Pollution transport mechanisms in a regional karst aquifer under extreme precipitation events (Murgia, Southern Italy)

Based on the results of monitoring surveys carried out in the period 1995-1997 at the wells of the Regional Monitoring Net of Murgia aquifer (Puglia Region, Southern Italy), which includes two main recharge areas, a study was achieved with the aim of recognizing the mechanisms of recharge of the karst system. The knowledge of the recharge mechanisms is crucial in assessing the impact of pollutants on the quality of groundwater: given the complex karst system structure, the mechanisms can differ from place to place, resulting in a wide range of values of intrinsic vulnerability. Under the pressure of extreme rainfall events (intense and/or long term), the removal of water volumes and pollutants, stored in the different karst subsystems during a given period before an event, takes place at different times. In the recharge areas, monitoring shows different chemical characteristics of ground waters in the different periods. The cross-interpretation of precipitation pattern, hydraulic heads and chemical parameters (nitrates, total organic carbon and major constituents) allows formulating preliminary hypotheses about both the role played by the different sub-systems in the transfer of pollutants, and the duration of such transfer.