Influence of Heredity and Soil Forming Processes on the Distribution of Heavy Elements and Physical, Chemical Soil Properties

This research aimed to evaluate the physical and chemical properties and distribution of heavy metals in soils with different parent materials in the central part of Zanjan province.

In this study, 15 developed soil profiles were excavated on Granite, Basalt, Andesite, Porphyrite, Volcanic tuff Limeston, Conglomerates, Shale, Phyllites, Sandstone, Dolomite and Alluvium parent materials. Then, Pedons were described according to the USDA Soil Conservation Services instruction and diagnostic horizons and their classification were conducted up to the great group category, in accordance with soil taxonomy (2014). Soils were classified in Mollisols, Inceptisols and Entisols orders. All of the genetic horizons of pedons and their bedrock (apart from alluvial deposits) were sampled. Also, whole of the laboratory analysis related to the physicaochemical properties of heavy elements was conducted by conventional and standard methods.

The amount of CaCO3 (49.3%) and pH (0.8) in Calcareous soil, organic matter (1.6%), cation exchange capacity (26 cmol(+)kg soil-1), clay (24.4%) and silt (61.9%) was maximized in soils with Andesite, Porphyrite, Tuff and Dolomite parent materials, respectively. The average of nickel, lead and cadmium were the highest value (56, 74.1 and 0.23 mg/kg soil, respectively) in dolomite parent materials soils. Chromium and iron showed the highest value (41.3, 34800, 27.5 mg/kg soil, respectively) in soils formed from Shale parent materials. Copper also indicated the highest value (47.2, 130.3 and 28.3 mg/kg soil, respectively) in Porphyrite parent materials soil. Finally, zinc and cobalt were the highest value (47.2, 130.3 and 28.3 mg/kg soil, respectively) in basaltic parent material soils.

Cluster analysis algorithm was classified the pedogenic A and B soil horizons in three groups: the first group consists of soils formed from Conglomerate-Shale, Shale and Limestone parent materials. Second group includes Porphyrite, Basalt, and Andesite parent materials soils and the third group consists of soils formed from Tuff, Phyllites, and Alluvium parent materials. The results did not change by adding the parent material horizon (C and Cr). So, the amount of major elements in pedogenic soil horizons is largely controlled by soil heredity.