Phosphate-Induced Pb Immobilization in a Contaminated Soil Joon ki Yoon Department of Soil and Water Science University of Florida

RATIONALE S oil contamination by heavy metals from abandoned disposal and industrial sites is environmental concern S oil contamination by heavy metals from abandoned disposal and industrial sites is environmental concern A total of 1,208 Pb contaminated sites are currently listed on the EPA National Priority List A total of 1,208 Pb contaminated sites are currently listed on the EPA National Priority List T oxicity and bioaccumulation in food chain make it necessary to remediate Pb contaminated sites T oxicity and bioaccumulation in food chain make it necessary to remediate Pb contaminated sites

OBJECTIVES 1.E xamine the effectiveness of various phosphorous application methods on Pb immobilization in soil 2.E valuate the effects of plants on phosphate induced Pb immobilization in soil 3.E xplore metal accumulation in plants growing on a contaminated soil

The study site in Jacksonville Located in a urban area of Northwest Jacksonville Located in a urban area of Northwest Jacksonville Occupies approximately 1 acre Occupies approximately 1 acre Covered with vegetation Covered with vegetation Used to be gas station, salvage yard, and discharging area Used to be gas station, salvage yard, and discharging area

OBJECTIVE OBJECTIVE E xamine the effectiveness of various phosphorous application methods on Pb immobilization in soil Experiment 1-Application method

Effects of Phosphorous on Pb immobilization  Ca 9.5 (PO 4 ) 5 CO 3 FOH +10H +  9.5Ca H 2 PO 4- + CO F - + OH - (dissolution) 9.5Pb H 2 PO CO F - + OH -  Pb 9.5 (PO 4 ) 5 CO 3 FOH + 10H + (precipitation) 9.5Pb H 2 PO CO F - + OH -  Pb 9.5 (PO 4 ) 5 CO 3 FOH + 10H + (precipitation)  In situ Pb stabilization using phosphorous is sustainable and cost-effective.

Column leaching test 45 cm x 3.5 cm 45 cm x 3.5 cm PVC column PVC column 18 columns ( 3 rep) 18 columns ( 3 rep) Phosphoric acid (PA) Phosphoric acid (PA) Phosphate rock (PR) Phosphate rock (PR)

Column leaching test P/Pb ratio: 4 P/Pb ratio: 4 1 st 20-cm filled with contaminated soil (Total Pb 5012 ppm) 1 st 20-cm filled with contaminated soil (Total Pb 5012 ppm) 2 nd 20-cm with clean soil (Total Pb 77 ppm) to simulate field condition 2 nd 20-cm with clean soil (Total Pb 77 ppm) to simulate field condition Column incubated for 6 weeks after P application Column incubated for 6 weeks after P application Leaching test was conducted twice (after 1wk and 5 wks) Leaching test was conducted twice (after 1wk and 5 wks)

Five P treatments R phosphate Rock R phosphate Rock A phosphoric Acid A phosphoric Acid M Mixing M Mixing L Layer L Layer W Week W Week S Simultaneous S Simultaneous 1 1 time 1 1 time 2 2 times 2 2 times Ctd-soil (0-20 cm) Clean soil (20-40 cm) L M ½ PR + ½ PA R L A S 1 R M A S 1 R M A W1 ½ PR + ½ PA R L A S 1 R M A S 1 R M A W1 ½ PR + ¼ PA + ¼ PA R L A W2 R M A W2 ½ PR + ¼ PA + ¼ PA R L A W2 R M A W2W

Parameters determined Chemical Chemical - Soil pH - Soluble P and Pb concentrations in soil - Distribution of Pb in soil column - Toxicity Characteristic Leaching Procedure (TCLP) Biological Biological - Physiologically-Based bioavailibiity test (PBET) Mineralogical (not shown) Mineralogical (not shown) - X-ray diffraction (XRD) - Scanning Electron Microscopy (SEM)

