruns were increased, which is more consistent with the actual site conditions of high-speed railway. For other in-service high-speed railways which may be greatly affected by the settlement of the soft ground and with a higher proportion of the subgrade, this study can also provide some useful reference for the service status monitoring of them.

Abstract:The ground motions of foundations in mountainous regions vary at different elevation, and the degree of impacts on the seismic response of buildings in the areaneeds to be studied. By forming the Wenchuan earthquake records from Zigong observation array as the inputs, four RC (reinforced concrete) frame structures supported by stepped foundations were designed based on Chinese National Standard for seismic design of buildings. The elastic and elastoplastic time history analysis of the structure of the calculation example was carried out by inputting the ground motion signal at upper surface of the foundation, at lower surface or the multiple points at both surfaces. Structural seismic response difference coefficient is defined as the ratio of the response to the single excitation signal at one surface over the response to the multi-point excitation inputs at both surfaces. The influence of multipoint input on the seismic response of the spatial RC frame structures supported by stepped foundationsis analyzed in the aspects of structural seismic response difference coefficients and failure modes. The results are following:In the elastic analysis, the difference coefficient of seismic response of lateral deformation and storey shear of RC frame structure with long 1stnatural period is between 0.85 and 1.12, while the value is between 0.38 and 1.22 for similar structures with relatively shorter 1st natural period. Thus, the RC frame structures supported by stepped foundationsdesigned only based on the single ground motion signal on one surface may be unsafe. In the elastoplastic analysis, the seismic response of the RC frame structures supported by stepped foundations with both long and short periods under multi-input is obviously different from that under uniform input, and the minimum difference coefficient can reach 0.27; The failure state of the bottom of the RC frame structure under multi-point input is more severe than that under single inputunder the extremely rare earthquake. Proper seismic strengthening should be carried out for the step part and the first floor above the sill of the RC frame structures supported by stepped foundations.

Abstract:In order to study the normal section bearing capacity and the formation requirements of a novel inverted U-shaped steel-encased concrete composite beam, the nonlinear finite element models of the composite continuous beams have been established based on the existing U-shaped steel-encased concrete composite continuous beams. The load-deflection curve at mid-span of the composite continuous beam finite element model was plotted, and compared with other test results. It proves the rationality and effectiveness of the modeling method and parameter selection of the composite beam finite element models. Using the established finite element model of composite continuous beams, the main influential parameters of normal section bearing capacity of the inverted steel-encased concrete composite beams are analyzed. Based on the test and simulation results of normal section bearing capacity of inverted U-shaped steel-encased concrete composite continuous beams, it is proposed that when the normal section bearing capacity of the composite beam is calculated by the simplified plastic theory, the plastic theoretical calculation value of the normal section bearing capacity of the composite beam should be multiplied by a correction factor of 0.96. Comparing the calculated value of 0.96 times the plastic theoretical calculation value of the normal section bending capacity of the composite beam with the calculated value of the finite element model of the composite beam, the two values are found very close in safe side. The proposed modified simplified plastic theory calculation value of the normal section bending capacity of the composite beam is accurate and reliable enough.

