Natural Groundwater Background Levels of Nitrate and Landfill Effects (Apulia, Southern Italy)

High nitrate concentration of fresh groundwater of a coastal karstic aquifer, not far from the Apulian regional capital (Southern Italy), caused public concern and alarm from the authorities. The attention of local communities focused on the effect of a group of landfills, the use of which started from 1975, using improved technological and safety devices to reduce groundwater pollution risks. This chapter describes a simple approach based on the spatial and temporal variability of groundwater nitrate concentration (GNC) able to answer to public concern, circumscribing the main source of contamination, discussing of natural background values and spatial/temporal variability of GNC. For this purpose, a wide spatial and temporal range of data were discussed from 2006 to 2018. A regional survey of 2006-2007 was used to define background values or almost natural values of groundwater nitrate concentration (GNC). In the landfill sector, a monthly time series from 2007 to 2013 showed the GNC seasonality and the relationships with rainfall, and the periodical surveys of 2014-2018 showed the geochemical groundwater characteristics and the spatial variability of GNC, in both cases at the detailed scale of the study area. The results show the source is diffuse and should be related to the intensive agriculture activities in the area. The results correspond perfectly with the results obtained using a multimethodological complex and expensive approach based on the use of several parameters, including nitrogen isotopes.