Hydrogeochemical assessment of the sorption properties of heavy metals in the areas of the impact of solid waste landfills on groundwater

Summary

The fundamentals of the method for predicting the spread of heavy metals in the areas of groundwater pollution by leachate from solid municipal waste landfills are stated. The analysis of the leachate quality of municipal solid waste landfills and the applicability of statistical and empirical estimates of the sorption coefficient of heavy metals is carried out. The limited applicability of statistical estimates for analyzing the distribution of highly mineralized leachate is shown. Based on the method of geochemical simulation, a model has been developed for determining the exchange coefficients between the dissolved and solid phases, i. e. sorption coefficients. The results of determining the sorption coefficient for a wide range of cations are presented with regard to the conditions of natural water displacement by the leachate from solid waste landfills. The developed method can be used to estimate the impact of municipal solid waste landfills on groundwater quality, to predict the spread of heavy metals in the area of potential waste impact, to carry out works within the framework of EIA (Environmental Impact Assessment) and LEPM (List of Environmental Protection Measures), to develop systems for engineering protection of groundwater from pollution. The proposed model can serve as a basis for its further improvement with account of the processes of formation of stable organic metal complexes in leachate and complexation on the hard rocks.

Key words

ion exchange , heavy metals , geochemical modeling , cation sorption , municipal solid waste landfill

DOI 10.35776/VST.2021.11.05
UDC 550.461:550.424:543.383.2

KUZMIN V. V., Boldyrev Kirill

Hydrochemical modeling of migration of dissolved oil products in groundwater

Summary

A method for predicting the spread of BTEX group oil products (benzene, toluene, ethylbenzene, xylenes) in groundwater based on hydrochemical modeling with account of changes in the redox, acidity or alkalinity of the solution during the biodegradation of oil products is stated. A geochemical model of the biological decomposition of oil products of BTEX group based on modified Mono kinetics with account of the reactions between acceptors, biodegradation products and inorganic components of the solution is presented. Examples of geochemical modeling are given that demonstrate the importance of taking into account the processes associated with the changes in the hydrogeochemical environment in groundwater during the decomposition of hydrocarbons. The developed model can be used to carry out geochemical predictions of the spread of light-end oil products in groundwater, to carry out works within the framework of estimating the environmental impact, and to develop systems for engineering protection of groundwater from oil pollution.

Key words

ion exchange , geochemical modeling , dissolved oil products , oil products of BTEX group , biological decomposition of hydrocarbons , hydrocarbon sorption , electron donor , acceptor

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UDC 550.424:574

Boldyrev Kirill, Utkin S. S., Kazakov S. V.

Specificities of predicting metal distribution between aqueous phase and bottom sediments (by the example of strontium and cesium radionuclides)

Summary

The basic provisions of the developed methodological approach to predicting the coefficient of K_d radionuclide distribution on the material of bottom sediments and suspended substances in water bodies are presented. As a tool for predicting K_d coefficient of metals under the conditions of the changing chemical composition of water the use of geochemical modelling was suggested. The basic approaches, models and results of predicting the values of K_d coefficient of metals in a reference water body (a surface water reservoir – radioactive waste storage) characterized by high pollution with ⁹⁰Sr strontium and ¹³⁷Cs radionuclides as well as by the intensive decrease of water mineralization are laid out. During the research the specific features of hydrochemical and hydrodynamic behavior of metals in the water body system as well as the methods of geochemical modeling were studied in detail. The geochemical thermodynamic model of metal sorption (by the example of ⁹⁰Sr and ¹³⁷Сs) by the suspended matter and bottom sediment layer in the model water reservoir was developed that could be considered as a basis for modeling different scenarios of the evolution of real polluted water reservoirs. The values of K_d coefficient for ⁹⁰Sr and ¹³⁷Сs at decreasing water mineralization were calculated. It was determined that K_d value is increasing while water mineralization is decreasing. The model can be used for predicting the rate of metal elimination from polluted water bodies in the process of self-purification.

Key words

geochemical modeling , bottom deposits , surface water reservoir , sorption of heavy metals , radionuclide distribution coefficient , self-purification of a water reservoir

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UDC 628.171:556:661.843

Boldyrev Kirill, Savel'eva E. A., Kapyrin I. V., Rastorguev A. V.

Calculations of the metal sorption parameters by the example of strontium at high sodium nitrate concentrations

Summary

For the proper evaluation of underground water protection a comprehensive analysis of pollutant migration from the pollution source is required. The problem of solution salinity effect on the substance distribution between water and water-bearing material has been insufficiently covered in literature because of the low parametric support of the widely used geochemical models and also because of the imperfection of the applied thermodynamic data bases. In the process of geochemical modeling tabular values of interfacial distribution coefficient are often used. Another approach often used in practice is transferring laboratory measured Kd values to geochemical model. The use of tabular and experimental data on interfacial distribution coefficient without proper correction can result in falsified predictions since the available Kd tabular values for metals in the process of predicting sorption parameters, as a rule, provide for a recommended value only for a definite type of water-bearing material (sand, loam, clay) and (rarely) for one or two water types which is evidently insufficient for the correct choice of Kd coefficient. High solution mineralization reduces sorption of all the components because of the competition for the sorption sections and because of metal ion complexation with the solution components. In the article the difficulties in designing the geochemical model of 90S strontium sorption at high concentrations of dissolved sodium nitrate are considered. Strontium sorption by solid phases was considered in relation to ion exchange and surface complexation. The designed model was verified versus literature data. An algorithm of geochemical modeling of dissolved substances distribution between water and hard rock is recommended.

Key words

ground water , sorption , ion exchange , water-bearing material , geochemical modeling , interfacial distribution coefficient

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