Abstract:Debonding failure is a common early damage form of aluminum alloy plate strengthened RC beam. In order to avoid the occurrence of debonding failure, the experimental research on the mechanism of aluminum alloy plate strengthened RC beam debonding failure was conducted. 24 RC beams were fabricated, and the aluminum alloy plates were adhered to the bottom of the RC beams with structural adhesive. In order to study the effect of additional anchoring on debonding failure, part of the test beams is equipped with chemical bolts or U-shaped hoops at specific positions on the aluminum alloy plate. Through the three-point symmetrical monotonic loading test of simply supported beams with aluminum alloy plates strengthened RC beams, four failure modes of RC beams strengthened by aluminum alloy plates are obtained:suitable reinforcement failure, over-reinforced failure, debonding failure at end plate or at mid-span induced by crack. The debonding failure is mainly caused by the excessive interfacial shear stress. Therefore, the test data of the strain gauge of the aluminum alloy plate were used to obtain the interfacial stress distribution curves, and the principle of interface shear stress distribution is analyzed. After reaching the maximum value at plate end, the stress quickly falls to around null. The interfacial shear stress in the cracking section of RC beam has a sudden change. The mechanism of debonding failure was analyzed:the mechanism of debonding failure at plate end is that after the interfacial shear stress reaches the bonding strength of the aluminum alloy plate and concrete, the interfacial shear stress will peel off the concrete in the protective layer; The mechanism of mid-span crack induced debonding failure is that the interfacial shear stress peels off the concrete fragment blocks from the beam body after the normal stress generated at the end of the concrete block is greater than the concrete tensile strength. On this basis, the discriminant formulae of two kinds of debonding failure were obtained, and the accuracy of the discriminants was verified by combining the test data. Above work provides a theoretical basis for the engineering application of RC beams strengthened with aluminum alloy plates.

Abstract:In order to explore the influence of different steel plate strengthening methods on the bearing capacity of corroded RC beams, the strengthening effect of different strengthening schemes is explored. The characteristics in the bearing capacity, deformation, failure mode and ductility of corroded RC beams strengthening by steel plate with flexural strengthening schemes, shear strengthening scheme, and flexure-shear combination strengthening scheme are compared, respectively, and the advantages and disadvantages of different strengthening schemes are analyzed. The results show that for the flexure-strengthened corroded beam which steel plate thickness are 3 mm, 4 mm and 5 mm, respectively, the ultimate bearing capacity increased by 7~18 kN with 1 mm increases of steel plate thickness. The effect of combined strengthening is most significant, and the ultimate bearing capacity increased by 107.7% compared with corroded beams. Combined strengthened corroded beams have the strongest deformation resistance, the following is flexure-strengthened corroded beams, and the increases of steel plate thickness has a positive effect on the deformation resistance of flexure-strengthened corroded beam. The combined strengthening scheme is more effective in improving the ductility of corroded beam than the other two strengthening schemes, the ductility of which is improved by 320.4% compared with corroded beam, followed by shear strengthened corroded beams. The ductility of flexure-strengthened corroded beam is smaller than other two kinds of strengthened beams, and it increases in the begining and then decreases with the increases of steel plate thickness. The deformation resistance and ductility should be considered comprehensively when evaluating the strengthening effect of flexural and shear-strengthened corroded beams.

Abstract:Shape memory alloy(SMA) has "super elasticity", that is, it can recover original shape after deformation and unloading due to stress, and dissipate energy in this process. It has broad application prospect in seismic control of buildings and bridge vibration. The model parameters of SMA are often determined through optimization and treated as deterministic for dynamic analysis of structures with SMA based devices. In this study, the modified Metropolis-Hasting algorithm-DRAM algorithm, which is a combination of delay rejection and adaptive sampling, is utilized to characterize the uncertainties in modified Graesser & Cozzarelli SMA model parameters. A series of SMA bars with the same geometric size and heat treatment were tested under cyclic loads. The Markov Chain Monte Carlo (MCMC) method is applied to analyze the uncertainties of SMA in terms of model parameters and energy dissipation capacity. The analysis provide insight into the underlying mathematical form of a model, suggest simplifications or modifications and begin to indicate the relative significance of individual parameters, based on a limited set of experimental data. Besides, research shows thatthe energy dissipation of the SMA bar could have up to a relative error of 20% and 10% corresponding to the CDF of 15% and 85%.

