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Kinetic sorption and column miscible displacement transport experiments were performed to quantify the extent of retention and the mobility of Ni in different soils. Results from kinetic sorption indicated that sorption of Ni was time dependent and highly nonlinear, with the sorption affinity of Webster loam (a fine-loamy, mixed, superactive, mesic Typic Endoaquoll) > Olivier loam (a fine-silty, mixed, active, thermic Aquic Fraglossudalf) > Windsor sand (a mixed, mesic Typic Udipsamment). A multireaction and transport model (MRTM) was capable of describing the observed nonlinearity and time-dependent adsorption of Ni for all the soils. Column transport experiments showed that Ni mobility was strongly retarded, with extensive tailing or slow release during leaching. In the Webster soil, breakthrough results revealed that Ni was highly immobile, where <20% of the applied Ni was mobile. In contrast, for the Olivier and Windsor soil columns, 50.4 and 68.3%, respectively, of the applied Ni was recovered in the effluent solution. The MRTM model that accounted for nonlinear reversible kinetics and irreversible reactions is recommended to describe Ni transport in the soils, and incorporation of reversible equilibrium reaction was not necessary. Moreover, the model adequately predicted the Ni distribution with depth in the columns subsequent to pulse application and leaching.
Abbreviations: BTC, breakthrough curve; MRTM, multireaction and transport model.
(ProQuest: ... denotes formulae omitted.)
Heavy metals in soils pose serious threats to the ecosystem through groundwater contamination, plant uptake, and accumulation in the food chain. The mobility, bioavailability, and toxicity of Ni in soils is highly dependent on its affinity to bind with different reactive surfaces in the soil matrix and pore water such as particulate and dissolved organic matter, clays, or oxide surfaces (Dijkstra et al., 2004; Sauve et al., 2000). Th us, understanding of the complex interactions of Ni in the environment is a prerequisite in the effort to predict their behavior in the vadose zone.
Several soil properties influence Ni adsorption, desorption, and equilibrium between the solid and solution phases. These factors include soil pH, clay content, organic matter, cation exchange capacity, and Fe and Al oxides. Specifically, chemical and physical processes occurring at different reaction sites in the soil solution phase control the level of a heavy metal in solution and its transport, therefore infl uencing the...