Study on the two-dimensional transport characteristics of heavy metal pollutants in a non-homogeneous cutoff wall system considering the consolidation effect
Consolidation behaviour results in non-homogeneous engineering properties of the cutoff wall along the depth,thus affecting the transport characteristics of heavy metal pollutants(HMPs)in the cutoff wall.However,the associated studies are limited.In this paper,a two-dimensional transport model for HMPs in a non-homogeneous cutoff wall system(consisting of a buffer layer,a non-homogeneous cutoff wall and an aquifer)is developed,where the consolidation effect and the Langmuir adsorption features are considered.Then,the proposed model is solved through a numerical approach and its validity is verified by comparing with the experimental measurements and the calculation results of the two other calculation methods.On such basis,a study on the transport characteristics of HMPs is performed and the results show that the concentration in the upper zone of the cutoff wall increases and the concentration in the bottom zone reduces when the consolidation effect is considered compared to it is neglected.The transport rate of HMPs in the Langmuir adsorption scenario is higher than that in the linear adsorption scenario,and the difference in relative concentrations between the two scenarios becomes more significant with growing concentration of the pollution source.Furthermore,the evaluation of barrier performance reveals that the increase of the buffer layer's thickness is beneficial in prolonging the cutoff wall's service life.Nevertheless,the buffer layer's thickness should not be too large given that the"enclosure"cutoff wall is widely applied in practical engineering.Besides,ignoring the consolidation scenario may overestimate the barrier performance of the cutoff wall compared to considering the consolidation scenario.Both the increase in the cutoff wall's thickness and its adsorption capacity can improve its barrier performance,and the two aspects can be combined to conduct the design of anti-fouling barriers in engineering practice.The proposed model as well as the obtained laws in this paper can provide guidance for the effective design and the service performance evaluation of cutoff walls.
environmental sciencesconsolidationnon-homogeneous cutoff wallbuffer layerheavy metal pollutantstwo-dimensional transportLangmuir adsorption
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