Accumulation of Pb and Cd in tissue of leek (Allium ampeloprasum persicum) and peppermint (Mentha piperita) treated with sewage sludge of Qods town's treatment plant, Tehran

This study was carried out to investigate the accumulation of Pb and Cd in tissue of leek (Allium ampeloprasum persicum) and peppermint (Mentha piperita) treated with municipal sewage sludge of Qods town’s treatment plant, Tehran. For this purpose, after soil preparation, sampling of sewage sludge and assessment of the physicochemical properties of the samples, leek and peppermint plants were divided as treatment and control groups. Afterwards, using ICP-OES the concentrations of Pb and Cd were determined in the tissues of peppermint and leek. Results showed that the concentration (mean ± SD) of Pb in the control and treatment groups was 0.26±0.08 and 0.55±0.16 mg/kg, respectively. Pb concentration in peppermint samples was estimated as 0.26±0.06 and 2.41±0.79 mg/kg for control and treatment group, respectively. Moreover, the mean concentration of Cd in control and treatment groups of leek was 0.083±0.003 and 0.26±0.05 mg/kg and for peppermint 0.057±0.002 and 0.14±0.02 mg/kg, respectively. Comparative evaluation of the evaluated treatments showed that except for Cd in leek and peppermint treatment samples, the mean concentrations of Pb and Cd in both vegetables were significantly lower than EPA permissible limits for human consumption. The results of this study indicated that for reducing the health risks of long-term use of sewage sludge as fertilizer, further monitoring should be performed.