Abstract:An indirect measurement method is adopted to identify the bridge's natural vibration characteristics by vibration response of vehicles crossing the bridge,it can avoid the disadvantages of the traditional method of measuring bridge frequency in dynamic load test, such as complicated operation and high cost. Based on the theory of vehicle-bridge coupling vibration and the basic principle of bridge indirect measurement method, the finite element model of vehicle-bridge coupling vibration is established for a skew beam bridge in practical engineering. A biaxial half-car model is used to measure the vehicle and extract the time-history response of the vehicle acceleration when the vehicle passes the bridge at a constant speed. Excluding known vehicle-related frequencies.The first three natural frequencies of the bridge are identified.The influence of six different vehicle speeds, six different vehicle weights and eight different bridge skew angles on the bridge frequency identification is analyzed. The results show that the indirect measurement method can effectively identify the frequency of bridges with high density. When the speed is less than 20 km/h, the third-order frequency of skew beam bridge can be well recognized. When the speed is high, the frequency information of the bridge cannot be recognized.The relatively small ratio of vehicle and bridge mass to bridge frequency identification is advantageous. The accuracy of frequency identification is not affected by the different angle of oblique beam bridge.When the bridge deck is rough, the method of acceleration subtraction can still be used for frequency identification. Numerical simulation shows that the indirect measurement method still has a good recognition effect for the irregular skew beam bridge frequency. To promote the application of motion sensing indirect measurement method in bridge inspection engineering.

Abstract:Using a combination of experimental research and numerical simulation, the effects of coarse aggregate content, interface area, and porosity on the permeability of chloridion in concrete were studied from a mesoscopic perspective.Firstly, through the RCM chloridion diffusion coefficient rapid determination test and mercury injection test, the relationship between different coarse aggregate content, water-binder ratio, porosity and chloride ionization diffusion coefficient was analyzed; then a program was established to build a concrete meso-random random aggregate model. Furthermore, the numerical simulation of chloridion diffusion performance was conducted, and the effects of meso-parameters such as coarse aggregate content and interface area on the permeation and diffusion of chloridion were analyzed.The results show that the numerical simulation is in good agreement with the test results, verifying the validity of the meso-scale numerical model; the chloridion diffusion coefficient decreases with increasing coarse aggregate content; the concrete porosity increases with increasing water-binder ratio, and further Increase the permeability of concrete; the permeability of concrete increases with the thickness of the interface zone and the diffusion coefficient of the interface zone.

Abstract:The sources and components of hospital sewage are complex, including pathogenic microorganisms, drugs, metabolites, antibiotic resistant genes, heavy metals, contrast agents, etc. It will become an important way of epidemic spread and a serious source of environmental pollution without effective treatment. Moreover, the emerging contaminants, such as drugs, have become a hotspot in water environment and water pollution control, and the hospital sewage is one of important sources of these contaminants. Based on the impact of COVID-19 on the prevention and control system of the medical system during the current epidemic period, this review illustrated the distribution of drugs and pathogenic microorganisms in hospital sewage, summarized the progress and problems of domestic and foreign hospital sewage treatment technology, and also proposed the future development direction of hospital sewage treatment technology. More importantly, under the special circumstances of COVID-19 epidemic, higher requirements and standards are needed for the construction of hospital sewage control system. Specifically, the simultaneous degradation of drugs and disinfection of pathogenic microorganisms may be the "hotspot" for the development of hospital sewage treatment technology and equipment in the future.

Abstract:In recent years, antimony pollution in water has drawn more and more attention. Studies on theantimony removal have been increasing year by year. Due to its high efficiency, economy, and ease of operation, adsorption technology is considered to be one of the most promising and practical water treatment methods. In this review, we summarized the application of various adsorbents, such as activated carbon, activated alumina, silicate minerals, iron (hydr)oxide and composite materials, for antimony removal. The main removal mechanism of antimony on these adsorbents of these adsorbents were introduced. Furthermore, the reaction conditions and corresponding maximum capacity of antimony removal in the literature were compared. Combining previous studies in this field, the future research needswere put forward. This study aims to provide a theoretical reference for the treatment of antimony pollution.

