Principal Investigator: Gian S. Ghuman (Savannah State College)
Principal Investigator: Kamalakar B. Raut (Savannah State College)
Sponsor: GWRI
Start Date: 1988-06-01; Completion Date: 1989-07-01;
Keywords: ion exchange, soil erosion, solute transport, toxic substances.
Description:
During 1988-89, release of major and toxic (trace) metals from two soil types in coastal Georgia was studied regarding the impact of rainfall. Results were compared in the runoff water from plots under grass and forest vegetation. Leaching experiments were conducted to evaluate the effect of two leaching solutions on the downward transport of metals. Runoff water samples were collected from four field plots (4m x 4m) into plastic buckets via a spillway laid-out in the corner of each plot. Four periodic collections of samples of runoff water were made after significant rainfall events from August to September, 1988. Water samples were filtered through 0.45 mMillipore filters and their pH was adjusted to 2.0 for the estimation of metals by atomic absorption spectroscopy. Six sequential leachings were conducted in 40 cm long (6 cm I.D.) PVC columns packed with reconstructed field soil profiles to a depth of 36 cm. Two leaching solutions were, (i) deionized water adjusted to pH 6.5 with nitric acid, and (ii) deionized water adjusted to pH 5.0 with carbon dioxide. Exchangeable metals of the surface soil were determined in IN ammonium acetate extract. In both the runoff water and the leachates, there was greater removal of metals from forested soil than the grass-covered soil. Losses of K and Na far exceeded the losses of Ca and Mg. Release of K was consistent in both sandy and loamy soil plots probably due to K-rich minerals in coastal soils. Slightly high concentrations of Mn, Ni, Zn and Cu and low concentrations of Cd were released by both mechanisms (runoff and leaching), but all were below toxic limits. Removal of trace metals was greater by acidified water than by carbonated water. Ammonium acetate-extractable metals were diminished in the forested soil due to its lower pH than the grass-covered soil. Resutls are important for the maintenance of soil fertility and observing the quality of effluent water to prevent any toxicity.