TRACE METAL SOLUBILITY AND SPECIATION IN A CALCAREOUS SOIL 18 YEARS AFTER NO-TILL SLUDGE APPLICATION

Abstract

To understand the long-term fate of heavy metals applied to agricultural soils via sewage sludges, it is necessary to measure metal speciation and solubility in the soil for many years after application. With this as our objective, we measured total and dissolved trace element concentrations, including potentially toxic heavy metals, in the contaminated 0 to 5-cm surface soil layer of a long-term, no-till continuous bromegrass experiment about 18 years after the last application of three chemically different sewage sludges. For each particular sludge, long-term heavy metal solubility was generally linearly correlated to the remaining heavy metal concentration in the soil, with the nature of the sludges applied affecting the partition coefficient (KD) for some elements and heavy metals. Most of the dissolved Cu and Pb (generally >75%) was not labile by anodic stripping voltammetry (ASV), indicating a high degree of complexation of these two metals by soluble organic matter. A smaller degree of complexation (