Transport of organochlorine pesticides in soil columns enhanced by dissolved organic carbon

1997 ◽  
Vol 35 (7) ◽  
pp. 139-145 ◽  
Author(s):  
Jiann-Yuan Ding ◽  
Shian-Chee Wu
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Organochlorine Pesticides ◽  
Transport Model ◽  
Phase Model ◽  
Soil Columns ◽  
Two Phase ◽  
Three Phase ◽  
Phase Transport ◽  
Remediation Of Soil

The objective of this study is to quantify the effects of humic acid solution infiltration on the transport of organochlorine pesticides (OCPs) in soil columns using a three-phase transport model. From experimental results, it is found that the dissolved organic carbon enhances the transport of OCPs in the soil columns. In the OCPs-only column, the concentration profiles of OCPs can be simulated well using a two-phase transport model with numerical method or analytical solution. In the OCPs-DOC column, the migrations of aldrin, DDT and its daughter compounds are faster than those in the OCPs-only column. The simulation with the three-phase model is more accurate than that with the two-phase model. In addition, significant decrease of the fluid pore velocities of the OCPs-DOC column was found. When DOC leachate is applied for remediation of soil or groundwater pollution, the decrease of mean pore velocities will be a crucial affecting factor.

Laboratory Studies of the Effects of Dissolved Organic Material on the Adsorption of Organochlorine Pesticides by Sediments and Transport in Rivers

1993 ◽  
Vol 28 (8-9) ◽  
pp. 199-208 ◽  
Author(s):  
J.-Y. Ding ◽  
S.-C. Wu
Keyword(s):  
Organic Matter ◽  
Molecular Diffusion ◽  
Transport Model ◽  
Water System ◽  
High Rate ◽  
Sensitivity Analyses ◽  
Overlying Water ◽  
Sediment Bed ◽  
Three Phase ◽  
Phase Transport

In this study experiments simulating sediment/water system were carried on with sediments spiked with aldrin, heptachlor epoxide and p,p'-DDE. It was expected that these hydrophobic contaminants would be released to the overlying water column from sediment bed with molecular diffusion and co-diffusion with dissolved organic matter (DOM) as well. A three-phase-transport model including aqueous, solid and mobile adsorptive phases was developed and used to describe the behavior of these contaminants and to explain the results of the experiments. Sensitivity analyses show that observable effects of DOM occur only under conditions of high partition coefficient (Koc) of the contaminant and high rate of transfer from sediment organic matter to DOM. In this study, owing to the low concentration of DOM and relatively low hydrophobicity of the compounds, the DOM-associated pollutant flux does not significantly contribute to the total flux. Also, the simulated results of the model can reasonably explain the variations of the concentrations of the spiked compounds observed in the microcosms.

An Edge Dislocation in a Three-Phase Composite Cylinder Model

1991 ◽  
Vol 58 (1) ◽  
pp. 75-86 ◽  
Author(s):  
H. A. Luo ◽  
Y. Chen
Keyword(s):  
Edge Dislocation ◽  
Stable Equilibrium ◽  
Phase Model ◽  
Composite Cylinder ◽  
Two Phase ◽  
Trapping Mechanism ◽  
Three Phase ◽  
Cylinder Model ◽  
Stable Equilibrium Position ◽  
The Stability

An exact solution is given for the stress field due to an edge dislocation embedded in a three-phase composite cylinder. The force on the dislocation is then derived, from which a set of simple approximate formulae is also suggested. It is shown that, in comparison with the two-phase model adopted by Dundurs and Mura (1964), the three-phase model allows the dislocation to have a stable equilibrium position under much less stringent combinations of the material constants. As a result, the so-called trapping mechanism of dislocations is more likely to take place in the three-phase model. Also, the analysis and calculation show that in the three-phase model the orientation of Burgers vector has only limited influence on the stability of dislocation. This behavior is pronouncedly different from that predicted by the two-phase model.

