Numerical modeling of glyphosate transfer to underground water: Application to the Djuttitsa watershed in the Bamboutos mountain, West-Cameroon

The world population increases at an alarming rate, with about 52% of this population expected to be found in urban areas in 2025. Africa has the highest population growth rate in the world, estimated as 2,55% each year from 2010 to 2015. By 2050, Africa is expected to represent about four quarter of the world's population estimated as 1,3 billion inhabitants (AFD, 2014). Therefore, modern agricultural practices become an important challenge for food security (Abass et al., 2016). To increase food yield, Africa is faced by an excessive usage of pesticides without respect of recommended doses and frequency of application (white and Bunn, 2017). Soil and water pollution are direct consequences of this, with levels more than the authorised levels of 0.1 and 0.5 for maximal concentration of an individual pesticide and the total of all pesticides in water (Sousa et al., 2018). This shift from normal concentrations can induce severe consequences on population health (cancers, infertility, developmental abnormalities, neurotoxicity) (Huang et al., 2018). Pesticides intoxication is estimated at about 1 to 5 million cases per year in the world, with about 220 000 deaths each year. Developing countries use only 25% of the pesticides produced in the world but they account for 99% of deaths in the world due to pesticides poisoning especially in rural areas. To follow the evolution of pesticides in the soil and evaluate the risk of pollution, researchers have developed some numerical transfer models. However, the use of these models remains difficult in Sub-Saharan Africa due to insufficient data and inability to get some parameters. In this study, we therefore developed a 1D numerical model which was tested to study the glyphosate transfer at the watershed of Djuttitsa in West region of Cameroon. Their validation was done after statistical comparison of concentrations obtained from the model to those from the laboratory.