Effect of Municipal Wastewater on the Accumulation of Heavy Metals Cadmium and Lead in Soil and Corn

Using wastewater as a renewable water source to irrigate plants is a safe and effective solution. In contrast, the accumulation of heavy elements in soil and plants is one of the concerns of the use of wastewater in agriculture. This study was conducted to investigate the effects of urban wastewater use on the most important physiological parameters related to the growth of corn (Zea mays L., KSC 704) and the accumulation of heavy metals lead and cadmium in the soil in a field Bushkan area of Dashtestan, Bushehr in a pot.

This study was performed in 4 treatments: wastewater of the treatment plant, wastewater diluted with drinking water (1/2), Irrigation one on one with wastewater and drinking water and drinking water treatment, in 3 replications in a completely randomized design. Lead (Pb) and cadmium (Cd) content in soil and plants were measured by ICP. pH and Electrical conductivity (EC) of soil and wet and dry weight of the Corn organs were measured. The means were compared using one-way analysis of variance (ANOVA), and the Duncan test was used to determine the differences between groups (p <0.05).

The results of this study showed that irrigation with EC wastewater increased the soil by 1.1 (ds.m-1), also increased soil cadmium by 0.03 (mg.kg-1) and lead by 0.02 (mg.kg-1). Dilution of the wastewater reduced the negative effects of the wastewater on the soil. The highest wet weight added of 1500 g was related to irrigation treatment with diluted wastewater. The highest dry weight added was observed with 600 g of irrigation treatment with diluted wastewater. The lowest total wet weight added of 1100 g and total dry weight added of 400 g were observed in the wastewater treatment.  The accumulation of lead and cadmium in the corn seed was (0.6 lead, 0.5 cadmium) <stem (0.9 lead, 0.8 cadmium) <root (lead 1.9, 0.95 cadmium), respectively. The highest accumulation of lead and cadmium was related to wastewater treatment and the lowest was related to drinking water treatment.

The higher the cadmium levels in the soil, the higher the concentration and content of cadmium in the roots and shoots. The results showed that the corn plant has a high ability to absorb and transport cadmium and lead. Due to the pattern of accumulation of heavy elements of lead and cadmium in the roots of corn, this plant can be used for accumulation of fields irrigated with wastewater. The continuation of this study is recommended to evaluate the long-term effects of municipal treated wastewater on the concentration of heavy elements in soil and plants, and soil properties, although it should be noted that based on technical recommendations, the use of treated wastewater are not recommended, however, in necessary cases, diluting of wastewater by reducing the destructive effects and providing the necessary elements for the growth of the Corn can be used as an indicator treatment in irrigation. Also, it is suggested that in order to use the wastewater in corn cultivation, while increasing growth and yield, the risk of using the wastewater in corn cultivation should be evaluated from an environmental point of view.