Abstract:With the rapid development of industrial technology in China, the output of industrial wastewater is also increasing day by day, in which coking wastewater discharge is large, composition is complex, influence degree is deep, the environmental pollution caused by it is especially prominent, a series of discharge standards are becoming more and more strict, and the treatment of coking wastewater is imminent. In order to realize the policy requirement of "zero discharge" of enterprise wastewater as soon as possible, various new treatment technologies emerge as the times require, and the treatment effect and application scope are obviously improved. In this paper, the characteristics and limitations of the existing coking wastewater treatment technology are reviewed. At present, the coking wastewater treatment methods are mostly focused on biological treatment technology and advanced oxidation method, but there are still some problems and challenges in the actual operation of the two commonly used technologies, such as poor treatment effect and high operating cost. However, the technology of biodegradation and advanced oxidation coupling treatment has a broad prospect, which not only improves the treatment efficiency, but also opens up the field of multi-dimensional exploration. A large number of studies have shown that it has great feasibility for the treatment of refractory and polluted wastewater.

Abstract:Based on the advantages of zero-valent iron permeable reactive barrier (PRB) technology, Fe/Cu bimetal materials were prepared by thechemical deposition method in this study. The Fe/Cu materials was non-uniform particles, and the chemical composition was Cu coated on the surface of iron particle. Through static test systematically examines the reaction temperature, solution pH, average flow velocity, isothermal adsorption, and of the ratio bimetallic material to river sand, etc, the effects of the Cr(Ⅵ) remove and adjust the water flow to realize the simulation of the dynamic test. Cr(Ⅵ) to remove the static experiments show that when the mFe:mCu=10:2, dosing quantity of 40 mg/mL, Cr(Ⅵ) initial concentration was 50 mg/L, pH=7.5, temperature 298 K, the removal of Cr(Ⅵ) in water effect is best, in about 15 min reaction of Cr(Ⅵ) remove rate as high as 99.4%; Dynamic experiments show that the group velocities (104 mL/h) Cr(Ⅵ) adsorption amount to an average of 0.869 mg/g, slow velocity group (28mL/h) adsorption of Cr(Ⅵ) average of 0.920 mg/g, the total adsorption from the slow group velocity is higher. The results of theLangmuirmodel and Freundlichmodel show that the adsorption reaction belongs to the monolayer adsorption process, and the temperature rise is conducive to the adsorption reaction. This study realized the preparation of Fe/Cu bimetal, and the Cr(Ⅵ) has good removal efficiency, combining withPRB technology, to realize the groundwater water such as the effective removal and application of Cr(Ⅵ).

Abstract:The combination of pretreatment, biochemical method and membrane treatment is the mainstream process of domestic landfill leachate treatment. Although it can quickly and stably reduce various pollutants in the leachate, the produced leachate membrane concentrate contains high concentrations of refractory organics, salts and other inorganics. The removal of refractory organic matter is a problem for the treatment of leachate concentrate.The landfill leachate membrane concentrate from a landfill sitein Shenzhen was treated bythree-dimensional electrochemical oxidation,UV-Fenton and electrochemical oxidation-UV/Fenton-electrocatalytic oxidation combination process. The removal efficiency of COD, ammonia nitrogen, and total nitrogen were 97.6%, 98.8%, and 93.5% followingelectrochemical oxidation for 2 h, UV/Fenton treatment for 1.5 h, and electrocatalytic oxidation for 2 h, respectively. The effluent met the direct discharge requirements of the pollution control standard of the domestic landfill (GB16889-2008). The operational cost of landfill leachate membrane concentrate by such process treatment is 93.2RMB/m³.

Abstract:The traditional constructed wetland is considered to have a low natural oxygen enrichment rate and low removal efficiency of N and P nutrients. Therefore, a micro-aerated constructed wetland was designed and developed to enhance the removal of C, N and P from domestic sewage in constructed wetlands. By changing the aeration amount (gas-water ratio) and detecting the effect of the constructed wetland on domestic sewage treatment under different temperature conditions, the COD, TP and various nitrogen pollutants along the system in the artificial wetland enhanced by the micro-aeration system were analyzed in detail. The results show that the micro-aeration system can significantly enhance the treatment effect of wetland on domestic sewage. With the gas-water ratio rising from 0:1 to 4:1, the COD and TP removal rate in the wetland increased from80% and 60% to 93%and 79%. TN removal rate decreased after reaching the top of 75% at gas-water ratio of 3:1 condition. The low temperature also shows a great impact on the removal of carbon and nitrogen. Compared with high temperature, the remove rate of COD and TN decreased by 7%and8% in the low temperature. The change of pollutantconcentration along the wetland shows that the removal process of pollutants mainly occurs in the second wetland system.

