Zn Ecotoxicological Endpoints in Metal Contaminated Soils

Zn Ecotoxicological Endpoints in Metal Contaminated Soils

Gary Pierzynski, Arline Novak, and Walter Fick

Kansas State University

ObjectivesObjectives

• Assess the potential for Zn phytotoxicity in the Tri-State Mining region through field and greenhouse studies

• Evaluate the use of diffusive gradients in thin film (DGT) for the assessment of Zn bioavailability to plants

Methods – Field StudyMethods – Field Study

• Eight 100 m transects laid out in areas impacted by mine wastes

• Plant community structure was assessed every 5 m in 0.5 m2 frames in June 2002– Species identification– Relative abundance of each species– Soil samples collected from 0-5 and 5-10 cm around

perimeter of each frame

• Biomass production determined every 10 m in October 2002

y = -0.7125Ln(x) + 10.417R2 = 0.2794

0

2

4

6

8

10

12

14

0 10000 20000 30000 40000 50000 60000 70000 80000

Total Zn at 0-5 cm (mg/kg)

Num

ber

of S

peci

es

y = -0.4836Ln(x) + 7.4786

R2 = 0.1605

0

2

4

6

8

10

12

14

0 1000 2000 3000 4000 5000

CE (umol/L)

Nu

mb

er o

f S

pec

ies

Total Zn No. Species Biomass

Dominant Species

- mg/kg - -- kg/ha --

>2000 3.3a 973a C. Ragweed

<2000 6.2b 1328b B. Bluestem

>1000 3.9a 978a C. Ragweed

<1000 7.2b 1436b B. Bluestem

>500 4.0a 1000a C. Ragweed

<500 7.6b 1532b B. Bluestem

Sample n No. Species Dominant Species

Chat,>2000 65 3.5a C. ragweed, moss

Chat,<2000 5 4.8a S. sumac,

G. goldenrod

Soil, >2000 43 4.7a C. ragweed, moss

Soil, <2000 47 6.3b B. bluestem,

L. bluestem

Total Zn (mg kg-1)

0 10000 20000 30000 40000 50000 60000

Sho

ot Z

n C

onc

en

trat

ion

(mg

kg-1

)

0

2000

4000

6000

8000

10000

Common Ragweed

r2 = 0.03

Total Zn (mg kg-1)

0 5000 10000 15000 20000 25000 30000

Sho

ot Z

n C

onc

en

trat

ion

(mg

kg-1

)

0

2000

4000

6000

8000

10000

Common Ragweed

r2 = 0.21

CE (mol L-1)

0 500 1000 1500 2000 2500 3000 3500

Sh

oot

Zn

Con

cent

ratio

n (m

g kg

-1)

0

2000

4000

6000

8000

10000

Common Ragweed

r2 = 0.47

Methods – GreenhouseMethods – Greenhouse

• Sand/nutrient cultures– Zn sources: ZnSO4, chat, smelter slag

– Zn sources mixed with sand to provide a wide range of Zn concentrations

– Big bluestem, pigweed, switchgrass– Zn bioavailability assessed with DGT and 0.1 M Ca(NO3)2 extraction

Total Zn in Media (mg/kg)

0 2000 4000 6000 8000 10000 12000 14000 16000

CE ( m

ol L

-1)

-500

0

500

1000

1500

2000

2500

ChatDearingZnSO4

0

0.2

0.4

0.6

0.8

1

1.2

Rel

ativ

e Y

ield

0 1 2 3 4 5

Zn Level

00.10.20.30.40.50.60.70.80.9

1

Rel

ativ

e Y

ield

0 5 10 25 50 100

Zn Level (mg/kg)

ZnSO4 -Pigweed

Chat - Pigweed

0

50

100

150

200

250

300

350

400

450

Pla

nt

Zn

(m

g/k

g)

0 1 2 3 4 5

Zn Level

0

200

400

600

800

1000

1200

1400

Pla

nt

Zn

(m

g/k

g)

0 5 10 25 10 100

Zn Level (mg/kg)

ZnSO4 – Big bluestem

Chat – Big bluestem

0

50

100

150

200

250

300

350

400

450

Pla

nt

Zn

(m

g/k

g)

0 1 2 3 4 5

Zn Level

0100200300400500600700800900

1000

Pla

nt

Zn

(m

g/k

g)

0 1 2 3 4 5

Zn Level (mg/kg)

Chat - Switchgrass

Chat – Big bluestem

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Pla

nt

P (

mg

/kg

)

0 1 2 3 4 5

Zn Level

05

1015202530354045

Pla

nt

Fe

(mg

/kg

)

0 1 2 3 4 5

Zn Level (mg/kg)

ZnSO4 – Big bluestem - Fe

ZnSO4 – Big bluestem - P

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Pla

nt

P (

mg

/kg

)

0 1 2 3 4 5

Zn Level

05

1015202530354045

Pla

nt

Fe

(mg

/kg

)

0 1 2 3 4 5

Zn Level (mg/kg)

Chat – Big bluestem - Fe

Chat – Big bluestem - P

Ca(NO3)2 - extractable Zn (mg/kg)

0 50 100 150 200 250 300

Pla

nt T

issu

e Z

n C

once

ntra

tion

(mg/

kg)

0

200

400

600

800

1000

1200

1400

1600

1800Big bluestemPigweedSwitchgrass

r2=0.49

r2=0.25

r2=0.13

CE (mol/L)

0 500 1000 1500 2000 2500 3000

Pla

nt T

issu

e Z

n C

once

ntra

tion

(mg/

kg)

-200

0

200

400

600

800

1000

1200

1400

1600

1800

2000Big bluestemPigweedSwitchgrass

r2=0.59

r2=0.67

r2=0.71

Critical values for 75% of control yield – Big bluestem

Critical values for 75% of control yield – Big bluestem

--------------- critical value -------------

Zn Source Total Zn DGT Zn Ca(NO3)2 Shoot Zn

- mg/kg - -umol/L- ------ mg/kg ------

Chat 5547a 1592a 195a 352ab

Dearing 6901a 600b 163a 185b

ZnSO4 61b 1292a 81b 600a

Critical values for 75% of control yield – Pigweed

Critical values for 75% of control yield – Pigweed

--------------- critical value -------------

Zn Source Total Zn DGT Zn Ca(NO3)2 Shoot Zn

- mg/kg - -umol/L- ------ mg/kg ------

Chat 4127b 1438a 174b 1210a

Dearing 10062a 583b 213a 1237a

ZnSO4 44b 1204a 55c 1607a

Critical values for 75% of control yield – SwitchgrassCritical values for 75% of

control yield – Switchgrass--------------- critical value -------------

Zn Source Total Zn DGT Zn Ca(NO3)2 Shoot Zn

- mg/kg - -umol/L- ------ mg/kg ------

Chat 2216a 700a 121a 220a

Dearing 3360a 379a 103a 208a

ZnSO4 23b 558a 24a 244a

ConclusionsConclusions

• Field data suggest that Zn may play a role in species richness, species present, and biomass production.

• Greenhouse data indicate Zn phytotoxicity can be induced with mine wastes.

• DGT was superior to batch extractions

• Further evaluation of DGT for assessment of ecotoxicologial endpoints is warranted