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Currently, the aviation industry is facing an oil and energy crisis and is contributing much more greenhouse gas emissions to the environment. Aircraft design approaches, such as aerodynamic shape optimization, new configuration concepts, and active control technology, have been the primary and effective means of achieving goals concerning fuel burn, noise, and emissions. For now, the design problems of relaxed static stability (RSS, an active control technique) and truss-braced wing (TBW) configurations with high-fidelity aerodynamic shape optimization methods have been investigated widely to promote aerodynamic performance. Nevertheless, they are studied almost always separately, and the combination of exploration and refined design is rarely presented. Therefore, the purposes of this work are to evaluate the benefits of RSS on a full TBW wing–body–tail configuration under various flight conditions and the effects on multi-components and to further explore the potential and analyze the aerodynamic features with the combination of shape optimization and RSS. To address these issues, on the one hand, a range of seven static stability margins are adopted to evaluate its effects with a high-fidelity Reynolds-averaged Navier–Stokes solver. On the other hand, seven cases of drag minimization multipoint aerodynamic design optimization are performed, which are with 600 shape variables and 13 twist variables, subject to lift coefficient, trim, and thickness constraints. The results indicate that with RSS only, the initial configuration has a 2.39% drag reduction under cruise conditions and a 3.01% and a 5.24% drag reduction under two off-design conditions. Additionally, the effects on the multi-components are observed and analyzed. Moreover, all of the optimized configurations with RSS have 2.13%, 2.42%, and 2.12% drag reductions under cruise conditions, drag divergence conditions, and near-buffet-onset conditions, respectively. The most promising optimized configuration has a lift-to-drag ratio of 24.48 with an aerodynamic efficiency of 17.14. The evaluations with a series of off-design points also present high-level aerodynamic efficiency.

When studying instability of weakly non-parallel flows, it is often desirable to convert temporal growth rates of unstable modes, which can readily be computed, to physically more relevant spatial growth rates. This has been performed using the well-known Gaster's transformation for primary instability and Herbert's transformation for the secondary instability of a saturated primary mode. The issue of temporal–spatial transformation is revisited in the present paper to clarify/rectify the ambiguity/misunderstanding that appears to exist in the literature. A temporal mode and its spatial counterpart may be related by sharing either the real frequency or wavenumber, and the respective transformations between their growth rates are obtained by a simpler consistent derivation than the original one. These transformations, which consist of first- and second-order versions, are valid under conditions less restrictive than those for Gaster's and Herbert's transformations, and reduce to the latter under additional conditions, which are not always satisfied in practice. The transformations are applied to inviscid Rayleigh instability of a mixing layer and a jet, secondary instability of a streaky flow as well as general detuned secondary instability (including subharmonic and fundamental resonances) of primary Mack modes in a supersonic boundary layer. Comparison of the transformed growth rates with the directly calculated spatial growth rates shows that the transformations derived in this paper outperform Gaster's and Herbert's transformations consistently. The first-order transformation is accurate when the growth rates are small or moderate, while the second-order transformations are sufficiently accurate across the entire instability bands, and thus stand as a useful tool for obtaining spatial instability characteristics via temporal stability analysis.

A computational fluid dynamics (CFD) compatible and fully local transition closure model is proposed for three-dimensional hypersonic boundary layers considering crossflow effects. The transition m...

