Transfer and degradation of the common pesticide atrazine through the unsaturated zone of the Chalk aquifer (Northern France)

Ningxin Chen (1) , Danièle Valdes (1) , Christelle Marlin (2) , Pierre Ribstein (1) , Fabrice Alliot (1) , Emmanuel Aubry (1) , Hélène Blanchoud (1)

1 METIS - Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols
2 GEOPS - Géosciences Paris Sud

(Saint-Martin-le-Noeud), which provides a direct access to the water table and intercepts the unsaturated zone at different depths. The lake and the ceiling percolation of 16 sites throughout the quarry were followed. For 16 sites, the percolating flow rate and lake level were measured and the lake water was sampled for nitrate, atrazine and deethylatrazine (DEA, main degradation product of atrazine) analysis over 2.5 years. High spatial variations in hydrodynamics (percolating flow rate and lake level) and in lake water quality (atrazine between and ng and DEA between and ng ) indicate that the properties of the unsaturated zone influence the transfer and the degradation of atrazine. A counterclockwise hysteresis characterizes the relationship between the lake level and atrazine concentration. Temporal variation shows that the atrazine is transferred through the matrix and fractures with a delay caused by the sorption process that differs in atrazine and DEA. The layer of clay-with-flints is shown to favor the degradation of atrazine near the surface. Preferential pathways may be created below clay-with-flints, through which the transfer of atrazine is quicker.

Domaines: Planète et Univers [physics]; Sciences de la Terre

Ningxin Chen, Danièle Valdes, Christelle Marlin, Pierre Ribstein, Fabrice Alliot, et al.. Transfer and degradation of the common pesticide atrazine through the unsaturated zone of the Chalk aquifer (Northern France). Environmental Pollution, 2019, 255, pp.113125 (IF 5,98). ⟨10.1016/j.envpol.2019.113125⟩. ⟨hal-02319621⟩