1. Fayiga Abioye, Uttam Saha, and Lena Q Ma
Effects of phosphate amendments on TCLP-leachable Pb in Florida shooting range soils
Fayiga Abioye, Uttam Saha, and Lena Q Ma
Abstract
Results
This study evaluated the efficacy of phosphate rock (PR) and phosphoric acid (PA) to reduce TCLP-leachable Pb in shooting range soils via column experiments.
Phosphate was applied at a molar ratio of P/Pb 4:1 with 2/3PR and 1/3PA
The P treatment effectively reduced TCLP-leachable Pb by 92 to 99.8% in four shooting range soils.
A typical shooting range in Florida A B
Fig 2. TCLP-leachable Pb from shooting range soils during 8 leaching over 1 wk a) control and b) P-amendments. Significant reduction in TCLP-leachable Pb was observed in all leaching events in all soils.
Introduction
Lead contamination in shooting range soils has been of great concern.
Phosphate-induced Pb immobilization minimizes lead migration and subsequent environmental pollution.
Phosphate rock and phosphoric acid are effective in reducing TCLP-Pb in soils.
TCLP used 20:1 solution:solid ratio
The objective was to evaluate the effectiveness of P in reducing TCLP-leachable Pb in shooting range soils using column experiments.
Weathered bullets in shooting range A B
Conclusions
Fig 3. pH of TCLP leachates from soils a) control. b) P-treated. pH of TCLP solution increased in the control and decreased in P-treated soil during the 1st leaching and pH stabilized in subsequent leaching
P treatment using phosphate rock (PR) and phosphoric acid (PA) was effective in reducing TCLP-leachable Pb in column experiments.
Addition of PA reduced TCLP leachate pH and increased TCLP-leachable P
The amount of PA should be further reduced to minimize potential P pollution and pH reduction in the soil
Materials & Method
Soil was collected from mid-berm of three rifle ranges and one pistol range and characterized.
P was supplied with 2/3 phosphate rock (PR) and 1/3 phosphoric acid (PA) at a molar ratio of P/Pb 4:1.
TCLP (40 mL fluid 1 at pH 4.93) was used to leach the soil after 18 h incubation in a column.
Twenty leaching events were done using TCLP fluid over a week, simulating the 20:1 (800 mL:40 g) solution:solid ratio.
Flame atomic absorption spectrometer (FAAS) was used to analyze Pb concentrations in samples.
Fig 4: Reduction in TCLP-leachable Pb during the 1st leaching after 18h and accumulative leaching over 1 wk. P reduced TCLP-leachable Pb from the soils by % after 18h.
Fig 5: P concentration in leachates during 8 leaching over 1 week. TCLP-leachable P was high during the 1st two leaching and thereafter was significantly reduced.
This research was supported in part by the Florida Department of Environmental Protection
Acknowledgement