Abstract
Heavy metal contamination of soils is a widespread problem in Zanjan province located in North West Iran due to natural pedo geochemical background and anthropogenic sources. The province is highly polluted by some heavy metals due to the presence of mineral resources notably Lead and Zinc, their improper utilization, and also the development of a number of related industries. Bonab district was selected for detail study and the objectives of the study were set to evaluate the total as well as bioavailable fraction of heavy metals in surficial soils within the studied area. 72 soil samples were collected and analyzed for heavy metal contamination by Atomic Absorption Spectrometry (AAS). The obtained results when compared with WHO and USEPA standards show a very high concentration of some toxic metals. Soils were basically polluted by Pb, Zn, Cu, and Cd. Bioavailable fraction of studied metals were also measured with formation of metal complex with Diethylene tri amine penta acetic acid (DTPA) agent. To find the share of the anthropogenic sources in the contamination of soils, the Enrichment factor (EF) and Geological Accumulation Index were measured and the distribution maps were drawn using Arc GIS (9.3). Highest concentrations of some toxic metals were found as isolated patches around the Bonab Industrial Town as well as within and around the most populated areas of the district notably Zanjan city indicating its anthropogenic origin.
Highlights
Heavy metal contamination of soils is widespread and there is a risk of transfer of toxic and available metals to human, animals, and agricultural crops [1]
Bonab district was selected for detail study and the objectives of the study were set to evaluate the total as well as bioavailable fraction of heavy metals in surficial soils within the studied area. 72 soil samples were collected and analyzed for heavy metal contamination by Atomic Absorption Spectrometry (AAS)
Two main sources of heavy metals in soils can be considered: 1) the natural pedo-geochemical background, which represents the heavy metal concentration inherited from the parent rock [6] and 2) anthropogenic contamination, which can be directed via wastes, animal manure [7], compost [8], sewage sludge [9], or diffuse via aerosol deposition [10]
Summary
Heavy metal contamination of soils is widespread and there is a risk of transfer of toxic and available metals to human, animals, and agricultural crops [1]. In contrast with soils in agricultural areas, soils in urban environment, in parks and gardens, have a direct influence on public health not related with production of food. This is due to that they come in contact with humans and are transferred to them, either as suspended dust or by direct contact [5]. Two main sources of heavy metals in soils can be considered: 1) the natural pedo-geochemical background, which represents the heavy metal concentration inherited from the parent rock [6] and 2) anthropogenic contamination, which can be directed via wastes, animal manure [7], compost [8], sewage sludge [9], or diffuse via aerosol deposition [10]
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