Copper Reactivity and Mobility in Acidic and Alkaline Soils: Modeling the Distributions Versus Soil Depth.

In this study, Sorption-desorption batch and miscible displacement column methods were used to assess the reactivity and predicate mobility of copper (Cu) in acidic and alkaline soils.  Two soils were used a Windsor loamy sand surface soil from New Hampshire and Bustan sand surface and subsurface soils from Northwestern Egypt.  Variations in soil pH, calcium carbonates and oxides content influence Cu retention and mobility in all studied soils. Cu isotherms exhibited nonlinearities and nonsingularity. Higher affinities of Cu on alkaline soils compared with acidic Windsor soil were observed.  Very limited Cu mobility was occurred in alkaline soil (recovery < 1%) whereas 11.8 % recovery of applied Cu was obtained for acidic soil. Applying longer time pulse depicted higher Cu mobility in Bustan soils, specifically 27.0 % and 59.6 % recoveries of applied Cu were obtained for Bustan-surface and Bustan-subsurface soils, respectively. Additionally, removing CaCO₃ from Bustan-surface soil led to increase Cu mobility and change the pattern of Cu distribution versus soil depth. A multireaction and transport model (MRTM) provided good simulations for breakthrough curves (BTCs) of Cu and satisfactory predictions of sorbed Cu versus depth for all studied soils. Moreover, results based on sequential extractions supported the occurrence of several interactions of Cu with soil matrix surfaces during transport in soils.

 Keywords: Cu; Advection dispersion equation; MRTM, sequential extraction