Архив метки: groundwater

USE OF A NUMERICAL EXPERIMENT IN STUDYING MIGRATION OF DIFFERENT POLLUTANTS IN THE GROUNDWATER OF THE KALUGA REGION IN THE AREA OF RADIOACTIVE ZONE

Ecology and dynamics Опубликовано автором

Belousova A.P.,  Rudenko E.E.,  Vlasov K.G. Use of a Numerical Experiment in Studying the Migration of Different Pollutants in the Groundwater of the Kaluga Region in the Area of the Radioactive Trace // Ecosystems: ecology and dynamics. No 2. 2023. P. 40-72. | Abstract | PDF | Reference

 

 

The purpose of this article was to use a mathematical modeling in order to study the migration of various pollutants, including radionuclides, from poorly sorbed to highly sorbed ones that travel from groundwater to pressure groundwater through a separating layer, an aquiclude, and has varying permeability. Among others, the field of hydrogeological researches performs search and exploration of groundwater deposits. Search is the first stage which is carried out in unexplored territories, followed by exploration, the second stage, which is performed in the promising territories that were revealed during the first stage.

Our studies follow the first stage, because the territories of our choice, located in the Kaluga Region and affected by the Chernobyl accident, were unexplored. We focused on studying the migration of pollutants from groundwater through the aquiclude of the pressure waters. The direction of our search was determined by the aquiclude’s ability to let the pollutants through, which is considered the most unfavorable conditions for groundwater, or its ability to keep the pollutants out, which is considered a favorable condition. However, both of these stages do not exist separately in natural and artificial conditions, because they simply merge together, but, in order to study that, a thorough geological and hydrogeological knowledge of the territory is needed, which we do not possess for the study area. Therefore, our research was carried for both stages: in the first one, the aquiclude was assumed to be permeable, while in the second one it was assumed impermeable.

For each stage, exploratory numerical experiments were carried out using mathematical modeling. The object of those studies was the part of the Kaluga Region, most affected by the accident at the Chernobyl nuclear power plant. Studies concerning the first stage have been already completed and published by our crew (Belousova, Rudenko, 2021a, 2021b), while the results of the second stage and generalizing results of both studies are presented in this article. We studied the migration of various pollutants, including radionuclides, from groundwater through an impermeable aquiclude to the confined aquifer. We used the same profiles that were studied in the first stage, but applied slightly modified scenarios and used different coefficients of pollutant sorption distribution (Kd).

Numerical experiments of the second stage were carried out according to the following scenarios: 1 – (1-3-1), 2 – (1-6-1), 3 – (1-10-1), 4 – (6-60-6), 5 – (26-260-26), 6 – (100-1000-100). The first digit is the Kd value (l/kg) in the 1st layer, the second digit – 2nd layer, the third digit – 3rd layer. This selection of coefficients was determined by the fact that their values were assigned to be higher in the aquiclude than in the upper and lower aquifers.

Each scenario was applied for two conditions: with and without radioactive decay. The starting condition was the contamination degree of groundwater, just like the contamination degree of the ground in the radioactive trace zone of the study area. However, such a spread of contamination by either radionuclides or other pollutants is not actually (in natural conditions) observed in the groundwater of this territory. Pollutant concentrations can be specified in g/l, maximum permissible concentration (MPC) and background concentrations, but we used MPC. Kd of various pollutants were selected from the known values for the Bryansk Region (Belousova, Rudenko, 2021a, 2021b); regarding radionuclides, the Kd values mainly refer to the unsaturated zone of contamination.

We established that the main factors forming the pollutant migration are the radioactive decay of the said pollutants, their sorption properties, and the hydrodynamic dispersion of groundwater flow, which, in turn, depends on the geological and hydrogeological conditions of the study area and the aquiclude permeability. The studied situation proves that aquicludes cannot ensure a full protection of pressure groundwater from pollution.

Keywords: groundwater, underground confined waters, modeling of migration processes, pollutant, radionuclides, sorption, radioactive decay.

Acknowledgments. We would like to thank Yu.V. Minyaeva who prepared materials for this article before her saddening demise.

Funding. This work was carried out for the Water Problems Institute of the Russian Academy of Sciences, No. FMWZ-2022-0002 “Research of Geoecological Processes in Hydrological Systems of Land, Formation of the Quality of Surface and Ground Waters, Problems of Water Resources Management and Water Use under Conditions of Climate Change and Anthropogenic Impacts”.

DOI: 10.24412/2542-2006-2023-2-40-72

EDN: UEXKOC

INTEGRATED METHODOLOGY AND ITS APPLICATION FOR ASSESSING THE PROTECTION OF GROUND AND CONFINED SUBTERRANEAN WATERS FROM VARIOUS POLLUTANTS AND THEIR VULNERABILITY TO POLLUTION IN THE KALUGA REGION IN THE RADIOACTIVE TRACE FROM THE ACCIDENT AT THE CHERNOBYL NPP

Ecology and dynamics Опубликовано автором

Belousova A.P., Rudenko E.E. Integrated Methodology for Assessing the Protection Degree of Ground and Confined Subterranean Water from Different Pollutants as Well as Their Vulnerability to Pollution and Its Application in the Kaluga Region in the Radioactive Trace from the Accident at the Chernobyl NPP // Ecosystems: Ecology and Dynamic. No. 2. 2022. P. 99-122. | Abstract | PDF | Reference |

 

 

The object of our research is groundwater and confined subterranean waters in the territory of the Kaluga Region, most affected by the accident at the Chernobyl Nuclear Power Plant. Our aim was to develop a complex methodology to assess the level of protection and vulnerability of groundwater and confined subterranean water against various pollutants, including radionuclides.

