Application of a multi-layer sampler based on the dialysis cell technique for the study of trace metals in groundwater

Most studies of metals in groundwater involve sample filtration. A water sampling technique based on dialysis cells has an advantage of in situ separation of particulate (colloidal) matter from the fluid, thus avoiding overload of the membrane during laboratory filtration. A series of laboratory and field experiments were carried out with a multi-layer sampler based on the dialysis cell technique. Results show that (1) the time of equilibration for Cu and Mn is within 2 d, (2) dialysis cells do not absorb these metals, and (3) the metal content measured in the dialysis cells is much lower than that in water taken by bailer and filtered in the laboratory. Measurements of metal profiles in the water table zone of the phreatic Coastal Plain Aquifer of Israel show both vertical and horizontal variations in Mn content which can be related to changes in pH due to biological activity in this aquifer.