A new in situ method to analyze mineral particle reactions in soils

We developed a simple method to monitor the transformation of particles in soils under in situ conditions. The particles were fixed on small polymer supports (2 cm x 2 cm) with a thin film of epoxy resin. Attached to these carriers, the particles could be put into close contact with soil at a chosen site and easily recovered after extended periods of time. The method was tested with lead oxide and copper concentrate in the field. Quartz and copper oxide particles were used in preliminary laboratory experiments. The used particles sizes ranged from 20 to 200 mu m. Laboratory and field experiments with acidic and calcareous soils showed that the PbO and Cu concentrate coated polymer supports were stable under field conditions for at least one year. Nondestructive X-ray fluorescence spectroscopy was used to quantify the metals before and after exposure. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy as well as micro-Raman spectroscopy was used to identify signs of dissolution and newly formed mineral phases. The mineral dissolution rate could be determined under field conditions. The new method has the potential to be used in other environmental media such as sediments or water to study the reactions of a variety of particles larger than 20 mu m.