Distribution of lead and chromium in soil and plants as affected by soil texture and amendments

A study was conducted to investigate the effect of sewage irrigation on the distribution of Pb and Cr in soil and plants. In laboratory the leaching of Pb and Cr as affected by soil texture and addition of organic matter (OM) and gypsum (CaSO₄.2H₂O) was studied. The concentration of Pb and Cr in municipal effluent was within the permissible limits. The concentration of Cr was four times higher than that of Pb. Contrary to this, the content of Pb was much higher than Cr in soils. Although still below safe limits, considerably high concentration of Pb and Cr in surface soil layer (0–15 cm) than that in the lower soil depths indicates their tendency to accumulate in the surface layer. In crops, the concentration of both the metals was above safe levels. Leaching of Pb and Cr remained low through soil columns. In leachate, removal of Cr remained about 10% of the added Cr and that of Pb about 4% of the added Pb. In combined application, both Pb and Cr showed synergistic effect on leaching of each other. Application of gypsum and OM inconsistently affected leaching and AB-DTPA extractable Pb and Cr in soil.