Contamination of Soil, Water, Plant and Dust by Zinc, Lead and Cadmium in Southwest Isfahan

Due to mining, considerable amounts of heavy metal bearing mineralsare scattered in the atmosphere in the form of dust and make the surrounding air, water and soils polluted.Runoff water movingfrom the mountainstowardsplains may also transport heavy metals from mines to the soils.One type ofpollutions is contamination withheavy metals.The purpose of the present research has been to investigate the effect of heavy metals of mine on soil, water, plant and dust pollution.

Gushfil mine is located 3 kilometers southwest of Sepahanshahr, Isfahan. Soil profiles were dug 500 meters apart along three parallel transects, between east of Sepahanshahr and Gushfil mine. The profiles were described and samples were collected from their horizons. Ore, wells, plant and dust were sampled as well. Total concentrations of lead, zinc and cadmium were measured in the samples. To find the origin of polluted dust and soil, lead isotopes contents in the samples were measured and regressional relationships between the ratios of these contents were investigated.

Sepahanshahr soils are not contaminated by zinc, lead and cadmium, but within a distance of one to two kilometers from the Gushfil mine, the soils are polluted by zinc and lead. Cadmium contamination was not observed in the studied soils. In all of the soils, the heavy metals content varies downwards irregularly. The reason for this variation trend is that the studied soils are alluvial. In different periods of time, alluvium parent materials have been transported by runoff water from the lead and zinc mines towards the alluvial piedmont plain. The studied heavy metals have been distributed irregularly in different horizons of the soils that have been formed in these parent materials. Lead and cadmium concentrations of drinking water in the studied area are much higher than the maximum amount allowed by the World Health Organization. Cadmium content in all trees of the Sepahanshahr urban park and in alfalfa, lead content in olive trees and lead and cadmium concentrations in Holly hock (Althaea officinalis), Spurge (Euphorbiarigida) and Rhizome (Acanthe phylum bracteatum)are higher than dietaryallowance. Significant correlation between heavy metal concentrations reduction in dust samples and increase of distance from the mine expresses that contaminant heavy metals enter the atmosphere due to mine explosions. In dolomitic sandstone rich in sphalerite mineral, the total amounts of lead and zinc are maximum. The maximum amount of cadmium and too much lead and zinc were observed in a shale fragment, sampled from a location of a fault in the mine. Contents of the three metals were less in black and green shales, compared with the other samples. In dolomitic sandstone rich in gallon mineral, the amounts of the three metals are high and its lead content is maximum with respect to other rocks excluding dolomitic sandstone rich in sphalerite mineral. Significant correlation between ratios of lead isotopes contents of the rocks, soil and dust showed that the soils of the alluvial piedmont plain located at the footslope of the western mountains of the studied area have formed in alluvium parent materials originated from western mountains. The studied heavy metals have been transported together with these alluviums from the mine towards the alluvial piedmont plain. The other origin of these metals is the dust which is produced during the Gushfil mine explosions. This dust is translocated towards the Sepahanshahr and makes the surrounding environment of the mine polluted.

Origin of zinc, lead and cadmium in soil, water, plant and dust in the studied area is rocks of Gushfil mine. Transportation of these metals from the mine towards the environment can be explained by two mechanisms: 1) together with runoff water flowing from the western mountains towards the alluvial piedmont plain and 2) in the form of dust which originates from the mine and moves eastwards. The soils are not contaminated with cadmium. With increase of distance from the mine, contamination of lead and zinc decreases in soil and dust in such a way that in the Sepahanshahr soils, pollution of these metals is not observed. The soils located within a distance of 1 to 2 kilometers from the Gushfil mine are contaminated with lead and zinc. Water is polluted with lead and cadmium and the cadmium content of the plants is higher than dietaryallowance.