the impact of anjir –tangeh coal washing plant on concentration of some heavy metals in the native vegetation, mazandaran province, iran

a large volume of tailings has been produced in anjir-tangeh coal washing plant for 22 years of human activity. the coal washing activities have reduced plant diversity near the plant. the environmental impact of coal washing plant on the vegetation around the factory was studied in two seasons. the concentrations of pb, cd and cr, measured in different native plant species, were in normal ranges in summer. in fall, the concentrations of pb, cd and cr in the plants around the factory were similar to those in plants in the control area. in summer, however, the metal concentrations were considerably higher in plants grown near the factory than in the plants of the control area. this difference was statistically significant at 0.01 levels for cd, but not for pb and cr. among the studied plant species, oxalis sphad the highest cd concentration (0.409 ppm), but chenopodium album l had the lowest cr concentration in summer. season was an effective factor in the uptake of heavy metals by plants; metal concentration in plants was considerably higher in fall than in summer.