Development of a new water sampling device to measure biologically-available metals in natural waters and mine effluents

CIM Bulletin, Vol. 93, No. 1037, 2000

J.J. McNee, Lorax Environmental Services Ltd., Vancouver, British Columbia, and J.D. Robertson, Placer Dome Inc., Vancouver, British Columbia

An in situ water sampling device has been developed to measure biologically-available or ÒlabileÓ metals in natural waters and effluents. The active mechanism involves the use of a polyacrylamide gel layer to quantitatively control metal transfer to a trace-metal-adsorbing, gel-imbedded resin. Because the resin only adsorbs free metal ions (the gel sampler methodology is a kinetic speciation technique), and because metal bioavailability is related to the free-ion activity, the device provides a direct measure of the biological-availability of metals in the environment sampled. The prototype consists of a layer of ion-permeable polyacrylamide gel which separates the solution to be sampled from an ion exchange resin. Because approximately 90% of the polyacrylamide gel is water, mass transport through the gel is diffusion-controlled, and is therefore well defined. Metal ions are rapidly bound by the resin, creating a steep concentration gradient in the gel. The amount of labile trace metal that accumulates on the resin can be related directly to the concentration of the metal in solution, the expos

Keywords: Trace metals, Water sampling devices, Mine effluents.