The Effect of Low-Molecular-Weight Organic Acids on Cadmium Assay Using Diffusive Gradient in Thin Film Technique

Low-molecular-weight organic acids (citric, acetic and oxalic), which are common in soil solutions, decrease accumulation and diffusion flow of cadmium. The flows depend on the amount and type of organic acid in solution. The order of focused acids according to the degree of diffusion retardation is: acetic < oxalic < citric acid. The relative diffusion flow (Fr) was obtained as the gradient of the time dependences of real amounts of accumulated Cd. From Fr and real flow of free Cd, the kinetic flow was calculated, which characterizes the retardation impact of the acids on cadmium diffusion.