Investigating Temporal and Spatial Variations of Nutrient and Trace Metal Loading to Utah Lake

Utah Lake, the largest freshwater lake in the United States west of the Mississippi River, has received
heavy loading of various contaminants, such as high concentrations of phosphorus (P) and nitrogen (N) wastes
from raw sewage, effluent from sewage treatment plants, runoff from surrounding agricultural and farming land,
and metals from mining and industrial activities since European settlement. However, the rate of loading of N, P,
and trace metals to Utah Lake varies both in space and time. Therefore, a good understanding of such spatial and
temporal variability is critical for developing integrated approaches to managing lake water quality. In this project,
we took water and floc layer sediment samples from the American Fork River, Provo River, Hobble Creek,
Spanish Fork River, Jordan River and Utah Lake to investigate the temporal and spatial variations in nutrient (P,
N) load and trace metal (mercury/methylmercury, arsenic, lead, cadmium, etc.) concentrations. In addition, water
samples were analyzed for H and O stable isotopes to establish a water budget for Utah Lake, and floc layer
sediment samples were analyzed for C and N stable isotopes to differentiate organic matter sources to Utah
Lake. Upon completion of this project, we were able to quantify spatial and temporal variations in nutrient and
metal loading to Utah Lake and to examine how this variability affected water quality. Furthermore, we were
able to trace the origins of organic matter sources to the lake and establish nutrient, metal, and water budget for
Utah Lake. The knowledge from this project can guide actions that are increasingly required to safeguard the
services provided by Utah Lake ecosystem in a future with increasing pressure on freshwater resources. The water,
nutrient, and trace metal budgets developed in this project provide important information for determining
which inflows are contributing the largest contaminant loads to Utah Lake. Consequently, the data derived from
this project can help state agencies to address significant questions in water quality, hydrologic, environmental,
and biogeochemical sciences and management related to human-environment interactions.