The study of differential schemes with high accuracy and low dispersion is of great significance for the numerical simulation of aeroacoustics over complex geometries. The midpoint-and-node-to-node explicit finite difference is employed to solve the flux derivatives of the linear Euler equations for improving the robustness. To obtain the numerical flux at the center of the grid element, we adopted a hybrid interpolation method of center and upwind interpolations, combined with a symmetrical conservative metric method, to achieve high-resolution discretization of the acoustic field variables and geometric variables of the structural grid. To suppress spurious oscillations and improve the resolution of discontinuous regions, a family of mapping functions is developed to establish different smoothness indicators and applied to the sixth-order weighted compact nonlinear hybrid scheme (WCNHS), forming a new WCNHS scheme based on piecewise exponential mapping functions (WCNHS-Pe). The approximate dispersion relation shows that the dispersion error and numerical dissipation of WCNHS-Pe are smaller than those of WCNHS with a simple mapping function to the original weights in Jiang and Shu and other mapping function-weighted WCNHS schemes. We have applied various WCNHS schemes to the numerical simulation of the Shu–Osher problem, propagation of Gaussian impulses on two-dimensional wavy grids, sound transmission at discontinuous interfaces, propagation of Gaussian impulses on three-dimensional wavy grids, etc. Numerical results indicate that the WCNHS-Pe scheme has better discontinuity capture capability, higher resolution, and lower dispersion under the same differential stencil, and is suitable for computational aeroacoustics of complex geometries.

The streaky boundary layers have very important roles in laminar-turbulent transition. Streaks of appropriate size can influence stabilities in boundary layers. In this paper, the effect of steady streamwise elongated, spanwise periodic wall heating elements on the first mode instability in supersonic flat plate boundary layers was investigated. For the balance of the efficient and accuracy, the linearized Navier–Stokes equations are used to obtain the base flow and compared with compressible Navier–Stokes equations. A bi-global analysis tool is used for the instability analysis because the heating source has a much larger length-scale in the streamwise direction than that in the spanwise direction, and the streamwise velocity is much larger than the normal velocity and the spanwise one. Results indicated that the distortion caused by the three-dimensional surface heating elements could modify the first mode, resulting in a lower frequency but with an uncertain effect on the higher frequency modes. Additionally, the streaks make the lower spanwise wave number components of the even first mode disturbance in a three-dimensional supersonic boundary layer in the freestream. As a result, the spontaneous radiation of an acoustic wave to the far field was found for the even mode. These findings suggest that laminar-turbulence transition can be suppressed or enhanced by the three-dimensional wall heating.

Transition prediction is a hot research topic of fluid mechanics. For subsonic and transonic aerodynamic flows, eN method based on Linear Stability Theory (LST) is usually adopted reliably to predict transition. In 2013, Coder and Maughmer established a transport equation for Tollmien-Schlichting (T-S) instability so that the eN method can be applied to general Reynolds-Average-Navier-Stokes (RANS) solvers conveniently. However, this equation focuses on T-S instability, and is invalid for crossflow instability induced transition which plays a crucial role in flow instability of three-dimensional boundary layers. Subsequently, a transport equation for crossflow instability was developed in 2016, which is restricted to wing-like geometries. Then, in 2019, this model was extended to arbitrarily shaped geometries based on local variables. However, there are too many tedious functions and parameters in this version, and it can only be used for incompressible flows. Hence, in this paper, after a large amount of LST analyses and parameter optimization, an improved version for subsonic and transonic boundary layers is built. The present improved model is more robust and more concise, and it can be applied widely in aeronautical flows, which has great engineering application value and significance. An extensive validation study for this improved transition model will be performed.

It is known that boundary layer transition and turbulent separation flow after transition can be influenced significantly by surface roughness. Because the traditional hybrid Reynolds-averaged-Navier–Stokes (RANS)/large eddy simulation method cannot predict the boundary layer transition, and the RANS-based transition model cannot accurately simulate the massively separated flow, the present study sought to build an effective modeling strategy for the laminar, roughness-induced-transition and attached turbulence/massively separated flows that couple the very-large-eddy-simulation model and a transition model considering roughness effects. This new hybrid model was examined in the cases of the separated flat plate and the rough cylinder. Our analysis shows that the new hybrid model operates in these transitional separated flows over smooth and rough walls. Compared with the results of other classical methods, the present results are more consistent with the measured data. Furthermore, the “drag crisis” phenomenon of the cylinder is accurately simulated by the present model.

