Origin and fate of nitrates in groundwater from the central Po plain: Insights from isotopic investigations

Tracing freshwater nitrate sources in pre-alpine groundwater catchments using environmental tracers

“…Biogeochemical processes, such as mineralization and denitrification, lead to the fractionation of the initial composition of stable isotopes of nitrate. For example, during denitrification the δ 15 N:δ 18 O ratio of the residual nitrate evolves along a slope of approximately 1:2, which is frequently used as evidence that denitrification has taken place (Aravena and Robertson, 1998;Böttcher et al, 1990;Sacchi et al, 2013). Since the described biogeochemical processes mainly occur in soil, soil acts as reactor for nitrogen transformation and needs to be included into nitrate-source studies.…”

Groundwater vulnerability assessment: from overlay methods to statistical methods in the Lombardy Plain area

“…In particular, occurrence of denitrification in the southern sector of the Lombardy Plain area has been identified and confirmed by Sacchi et al (2013). The explanation can be found in bio-geochemical conditions of the vadose zone.…”

“…An increase of nitrate concentrations correlated to the increase of groundwater depth has been observed at different scales, from the field dimension (Best et al 2015), to subbasins (e.g., Masetti et al 2008), to regional (Sacchi et al 2013) and country scales (e.g., Nolan et al 2002). In particular, occurrence of denitrification in the southern sector of the Lombardy Plain area has been identified and confirmed by Sacchi et al (2013).…”

“…This is due to the combined presence of (a) extensive urban and industrial areas with high population density, as nitrate sources, (b) high permeability of both the unsaturated and the aquifer zones and (c) the great depth of the water table. Such conditions do not favor denitrification processes (Sacchi et al 2013). Extensive agricultural fields, where fertilizers and manures are intensively adopted, and point sources of pollution such as septic tanks or sewage characterize the southern sector.…”

“…Extensive agricultural fields, where fertilizers and manures are intensively adopted, and point sources of pollution such as septic tanks or sewage characterize the southern sector. Despite these nitrate sources, the combined presence of low permeable sediments and shallow water table (Sacchi et al 2013) or redox conditions (Pilla et al 2006) creates the favorable conditions to denitrification. Thus, contrary to Beretta et al (2005), the southern sector of the Lombardy Plain is less vulnerable to nitrate contamination.…”