Transport of copper oxychloride-based fungicide particles in saturated quartz sand.

Intensive use of copper-based fungicides in agriculture causes contamination of subsurface environment. While the transport of dissolved copper in porous media has been widely studied, transport mechanisms of particles of copper-based fungicides are poorly understood. This paper reports the results of tests involving the transport of colloid-size particles of a copper oxychloride-based fungicide (COF) in water-saturated quartz sand columns under varying electrochemical and hydrodynamic conditions. The effect of the ionic strength on colloid attachment and exclusion suggests that interactions of COF in water depend on the characteristics of the diffuse layer. Hydrodynamic shear influences the deposition of fungicide particles, indicating that attachment forces are weak. Particle deposition dynamics was well-fitted with the two-site kinetic attachment model, which reflects the heterogeneity of the quartz surface. Retention also occurs for unfavorable electrochemical conditions, which was attributed to stagnation zones arising from the physical and chemical heterogeneity of the quartz surface.