The traditional linear stability analysis for transition prediction includes the following steps: solving velocity profiles using boundary-layer equations or a computational fluid dynamics solver, ...

Because of the great influence of transition phenomena in aerodynamic property calculations, boundary layer transition has always been a hot research topic in the past few decades. Meanwhile, the prediction methods for boundary layer transition need to be established, researched and enhanced. In order to build a computational fluid dynamics (CFD) compatible transition model, the authors propose a two-equation transport transition model in this paper considering analysis results through linear stability theory (LST). This new transition model consists of one transport equation for laminar fluctuation kinetic energy and another for intermittency factor. Without boundary layer integration and other nonlocal operations, all the variables in this new transition model can be calculated locally so that present model is compatible with CFD parallel computation. Laminar separation bubble induced transition, Tollmien–Schlichting (T–S) instabilities and stationary crossflow instabilities (CF) dominated transition are modeled in the transport equation. The validation tests have been conducted on the classical Schubauer & Klebanoff flat plate, natural laminar airfoil NLF(1)-0416, NLF(2)-0415 infinite swept wing, classical sickle swept wing and 6:1 inclined prolate spheroid using this fully-local transition model. Since all the test cases are in accord with experimental data, the present transition model could be widely applied to aeronautical flows in low-disturbance environment.

In hypersonic boundary layers, Mack modes play a crucial role in flow instability, whose secondary instability is a hot research topic. Since hypersonic flight vehicles will probably work under high-stagnation temperature conditions, which significantly affect the aerodynamic heating calculation and aero-thermal protection design of hypersonic vehicles, it is necessary to compare the primary and secondary instabilities in high-stagnation temperature boundary layers and that in the Boeing/AFOSR Mach 6 quiet tunnel (BAM6QT). Herein, wall-cooling is adopted in order not to consider chemical reactions. With the same freestream temperature of 100 K, two Mach 6 boundary layers with the wall temperature of 20 and 600 K, corresponding to the cooled wall condition and the quiet wind tunnel condition, respectively, are chosen to conduct the linear/non-linear stability and the secondary instability analysis. Our results show that the most dangerous Mack mode originates from a fast discrete mode in the present cooled-wall flow and the most dangerous Mack mode is born from the slow discrete modes in BAM6QT boundary layers. Furthermore, when the primary amplitude of Mack mode disturbances is large, the fundamental resonance always dominates the secondary instability, resulting in steady streaky structures that have the largest amplitude in the spectrum. In addition, the present results point out that the distribution of the eigenfunctions of the fundamental modes and subharmonic modes are significantly different under various wall-temperatures. What is more, different ratios of wall temperature to incoming flow temperature have changed the spanwise wave-angle of the secondary disturbances.

In a previous study, we developed a one-equation transition model for the bypass and laminar separation bubble (LSB)-induced transition based on local variables. In this paper, distributed surface roughness effects are taken into account by constructing a new transport equation for the roughness amplification factor Ar. Modified criteria taking account of Ar are proposed to describe the roughness effects on the bypass and LSB-induced transitions. Moreover, to predict the flow properties in the laminar–turbulent region more accurately, a modified boundary condition for rough surfaces is employed. The calculations show that, overall, the rough wall promotes the bypass transition and reduces the size, or even causes the disappearance, of the LSBs. Good agreement of the numerical results from the proposed model with the experimental data indicates that the present roughness correction formula is reasonable and accurate.

