Effect of clay on the fractions of potentially toxic elements in contaminated soil

The aim of the study was to evaluate the effect of clay as an amendment to decrease the mobility and plant availability of potentially toxic elements (PTEs). Kaolinite and vermiculite were added at a 9% application rate to a contaminated garden soil from Kutna Hora. Half of the original soil was acidified by the addition of HNO3, to observe the effect of the pH on the adsorption of the PTEs. The samples were analysed four times over an eight-week period to evaluate the effect of the clay additions on the As, Cd, Pb and Zn plant availability and different fractions of the BCR sequential extraction. The results indicate that the PTEs were mainly bound by ion/cation exchange on the edges of the clay minerals and onto the Fe/Mn oxides and organic fractions in the soils. The significance (P < 0.05) of the pH was observed for the plant availability of the PTE, especially on the As and Cd. A comparison of the vermiculite in the form of chunks and as powder displayed the most statistically significant results, where the vermiculite powder significantly decreased the plant availability of the As, Cd and Pb, while the opposite effect was observed for the Zn.