ZN. LEACHING FROM SOILS DURING INFILTRATION AND SURFACE RUN-OFF

Abstract

Public concern with environmental deterioration has heighte-ned support for the abatement of a number of waste disposal practices. The discharge of wastewater into surface water is specially coming under intensive scrutiny. In this regard disposal of wastewater on land appears to be an attractive alternative. However, among the main disadvantages associated with land appli-cation is the heavy metal ions contamination and their movement in the soil. Keeping this in view the present study concerns leaching of zinc ion salts in soil column. The investigation also includes a study on the leaching of zinc ion due to surface flow on soil containing zinc. Three different soil samples, on each from Solani river bed, University Campus and agricultural field were collected and analyzed. These soils were classified as fine sand and silty fine sand. The permeability of the campus soil and agricultural field soil is quite low and therefore these soil samples were considered to be suitable for surface run off studies. Solani sand having relatively a high value of permeability was used for column test. In the zinc leaching through water percolation five different zinc loads were applied to five different columns of same size and lap water was allowed to pass continuously at a constant flow rate, the run was also done in another sixth column without apply-i.ng any zinc externally. In the column sorption test, a solution of constant zinc concentration at constant flow rate was allowed to pass through a column of soil and the effluent was analy zed for the amount of zinc leached% The surface run off study consists of a tray with baffles , so as to increase the length of channel, and containing zinc embedded soil ( campus soil) over which water was allowed to flow through the channel at a constant rate and with a fixed retention time. The effluent was collected once in a day and analyzed for zinc leached. It is observed that the leaching of zinc is a function of time of run and the initial zinc load applied. Zinc leaches gradually with time attains maximum then decreases and attains equili-brium. The rate of zinc leach with applied zinc load and kinetics of the zinc leaching is also studied .