An experiment over a period of 14 months was carried out on duplicate undisturbed
cores of 3 soils, with different textures using one sludge in order to obtain more
information on the vertical movement of heavy metals through sludge treated soil.
Over the first 8 months the pH values were in this order : sandy silt loam > sandy
clay> loamy sand of both control and sludge amended soils. The rainwater pH values
during the first 8 months were acidic, but during the following six months, they
increased loan alkaline value. At the end weathering, it was found that only the
amended surface and upper layers contained elevated concentrations of heavy metals.
Thus the nature of soil was an extremely important factor in the downward
movement of constituents. It appears that a guideline for sludge application to land
the pH of soils should be maintained at or above 6.5. Groundwater pollution was
likely to be the greatest in highly permeable sandy soils and these should not be used
for the application of heavy metals. Soil water influenced the chemistry of surface
waters and this affected the survival of fresh water fauna and flora.
J. Nouri , B. J. Alloway and P.J. Peterson , 2001. The Vertical Movement of Cadmium, Nickel and Lead Through Undisturbed Cores Having a Surface Amended of Sewage Sludge. Journal of Biological Sciences, 1: 986-988.