Relationships of Physico-Chemical Characteristics of Calcareous Soils of Qorveh Watershed with Soil Arsenic

Arsenic abundance in calcareous soils of Qorveh watershed, which is the most important agricultural region in Kurdistan Province, has caused arsenic pollution in agricultural products and water resources. In an attempt to investigate the relationships between arsenate (as less soluble fraction of soil arsenic) and the soils physico-chemical characteristics, eight pedons from the most polluted parts across the study area were sampled. Analysis of the results for the 38 soil samples revealed significant relationships between arsenate (considered as major less toxic fraction of soil arsenic) with sand, silt, organic carbon, free iron oxides, nitrate, and phosphate. The most significant relationship found was between arsenate and free iron oxides (r=0.748, α=0.01). Regarding the low quantities of free iron oxides among the studied soils, application of iron fertilizers or iron soluble compounds alongside with efforts to improve soil pH are recommended to reduce arsenic solubility and, consequently, arsenic pollution in the studied soils, while application of nitrate and phosphate fertilizers need to become limited as well.