INVESTIGATING TEMPORAL AND SPATIAL VARIATIONS OF TRACE METAL LOADING TO UTAH LAKE, UT (USA)

Utah Lake has long been considered severely polluted and undesirable for recreation due to the heavy loadings of various pollutants related to anthropogenic activities. In this project, we collected floc layer sediment samples as well as monthly water samples from Utah Lake’s four major inlets, from the Jordan River outlet, and from the lake itself for trace metal analysis. In addition, to examine the lake’s vertical mixing condition we collected depth profile samples at an interval of 0.5 m in the water column at the deepest site of the lake. We integrated geochemical data with GIS spatial mapping techniques to (1) investigate the temporal and spatial variations of trace metals in Utah Lake, its four inlets, and the outlet, and (2) assess the spatial variation of trace metal concentrations across the lake using GIS modeling. Elevated trace metal concentrations in river and lake water samples have been detected, especially in June. Arsenic in both lake and river sediment samples exceeded its respective background concentrations and was particularly high in the Jordan River outlet in November. The concentration of trace metals at the lake locations tend to be higher than that at the river locations. The GIS modeling revealed that the highest trace metal concentration was located at the deepest part of the lake, and the trace metal concentration in lake water showed large seasonal variations across the lake. In contrast, water samples taken from the depth profile site imply relatively uniform concentrations of trace metals. These results indicate that Utah Lake is not well mixed horizontally but it is well mixed vertically. In addition, trace metals from non-point pollution sources are suspected to be a significant contributor of trace metals to the lake, which indicates that the lake acts as a sink for trace metals. Elevated levels of arsenic and lead in water samples during the summer months could be due to the application of manure as fertilizers in the agricultural practice and the runoff from mine tailings.