Relationship of soil characteristics in different geomorphic surfaces with spatial variability of soil arsenic (Case study: Bijar, Kurdistan Province)

In order to investigate the sources of arsenic contamination and assessing the role of geomorphic properties on its distribution in Bijar area, 83 profiles were selected based on the prepared geopedology map and 227 soil and 20 water samples were collected. Routine physical and chemical characteristics, iron oxides and soil arsenic contents were measured in 227 samples. Arsenic probability risk was computed using indicator Kriging (IK) to assess the arsenic (As) contamination potential. Topsoil arsenic concentration showed significant correlations at the level 0.01 with clay (r=0.77), sand (r= -0.45), silt (r= -0.48), CEC (r=0.65), and Fe oxides (r=0.65) statistically. Subsoil arsenic concentrations showed similar correlations with soil properties. Significant differences in clay, silt, sand, Fe2O3 percentages and CEC in arsenic source landforms with Fe- rich rock and mud stone have led to their higher arsenic concentration compared to the other landforms. Arsenic content of water resources located at higher altitudes were lower than EPA and WHO guideline level, while the opposite was true (2-130 times) about the landforms located at lower altitudes. The distribution of high arsenic areas rasterized by IK confirmed that, from the arsenic sources (arsenic source landforms with Fe- rich rock and mud stone), the arsenic is spread to lower positions by erosion-deposition processes or soluble form. Soils with such concentrations of arsenic may be hazardous for human being and ecosystems.