Effects of Land Use and Land Cover on Concentrations of Heavy Metals in Surface Soils of Lesser Zab River Basin, NE Iraq

Abstract

To investigate and assess the effects of land use and land cover (LULC) on concentrations of heavy metals in the surface soils of Lesser Zab River Basin (LZRB), 25 surface soil samples were taken from different LULC classes. Heavy metals concentrations were measured and their enrichment factors were calculated. Most of the LZRB soil samples are moderately alkaline with pH>8 and characterized by low organic content. The average abundance of the major oxides follow the decreasing order of SiO2 % > CaO % > Al2O3 % > Fe2O3 %> MgO > K2O % > TiO2 % > Na2O % > SO3 % > P2O5 %. A correlation matrix revealed that clay and feldspar minerals, Fe and Mn oxides / hydroxides are the most important carrier phase for several heavy metals as their correlation of high significant values. The average values of the heavy metal contents are arranged in the following decreasing order: Mn> Cr> Ni>Zn> Cu> Co>Pb>Cd. The LZRB soils exhibits concentration higher than direct geochemical background (DGB), and lower than indirect geochemical background (IGB) and there is a clear difference in the accumulation of heavy metal in soils under different LULC classes. The highest accumulation of heavy metals has been found in agricultural land and next highest concentration in urban and built up land. Assessment of soil contamination is conducted using enrichment factor (Ef), contamination factor (Cf), and contamination degree CD. According to these factors the soils of LZRB showed no or minimal contamination for most metals in different LULC classes.