Copper Distribution and Dynamics in Acid Vineyard Soils Treated With Copper-Based Fungicides

Vineyards often receive large amounts of copper salts as fungicide treatments. This study investigated the presence, form distribution, adsorption-desorption dynamics, and transport of copper in 20 acid vineyard soils from northwest Spain. Total copper concentration varied considerably but exceeded 100 mg kg−1 in 60% of the soils. Large proportions of total copper were associated with organic matter and with amorphous inorganic oxides. Despite the existing high copper concentrations, all soils showed a strong capacity to adsorb additional copper, and in all cases less than 8% of this additional copper was subsequently desorbable. Maximum adsorption (Xm, as obtained by fitting the Langmuir equation) was strongly dependent on organic matter content and on iron oxide content. Copper breakthrough curves obtained in transport experiments using saturated and unsaturated columns were either predicted satisfactorily or were reproduced using models assuming Langmuir-type sorption with the parameter values obtained in the earlier adsorption-desorption experiments, whereas incorporation of the corresponding Freundlich parameters in models assuming Freundlich-type sorption afforded curves that were either too steep (in the case of the saturated column) or premature (in the case of the unsaturated column).