Effects of phosphoric acid addition on soil pH Soil layer (cm) ControlR M A S1 R M A W1 R L A S1 R M A W2 R L A W R:Phosphate rock M: Mixing W:Week 1: 1 time A: Phosphoric acid L:Layer S:Simultaneous 2: 2 time

Leachate Pb (ppb) in soil column First leachingSecond leaching Control33.6± ±1.7 R M A S1 nd R M A W1 nd R L A S1 nd R M A W2 11±1.95.7±0.9 R L A W2 2.3±0.5nd R:Phosphate rock M: Mixing W:Week 1: 1 time A: Phosphoric acid L:Layer S:Simultaneous 2: 2 time

Leachate P (ppm) in soil column R:Phosphate rock M: Mixing W:Week 1: 1 time A: Phosphoric acid L:Layer S:Simultaneous 2: 2 time

Distribution of Pb in column c c c ab b b a b a R:Phosphate rock A:Phosphoric acid M:Mixing L:Layer W:Week S:Simultaneous1:1 time 2:2 timeR:Phosphate rock A:Phosphoric acid M:Mixing L:Layer W:Week S:Simultaneous1:1 time 2:2 time R:Phosphate rock M: Mixing W:Week 1: 1 time A: Phosphoric acid L:Layer S:Simultaneous 2: 2 time

TCLP analysis c b b a b b ab a R:Phosphate rock M: Mixing W:Week 1: 1 time A: Phosphoric acid L:Layer S:Simultaneous 2: 2 time

Pb bioavailability- PBET (mg/L) PBET Pb(mg/l) R R:Phosphate rock M: Mixing W:Week 1: 1 time A: Phosphoric acid L:Layer S:Simultaneous 2: 2 time

SUMMARY 1 A pplication of PA reduced soil pH by 1 unit, within Florida soil range A pplication of PA reduced soil pH by 1 unit, within Florida soil range A pplying mixture of PA and PR effectively reduced TCLP-Pb (<95%), bioavailable Pb (<42%) and vertical Pb migration (<80%)in soil A pplying mixture of PA and PR effectively reduced TCLP-Pb (<95%), bioavailable Pb (<42%) and vertical Pb migration (<80%)in soil A pplication of phosphate rock as a layer was effective in Pb migration reduction A pplication of phosphate rock as a layer was effective in Pb migration reduction R M A S1 was overall the most effective in Pb immobilization R M A S1 was overall the most effective in Pb immobilization

OBJECTIVE OBJECTIVE - To determine the effects of plants on phosphate induced Pb immobilization Experiment 2-Plant effect

Methods 3 plant species 3 plant species - Agrostis capillaris - Agrostis capillaris - Lolium rigidum - Lolium rigidum - Brassica napus - Brassica napus 2 phosphorous application methods 2 phosphorous application methods - PR - PR - ½ PR + ½ PA - ½ PR + ½ PA Plants grown in a Pb- contaminated soil(Total Pb 5012ppm) for 4 wks Plants grown in a Pb- contaminated soil(Total Pb 5012ppm) for 4 wks Plant and soil samples were characterized Plant and soil samples were characterized - PBET - PBET - SEM - SEM

Control 1: Soil + PR Control 1: Soil + PR Control 2: Soil + ½ PR + ½ PA Control 2: Soil + ½ PR + ½ PA Treatment 1: Soil + PR + Plant Treatment 1: Soil + PR + Plant Treatment 2: Soil + ½ PR + ½ PA + Plant Treatment 2: Soil + ½ PR + ½ PA + Plant Treatments

Effects on bioavailable Pb- PBET PBET Pb(mg/l)

Scanning electron microscopy elemental dot map of Agrostis capillaris roots(PR only) Si P PbCa

Scanning electron microscopy elemental dot map of Lolium rigidum roots (PR only) AlSi P PbCa

Scanning electron microscopy elemental dot map of Brassica napus roots (PR only) AlSi PPb Ca