In laminar hypersonic boundary layers, it is known that secondary instability plays a crucial role in transition to turbulence. The secondary instability usually includes the fundamental mode, the subharmonic mode, and the detuned mode. Considerable research exists on the secondary instability mechanism in hypersonic boundary layers with the smooth wall condition. The topic of using micro-porous surfaces for disturbance stabilization has recently drawn interest. The stabilization and, thus, a possible delay in the transition arise due to a reduction in the growth rate of the primary Mack mode by the porous surface. This paper focuses on investigating whether the secondary instability mechanism of Mack modes can also be affected by a surface porosity condition. It is known that the primary Mack mode linear disturbances are changed significantly on the porous surface, and how it subsequently influences the secondary instability of the modified time varying basic flow is our concern. The analysis demonstrates that on the porous surface, as the amplitude of the primary Mack mode increases, the fundamental mode is not stable. Instead, the fundamental mode amplifies rapidly with increasing primary amplitudes. At larger secondary instability spanwise wavenumbers, when the primary amplitude exceeds a certain threshold value, the fundamental modes surpass the subharmonic modes and dominate the secondary instability. However, when the spanwise wavenumber is relatively small, especially at the spanwise wavenumber corresponding to the maximum growth rate of the subharmonic mode, the fundamental modes are weakened and lose their dominant position. We find that corresponding to different amplitudes of primary Mack mode disturbances affected by the porosity parameters, there are no strongly preferred interaction modes that dominate the secondary instability; this contrasts with smooth wall findings. We further find that the larger the pore size or porosity, the more severe the suppression of the fundamental mode.

This paper presents a new extension of the realizable K−ε model that accounts for streamline curvature, system rotation, and surface roughness. The model is a type of realizable K−ε model, but the transport equations and the eddy-viscosity damping functions are modified, based on the Richardson number and roughness height; the roughness correction covers both the transitional and fully rough regimes. Flows in a rotating channel and a U-bend duct are used to validate the response of the new model to the system rotation and streamline curvature. The flow in a plane channel and the flow over a dune are used to validate the roughness extension. Finally, a rotating channel with rough walls is studied, to test the new model when both rotation and roughness are present.

In order to achieve the goal of green aviation, energy conservation and emission reduction, laminar flow design technology has become a hot research topic. For transonic airliners, supercritical natural laminar flow wing design technology will significantly improve the aerodynamic performance (reduce flight drag, decrease fuel consumption and pollutant emissions). In this paper, airfoil optimization design system is applied to design the supercritical natural laminar flow airfoils based on high-precision boundary layer transition prediction technique. Then, three-dimensional layout of supercritical natural laminar flow wing is formed. Numerical simulations have been conducted to verify the laminar flow properties. In addition, the aerodynamic model with ratio of 1:10.4 is processed to measure boundary layer transition phenomena in the high speed and low turbulence wind tunnel in Netherlands. Temperature sensitive paint (TSP) technique is used to photograph laminar-turbulent distribution at different Mach numbers, Reynolds numbers and angels of attack. In the following content, boundary layer transition properties of the supercritical natural laminar flow wing are analyzed using TSP results and CFD simulations. Finally, key factors of supercritical natural laminar wing design and corresponding boundary layer transition properties are summarized. In addition, the research about transition properties of supercritical natural laminar flow wing at high Reynolds numbers have guiding significance for aircraft designers and transition researchers.

During the process of aerodynamic shape design of supersonic and hypersonic space planes, laminar flow design and boundary layer transition prediction play important roles in aero-thermal numerical simulations and aero-thermal protection design. Therefore, in this study, a computational fluid dynamics compatible transition closure model for high speed laminar-to-turbulent transitional flows is formulated with consideration of the analysis results from stability theory. The proposed model contains two transport equations to describe the transition mechanism using local variables. Specifically, the eddy viscosity of laminar fluctuations and intermittency factor are chosen to be the characteristic parameters and modeled by transport equations. Accounting for the dominant instability modes at supersonic/hypersonic conditions, the first- and second- modes are modeled using local variables through the analysis of laminar self-similar boundary layers. Then, the present transition model is applied with compressibility corrected k $k$ - ω $\omega$ shear stress transport turbulence model. Thus, as the main significance of the current work, the present model is enabled to capture the overshoot phenomena as well as predict the transition onset position. Finally, comparisons between the predictions using the present model and the wind tunnel experimental results of several well-documented flow cases are provided to validate the proposed transition turbulence model.

