NO3 Nitrates and plant protection products can be usually found in the portion of plain where the agricultural activities are concentrated. Nitrates are essential plant nutrients. However, if nitrogen fertilizers are overused and soil is managed inappropriately, excessive amounts of nitrates can enter waterbodies. Nitrates either enter the soil through the application of farmyard manure or mineral fertilizers or arise as a result of the breakdown of organic materials by bacteria. Nitrates are highly soluble in water. Often, because not all the nitrates present in the soil can be taken up by plants, a proportion is leached out by rainfall into groundwater. Nitrates may also indicate the presence of other contaminants, such as pesticides or residues of veterinary medicines in liquid manure. The nitrate content of uncontaminated groundwater is less than 10 mg/l. In intensively farmed areas, however, concentrations are markedly higher. Regions with a high proportion of cropland, in particular, show nitrate concentrations in groundwater of more than 25 mg/l or even 40 mg/l (the tolerance value specified for drinking water).
Mean concentration of NO3 in the Lombardy plain over 50,0 mg/l 40,1-50,0 mg/l 25,1 - 40,0 mg/l less than 25,0 mg/l
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