Adsorption-desorption and leaching behavior of diuron on selected Kenyan agricultural soils
Boniface M. Muendo,
Victor O. Shikuku,
Zachary M. Getenga,
Joseph O. Lalah,
Shem O. Wandiga,
Michael Rothballer
Affiliations
Boniface M. Muendo
Department of Chemical Science and Technology, Technical University of Kenya, P.O Box 52428-00200, Nairobi, Kenya; Kenya Bureau of Standards, P.O. Box 54974-00200, Nairobi, Kenya
Department of Physical Sciences, Machakos University, P.O. Box 136-90400, Machakos, Kenya
Joseph O. Lalah
Department of Chemical Science and Technology, Technical University of Kenya, P.O Box 52428-00200, Nairobi, Kenya
Shem O. Wandiga
Department of Physical Sciences, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
Michael Rothballer
Helmholtz Zentrum Munchen, German Research Centre for Environmental Health (GmbH), Department of Environmental Sciences, Research Unit Microbe Plant Interactions, 85764 Neuherberg, Germany
In this work, the adsorption-desorption dynamics of diuron in three typical Kenyan agricultural soils, Nzoia (NZ), Thika (TH) and Machakos (MK) was investigated. The equilibrium adsorption data, tested against three classical nonlinear adsorption isotherms, was best described by the Freundlich model. The Freundlich adsorption constant, (KF), increased in the order MK > TH > NZ soil. Additionally, the negative Gibb's free energy values indicate the adsorption processes were thermodynamically spontaneous and physical. Multiple linear regression analysis indicated that the adsorption-desorption behavior was controlled by the clay and phosphorus contents of the soil. Phosphorus negatively affected the adsorption of diuron and promoted desorption. The groundwater ubiquity score (GUS) indicated that diuron movement rating in MK soil was ‘moderate’ while the movement in TH and NZ soils was ‘high’.