The methodology was tested in the territory of the Kaluga Region, in its zone of the radioactive contamination zone from the Chernobyl Accident.

Our earlier studies that assessed protection and vulnerability of subterranean waters began almost immediately after the accident and were carried out according to the original methodology, developed by the authors of this article. They were fully focused on groundwater only or, more specifically, on the first aquifer under the ground surface. However, this research studies both groundwater and confined subterranean water, located below the groundwater aquifer.

Depending on the location of pollution source, two approaches are considered to solve our main aim. The first option involves a pollution source placed on the ground surface, the way it was observed right after the Chernobyl Accident. The second option involves a pollution source located directly in the groundwater or spreading over a large area, in which case the number of study objects decreases, and it becomes a specific case of the first option.

The results of our research and the methodology we offer for the further use can be applied for assessment of the ecological state of subterranean waters in different country territories, at different scales; for design and construction of fresh subterranean water intakes for drinking purposes; for design and organization of subterranean water monitoring in the areas affected by the Chernobyl Accident. The results of our research are new and significant for further studies.

Keywords: groundwater, subterranean confined water, pollutant, subterranean water protection from pollution, subterranean water vulnerability to pollution, radionuclides, sorption, migration period.

DOI: 10.24412/2542-2006-2022-2-99–122

EDN: CFVOIW

MODELING OF THE POLLUTED GROUNDWATER FLOW INTO CONFINED WATER IN THE FOREST ECOSYSTEMS BY THE EXAMPLE OF THE KALUGA REGION IN THE RADIOACTIVE CONTAMINATION ZONE

Ecology and dynamics Опубликовано автором

Belousova A.P., Rudenko E.E. MODELING OF THE POLLUTED GROUNDWATER FLOW INTO CONFINED WATER IN THE FOREST ECOSYSTEMS BY THE EXAMPLE OF THE KALUGA REGION IN THE RADIOACTIVE CONTAMINATION ZONE // Ecosystems: ecology and dynamics. 2021. Vol. 5. No 3. P. 192-224. | Abstract | PDF | Reference |

 

 

The purpose of this article is to study the migration processes of various pollutants, including radionuclides, from poorly sorbed to highly sorbed ones, in the groundwater and confined water, using the method of mathematical modeling. The object of the study is the part of the Kaluga Region that was affected by the accident at the Chernobyl Nuclear Power Plant the most.

The modeling of contamination processes in the groundwater and confined water in the radioactive contamination zone was carried out according to 3 scenarios of the development of such processes. We took into account various pollutants and mass transfer processes, using the mathematical MT3D program, and made a series of numerical experiments. Scenario 1) groundwater contamination with highly sorbed pollutants; scenario 2) contamination with highly sorbed pollutants and radioactive pollutants; scenario 3) contamination with poorly sorbed pollutants.

Besides, an unfavorable option for the ecological condition of confined waters was considered, due to the impervious horizon being insufficiently impermeable to the polluted waters, flowing from the aquifer. This situation was probably caused by the natural lithological structure (interlayers, sand lenses, sandy loams, insufficient depth) and industrial factors (poorly insulated holes, wells and other structures that open the aquifer). All the factors listed above are the “fast migration routes” that make it possible for a lot of pollutants to penetrate the confined aquifers, where the fresh water is contained.

To study the pollutants migration in the previously created MT3D model, we selected two profiles. They were located along the lines of groundwater flow, stretching from the watershed to the area of discharge, i.e. the rivers. The ecological situation was analyzed for 4 calculation periods of 30, 60, 100 and 300 years (to link it to the half-lives of radionuclides), for 4 coefficients of sorption distribution (Cd) of pollutants: 6, 26, 200 and 1000 l/kg for radionuclides with decay and other toxic, strongly sorbed pollutants without it; 0.5, 1.0 and 3.0 l/kg for poorly sorbed pollutants. We assessed the ecological situation in the first layer (groundwater), the second one (watershed layer and pore solutions) and the third one (confined water).

In addition, several spots were selected for the analysis of the ecological situation.

The modeling resulted in a comparison of all development scenarios of the pollution processes and analysis of the factors that determined them. In addition, we studied the capabilities of the process of pollutant diffusion and its impact on pollutant migration. Therefore, the main factors to form the processes of pollutant migration are their radioactive decay, their sorption characteristics, and the hydrodispersion of groundwater flows, which depends on the geological and hydrogeological conditions of the studied territory. Aside from this, diffusion plays an insignificant role in their migration as well.

Keywords: groundwater, confined water, migration processes modeling, pollutants, radionuclides, sorption, molecular diffusion, radioactive decay.

DOI: 10.24412/2542-2006-2021-3-192-224