Pollutants Transported Rapidly Into Drinking Water

The entire ecosystem of the planet as well as humans depend on clean water. When carbonate rocks weather, karst areas develop, from which around a quarter of the world's population gets their drinking water. Scientists have investigated how quickly pollutants can reach the groundwater deposits in karst areas and how this could impair the quality of drinking water. An international team led by junior professor Dr. Andreas Hartmannfrom the Professorship for Hydrological Modeling and Water Resources at the University of Freiburg compared the transport time of water from the surface to the subsurface with the degradation time of pollutants in carbonate rock regions in Europe, North Africa and the Middle East. The researchers have published their results in the journal Proceedings of the National Academy of Sciences (PNAS).

Previous continental or global hydrological model applications have mainly focused on the occurrence of floods or dry seasons and the general availability of drinking water. Scientists, however, have largely neglected the water quality as an important factor for the drinkability of the water on these large scales, in particular how quickly pollutants can seep through cracks or crevices from the earth's surface into the groundwater.

The current research results by Hartmann and his team show that in karst regions, which are characterized by the increased occurrence of cracks or crevices, the risk of pollution from degradable pollutants such as pesticides, drugs or pathogens is significantly higher than previously expected. Although pollutants are considered to be short-lived, up to 50 percent of them can still reach the groundwater, depending on the degradation time. The main reason for this, the researchers show, are fast seepage paths that allow large amounts of infiltrating water to reach groundwater in a short time. Especially in regions with less thick soils such as the Mediterranean area, the pollutants on the surface can be transported into the subsoil quickly and in high concentrations during large rain events. Hartmann's scientists demonstrated the consequences using the example of the degradable pesticide glyphosate. According to their calculations, this can exceed its permitted limit value by up to 19 times as a result of rapid transport into the groundwater. The increased risk of pollution for drinking water or ecosystems that are dependent on groundwater is particularly relevant for regions in which agriculture is dependent on degradable fertilizers and pesticides.

Reference
Hartmann A, Jasechko S, Gleeson T, et al. Risk of groundwater contamination widely underestimated because of fast flow into aquifers. PNAS. 2021;118(20). doi:10.1073/pnas.2024492118

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