The mechanism of oblique shock wave control by surface arc discharge plasma is explored through a combined numerical and experimental study. The experiments are conducted in a supersonic wind tunne...

A one-equation Reynolds-averaged Navier–Stokes closure model is established for bypass transition in this paper. A new local indicator is proposed to describe the variation of turbulence intensities and pressure gradients. Based on this new indicator, a novel and efficient transition criterion is formulated. For laminar separation bubble induced transition, a reasonable modified intermittency factor is developed to complete the reattachment process and control the size of separation bubbles. Incorporated with Menter's k−ω shear stress transport turbulence model, the new transition-turbulence model is built for a high turbulence intensity environment. Several classical flow cases, including the ERCOFTAC (European Research Community on Flow, Turbulence and Combustion) series flat plates with various pressure gradients, the Pratt and Whitney low pressure turbine cascade, and a highly loaded linear compressor cascade, are all employed for the model verifications. Decent agreement with the experimental data and direct numerical simulation data can be obtained in a wide range of incoming flow conditions.

A single-point transition closure model that incorporates analytical results by stability theory in a reasonably wide range of Mach numbers has been formulated for supersonic/hypersonic boundary-la...

This article presents a method for online health monitoring of machining tools using massive sensor signals. The features of the signals were extracted from three domains. With the intent at reducing the data, the vital features are selected with the use of Pearson correlation coefficient (PCC) analysis. Then fusion of the significant features of the signals is made with the use of the Growing Self-Organizing Map(GSOM) to get the Minimum Quantization Error (MQE), which is proved to have a similar trend with tool flank wear. On the basis of MQE, the state of machining tool is identified by Particle Swarm Optimization- Support Vector Machine (PSO-SVM). The experimental results verify the effectiveness and feasibility of the proposed methodology, as well as the superiority to Back-Propagation (BP) method and Adaptive Network-based Fuzzy Inference System (ANFIS).

Bypass and laminar-separation-bubble induced transition phenomena are very common in turbine blade cascade flow with high turbulence environment. In order to predict the transition position and aerodynamic characteristics accurately in high turbulence environment, the similarity velocity profiles at various shape factors are obtained by solving the Falkner-Skan boundary layer similarity equations. Then, the local formulas of non-local variables are fitted based on the similarity velocity profiles and combined with a new indicator factor to form transition criterion, so as to construct the turbulence transition model. The transition model was used to predict and simulate the flows of zero pressure gradient plates, T3C series pressure gradient plates, and PAK-B turbine blade cascade. The predicted results under various turbulence and pressure gradients are all according with the experimental data. It proves to be that the model proposed in this paper is reasonable and feasible.

A new computational fluid dynamics compatible transition model for the natural transition and laminar separation bubble induced transition is established using two transport equations with consideration of analysis results through linear stability theory linear stability theory. One transport equation is introduced to describe the growth of the laminar kinetic energy in the boundary layer. In addition, another transport equation of intermittency factor is built to trigger the transition by controlling the source term of turbulent kinetic energy equation. Finally, applying the two transport equations to a shear stress transport turbulence model completes a four-equation transition turbulence model. Comparisons of predictions using the new model with wind-tunnel experiments of the Schubauer and Klebanoff flat plate, S809 airfoil, Aerospatiale-A airfoil, and DLR-F5 wing validate the predictive qualities of the new transition turbulence model.