Water Crossover Reduction in DMFC Utilizing Hydrophobic Anode MPL

2008 ◽  
Author(s):  
Christian E. Shaffer ◽  
Chao-Yang Wang
Keyword(s):  
Water Transport ◽  
Water Loss ◽  
Transport Model ◽  
Flow In Porous Media ◽  
Cathode Side ◽  
Two Phase ◽  
Direct Methanol ◽  
Lower Permeability ◽  
Phase Transport

Reducing the water crossover from anode to cathode is an important goal for direct methanol fuel cell (DMFC) technology, especially if highly concentrated methanol fuel is to be used. A well-documented way to reduce this water loss to the cathode side is by using a hydrophobic cathode microporous layer (MPL). Recently, however, it has been demonstrated that in addition to a cathode MPL, the use of a hydrophobic anode MPL further reduces the water loss to the cathode. In this work, we use a two-phase transport model that accounts for capillary induced liquid flow in porous media to explain physically how a hydrophobic anode MPL acts to control the net water transport from anode to cathode. Additionally, we perform a case study and show that a thicker, more hydrophobic anode MPL with lower permeability is most effective in controlling the net water transport from anode to cathode.

scholarly journals Development of LDPE Crystallinity in LDPE/Cu Composites

2021 ◽  
Author(s):  
Makki Abdelmouleh ◽  
Ilyes Jedidi
Keyword(s):  
Phase Change Materials ◽  
Research Work ◽  
Orthorhombic Phase ◽  
Copper Particle ◽  
Phase Model ◽  
Spectral Simulation ◽  
Two Phase ◽  
Cu Films ◽  
Three Phase

This chapter summarizes the study of the filler (ie copper) effect on LDPE phasic composition in LDPE/Cu composites prepared in solution. During this research work, a particular effort is focused on the use of DSC under non-standard conditions. Therewith, the presence of copper microparticles has a great effect on the network phase than on the crystalline long-range-order phase of LDPE structure. Furthermore, LDPE phasic composition in absence and presence of copper microparticles is investigated by FTIR spectroscopy followed by a spectral simulation of the band that appeared at 720 cm−1 corresponding to the CH2. Anywise, the two-phase model confirmed that no variation is observed of LDPE phase composition for all copper contents into LDPE/Cu films. However, with the three-phase model the orthorhombic phase fraction was found to be constant compared to the fraction of amorphous and that of network phase were found to increase and decrease respectively with increase in the copper particle load in the film. Overall, the thermal and structural behavior of LDPE in presence of copper particles allows this type to be used as phase change materials (PCMs) by adding a paraffin fraction in the LDPE/Cu composite. An update of the most relevant work carried out in the field of phasic characterization of polyethylene is presented in this chapter.

Watershed dissolved organic carbon transport: a modeling approach combining water travel times and reactivity continuum

2020 ◽  
Author(s):  
Giulia Grandi ◽  
Enrico Bertuzzo
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Dissolved Organic Carbon ◽  
Transport Model ◽  
Terrestrial Ecosystems ◽  
Riverine Ecosystems ◽  
Doc Concentration ◽  
Tightly Coupled ◽  
Reactivity Continuum ◽  
Carbon Degradation

<p>Although their contribution was neglected in the past, inland waters play a significant role in the carbon cycle and affect CO<sub>2</sub> global balance. Streams and rivers are now considered not only as pipelines but as active reactors able to collect and transform carbon from terrestrial ecosystems trough drainage, erosion, deposition and respiration. Quantifying the transfer of carbon from the terrestrial to the riverine ecosystems is thus of crucial importance to fully appreciate carbon cycle at the watershed, regional and global scales. Such transfer is largely controlled by the processes occurring in the critical zone where the carbon and water cycles are tightly coupled. Previous studies investigated how hydrological drivers can affect Dissolved Organic Carbon (DOC) concentration in streams highlighting an hysteretic and unsteady behavior for the DOC-discharge relationship. In this study, we focus on the drainage flux from hillslopes to stream and river networks during rainfall events combining a transport model for water and a model of carbon degradation in soil. Using high-frequency records of chloride and DOC in Plynlimon catchments (UK), we employ the recently developed StorAge Selection (SAS) theory to evaluate water travel time and its partition as evapotranspiration, discharge and storage. We combine this approach with the reactivity continuum  theory to model  carbon degradation along the flow paths using a gamma-distribution as probability density function of the quality. The developed model can thus predict not only the flux of DOC released from hillslopes but also its quality (i.e. lability). We also show how the variability of the DOC-discharge relationship can partially be explained by hydrological fluctuations.</p>

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