ELEMENTAL COMPOSITION OF THE RESPIRABLE FRACTION OF MINERAL DUST FROM THE EXPOSED PLAYA OF THE GREAT SALT LAKE, USA

Due to a combination of water diversion and drought, the terminal basin Great Salt Lake (GSL) has receded significantly exposing more than 1960 km² (~757 mi²) of playa. Dust plumes emanating from the playa now frequently degrade local air quality, potentially impacting the health of more than 2 million adjacent residents. The goal of this study was to measure the elemental composition of the respirable (i.e., PM₁₀) fraction of soil collected from the entire playa surface of the GSL and determine whether heavy metals contained in the soil might pose a health risk to adjacent populations.

A systematic soil sampling campaign was conducted between June 2016 and August 2018 using Incremental Sampling Methodology. Surface crust samples were collected at 5246 locations and composited into 122 samples which were then dried and sieved. The silt and clay fractions were then placed in a resuspension chamber. The PM₁₀ fraction was extracted and analyzed by a combination of Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) and Synchrotron X-ray Fluorescence (S-XRF). The combination of these two analytical techniques was able to quantify the mass fraction of 53 elements. The PM₁₀ soil from the GSL lakebed is highly enriched in elements associated with evaporite minerals (e.g., Ca, Mg, S, Sr, Cl, Li, and B). Five elements (Co, Cu, Mn, Sb, and V) had some values which exceeded the Residential, but not the Industrial, Regional Screening Levels (RSLs) established by the EPA for soils. Three elements (La, Li, and Zr) had some values which exceeded both the Residential and Industrial RSLs. Arsenic was the only element measured for which all values exceeded both the Residential and Industrial RSLs. Site-specific exposure assessments should be performed for As, Co, Cu, La, Li, Mn, Sb, V, and Zr to determine whether the measured concentrations of these elements pose health risks at the observed exposure frequencies.