An Investigation of Heavy Metals in Canola and Soil of Farms Irrigated with Wastewater of the Industrial City of Amol

To study the effects of industrial effluents on accumulation of heavy metals in soil and cultivated canola, the farms irrigated with the wastewater of Amol Industrial City were selected and samples of wastewater, irrigation water, soil, roots, stems, leaves, and grains of canola were collected. Then, the amount of chromium, cadmium, nickel and lead in samples of soil, water and canola organs were determined. The data were analyzed based on statistical factorial analysis in complete randomized block design. Mixing of industrial wastewater with irrigation water increased concentrations of chromium, cadmium, nickel and lead in irrigation water. pH of irrigation water decreased under the effect of industrial wastewater, although EC increased. Industrial wastewater also increased the accumulation of heavy metals in soil. Accumulation of available chromium was affected by wastewater in locations 1, 2, and 3, increasing to 0.11, 0.14 and 0.13 mg/kg, respectively. Accumulation of elements in the surface layer (0-20 cm) of soil was more than the subsurface (20-40 cm). Amounts of total and available cadmium in surface layer of soil in the control site were 1.07 and 0.1 mg/kg, which was affected by wastewater, with the greatest increase in the third location reaching 1.48 and 0.16 mg/kg. Also, nickel and lead increased by wastewater. Accumulation of Cr, Cd, Ni, and Pb in rapeseed organs increased by wastewater application. Accumulation of Cr in leaves and shoot of canola in the second location increased by, respectively, 57.45% [S1] and 2.62 times compared to the control. Transfer factor of metals from soil to shoot was more than the other organs. Accumulation of chromium and nickel in canola leaves exceeded the permissible level. Risk Index of the investigated elements in canola grain increased by irrigation with industrial wastewater. Accumulation of cadmium in canola grain reached dangerous levels.



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