DISTRIBUTION OF TRACE-ELEMENTS IN SOIL FROM REPEATED SEWAGE-SLUDGE APPLICATIONS

We studied the horizontal and vertical distribution In a soil profile (Metea sandy loam; loamy, mixed, mesic Typic Hapludalf) of trace eleme nts as a result of their loading at phytotoxic levels to cropland. Mun icipal sludges containing high concentrations of Cd, Cr, Cu, Ph, Ni, a nd Zn were applied to cropland from 1977 to 1986 at three rates plus a n untreated control. Total elemental analysis of soils collected in 19 89 and 1990 indicated that lateral distribution of trace elements had occurred, This lateral distribution was most likely a result of the ph ysical movement of! soil particles with agronomic operations, We eleme nts, however, were not distributed below the sampling depth of from 15 to 30 cm, Mass balance calculations resulted in average trace element recoveries that ranged from 45 to 155% of the total applied. These ca lculations were highly variable, indicative of the highly variable nat ure of sludge composition, lack of total uniform sludge applications, soil movement due to tillage operations, and sambling methods. Because of the potential errors associated in mass balance calculations, reco veries that have been calculated in this and other studies that deviat e substantially from 100% should reasonably he expected, Direct examin ation of the relatively few ways in which trace elements are lost from a soil (i.e., plant uptake, soil movement via tillage, water and wind erosion, and deep leaching) may he more meaningful than mass balance calculations to determine the fate of trace elements applied to soil.