Chlorpyrifos residue contents in market water dropwort, residue dynamics of chlorpyrifos and the safe pre-harvest interval (SPHI) in field water dropwort were conducted in Changzhou, Jiangsu Province, China. The results showed that concentrations of chlorpyrifos residues in more than half of the market samples (57%) exceeded the maximum allowable concentration (MAC, 0.05 mg kg-1), according to the Chinese Standard (GB 2763 – 2014). The average chlorpyrifos content in the samples was 0.23 mg kg-1 that was 3.6 times higher than the MAC. Study on the residue dynamics of chlorpyrifos demonstrated that the half-life of chlorpyrifos residues in the water dropwort of early-sowing (in summer) and late-sowing (in autumn) were 4.1 and 5.4 days, respectively, and it took 31.2 and 43.1 days, respectively, for chlorpyrifos residues to decrease to the MAC level. In normal application dosage (recommended for vegetables), the SPHI was 30-35 days for the water dropwort of early-sowing, and 40 days for the water dropwort of late-sowing, which were much longer than the recommended pre-harvest interval (seven days) according to the Chinese Standard ((GB/T 8321 – 2000)). It may be the cause of high chlorpyrifos residue concentrations in market water dropwort.

The prediction of cross-flow instabilities transition phenomenon is difficult to be combined with modern CFD parallel computation. To solve this problem, on the basis of SA-γ-Re θt transition model, a new transition model is presented here, which solves cross-flow displacement thickness Reynolds number locally using three-dimentional boundary layer similar solution and also sets cross-flow instabilities transition criterion referring to C1-criterion. Thereby, it can solve the cross-flow instabilities transition prediction method locally and parallelly. Then, adopting the present SA-γ-Re θt - CF transition model, numerical simulations of cross-flow instabilities transition are conducted for both infinite swept NLF(2)-0415 wing and standard 6∶1 prolate spheroid. And calculating transition locations are in good agreement with experimental data, which demonstrates the rationality of the model presented.

Uptake and distribution of Cd, Pb and Zn by 19 wetland plant species were investigated with experiments in small-scale plot constructed wetlands, into which artificial wastewater dosed with Cd, Pb and Zn at concentrations of 0.5, 2.0 and 5.0mgl(-1) was irrigated. The results showed that the removal efficiency of Cd, Pb and Zn from the wastewater were more than 90%. Generally, there were tens differences among the 19 plant species in the concentrations and quantity accumulations of the heavy metals in aboveground part, underground part and whole plants. The distribution ratios into aboveground parts for the metals absorbed by plants varied also largely from about 30% to about 90%. All the plants accumulated, in one harvest, 19.85% of Cd, 22.55% of Pb and 23.75% of Zn that were added into the wastewater. Four plant species, e.g. Alternanthera philoxeroides, Zizania latifolia, Echinochloa crus-galli and Polygonum hydropiper, accumulated high amounts of Cd, Pb and Zn. Monochoria vaginalis was capable for accumulating Cd and Pb, Isachne globosa for Cd and Zn, and Digitaria sanguinalis and Fimbristylis miliacea for Zn. The results indicated that the plants, in constructed wetland for the treatment of wastewater polluted by heavy metals, can play important roles for removal of heavy metals through phytoextraction. Selection of plant species for use in constructed wetland will influence considerably removal efficiency and the function duration of the wetland.

Pot soil experiments showed that there were great variations among six rice cultivars in their tolerance to soil Cd stress, with respect to tillering, plant height, leaf area, dry matter accumulation and grain yield. Some cultivars were highly tolerant of Cd and showed little toxicity under high levels of soil Cd stress (100 mg kg−1), while others were much more sensitive. Roots were not necessarily more sensitive than above-ground parts, but the diversities among rice cultivars with regard to the relative changes in dry matter accumulation under soil Cd stress were greater in roots than those observed in straw and grain. The toxicity effects of Cd on rice growth and development lessened as plants grew and matured, indicating that rice plants show adaptation and growth compensation in response to soil Cd stress during prolonged exposure. The relative change in the number of grains per panicle showed a strong positive correlation with relative change in grain yield and, of the four grain yield components measured (panicles per pot; grains per panicle; filled grain percentage; weight per grain), it appeared to be the one most influenced by Cd stress. Thus the reduction of grains per panicle is the main cause of grain yield loss under soil Cd stress. Copyright © 2007 Society of Chemical Industry

