Browsing by Subject "groundwater"

In this thesis, the migration patterns of the legacy pesticide called atrazine were studied in the Laune aquifer in Lahti, Finland, using the MODFLOW groundwater modelling program connected to the MT3D tool. Three models were built for the thesis. In the first model, the migration of atrazine in the Laune aquifer was studied by simulating the steady release of 1.22 µg/L atrazine concentration from sediments in the Lahti railway area over 15 years. In the second model, the depletion of atrazine from soil deposits was studied over time in both sudden and gradual depletion scenarios for 10 and 30 years. In the third model, the effect of pumping contaminated groundwater from an extraction well and injecting remediated water back into the aquifer from another well was investigated on the atrazine concentration in groundwater in the study area for 15 years. Concentrations of atrazine in the aquifer either increased or decreased from the baseline concentrations in the first model. In certain areas in Laune, atrazine concentrations exceeded the EU safe limit values during the whole modelling period. In the second model, the dilution of atrazine was relatively slow, even in the scenario of sudden depletion. It can take decades for the groundwater concentrations to dilute to EU-safe limits once the limits have been exceeded. In the last model, the pumping and injection of remediated groundwater showed a decline in concentration of atrazine over time. However, the effects were only local. Regional effects would have required a higher number of injection wells covering a larger area. Modelling tools are an important part of ethical ecotoxicological research solving many logistical problems related to field studies. However, as the results are highly depend- ent on the parameters, the results should be critically evaluated and used as part of other research methods. In environmental restoration work, understanding and modelling the pa- rameters related to leaching risk can be used as part of risk management. Understanding the migration of stored pesticides into the environment, the development of environmental restoration methods, and preventive measures are crucial to securing clean drinking water quality and quantity in the future.