Pb2+ and Zn2+ adsorption by a natural aluminum- and iron-bearing surface coating on an aquifer sand

Pb²⁺ and Zn²⁺ adsorption was studied in batch experiments with material collected from a shallow, unconfined aquifer of glacial outwash sand and gravel in Falmouth, Massachusetts, USA. The aquifer solids contain primarily quartz (95% w/w), with minor amounts of alkali feldspars and ferromagnetic minerals. Pb²⁺ and Zn²⁺ adsorption experiments with various grain size and mineral fractions of the aquifer solids showed that (1) Zn²⁺ adsorption was independent of grain size, but Pb²⁺ was preferentially adsorbed by the