Heavy metal contamination in soils developed on igneous and sedimentary rocks in northwest of west Azarbaijan province.

Amount of elements in soil affected by parent materials and geochemical and pedogenesis processes. Many studies done about heavy metals concentration in different parent materials and developed soils on them in the world. Mean concentration of elements in soils are similar to mean concentration of them in parent materials, mostly. Difference between element concentrations in parent material and soils developed on them in natural conditions, is derived from pedogenesis processes. Due to the soil pollution with heavy metals is almost permanent and local in any region, this research done about trace element concentration in surface soils with different parent materials in northwest of west Azarbaijan province.

Concentration of some trace elements in 105 surface soil samples developed on 8 different rock mass (Granite, Andesite, Basalt, Ultrabasic, Marl and sand stone, Ghom formation, Lime and Shale) from back slope position, and also their concentration in rock samples in northwest of west Azarbaijan was determined by atomic absorption method. Geo- accumulation index used to estimation of soil contamination to heavy metals.

Highest amount of clay was observed in soils derived from Andesite and Basalt and then sedimentary rocks. Highest amount of total Fe (27231.25 mg/kg), Mn (730 mg/kg), Cu (28.5 mg/kg) and Zn (50.25 mg/kg) was observed in Andesite rock. Total Ni (1937.50 mg/kg), Co (92.50 mg/kg) and Cr (786 mg/kg) is more in ultrabasic rock compared to other rocks. The highest and least concentration of soil total Fe was observed in soils developed on ultrabasic (22062.42 mg/kg) and Ghom formation (6885.42 mg/kg) parent materials, respectively. High Mn concentration is in soils derived from igneous rocks. The highest of Cu (53.17 mg/kg) and Zn (67.75 mg/kg) concentration was observed in soils developed on Andesite and Granite rocks, respectively. Amount of Ni (1667 mg/kg), Co (94.89 mg/kg) and Cr (304.09 mg/kg) in soils derived from ultrabasic parent material is more than others. Positive and significant correlation was observed between studied trace elements in soils and parent materials.

Significance of the entry of trace elements in region soils is parent materials. Fe pollution in soils was not observed compared to global soils, but some of soils were infected to Mn element. Also, most soils were affected to Ni and about of half of them to Cr and Co in the region according to Iran̕̕̕ʼs standard. Keywords: Contamination, Trace elements, Igneous rock, Sedimentary rock, Surface soil.