CONCLUSIONS - Hydrogeology: Objectives, Methods, Applications - page 316

Saline intrusions are diffi cult to control, and a return to initial condition
through the stoppage or reduction of pumping is not always possible.
4.2.2 Nitrates
The water of the Brittany and Normandy aquifers in western France does not
currently meet potability standards, due to an elevated nitrate concentration
tied to agriculture and particularly to the spreading of liquid hog manure
(see chap. C3.5). In the absence of new contamination, it is estimated that
it would take 30 years to return to initial conditions. In addition, given the
slow kinetics of migration below ground, the nitrate pollution front has not
yet reached aquifers everywhere.
4.2.3 Pesticides
The behavior of pesticides below ground remains poorly understood,
despite numerous studies, and the long term contamination risks are high. In
addition, the problem of identifi cation arises, as new products are regularly
offered by manufacturers.
4.2.4 Recent or unknown pollutants
Sanitation studies have revealed the existence of new types of pollutants
with the potential for serious consequences in terms of public health:
antibiotics and hormones, widely used in human and animal medicine.
They are passed into water by urine, they degrade very slowly, and their
concentrations are constantly increasing.
Finally, it is important to keep in mind that only what is looked for can
be analyzed and measured, and there are therefore very probably substances
in the water that have not yet been recognized at noxious, and which are
therefore not looked for during analysis.