Ecological and hydrogeological assessment of the state of groundwater in the aquiferous Turonian-Coniacian carbonate complex near the village of Staraya Kalitva in the Rossosh district of the Voronezh region

Abstract

in the Rossosh district of the Voronezh region. Methodology: The assessment of the state of the aquiferous Turonian-Coniacian carbonate complex was based on the study of the ecological functions of groundwater. The resource ecological state of the aquiferous Turonian-Coniacian carbonate complex was assessed based on the calculation and analysis of the following parameters: the lithology of water-bearing rocks, the thickness of the aquifer, the depth of groundwater occurrence, the position of the static level; the size of the sanitary protection zones of ground-water, bacteriological characteristics of groundwater, and organoleptic characteristics of groundwater. The ecological and hydrogeochemical assessment of the aquiferous Turonian-Coniacian carbonate complex was based on comparing the actual concentrations of substances with the maximum permissible concentrations, calculating the average and maximum values of the total pollution index. The quality of groundwater was monitored from 2012 to 2019. The ecological and geophysical assessment of groundwater was carried out considering the following indicators: specific total α-activity, specific total β-activity, and specific activity of radon-222. The ecological and hydrodynamic assessment of the aquiferous Turonian-Coniacian carbonate complex was based on the calculation of the main hydrodynamic parameters. Results and discussion: For the research, 3 exploration and production wells with a depth of 95 m each were used. It was found that the water-bearing rocks were represented by 20 m thick jointing Cretaceous deposits, the pressure head is 15–19 meters. The size of the sanitary protection zones of the first ring is 30 m, the second ring is 86.7 m, and the third ring is 1061.3 m. According to the results of the assessment, excessive values were recorded for the following indicators: turbidity (16.6 MPC), dry residue (3.21 MPC), total hardness (4.39 MPC), chlorides (4 MPC), magnesium (1.63 MPC), and total iron (10.7 MPC). As a result of the ecological and hydrodynamic assessment, it was determined that the specific discharge of wells is 0.14 l/s/m, the water transmissivity coefficient is 17 m2/day, the coefficient of layer conductivity is 104 m2/day, the permissible decrease is 27.7 m, the estimated lowering of the groundwater level is 24.18 m, and the maximum permissible water consumption is 405.09 m3/day. The maximum excess of the content of pollutants in groundwater was recorded for the concentration of iron: 3.2 mg/dm3 (10.7 MPC), and the total pollution index, which is 10.7. Conclusions: Based on the results of the assessment, a set of environmental protection measures was designed. One of the main measures is the installation of a reverse osmosis system to reduce the concentration of chlorides, magnesium, iron, dry residue, as well as to reduce the hardness and turbidity. A conclusion was made about the issues of applying the existing theory of studying the ecological functions of the lithosphere to the assessment of the ecological state of groundwater. The study demonstrated the need to revise the theory and ensure the correlation between the theory and the real situation.