Accumulation of heavy metals in agricultural products irrigated with treated municipal wastewater

Aims : 

The aim of this study was to measure the concentration of Pb, Cd, and Ni in the effluent of Isfahan north wastewater treatment plant as well as in the soils and agricultural products irrigated with that effluent. 

 In the selected area around of the treatment plant, treated wastewater, soil, wheat, wheat stem, and corn were sampled. The samples were digested with nitric acid procedure and analyzed with a flameless atomic absorption spectrometer. 

 The results shows the average concentration of Pb, Cd, and Ni was 0.02, 0.006, and 0.062 mg/1 in the effluent; 13.9, 1.67, and 2.23 μg/g in the deep soil; 0.366, 1.02, and 0.79 μg/g in the wheat; 0.67, 0.86, and 1.32 μg/g in the wheat stem; and 6.37, 0.62, and 0.52 μg/g in the corn, respectively. 

 The average concentration of Pb, Cd, and Ni were less than the critical limits in the effluent (0.01, 0.2, and 5 mg/1) and the amounts were currently within the permitted range for soil (2-100, 10-1000, and 10-7 mg/g). In some farming lands, the amounts were beyond the permitted range for plants (1-10, 1-10, and 0.2-0.8 mg/g). There was a meaningful relationship between the average concentration of these metals and the kind of sample. In addition, the accumulation of heavy metals in all samples irrigated with wastewater was more compared to samples irrigated with groundwater. So irrigation of farmland with effluent should be monitored. Farmers in the area must be advised to grow shrubs with smaller roots rather than big-rooted plants like sugar beet.