Selenium dynamics in Farmington Bay wetlands, Great Salt Lake, Salt Lake City, Utah, USA.

The dynamics of Selenium (Se) and other water quality parameters in the Farmington Bay wetlands were presented. This is the first time that the fate and transport of selenium is being studied in Farmington Bay wetlands. The significant salinity gradient between wetland impoundments and the hypersaline condition of the Great Salt Lake (GSL) make these wetlands systems unique. Selenium has been observed for the first time to cycle diurnally. A 100% increase of total selenium was measured during a 24-hour study in October 2005 at site #5320 at nighttime (i.e., 1.99 micrograms/L at 3:00 a.m. MST) compared to daytime (i.e., 0.99 micrograms/L at 2:00 p.m. MST). Particulate selenium also increased at the same site during nighttime and decreased during daylight. No significant daily changes were measured in dissolved selenium concentrations between day and night. Total suspended solids (TSS) measured during the same time period increased to a maximum concentration of 107 mg/L (at 4:21 a.m. MST) during nighttime and dramatically decreased after sunrise (i.e., 18.8 mg/L at 8:21 a.m. MST). Particulate generation at night could be linked to total and particulate selenium increase during this time period. Later studies in May 2006 have shown that total organic carbon (TOC) increased about 3.5-folds (i.e., from 2.9 mg/L to 12.9 mg/L) during nighttime (with high peak at 4:00 a.m. MST) and decreased dramatically at sunrise (about 6:30 a.m. MST) in May 2006. Seasonal selenium speciation showed for the first time that the predominant species reaching the Farmington Bay are elemental selenium and selenide species (organic and inorganic) (Se(0) + Se(-2)). This is a significant finding toward a better understand of the bioavailability of selenium to birds and aquatic life in Farmington Bay. The selenium concentration as water parcels moved through the system showed to be reduced up to 186%. Also, average monthly loads of selenium to Farmington Bay from Ambassador Duck Club wetlands were determined. The highest Se load to the Bay was experienced in August 2005 (i.e., 0.46 Kg Se/month).