Source Attribution of Atmospheric Dust Deposition to Utah Lake

Abstract

Atmospheric deposition (AD) is a significant source of nutrient loading to waterbodies around the world. However, the sources and loading rates are poorly understood for major waterbodies and even less understood for local waterbodies. Utah Lake is a eutrophic lake located in central Utah, USA, and has high-nutrient levels. Recent research has identified AD as a significant source of nutrient loading to the lake, though contributions from dust particles make up 10% of total AD. To better understand the dust AD sources, we sampled suspected source locations and collected deposition samples around the lake. We analyzed these samples using Inductively Coupled Plasma (ICP) for 25 metals to characterize their elemental fingerprints. We then compared the lake samples to the source samples to determine likely source locations. We computed spectral angle, coefficient of determination, multi-dimensional scaling, and radar plots to characterize the similarity of the samples. We found that samples from local dust sources were more similar to dust in lake AD samples than samples from distant sources. This suggests that the major source of the dust portion of AD onto Utah Lake is the local empty fields south and west of the lake, and not the farther playa and desert sources as previously suggested. Preliminary data suggest that dust AD is associated with dry, windy conditions and is episodic in nature. We show that AD from dust particles is likely a small portion of the overall AD nutrient loading on Utah Lake, with the dry and precipitation sources contributing most of the load. This case identifies AD sources to Utah Lake and provides an example of data and methods that can be used to assess similarity or perform attribution for dust, soil, and other environmental data. While we use ICP metals, any number of features can be used with these methods if normalized.

Historical Phosphorus Mass and Concentrations in Utah Lake: A Case Study with Implications for Nutrient Load Management in a Sorption-Dominated Shallow Lake

“…We estimate the mass of DP in Utah Lake to be between 10 and 50 t at any given time (Figure 19), with monthly mass changes that can be either positive or negative, increasing or decreasing by as much as 15 t (Figure 20). Current estimates for external TP loading, however, are between 18 and 35 t/month and are always positive [4][5][6][7][8]. We show that the monthly change in DP mass in Utah Lake is comparable in magnitude or exceeds the estimated total P load to the lake and that the differences in loading must be attributable to internal cycling caused by sediment-water interactions.…”

“…There are conflicting estimates for Utah Lake P loads. For example, AD studies performed by Brown et al [5], Barrus et al [6], Olsen et al [7], and Telfer et al [8] measured AD rates from 75 to 235 t of TP/year (approximately 2 to 7 times more AD mass than estimated by the ULWQS model). Other studies have shown that internal loading from lakebed sediments could contribute significantly to Utah Lake's P content.…”