Spectroscopic investigation of Cadmium sorption to Oncoids

There is a growing interest in preserving water quality, prevention of contamination and remediation of water systems. Once a metal contaminant enters a system, it is important to understand how the minerals and microbes making up a system will react to the contaminant. In this study, we are interested in how oncoids, nodular coated grains formed by biological activity in water environments, found in an alkaline lake in the Canadian Rockies, would take up metals in a contamination event. Oncoids were collected from a carbonate-rich mountain lake in western Alberta. The oncoid material was dissected and exposed to Cadmium (Cd), a highly toxic metal. The pH range studied was between 4-11. Following exposure, the oncoid was removed from the solution and the aqueous phase was analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES), while the oncoid was analyzed using Fourier transform infrared (FTIR) spectroscopy. Raman spectrometry was used to characterize variations in the Cd binding across the oncoid. Adsorption of Cd by the oncoid was found to increase as a function of pH, 24% at pH 4 rising to as high as 96% at pH 11, however above pH 8 much of that removal from solution was related to Cd precipitation. Assessing how environmental components, such as oncoids take up metals, such as Cd, is important as it could inform us on possible syncs of metals, to improve water qualities and environmental hazards in present day contamination events, but also inform us of potential metal syncs in geologic history. Department: Physical Sciences Faculty Mentor: Dr. Janice Kenne