Author: Wenzheng Du

Publisher:

Published: 1998

Total Pages: 348

ISBN-13:

The potential movement of heavy metals in soil beyond the application zone is a cause for public concern. Structural features of the argillic horizon in soils such as the Tuskeego (fine, montmorillonitic, mesic Mollic Oschraqualfs) would allow flow along the ped surface into the subsoil horizons. Experimental plots, which had received large amounts of Cu and Zn with 96 ton/acre sewage sludge application, were sampled 10 years after the applications and analyzed for Cu, Zn, and P. Samples of the vertical, horizontal, and internal structure surfaces of the Btg1 and Btg2 horizons samples were carefully removed with a knife. Total soil P, Cu, and Zn levels significantly increased in the Ap and BE horizons due to the sludge addition. Sludge addition did not significantly increase Cu or P concentrations along vertical or horizontal ped faces or in the ped interiors of Btg1 or Btg2 horizons. Sludge addition numerically, but not significantly, increased Zn concentrations in the Btg1 and Btg2 horizons. It was concluded that there was no Cu, Zn, or P movement into Btg horizons due to sludge treatment. Humic (HA) and fulvic (FA) acids were extracted from the surface soils of control and sludge-treated plots. Sludge treatment increased the amount of HA, had no effect on the C and N concentrations of HA, and decreased the total acidity and ash content of HA. Sludge treatment had no effect on the amount of FA, increased N concentration of FA, and decreased the total acidity of FA. Properties of HA and FA as indicated by infrared spectroscopy, scanning electron microscope (SEM) examination, or Cu and Pb stability constants were not altered by sludge addition. Potentiometric titration with ion selective electrodes and the Scatchard plotting method was used to estimate the stability of Cu and Pb complexes with citrate, HA, and FA in the solution phase. Based upon intrinsic stability constants the following conclusions were drawn: HA complexes with Cu and Pb were more stable than FA complexes. Cu complexes with FA and HA were more stable than Pb complexes. Increasing pH from 4 to 5 or 6 increased the stability of Cu and Pb complexes with citrate, FA, and HA, and the addition of Ca did not change the stability of citrate or HA complexes with Cu or Pb. The appearance of HA particles viewed by SEM was altered by pH, Ca, Cu, and Pb saturation, and whether the complexes were soluble or precipitated.