Distribution of zinc and copper chemical forms and their relationship with some physico-chemical properties and clay minerals in some calcareous soils

Determination and recognition of relative distribution of chemical forms of each element and their relationship with physical, chemical and soil clay minerals can help researchers to manage soil fertility better. This research attempted to recognize chemical fractions of zinc (Zn) and copper (Cu) in some surface and subsurface soil samples of Kohgiluyeh and Boyer-Ahmad province and their relation with physico-chemical properties and clay minerals. In order to carry out this research, surface and subsurface soil samples were collected in different physiographic units of the province and chemical fractions of Zn and Cu were measured by sequential extraction method and ultimately their relationship with different soil characteristics was investigated. Results showed that exchangeable and sorbed chemical fractions of Cu and Zn in all soil samples were lower than the detection limit of atomic absorption spectroscopy. Distribution of chemical fractions of both Zn and Cu followed the order: residual> carbonate> organic fractions. The low and medium mobility factor of Zn and Cu, respectively, in the studied soils indicated the different behavior of these elements in calcareous soils. Among all soil physico-chemical characteristics, organic carbon showed more obvious effects on controlling the chemical fractions of Zn. On the other hand, chemical fractions of Cu showed significant correlations with clay and silt content, as well as cation exchange capacity. The correlation between the clay minerals content with chemical forms of these elements showed that the amount of different forms of Zn and Cu is directly related with 2:1 clay minerals (especially vermiculite).