A pot trial was conducted with 52 rice cultivars of different types collected from different origins. The results showed that there were great differences in Cd concentrations in straw, brown rice and grain chaff among the rice cultivars grown in a soil containing a Cd concentration of 100 mg kg−1; the Cd concentrations in brown rice ranged from 0.22 to 2.86 mg kg−1. The great genotypic differences in Cd concentrations indicated that it is possible to lower the Cd content of rice through cultivar selection and breeding. Significant differences were found in the Cd concentrations of the rice types of Indica consanguinity and those of Japonica consanguinity, but not between their origins. There were significant correlations between straw and brown rice in Cd concentration and in the total amount of Cd accumulated. The distribution ratios of the Cd accumulated in brown rice to the total Cd accumulation in the above-ground rice plant varied greatly from 12.9 to 137.8 g kg−1, and there was significant correlation between the distribution ratios and Cd concentrations in brown rice. These indicated that Cd concentration in rice grain is governed by the transport of Cd from root to shoot and also from shoot to grain. Cd concentrations in brown rice also correlated significantly with some important agronomic traits, as well as with nitrogen concentrations, one of the most important criteria for rice quality. Copyright © 2004 Society of Chemical Industry

A pot soil experiment with 20 rice cultivars of different genotypes from different origins showed that the effects of lead (800 mg/kg Pb in soil) on rice growth and development varied greatly with different cultivars. The increases or decreases of the grain yields mainly resulted from the changes of the spikelets per panicle under soil lead treatment. Furthermore, the changes of spikelets per panicle correlated significantly and positively with the changes of dry straw weights. There existed significant differences among the cultivars in the lead uptake and translocation by rice plants, but the differences had no obvious relationship with rice genotypes. The lead concentrations decreased rapidly from roots to grains along rice plants, so the concentrations of lead in the grains were very low compared to other parts of the rice plants. The regression analysis showed that there were significant and negative correlations between connected organs of the rice plants, but positive correlations, mostly significant, between disconnected organs, for the lead concentrations in them. Lead concentrations in the leaves of heading stage showed a significant and positive correlation with that of the grains at ripening stage. Lead was not distributed uniformly in different parts of grain structure, and the lead accumulated in polished rice was only 32.88% of the total lead accumulated in grain.

Pot experiments were conducted on 20 rice cultivars of different genotypes and origins by adding 100 mg/kg of cadmium (Cd) to soil. The aim was to investigate the effects of Cd on the dry matter accumulation and grain yield of different rice cultivars, the differences among rice cultivars and genotypes in Cd uptake and translocation, the interactions between Cd and five mineral nutrients Fe, Zn, Mn, Cu and Mg in response of the uptake and translocation in rice plant. The results showed that the effects of Cd on rice growth and development were variety dependent; some cultivars were strongly tolerant to soil Cd stress, while others were very sensitive. Differences existed among the cultivars for Cd uptake and distribution in rice plants, but the differences were not necessarily related to rice genotypes. Cd concentrations fell rapidly from roots to brown rice along rice plants, so the concentrations of Cd were very low in brown rice compared with other parts of rice plants. The effects of Cd on the concentrations of the mineral nutrients in the rice roots and leaves were mostly significant, however, the results varied with metal elements, rice plant organs and growing stages. Under soil Cd stress, the variations of the grain and straw yield of the cultivars were not correlated with the changes of any mineral nutrient in the rice plant. The regression analysis showed that, for their concentrations in roots and leaves, significant positive correlations between Cd and Fe, Cd and Zn, Cd and Cu existed, but no significant correlation between Cd and Mg, and the relationship between Cd and Mn varied with the organs of rice plant. These results suggested that rice cultivars differed greatly in growth and development responses to Cd and in absorption and translocation of Cd, Fe, Zn, Cu, Mn and Mg. The effects of Cd on the five mineral nutrients were not the main causes of the inhibition of Cd on rice growth and development. The interactions of Cd and Fe, Zn, Cu are synergetic in uptake and translocation from root to shoot by rice plants.