Abstract:To investigate the impact of damming on CO₂ partial pressure and CO₂ release from water-air interface in tail tributary of the Three Gorges Reservoir during low water level period, the Yulin River, one of the dam-building tail tributaries of Three Gorges Reservoir was sampled in August 2019. The key physical and chemical environmental factors were measured in situ, the CO₂ partial pressure (p_CO2) and water-air interface diffusion flux (Flux(CO₂)) were calculated by headspace equilibrium method combined with Henry's law and thin boundary layer theory. The results show that the surface water p_CO2 of the Yulin River during low water level period is 54.55~336.73 Pa, with an average of 206.68 Pa, the Flux(CO₂) is 1.65~67.84 mmol/(m²·d), with an average of 39.01 mmol/(m²·d), which is the source of atmospheric CO₂ emission. The emission level of CO₂ from the Yulin River is significantly higher than that of the tributaries in the middle and lower reaches of the Three Gorges Reservoir area. The near reach of the upstream of the dam is lake-type's water (velocity <0.05 m/s), while the far reach of the upstream and downstream are transition-type's water (velocity:0.05~0.2 m/s). The p_CO2 and Flux(CO₂) of lake-type's water are significantly lower than that of transition-type's water, and p_CO2 increases rapidly with the increase of water depth. Correlation analysis and multiple stepwise regression analysis show that p_CO2 and Flux(CO₂) in the Yulin River during low water level period were significantly affected by physical and chemical environmental indexes such as water temperature, pH, DO and Chl-a, and Chl-a is the most important factor affecting p_CO2, while p_CO2 is the most important factor affecting Flux(CO₂).

Abstract:In view of the frequent blooms of filamentous cyanobacteria in recent years, the response of growth to temperature and the relationship between growth and functional characteristics of three common filamentous algae were studied.The results showed that when the temperature increased from 15℃ to 30℃, the specific growth rate of Cylindrospermopsisraciborskii increased from 0.28 d^-1 to 0.70 d^-1, the photosynthetic activity (F_v/F_m) fluctuated within the range of 0.40 to 0.61, and the consumption of dissolved total nitrogen (DTN) and soluble reactive phosphorus (SRP) per unit algal cell also increased by 6.36 mg-DTN/mg-Chl.a and 0.15 mg-SRP/mg-Chl.a. The specific growth rate of Pseudanabaena sp. increased from 0.12 d^-1 to 0.60 d^-1, the F_v/F_m reached a minimum of 0.12 at 15℃, and the consumption of nitrogen and phosphorus per unit of algal cell increased by 21.72 mg-DTN/mg-Chl.a and 1.71 mg-SRP/mg-Chl.a. The specific growth rate of Aphanizomenonflos-aquae increased from 0.20 d^-1 to 0.44 d^-1, the F_v/F_m was less affected, and the nitrogen and phosphorus consumption per unit algal cell increased by 12.29 mg-DTN/mg-Chl.a and 0.83 mg-SRP/mg-Chl.a. Then, the increased temperature will promote the growth of three filamentous algae. The Cylindrospermopsisraciborskii is easy to form an advantage when the temperature higher than 30℃. The Pseudanabaena sp. has a wide range of temperature adaptation, but when the temperature is belower than 15℃, its growth will be inhibited. The optimal temperature of the Aphanizomenonflos-aquae is 25℃, and it can also achieve advantages at a lower temperature of 15℃, and has strong low temperature resistance. In addition, filamentous algae can maintain the growth advantages at different temperatures by balancing the physiological characteristics of algal cells.

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