HEAVY METALS IN WATER MIXING ZONES OF GREAT SALT LAKE, UTAH, USA

This project focuses on understanding the transport of heavy metals in rivers discharging into Great Salt Lake. Bioaccumulation of heavy metals through the food webs of the lake are an ongoing concern, particularly to waterfowl. The need to collect additional baseline data is a priority as the Bear River is being assessed for a dam project that could change flow dynamics. Water samples collected along the north shore of the lake were acidified with nitric acid and filtered through a 0.2 micrometer filter. In-situ data on temperature, pH, ORP, dissolved oxygen, and electric conductance were measured using a Troll 9500 probe. Concentrations of forty elements were analyzed using both inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES). Field in-situ measurements indicated that the pH of the lake is weakly alkaline, with saline water being more alkaline than fresh water. Saline water in the Great Salt Lake was found to be more reducing than fresh water. The results indicate that the Bear River transports higher concentrations of heavy metals to the Great Salt Lake than the Ogden River. The pattern of elemental concentrations is complex. Fresh water fluxes penetrate shallow saline water over relatively long distances. The depth of brackish to saline lake water was predominantly less than 0.5 meter. ICP-MS measurements indicated that the Bear and Ogden Rivers share similar profiles in terms of trace elements. Both rivers have relatively high concentrations of Al, Fe, and Mn. Concentrations of Pb, As, Se, and Hg are also relatively high. Correlation between in-situ parameters indicates a complex relationship between different elements. Higher concentrations of metals correlated better with reducing conditions than with acidic conditions. Concentrations of metals did increase significantly in more acidic conditions, but they typically characterized less saline waters. It appears that dynamic flow systems in the Great Salt Lake are driven by wind and freshwater fluxes which push freshwater far into shallow saline water bodies. We suspect that these conditions might compromise the accuracy of thermodynamic computer modeling of the lake, and we plan to model the hydrochemical makeup in the next phase of research to test this question.