Competitive Uptake of

Plutonium and Iron in Corn

(Zea mays)

Stephanie HoelblingF. Molz, N. Tharayil, B. Powell, and N. MartinezGraduate Research Assistant

Introduction

• Interested in the plant mechanisms that influence iron

uptake, and subsequently plutonium uptake

• Two applications

– Phytoremediation

– Nuclear forensics/monitoring

Letsgarden.info Ec.Europa.eu

Introduction

• Iron is an essential nutrient for plants

• Pu is of concern due to the long-term

environmental and health concerns

• Is plutonium taken up through the same plant

pathway as iron?

Introduction

• Corn species of interest

– Trucker’s Favorite

– Yellow Stripe 1 (YS1)

• If YS1 uptakes Pu, then the Pu/Fe pathway is

different.

Trucker’s

Favorite YS1

Introduction• Initial experiments compare Pu(DFOB) and 59Fe(DFOB) corn

uptake

• Conducted two experiments: One compared plant uptake of

~37kBq Pu(DFOB) and ~37kBq of Fe(DFOB). The other compared

plant uptake of ~37kBq Pu(DFOB) and either 0 or 10x Fe

concentration found in nutrient solution

• Experiment 1:

More 59Fe activity was found in the shoots than Pu

More Pu was found in the roots than Fe

• Experiment 2:

Differences in iron concentrations

had no effect on Pu uptake

0

10

20

30

40

50

60

70

80

0 10 20 30 40

Shoot

Length

(cm

)

Concentration (Bq/g)

Plant B Pu Plant B Fe

Soil

HP

Hydroponic Solution and Foliar Fertilization

• Hydroponic nutrient (HP)

solution

– Allows nutrient control

• Foliar Fertilization

– Two different types of

foliar fertilization (FF)

techniques were

attempted

• Type 1: Hydroponic

nutrient solution

containing FeCl3

• Type 2: FeCl3 with DDI

Overall Experimental Setup

Analysis Methods

Harvest

Dry

Ash

Digest

Analyze

•Roots and shoots

•Cut, separate, and weigh

•Dry in oven at 50ºC for 72 hours

•Reweigh

•Determine moisture content

•Ash at 450ºC for 4 hours

•Microwave digestion using nitric

acid

• ICP-MS

Trial Experiments• Four trial experiments

– Trucker’s Favorite corn strain

– Two different types of HP solution: one with FeCl3and one without FeCl3

– Observe corn growth in presence and absence of iron

– Establish foliar fertilization techniques

• The control group and FF spray group should produce

similar results

Trial Experiments

Trial Experiments

• Corn was grown for 7 days once placed in HP solutions

• Roots and shoots were measured every day

• After 7 days, roots and shoots were cut, separated, and

dried

• Plant tissues will be digested

• Will be analyzed via Inductively Coupled Plasma-Mass

Spectroscopy (ICP-MS) for magnesium, potassium,

calcium, iron, and molybdenum

Trial Experiments - Results

0

5

10

15

20

25

0 2 4 6 8 10

Gro

wth

(cm

)

Time (days)

FF Type 1 FF Type 2

• FF type 1: FeCl3 Hydroponic spray

• FF type 2: 2x FeCl3 + DDI

Trial Experiments - Results

Planned Experiments

• Each experiment conducted twice: once with DFOB in

solution and once with citric acid in solution

– Comparison of two ligands

• Two citrate experiments were conducted based on

modeling

• 40 Bq/mL Pu-239

0E+00

2E-01

4E-01

6E-01

8E-01

1E+00

1E+00

0 E+00 1 E+06 2 E+06 3 E+06 4 E+06Fra

cti

on o

f Pu in P

hase

Citrate/Pu Molar Ratio

Fraction of Soluble Pu Fraction of Precipitated Pu

Citrate ExperimentsFirst round results:

106 [Pu]

104 [Pu]

Citrate ExperimentsSecond round results:

0.0

5.0

10.0

15.0

20.0

25.0

1 3 5 7 9

Media

n G

row

th (

cm

)

Time (days)

Median Root Growth

Control 10[Pu] 100[Pu] 1000[Pu]

0

2

4

6

8

10

12

14

1 3 5 7 9

Media

n G

row

th (

cm

)

Time (days)

Median Shoot Growth

Control 10[Pu] 100[Pu] 1000[Pu]

Planned Experiments

• Each experiment conducted twice: once with DFOB in

solution and once with citric acid in solution

– Comparison of two ligands

• 4 rounds per experiment:

Round 1 No plutonium

Round 2 High Pu/Low Fe ratio

Round 3 High Pu/High Fe ratio

Round 4 Low Pu/High Fe ratio

Round 1

No plutonium

Round 2 High Pu/Low Fe ratio

Planned Experiments

0.0

5.0

10.0

15.0

20.0

25.0

0 5 10

Gro

wth

(cm

)

Days

Median Shoot Growth

0.0

10.0

20.0

30.0

40.0

0 5 10G

row

th (

cm

)

Days

Median Root Growth

Future Work

• U238, Np237, Th232 experiments

• Continue to digest and analyze Trial Experiment corn

• Continue primary experiment rounds

Acknowledgments

Student and project funding provided by the United States Nuclear

Regulatory Commission Nuclear Education Grant #NRC-HQ-13-G-38-

0002.

I would also like to acknowledge Dr. Molz for providing preliminary

data, Dr. Powell for modeling assistance, and Dawn Montgomery and

Nate Conroy for their laboratory assistance.

References

Garland, T. R., Cataldo, D. A., Wildung, R. E. (1981). "Absorption,

Transport, and Chemical Fate of Plutonium in Soybean Plants." Journal of

Agricultural and Food Chemistry 29(5): 915-920.

“Improvement of Uncertainty Measurements in Nuclear Forensics.” ec.Europa.eu. European

Commission. 1 July 2015.

Lee, J. H., Hossner, L. R., Attrep, M., Kung, K. S. (2002). "Uptake and

translocation of plutonium in two plant species using hydroponics."

Environmental Pollution 117(1): 61-68.

“Phytoremediation.” letsgarden.info. Web. 1 July 2015.

Thompson, S.W., 2010. Mobility of Plutonium in Zea mays (Corn): Determination of Transport

Velocities, Spatial Distribution, and Correlations with Iron. Dissertation. Clemson University,

Clemson, SC.