Groundwater Chemistry and Stratification in the Flooded Hard-Coal Mine Shaft “Nowy I” (Nowa Ruda Region, SW Poland)

Abstract

The flooding of unprofitable underground mines is one of the methods of their closure. After the drainage of the mine has stopped, the voids left in the rock mass as a result of mining, are filled with inflowing groundwater. In this way, reservoirs of groundwater with specific physicochemical parameters are formed. These parameters depend on the interaction of the water flowing into the workings with the rock formations. It was the economic situation in the 1990s that led to the closure of hard coal mines in the Nowa Ruda Coal Basin, where the flooded “Nowy I” shaft is located. In that shaft, in 2008, hydrogeological research was performed and groundwater samples from five various depths were collected. The aim of the study was to recognize if groundwater stratification occurs in the shaft. In 2015, a sample of the water outflowing through the “Aleksander” adit was taken to check the potential influence of mine flooding on the environment and to confirm the changes in groundwater chemistry over time. These were the first, and so far, the only studies on the chemical composition of water in the flooded mine in that area. The article presents results of the preliminary research, which confirmed the existence of not obvious hydrogeochemical stratification in the shaft. It can be assumed that below the depth of 350 m, the water circulating through mining excavations exhibits the highest electrical conductivity and the highest concentration of Ca2+, K+, SO42−, Fetot. In the depth range of 320–380 m there is a transition zone, in which a decrease of Eh value and a change of reduction and oxidation is recorded. Above this zone, infiltration water inflow, from outside the shaft casing, dominates. The research shows that it would be necessary to perform additional sampling of the water in the shaft at greater depths, as well as to perform isotope analysis and periodical tests for at least several years. This would allow for a more complete characterisation of hydrogeochemical processes taking place in the flooded mine.

Mine Water as Geothermal Resource in Nowa Ruda Region (SW Poland)

“…For the described area we have information on changes in hydrogeochemical environment. Studies have been carried out on the chemical composition of the waters contained in the flooded "Nowy I" mine shaft [37]. The studies covered the upper zone of the water column accumulated in the shaft.…”

“…In the whole examined vertical profile a slightly alkaline pH was recorded, with low variability from 7.36 to 7.46. The water temperature was constant ranging from 14.2 to 14.7 • C. A detailed description can be found in the paper by Chudy et al [37]. Mine outflow.…”

“…On this basis it was assumed that 12-15 measurements are sufficient for general characterisation of a given outflow. In the years 2007-2008, works connected with recognition of water chemistry in the flooded "Nowy I" shaft [37] were carried out. Later, after 2008, studies were carried out on a non-systematic basis and were concentrated on on-site inspections and 1-2 measurement sessions per year, whose task was to check whether there were any changes in relation to the results found earlier.…”

Study on the Influence of Mining Activities on the Quality of Deep Karst Groundwater Based on Multivariate Statistical Analysis and Hydrochemical Analysis

“…In addition, there are thin coal seams in the limestone strata of Taiyuan Formation in the study area, and pyrite is rich in content. The oxidation of pyrite makes a large amount of sulfide insoluble in water enter the groundwater in the form of SO 4 2− , which may be another reason for the high content of SO 4 2− in karst groundwater [ 30 ].…”

Application and Evaluation of Regional Control Technology of Limestone Water Hazard: A Case Study of the Gubei Coal Mine, North China

“…As shown in Table 1, five of the eleven verification drillings have no water (Y3-1, Y3-4, two branches of Y3-4, and Y3-5); other drillings only drip occasionally in small water volume with lower water pressure in comparison with the water pressure measured before regional treatment. 9 Geofluids Furthermore, analysis of aquifer chemistry can discriminate the source of validation hole water compared with the water chemistry characteristics in Carboniferous and Ordovician limestone aquifers [33][34][35]. The result is that the quality type of the water samples (Y3-2, Y3-6, Y3-8, Y3-9, and Y3-10) is apparently different from that of Ordovician limestone, but similar to that of Taiyuan formation limestone aquifers, as shown in Figure 8.…”