Heavy metals are persistent pollutants in the environment. Problems associated with the cleanup of sites contaminated by metals have demonstrated the need to develop remediation technologies that are feasible, quick, ...Heavy metals are persistent pollutants in the environment. Problems associated with the cleanup of sites contaminated by metals have demonstrated the need to develop remediation technologies that are feasible, quick, and effective in a wide range of physical settings. In this study we have investigated the adsorption of Cu（lI）, onto red soil in single and multi-element systems as a function of soil and heavy metal concentrations. Before contamination, soils were characterized to determine particle size, pH, organic matter content and heavy metal contents. The results of experimental sorption data fitted very well the Freundlich isotherm model with n = 1.4 and k = 1.25 and first order kinetics model. The best pH for adsorption of Cu^2＋ on red soil was found to be 4.0. Adsorption of metals on soil increased in the order Cu 〉 Pb 〉 Zn ≈ Cd. This trend might be related to the increase in the electronegativity of the metal ion.展开更多
In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and othe...In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and other mathematical skills, some sufficient conditions for the extinction, nonpersistence in the mean, persistence in the mean, and stochastic permanence of the system are established. Furthermore, some asymptotic properties of the solutions are also investigated. Finally, a series of numerical examples are presented to support the theoretical results, and effects of different intensities of white noises perturbations and impulsive effects are discussed by the simu｜ations.展开更多
文摘Heavy metals are persistent pollutants in the environment. Problems associated with the cleanup of sites contaminated by metals have demonstrated the need to develop remediation technologies that are feasible, quick, and effective in a wide range of physical settings. In this study we have investigated the adsorption of Cu（lI）, onto red soil in single and multi-element systems as a function of soil and heavy metal concentrations. Before contamination, soils were characterized to determine particle size, pH, organic matter content and heavy metal contents. The results of experimental sorption data fitted very well the Freundlich isotherm model with n = 1.4 and k = 1.25 and first order kinetics model. The best pH for adsorption of Cu^2＋ on red soil was found to be 4.0. Adsorption of metals on soil increased in the order Cu 〉 Pb 〉 Zn ≈ Cd. This trend might be related to the increase in the electronegativity of the metal ion.
基金Acknowledgments The authors would like to thank the editors and the anonymous referees for their helpful suggestions and comments which led to the improvement of our original manuscript. This work is supported by the National Natural Science Foundation of China （11372294 and 11261017）, Scientific Research Fund of Sichuan Provincial Education Department （14ZB0115 and 15ZB0113）, Zhejiang Provincial Natural Science Foundation （LQ13A010023） and Doctorial Research Fund of Southwest University of Science and Technology （15zx7138）.
文摘In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and other mathematical skills, some sufficient conditions for the extinction, nonpersistence in the mean, persistence in the mean, and stochastic permanence of the system are established. Furthermore, some asymptotic properties of the solutions are also investigated. Finally, a series of numerical examples are presented to support the theoretical results, and effects of different intensities of white noises perturbations and impulsive effects are discussed by the simu｜ations.