SUMMARY 2 The presence of plant enhanced Pb immobilization when applied with PR but not with PR+PA The presence of plant enhanced Pb immobilization when applied with PR but not with PR+PA Reduction in Pb bioavailability in rhizosphere may be due to formation of Pb phosphate Reduction in Pb bioavailability in rhizosphere may be due to formation of Pb phosphate

OBJECTIVES OBJECTIVES - Determine the concentrations of Pb, Cu and Zn in plant biomass - Compare metals concentrations in the aboveground biomass to those in roots and in soils - Assess the feasibility to use these plants for phytoremediation purpose Experiment 3-metal accumulation

Sampling date: Sampling date: Plant sampling Plant sampling Coverage at the site Coverage at the site 36 samples of 18 species from 10 locations 36 samples of 18 species from 10 locations Divided into roots/shoots Divided into roots/shoots Air dried and ground Air dried and ground Experiment 3-metal accumulation Soil sampling Soil sampling Surface soil: 0-20 cm Surface soil: 0-20 cm Air dried and sieved (2-mm) Air dried and sieved (2-mm) Digested using the hot-block procedure (US EPA Method 3050) Digested using the hot-block procedure (US EPA Method 3050) Analyzed for total Pb, Zn, Cu using atomic absorption spectrophotometry Analyzed for total Pb, Zn, Cu using atomic absorption spectrophotometry

Sampling locations

Site characteristics Site #Soil pH Total Pb (mg/kg) Total Cu (mg/kg) Total Zn (mg/kg)

Criteria for hyperaccumulator T otal metal concentration in plant T otal metal concentration in plant >1,000 mg kg -1 of As, Cu, Co, Cr, Ni or Pb >1,000 mg kg -1 of As, Cu, Co, Cr, Ni or Pb >10,000 mg kg -1 of Mn or Zn >10,000 mg kg -1 of Mn or Zn B ioconcentration factor (BCF) > 1 B ioconcentration factor (BCF) > 1 Elemental concentration ratio of plant to soil Elemental concentration ratio of plant to soil Ability to accumulate elements from soils Ability to accumulate elements from soils T ranslocation factor (TF) > 1 T ranslocation factor (TF) > 1 Elemental concentration ratio of shoot to root Elemental concentration ratio of shoot to root Ability to translocate elements from root to shoot Ability to translocate elements from root to shoot

Metal concentrations in plants Pb concentrations 5 to 1,183 mg kg -1 Pb concentrations 5 to 1,183 mg kg -1 Cu concentrations 4 to 460 mg kg -1 Cu concentrations 4 to 460 mg kg -1 Zn concentrations 17 to 598 mg kg -1 Zn concentrations 17 to 598 mg kg -1 Maximum value found in the roots of Phyla nodiflora Maximum value found in the roots of Phyla nodiflora

Plants with high BCF and TF Bioconcentration factor Translocation factor PbCuZnPbCuZn Gentiana pennelliana Cyperus esculentus

SUMMARY 3  No plant species were identified as metal hyperaccumulators  was most effective in taking up all three metals, with BCFs ranging from  Gentiana pennelliana was most effective in taking up all three metals, with BCFs ranging from was most effective in translocating all three metals ranging from Cyperus esculentus was most effective in translocating all three metals ranging from

CONCLUSIONS Application of phosphoric acid and phosphate rock mixture was effective in reducing soluble, bioavailable, and TCLP Pb as well as Pb migration in soil Application of phosphoric acid and phosphate rock mixture was effective in reducing soluble, bioavailable, and TCLP Pb as well as Pb migration in soil The presence of plant enhanced Pb immobilization in soil when applied with PR but not with PR+PA The presence of plant enhanced Pb immobilization in soil when applied with PR but not with PR+PA No Pb hyperaccumulator was identified from plants growing on a contaminated-site in Jacksonville. No Pb hyperaccumulator was identified from plants growing on a contaminated-site in Jacksonville.

ACKNOWLEDGEMENT Advisor: Dr. Lena Q. Ma Committee: Dr. Jean-Claude Bonzongo Dr. Willie G. Harris Trace Metal Biogeochemistry lab group