The effect of glyphosate on lead mobility in soil and extraction of heavy metals from soils using accelerated solvent extraction.

摘要

The objective of the first study was to determine whether glyphosate affects the mobility of lead in soils by preventing direct binding to clay minerals. The proposal was that free glyphosate would complex lead through the phosphonate moiety and that bound glyphosate would also complex lead through the amine and carboxyl oxygen, thus making lead more susceptible to leaching.; Three reference soils were treated with Pb and glyphosate at varying pH (2, 4, 6, and 8) to determine any effect that glyphosate might have on Pb adsorption. Two soils common in middle Tennessee (Baxter and Maury soils) were treated with Pb and glyphosate and left outside for 16 weeks to determine if glyphosate influenced the leaching of Pb by rainwater.; Glyphosate decreased Pb adsorption in one reference soil for all experimental pH levels but increased Pb adsorption in another for all experimental pH levels except pH 8. Less Pb was adsorbed at higher pH in the presence of glyphosate. In the environmental experiments with Pb+2, glyphosate added prior to Pb+2 increased the content of Pb in rain leachate for the Baxter soil after the initial rain and for all of the Maury soil. Glyphosate increased the leaching of Pb from Pb shot in both the Baxter and Maury soils, although leaching was more pronounced in the Maury soil. Results indicate that the application of glyphosate to agricultural fields with Pb shot present can cause Pb leaching into groundwater.; The object of the second study was to determine whether a metal chelator in organic solvent could be used to selectively extract heavy metals from soils. Di-(2-ethyl)hexyl phosphoric acid (HDEHP) in octanol and Dipex RTM in butanol were tested with several reference soils. The study determined that a phosphoric acid derivative would be a poor choice for use in soils due to the affinity of the phosphonate group for iron and aluminum hydroxides in clay minerals.