Water-rock interactions in karst and pore water chemistry in sedimentary rocks

2010 ◽  
Keyword(s):  
Water Chemistry ◽  
Pore Water ◽  
Sedimentary Rocks ◽  
Pore Water Chemistry

Importance of site-specific factors for the immobilization of contaminants using biochar and wood-based activated carbon

2021 ◽  
Author(s):  
Sampriti Chaudhuri ◽  
Gabriel Sigmund ◽  
Hary von Rautenkranz ◽  
Thorsten Hueffer ◽  
Thilo Hofmann
Keyword(s):  
Activated Carbon ◽  
Ionic Strength ◽  
Water Chemistry ◽  
Pore Water ◽  
Electrostatic Attraction ◽  
Inorganic Contaminants ◽  
Diverse Range ◽  
Pore Water Chemistry ◽  
Specific Factors ◽  
Carbonaceous Sorbents

<p>The use of environmentally friendly low-cost sorbents such as biochar and wood-based activated carbon as soil amendment has shown promising results in immobilizing organic and inorganic contaminants. They can be suitable soil remediation options at sites with residual contamination, where the contaminated hotspot has been removed. The effectiveness of biochar and activated carbon application is site dependent. Specifically, dissolved organic carbon (DOC), pH, and ionic strength in the pore water are important factors which can influence the extent of contaminant immobilization. Although there has been significant progress in developing alternative carbonaceous sorbents, the efficiency of these materials in a diverse range of soil and pore water conditions remains an open question. To address this knowledge gap, the present study investigates the influence of pore water chemistry on sorption of organic and inorganic contaminants to biochar and wood-based activated carbon. Sorption of selected non-polar, polar and ionizable polycyclic aromatic compounds (PACs) and inorganic Cadmium (Cd) to biochar and a wood-based activated carbon was studied under different pore water chemistry conditions. Batch sorption experiments were conducted using an experimental design approach (Box Behnken Design) with three different levels of DOC, pH, and ionic strength, yielding background solutions mimicking a wide spectrum of pore water chemistries. Sorption K<sub>D</sub> values [L/kg] were calculated from aqueous contaminant concentrations after equilibration. Results were analyzed using a response surface methodology (RSM) approach on Minitab 19 and fitted to a model equation using linear, squared and two-way interactions terms.</p><p>Our results show that the ionizable PAC (phenyl phenol) and Cd were most affected by changes in pore water chemistries. For phenyl phenol, the presence of a phenolic group can cause H-bonding and electrostatic attraction and repulsion, while pH-dependent changes in speciation, precipitation and electrostatic attraction can occur for Cd. Sorption of all PACs negatively correlated with DOC, indicating competition of DOC with PACs for sorption sites. Sorption of non-polar (acenaphthene), polar N substituted (carbazole) and ionizable (phenyl phenol) PACs was hindered under acidic conditions, due to precipitation of DOC. For Cd, higher pH and low DOC levels favored sorption. This can be attributed to a lower Cd solubility in the presence of leached phosphate at higher pH, and a predominance of Cd(OH)<sub>2</sub> in the neutral to alkaline regime. Our findings highlight the importance of considering a combination of site- and contaminant-specific factors when planning to apply carbonaceous sorbents for contaminant immobilization, with pH and DOC generally being more important than ionic strength.</p>

Identifying spatiotemporal variations in groundwater-surface water interactions using shallow pore water chemistry in the lower Jordan river

2019 ◽  
Vol 131 ◽  
pp. 103388 ◽  
Author(s):  
Noa Hillel ◽  
Michael L. Wine ◽  
Jonathan B. Laronne ◽  
Tobias Licha ◽  
Yaron Be'eri-Shlevin ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Chemistry ◽  
Pore Water ◽  
Spatiotemporal Variations ◽  
Jordan River ◽  
Pore Water Chemistry

Pore Water Chemistry of the Febex Bentonite

2000 ◽  
Vol 663 ◽  
Author(s):  
A.M. Fernández ◽  
J. Cuevas ◽  
P. Rivas
Keyword(s):  
Water Chemistry ◽  
Pore Water ◽  
Nuclear Waste Repository ◽  
Exchange Reactions ◽  
Data Set ◽  
Mineralogical Characterization ◽  
Sulphate Content ◽  
Water Interaction ◽  
Water Composition ◽  
Pore Water Chemistry

ABSTRACTThe knowledge of pore water chemistry in the clay barrier is essential for performance assessment purposes in a nuclear waste repository, since the pore water composition controls the processes involved in the release and transport of the radionuclides. The methodology followed to define the representative composition of the FEBEX bentonite pore water is presented in this paper.A series of bentonite-water interaction tests have been performed with the aim of providing a database on the main chemical parameters of the bentonite. These tests were carried out both with high solid to liquid (s:l) ratios (squeezing tests) and low s:l ratios (aqueous extracts tests). The exchangeable cations have also been analyzed to determine the selectivity coefficient of the exchange reactions. To complete the data set, a physical and mineralogical characterization of the bentonite was made.The most significant bentonite-water interaction processes controlling the chemistry of the system was identified. The ion concentrations basically depend on the s:l ratio of the system, and the pore water composition is controlled by the dissolution of chlorides, dissolution/precipitation of carbonates and sulphates and the cation exchange reactions in the smectite.The bentonite/water system was modelled with the PHREEQC2 program to obtain the best possible estimation of the pore water composition for initial conditions of water content (≍14%), after checking the conceptual model with the experimental results. The model predictions fitted satisfactorily with the experimental data at low s:l ratios. At high s:l ratios, the modelled results agree adequately, except for the sulphate content, which could be affected by the effective porosity, anion exclusion or stagnant zones not taken into account in the model. According to the model, the FEBEX bentonite pore water at 14% moisture is a sodium-chloride type, with an ionic strength of 0.25 M and pH of 7.78.

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