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Groundwater vulnerability to pollution in degraded coal mining areas: modifying the DRASTIC method using the factor of exploitation impact on land surface

Krogulec Ewa, Bukowski Przemysław, Niedbalska Katarzyna, Trzeciak Joanna, Zabłocki Sebastian

Geology, Geophysics and Environment

2023

Vol. 49, no. 4

313--334

Mining activities such as underground exploitation of hard coal deposits and open cast mining are strong factors on groundwater depending on mine life cycle phases. The impact of coal mining activities on groundwater have been reported from many countries. In this case, a vulnerability assessment was conducted base on standard DRASTIC method and its modification DRASTIC MINE (DRASTICM) method. In order to take into account, the impact of mining activities, a new parameter was added which defined the impact of coal seams on the rock mass above, including the degree of its drainage and the range of its impact. In the standard DRASTIC method, the results indicate that groundwater vulnerability with high (38.6%) and very high occurrence classes (16.9% of the area), mostly covers the central part of the cast mine. In contrast, the reclaimed area of the excavation is a low-class area. The DRASTICM method increased the vulnerability index from 3 to 24 on 95% of the area, so a new vulnerability class of extremely high was delineated, which occurred in 1.6% of the area. This indicates areas that should be treated as a priority in order to avoid pollution, and in the final stage to plan activities in the field of the reclamation of mining areas. The results showed that groundwater vulnerability assessment in coal mining areas can be significantly improved.

Causes of groundwater level and chemistry changes in an urban area; a case study of Warsaw, Poland

Krogulec Ewa, Gruszczyński Tomasz, Kowalczyk Sebastian, Małecki Jerzy J., Porowska Dorota, Sawicka Katarzyna, Trzeciak Joanna, Wojdalska Anna, Zabłocki Sebastian, Zaszewski Daniel

Acta Geologica Polonica

2022

Vol. 72, no. 4

495--517

The presented studies focus on changes in groundwater levels and chemistry, and the identification of important factors influencing these changes on short- and long-term scales in urban areas. The results may be useful for rational and sustainable groundwater planning and management in cities. The studies concerned three aquifers: (1) the shallow Quaternary aquifer, (2) the deep Quaternary aquifer, and (3) the Oligocene aquifer in the capital city of Warsaw (Poland). The spatial variability of groundwater recharge was determined and its changes in time were characterized. The characteristics of groundwater levels were based on long-term monitoring series. The results indicate that urban development has caused overall reduction in infiltration recharge (from 54 to 51 mm/year), which is particularly clear in the city suburbs and in its centre, where land development has significantly densified during the last 30 years. Studies of groundwater levels indicate variable long-term trends. However, for the shallowest aquifer, the trends indicate a gradual decrease of the groundwater levels. In the case of the much deeper Oligocene aquifer, groundwater table rise is observed since the 1970s (averagely c. 20 m), which is related with excessive pumping. Based on the studied results, the groundwater chemistry in the subsurface aquifer indicates strong anthropogenic influence, which is reflected in multi-ionic hydrogeochemical types and the occurrence of chemical tracers typical of human activity. The Oligocene aquifer is characterized by a chemical composition indicating the influence of geogenic factors.