Research School for Socio-Economic and
Natural Sciences of the Environment
Research School for Socio-Economic and
Natural Sciences of the Environment

Célia Martins Bento

Date: 22 October 2018
Time: 13:30 - 15:00

Dissertation title: 

Glyphosate and aminomethylphosphonic acid (AMPA) behavior in loess soils and off-site transport risk assessment

Group: Wageningen University, Soil Physics and Land Management
Promotors: Prof.dr. V. Geissen and prof.dr. C.J. Ritsema
Copromotors: Dr. J.G.J. Mol and M.J.P.M. Riksen

Extra information:


This PhD thesis investigates the glyphosate decay kinetics and AMPA formation and decay kinetics in loess soil, and their off-site transport by wind and water erosion. The PhD thesis results indicate that:

  1. glyphosate and AMPA decay in loess soils is fastest under warm and moist soil conditions and slowest under cold and dry soil conditions;
  2. AMPA persists longer in soil than glyphosate, and tends to accumulate;
  3. glyphosate decay kinetics follows both first-order and bi-phasic models, depending on temperature and soil moisture;
  4. glyphosate degradation into AMPA is extremely variable (5-100%), depending on temperature and on laboratory and field conditions;
  5. glyphosate and AMPA long-range off-site transport risk with wind erosion is very high;
  6. glyphosate and AMPA particle-bound transport with water erosion is as or even more important than their water-dissolved transport;
  7. glyphosate and AMPA deposition risk into off-target downslope fields during water erosion events can be considerable;
  8. because glyphosate and AMPA remain mostly in the soil surface layer, water and wind erosion play an important role in glyphosate and AMPA dynamics in loess soils.

The insights of this PhD research are a valuable contribution to and basis for environmental fate modelling studies, and can help in the redesign and improvement of the principles behind exposure and human health risk assessments.

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