Department Environmental Chemistry

Pollutant dynamics in karstic hydrogeological settings

Karstic aquifers make up 20-25 % of the drinking water resources worldwide and contribute to 18 % of the Swiss drinking water. Due to their geological development and the resulting caves, pipes and fissures, they exhibit a high hydraulic conductivity. This enhanced hydraulic conductivity often leads to hydraulic shortcuts between surface and groundwater, and associated karstic springs. Due to fast transport, contaminants like pesticides and bacteria could reach the springs in high concentrations. However, the current monitoring strategies implemented in the national groundwater monitoring program NAQUA are not sufficient to resolve these fast concentration dynamics since the maximum number of samples taken per year is 4. This strategy allows for the long-term monitoring of water quality, but short-term changes are potentially missed. Within hours after a precipitation event, water quality could deteriorate to the extent that it should not be used as raw water in drinking water production anymore (groundwater limit for pesticides: 0.1 µg/L). To study these fast changes in water quality we want to use the MS2field to automatically and in-situ measure pesticides and their transformation products. With the MS2field, we are able to measure one sample every 20 minutes during several weeks and precipitation events. This enables us avoid tedious and error-prone grab sampling and lab analysis while covering a wide selection of substances. However, ionic, very polar and therefore very mobile compounds like glyphosate cannot be studied using the MS2field. Hence, we aim to develop an ion-chromatographic method which covers as many substances expressing such properties as possible. Overall, we propose to revise the current monitoring strategies concerning concentration dynamics in place by means of the gained insights.