An Investigation on Soil Pollution in Siahrud River Catchment Area

Investigation on soil pollution in Siahrud River catchment area indicated that concentration of heavy metals are within permissible limits set by various international bodies. Though the concentration of Cr is higher than the permissible levels set for plants in the Parchinak area but cluster analysis showed lithogenous source for this element in the area of study. It should be noted that concentration of As in east farms of Joybar, Shourka, north of Larim and forest area in the south of Chapi area is higher than. Permissible levels and thus possibility of pollution hazards for plants and cattle is high. Though the concentrations of heavy metals are within the permissible levels but it should be noted that most of the studied metals have higher concentrations when compared with reference sample that was taken from inner part of forest where pollution does not prevail. Thus, it can be concluded that agricultural activities have been the main source of increase in the concentration of heavy metals in the area of study. Besides in some areas discharge of municipal sewage can further added to the concentration of heavy metals. The average concentration of organic matters in the agricultural soils of Siahrud River catchment area is about 5% that can lead to chelatation of heavy metals in the presence of PH more than 7. This phenomenon can prepare suitable ground for adsorption of metals by plants in a much easier way. However, such phenomena has not only lead to plant pollution as the concentration of studied elements falls within permissible levels but also may sometimes supply essential elements for the growth of plants.