Characterizing the Fate and Mobility of Phosphorus in Utah Lake Sediments
Location
Logan Country CLub
Start Date
3-28-2017 2:50 PM
End Date
3-28-2017 2:55 PM
Description
An increasing number of lakes worldwide are impacted by eutrophication and harmful algal blooms due to nutrient inputs. Utah Lake is a unique eutrophic freshwater lake that is naturally shallow, turbid, and alkaline with high dissolved oxygen levels. Recently, the Utah Division of Water Quality has proposed a new limitation of phosphorus (P) loading to Utah Lake from wastewater treatment plants in an effort to mitigate eutrophication. However, reducing external P loads may not lead to immediate improvements in water quality due to the legacy pool of nutrients in lake sediments. The purpose of this study is to characterize the fate and mobility of P in Utah Lake sediments to better understand P cycling in this unique system. We analyzed P speciation, mineralogy, and binding capacity in lake sediment samples collected from 15 locations across Utah Lake. P concentrations in sediment ranged from 615 to 1711 ppm, with highest concentrations in Provo Bay near the major metropolitan area. Likewise, P concentrations in sediment pore water were highest in Provo Bay with concentrations up to 12.9 mg/L. Sequential leach tests indicate that 30-45% of P is bound to calcium and another 40-55% is adsorbed onto the surface of redox sensitive Fe-(oxy)hydroxides. This was confirmed by SEM images, which showed the highest P concentrations correlating with Ca (carbonate/apatite). The Ca-bound P fraction is likely immobile, but the P fraction sorbed to Fe-(oxy)hydroxides is potentially bioavailable under changing redox conditions. Batch sorption results indicate that lake sediments have a high capacity to absorb and remove P from the water column, with an average uptake of 70-96% of P from spiked surface water with concentrations ranging from 1-10 mg/L. Mineral precipitation and sorption to bottom sediments is an efficient removal mechanism of P in Utah Lake, but a significant portion of P may be available for resuspension and cycling in surface waters. Mitigating lake eutrophication is a complex problem that goes beyond reducing nutrient loads to the water body and requires a better understanding of internal P cycling.
Characterizing the Fate and Mobility of Phosphorus in Utah Lake Sediments
Logan Country CLub
An increasing number of lakes worldwide are impacted by eutrophication and harmful algal blooms due to nutrient inputs. Utah Lake is a unique eutrophic freshwater lake that is naturally shallow, turbid, and alkaline with high dissolved oxygen levels. Recently, the Utah Division of Water Quality has proposed a new limitation of phosphorus (P) loading to Utah Lake from wastewater treatment plants in an effort to mitigate eutrophication. However, reducing external P loads may not lead to immediate improvements in water quality due to the legacy pool of nutrients in lake sediments. The purpose of this study is to characterize the fate and mobility of P in Utah Lake sediments to better understand P cycling in this unique system. We analyzed P speciation, mineralogy, and binding capacity in lake sediment samples collected from 15 locations across Utah Lake. P concentrations in sediment ranged from 615 to 1711 ppm, with highest concentrations in Provo Bay near the major metropolitan area. Likewise, P concentrations in sediment pore water were highest in Provo Bay with concentrations up to 12.9 mg/L. Sequential leach tests indicate that 30-45% of P is bound to calcium and another 40-55% is adsorbed onto the surface of redox sensitive Fe-(oxy)hydroxides. This was confirmed by SEM images, which showed the highest P concentrations correlating with Ca (carbonate/apatite). The Ca-bound P fraction is likely immobile, but the P fraction sorbed to Fe-(oxy)hydroxides is potentially bioavailable under changing redox conditions. Batch sorption results indicate that lake sediments have a high capacity to absorb and remove P from the water column, with an average uptake of 70-96% of P from spiked surface water with concentrations ranging from 1-10 mg/L. Mineral precipitation and sorption to bottom sediments is an efficient removal mechanism of P in Utah Lake, but a significant portion of P may be available for resuspension and cycling in surface waters. Mitigating lake eutrophication is a complex problem that goes beyond reducing nutrient loads to the water body and requires a better understanding of internal P cycling.