District 21 of Tehran Municipality Soil Condition in Terms of Contamination with Some Heavy Metals

Increasing consumption of chemical compounds in industrial processes has led to the accumulation of pollutants, including heavy metals, which are very costly and difficult to absorb from the environment. The purpose of this applied research is to investigate the level of cadmium, chromium and lead contamination in the soil of western Tehran using pollution, enrichment and land geoaccumulation indices and pollution factors.

 In order to evaluate the concentration of heavy elements in the study area, sampling was done in all three areas of District 21 of Tehran Municipality and 10 samples from each area with three replications and a total of 90 samples were prepared in the spring of 2020 and the concentrations of cadmium, lead and chromium in Soltani acid extract was measured using an atomic absorption spectrometer. The present study is one of the descriptive-analytical researches and its data are of primary type which has been prepared by two methods of documentary and field studies.

The accumulation of these elements has been created in the surface soil. The mean concentrations of the studied elements in zones two and three were higher than one. The topsoil of area three had higher amounts of lead, cadmium and chromium than the other two areas, but these values were not significantly different from area two. The average amounts of lead, chromium and cadmium for the region were 38.1, 9.1 and 1.6 mg/kg, respectively. The enrichment index in zones two and three was more than one, but the numerical value of this index was less than one in zones one. Geoaccumulation index values for lead element in all three areas showed non-contaminated to slightly contaminated class and for cadmium and chromium showed non-contaminated class. The numerical value of the contamination factor, except for cadmium and in zone one, in other cases is one and more than one, which indicates the high concentration of these elements compared to the background concentration in the study area.

As a result of industrial and traffic activities, the accumulation of excess amounts of man-made elements in the study area has been created.