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G Q Chen - One of the best experts on this subject based on the ideXlab platform.

  • Ecological degradation and hydraulic dispersion of contaminant in wetland
    Ecological Modelling, 2011
    Co-Authors: L. Zeng, G Q Chen
    Abstract:

    For the typical case of a pulsed contaminant emission into a free surface wetland flow, a theoretical analysis is presented in this paper for the decay of the depth-averaged concentration under the combined action of ecological degradation and hydraulic dispersion. Based on a first-order reaction model extensively employed in related ecological risk assessment and Environmental hydraulic design, the effect of ecological degradation is separated from the hydraulic effect via an exponential transformation for the general formulation for contaminant transport. The speed profile of a fully developed steady flow through the wetland is obtained. A hydraulic dispersion model for the depth-averaged concentration is devised as an extension of Taylor’s classical analysis on dispersion, and corresponding hydraulic dispersivity is obtained by Aris’s method of moments. Analytical solution of depth-averaged concentration is rigorously derived and characterized. For typical pollutant constituents in wastewater emission, the evolution of contaminant cloud in the wetland flow is illustrated by critical length and duration of influenced region with contaminant concentration beyond given Environmental Standard level, with essential implications for ecological risk assessment and Environmental management.

  • an ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L. Zeng, Zi Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under Environmental dispersion. An Environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the Environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the Environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given Environmental Standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and Environmental Standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

  • an ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L. Zeng
    Abstract:

    Abstract As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under Environmental dispersion. An Environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the Environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the Environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given Environmental Standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and Environmental Standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

L. Zeng - One of the best experts on this subject based on the ideXlab platform.

  • Ecological degradation and hydraulic dispersion of contaminant in wetland
    Ecological Modelling, 2011
    Co-Authors: L. Zeng, G Q Chen
    Abstract:

    For the typical case of a pulsed contaminant emission into a free surface wetland flow, a theoretical analysis is presented in this paper for the decay of the depth-averaged concentration under the combined action of ecological degradation and hydraulic dispersion. Based on a first-order reaction model extensively employed in related ecological risk assessment and Environmental hydraulic design, the effect of ecological degradation is separated from the hydraulic effect via an exponential transformation for the general formulation for contaminant transport. The speed profile of a fully developed steady flow through the wetland is obtained. A hydraulic dispersion model for the depth-averaged concentration is devised as an extension of Taylor’s classical analysis on dispersion, and corresponding hydraulic dispersivity is obtained by Aris’s method of moments. Analytical solution of depth-averaged concentration is rigorously derived and characterized. For typical pollutant constituents in wastewater emission, the evolution of contaminant cloud in the wetland flow is illustrated by critical length and duration of influenced region with contaminant concentration beyond given Environmental Standard level, with essential implications for ecological risk assessment and Environmental management.

  • an ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L. Zeng, Zi Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under Environmental dispersion. An Environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the Environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the Environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given Environmental Standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and Environmental Standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

  • an ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L. Zeng
    Abstract:

    Abstract As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under Environmental dispersion. An Environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the Environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the Environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given Environmental Standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and Environmental Standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

Zi Wu - One of the best experts on this subject based on the ideXlab platform.

  • an ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow
    Ecological Modelling, 2010
    Co-Authors: G Q Chen, L. Zeng, Zi Wu
    Abstract:

    As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow is presented in this paper for the fate of cross-sectional mean concentration under Environmental dispersion. An Environmental dispersion model for the mean concentration is devised as an extension of Taylor’s classical analysis on dispersion in fluid flows. The velocity distribution and the Environmental dispersivity in the fully developed steady flow through the wetland is found and illustrated with limiting cases covering various known solutions for the porous media flow between parallel plates, flow in a shallow wetland, sweeping flow in a densely vegetated wetland, and single phase flow in a channel. Obtained by Aris’s method of moments, the Environmental dispersivity is shown characterized with multi-scale asymptotic time variations with stem dominated stage, transitional stage, and width–depth-stem dominated stage. Based on the solution for the evolution of contaminant cloud in the wetland channel flow, critical length and duration of the contaminant cloud with concentration beyond given Environmental Standard level are concretely illustrated for typical pollutant constituents in wastewater emission. Under the same emission intensity and Environmental Standard, the duration of contaminant cloud in the wetland channel is revealed shorter than that in a free surface wetland, due to the lateral effect.

Bin Chen - One of the best experts on this subject based on the ideXlab platform.

  • contaminant transport in a two zone wetland dispersion and ecological degradation
    Journal of Hydrology, 2013
    Co-Authors: Bin Chen
    Abstract:

    Summary Understanding the fate of contaminant in wetland flows is essential in applications such as ecological risk assessment and Environmental hydraulic design. Presented in this paper is an analytical study on the dispersion of contaminant in a two-zone wetland, with the effect of ecological degradation taken into consideration. Environmental dispersion is discussed separately via an exponential transformation for the general formulation of contaminant transport. Taylor’s classical analysis for solute dispersion in a long and thin tube flow is rigorously generalized for the dispersion of the lateral mean contaminant concentration in the longitudinal direction. A method of asymptotic analysis is adopted instead of the concentration moment method in order to simplify the process of deduction and the expression of the analytical solution. Gill’s method of mean concentration expansion is applied to model the concentration deviation terms produced in an averaging operation. With the velocity profile obtained previously, the enhancement of the Environmental dispersivity under long time evolution is determined and shown to be consistent with that obtained by the method of concentration moment. Analytical solutions for the evolution of the contaminant concentration and the influenced region of the contaminant cloud are obtained by combining both the hydraulic and the ecological effects. For typical pollutant as the heavy metal Hg, the evolution of contaminant cloud is illustrated by critical length and duration in an application with concentration beyond some given Environmental Standard level. Results show that for wetland flows with a two-zone structure, the influenced region is reduced evidently while the duration of the contaminant cloud remains nearly unchanged, compared with that for the single-zone wetland flow.

Ping Wang - One of the best experts on this subject based on the ideXlab platform.

  • contaminant transport in a three zone wetland dispersion and ecological degradation
    Journal of Hydrology, 2016
    Co-Authors: Jing Luo, Wenxin Huai, Ping Wang
    Abstract:

    To further understand the fate of contaminant transport in real waterways interacting with riparian buffers and adjacent aquatic vegetation, solute dispersion is analytically explored for three-zone wetland flows with usually high Peclet number in this paper. Ecological effects are also taken into account. Environmental dispersion is addressed independently via an exponential transformation of the basic formulation of mass transfer in the context of porous media flow. After rigorously generalizing Taylor’s classical analysis, asymptotic analysis was used instead of the method of concentration moment or multi-scale analysis to simplify the examination. The mean concentration expansion base in Gill’s method is adopted to model concentration deviations produced in the lateral-average operation. With a previously derived velocity profile, Environmental dispersivity is obtained, effectively illustrating the effects of critical dimensionless parameters. Analytical expressions for evolution of the lateral mean concentration and critical length of the contaminant cloud are determined by combining the effects of both hydraulic dispersion and ecological degradation. An application example is provided to illustrate the evolution of contaminant cloud in terms of the critical length and duration with concentration greater than a given Environmental Standard level. Results show that for three-zone wetlands, the duration is clearly increased while the region affected by the contaminant cloud is slightly smaller than that for two-zone wetland flows.