In order to investigate the environmental quality of agriculture in Changzhou, agricultural soils in 451 sampling points of six areas in Changzhou were sampled and tested for heavy metal concentrations. Single and compositive pollution indexes were used for the evaluation of the soils. The main results are listed below: (1) the soils were slightly polluted generally, and the compositive pollution index for Changzhou was less than 0.7, a safe grade. But the compositive pollution index for surburb area was 0.934, reaching a cautionary grade (0.7-1.0). (2) The levels of heavy metal pollution were higher in the areas near city zones, because of dense population and concentrated industries. (3) The major heavy metal pollutants are mercury (Hg), copper (Cu) and chromium (Cr).

To attempt to understand the differences between rice genotypes in lead (Pb) tolerance, pot soil experiments were conducted with two rice genotypes at different soil Pb levels, i.e. 0 (the control), 800, 2000 mg kg-1. The results showed that the soil Pb concentration of 800 mg kg-1 is moderately toxic to rice, with 10%-30% decreases in plant biomasses. The soil Pb concentration of 2000 mg kg-1 is a soil Pb level that will severely inhibit rice growth, with 20%-50% decreases in plant biomasses and significant reductions in grain yields (P shoot > grain, so rice root is more sensitive to soil Pb stress than shoot and grain. The toxicity of Pb on rice growth lessened as plant aged, so some adaptations and growth compensations to soil Pb stress may occur in rice plants along with plant growth and development.

Three years of pot soil experiments showed that copper (Cu) could be toxic to rice root depending on its concentrations. Root development began to be inhibited at the soil Cu concentration of 100 mg kg-1. About half of root dry weights lost at the soil Cu concentration of 300 - 500 mg kg-1. Root growth nearly stopped at the soil Cu concentration of 800 - 1000 mg kg-1. There were interactions between rice growth stages and soil Cu concentrations on Cu toxicity to rice root. The soil Cu level of 400 mg kg-1 inhibited total root length per plant and average length of root system significantly (P

Variations among 19 wetland plant species in the tolerance and uptake of Cd, Pb and Zn from wastewater were investigated. The results showed that there were obvious differences among the plant species in metal tolerance. In metal polluted water, plant biomass was significantly reduced for three species, but was significantly increased for three other species. The variation among 19 plant species in plant biomass was 37.7 times for the control, and 45.3 times for metal treatment. The variation among the plant species was 61.6 times for metal quantity accumulations, but only 8.6 times for metal concentrations. Plant metal accumulations correlated positively and significantly with plant biomass (r = 0.6114, P

Pot soil experiments showed that copper (Cu) is highly toxic to rice. Rice grain yields decreased exponentially and significantly with the increase of soil Cu levels. Rice grain yield was reduced about 10% by soil Cu level of 100 mg kg(-1), about 50% by soil Cu level of 300-500 mg kg(-1) and about 90% by soil Cu concentration of 1,000 mg kg(-1). Root was more sensitive to soil Cu toxicity than other parts of rice plant at relatively lower soil Cu levels (less than 300-500 mg kg(-1)), but the growth of whole rice plant was severely inhibited at high soil Cu levels (300-500 mg kg(-1) or above). Cu concentrations in rice grain increased with soil Cu levels below 150-200 mg kg(-1), but decreased with soil Cu levels above 150-200 mg kg(-1), with peak Cu concentration at soil Cu level of 150-20 mg kg(-1). Cu was not distributed evenly in different parts of rice grain. Cu concentration in cortex (embryo) was more than 2-fold that in chaff and polished rice. More than 60% of the Cu in grain was accumulated in polished rice, about 24% in cortex (embryo), and about 12% in chaff. So, about 1/3 of the Cu in rice grain was eliminated after grain processing (chaff, cortex and embryo was removed).