TRACE ELEMENT ACCUMULATION, MOVEMENT, AND DISTRIBUTION IN THE SOIL PROFILE FROM MASSIVE APPLICATIONS OF SEWAGE SLUDGE

Abstract

Sewage sludge was added annually, for a 3-year period, to a series of field plots. Application rates varied from 0 to 225 metric tons per hectare per year. The sludges were mixed into the surface 20 centimeters of soil and, in general, increased the amounts of HNO3-extractable heavy metals. The availability of metals added to soils by sewage sludges, as measured by DTPA extractions, showed cadmium, zinc, lead, and copper to be highly available, manganese, cobalt, and nickel to be moderately to slightly available, and iron and chromium to be relatively unavailable. Despite a marked increase in acidity, where a sludge high in metal was added to the soil, increased metal availability and metal movement in the soil were predominantly limited to a depth of 30 centimeters, or 10 centimeters below the area of sludge incorporation.