INVESTIGATION OF POTENTIALLY TOXIC HEAVY METALS IN AGRICULTURAL SOILS AND WHEAT SEED BY USING FLAME ATOMIC ABSORPTION SPECTROSCOPY

<strong>ABSTRACT </strong>Heavy metals are among the most serious environmental pollutants due to their high toxicity. The purpose of this study was to investigate the concentration of selected heavy metals in the agricultural soil and wheat seed in research area by using FAAS techniques. Composite soil sampling method was used to collect 36 representative soil samples from three sampling areas. Corresponding to each area 360gm representative sample was partitioned using quartering method and put in clean polyethylene plastic bags. Totally 900gram of wheat seed were purchased from three farmers in the research area and 150gm of each sample was taken as representative samples and put in clean polyethylene plastic bags. Each soil and wheat seed were labeled and each sample were separately packed in a cardboard box and transferred to Arbaminch University, chemistry laboratory for elemental analysis. Prior to FAAS analysis of the soil and wheat seed samples HCl, HNO3, HCLO4 and H2O2 acid were used to determine the optimum digestion condition. wet digestion was applied using 4:5:1 (v/v) of acid for soil and micro wave digestion was applied using 5:1:1 (v/v) of acid for wheat seed sample, 1gm of mass and 180 min at temp‘ 300 o c conditions were used for optimum digestion of samples. The Pearson‘s correlation (R2 ) indicated good positive correlation. The % recovery found in the range of (96.19 – 99.62) in soil and (99.7 – 100.23) in wheat seed. Transfer factor were found in (0.048 – 0.476). The mean concentration level (in mg/l) of the analyte heavy metals in the research area were [Pb (4.34034 ± 0.1447), Cd (0.1212 ± 0.0187), Cu (1.7849 ± 0.1134), Co (0.5962 ± 0.0590) and Mn (0.4048 ± 0.1184)] in agricultural soil, [Pb (3.3403±0.0127), Cd (0.0182±0.0017), Cu (0.7049±0.0104), Co (0.0507±0.0030) and Mn (0.2038±0.0012)] in control soil samples and [Pb (0.2115 ± 0.2036), Cd (0.0577 ± 0.0474), Cu (0.1252 ± 0.0998), Co (0.0434 ± 0.0261) and Mn (0.034 ± 0.0158)] in the wheat seed. This study showed that the agricultural soil is contaminated but not polluted as compared with the results of the control samples and the maximum allowable limit set by WHO and FAO.