Selenium Speciation and Distribution in a Wetland System of the Great Salt Lake, Utah

Abstract

Potential ecological risks of selenium (Se) to migratory birds in wetlands of the Great Salt Lake have not been previously studied. Monitoring results show that total Se concentrations coming from the Jordan River into the Ambassador Duck Club wetland ponds approached 2.0 μg L−1. Bioconcentration of Se occurred in all nine ponds of the wetland system of Ambassador Duck Club. Se bioconcentration factors were over 1,700 L kg−1 in plant tissue and 650 L kg−1 in microinvertebrate tissue above observed Se concentrations in surface water. Se concentration in plant tissue and sediments showed strong linear correlations (r = 0.99 and r = 0.93, respectively) to dissolved Se concentration, whereas macroinvertebrate tissue did not show a correlation with dissolved Se. In addition, plant tissue showed a strong correlation (r = 0.96) to selenate but no correlation to organic-selenide. Selenate was the major species of dissolved Se entering the wetland system and decreased significantly through the wetland ponds as Se speciation shifted to dissolved organic-selenide forms. Substantial decreases in dissolved and total Se concentrations (56% and 49%, respectively) occurred between the first and the seventh of nine ponds (total retention time of 25 to 465 h) of the wetland system. Removal of Se from the water column was caused by Se accumulation in plants, sorption, and sedimentation of Se with organic and inorganic matter, and microbial transformation to volatile Se forms. From the observed concentrations of Se in water, sediment, and biota, and by comparison to other studies in similar environments, we conclude that these wetlands do not currently pose an Se hazard to migratory birds.