Uptake of PAH compounds by specialty crops grown in biochar amended soils

Eric Nooker

Department of Soil, Water, and ClimateUniversity of Minnesota

6/14/13

Specialty Crops & Biochar

• Fruits, vegetables, tree nuts, and nursery crops• Half of the value of U.S. crop production• Safety issue with PAHs sorbed on biochar

• Composed solely of carbon and hydrogen atoms• Have two or more fused aromatic carbon rings in

the structure • Simplest PAH is naphthalene• Compose a large group of compounds (200+)

PAH – Polycyclic aromatic hydrocarbon

NaphthaleneBenzo(g,h,i)perylene

• PAHs are among the most common organic pollutants

• Ease of atmospheric transport• Universal environmental presence• US EPA lists 32 of these PAHs as priority

pollutants

PAH Occurrence

PAH Formation• Incomplete combustion

Burning of fossil fuels: coal, diesel, gasolineTransportation sector

Burning of biomass (e.g. wood, tobacco, brush fires)

Cooking for meal preparation

• PAH production has also been confirmed during:Production of charcoal by pyrolysis Present in bio-oil from biomass pyrolysis

Natural Sources of PAH• Present in:

Fossil fuelsCrude oilShale oilCoal

Coal tars

• Present in gases and ashes from:Forest firesGrassland firesVolcanoes

• Biological Routes:Microbial degradation of black carbonsMicrobial production during complex

organic matter formation (soil humic substances)

Primary sources: Anthropogenic• Largest stationary point source emissions:

• Paper mills• Consumer wood product factories• Petroleum refining

PAH Presence in Various Materials

PAH Sorbed to Black Carbon

• Observed biochar range: 0.01 to 45 µg g-1

Pyrolysis influence on PAH • PAH range from 0.01 to 83 µg g-1 • Naphthalene was present on all biochars• Possible influence of production technique

• Not statistically significant within this sample pool

BC

0 10 20 30 40 50 60 70 80 90 100

Tot

al P

AH

Con

cent

ratio

n (

g g-

1 )

0

20

40

60

80

100

Tradit

ional K

iln/S

oil

Mou

nd

Slo

w P

yro

lysi

s

Fast

Pyro

lysi

s

Unknow

n

Hyd

roth

erm

al

Microwave

Ass

iste

d Pyrolysis

Materials and Methods• Field and Greenhouse Experiments

• Field: One rate & biochar type • Greenhouse: Multiple rates, types of biochar, and soils

PAH Extraction

Field ResultsRosemount, MN

• Specialty crops grown in biochar amended soils bio-accumulate PAH compounds

• Could be contaminated from rainwater splash of BC-soils

Lettuce - grown in 1% biochar amended field plots

2-m

ethy

lnap

thal

ene

1-m

ethy

lnap

thal

ene

acen

apht

hyle

ne

acen

aopt

hale

ne

anth

race

ne

Ben

z(a)

anth

race

ne

Ben

zo(a

) py

rene

Ben

zo(b

) flu

oran

then

e

Ben

zo(g

,h,i)

pery

lene

Ben

zo(k

)flu

oran

then

e

Chr

ysen

e

Dib

enz(

a,h)

anth

race

ne

Flu

rant

hren

e

Flu

oren

e

Inde

no(1

,2,3

-cd)

pyre

ne

Nap

thal

ene

Phe

nant

hren

e

Pyr

ene

Con

cent

ratio

n (

g kg

-1)

0

50

100

150

200

Lettuce - grown in control field plots

Con

cent

ratio

n (

g kg

-1)

0.0

0.5

1.0

Potatoes - grown in 1% biochar in field plots2-

met

hyln

apth

alen

e

1-m

ethy

lnap

thal

ene

acen

apht

hyle

ne

acen

aopt

hale

ne

anth

race

ne

Ben

z(a)

anth

race

ne

Ben

zo(a

) py

rene

Ben

zo(b

) flu

oran

then

e

Ben

zo(g

,h,i)

pery

lene

Ben

zo(k

)flu

oran

then

e

Chr

ysen

e

Dib

enz(

a,h)

anth

race

ne

Flu

rant

hren

e

Con

cent

ratio

n (

g kg

-1)

0.0

0.5

1.0

Potatoes - grown in Rosemount, MN field plots

Con

cent

ratio

n (

g kg

-1)

0.0

0.5

1.0

Greenhouse TreatmentsSoil Types Biochars Evaluated Amendment

Amounts Specialty Crops

Potting Mix Macadamia Nut Shell Lettuce

Rosemount, MN Wood Pellet Radish

[Wauken silt loam] 1% Hayward, WI Waste Wood Biochar Sweet Corn

[Vials loamy sand] 5% Becker, MN Corn Cob Biochar Cabbage

[Hubbard loamy sand] 10% Morris, MN Wheat Mids Biochar Spinach

[Barnes-Aastad clay loam] 20% University Park, PA Pine Wood Biochar Broccoli

[Birdsboro silt loam] Basil

Greenhouse Results Plant Growth Facility,University of Minnesota

• Specialty crops grown in biochar amended soils bio-accumulate PAH compounds

• Levels are variable as a function of soil type and biochar

0

10

20

30

40

Soil

Compound

1-M

ethy

lnap

thal

ene

2-M

ethy

lnap

thel

ene

Ben

zo(a

)ant

hrac

ene

Ben

zo(a

)pyr

ene

Ben

zo(b

)flu

oran

thre

ne

Flu

oran

then

e

Nap

thal

ene

Phe

nant

hren

e

Pyr

ene

Ben

zo(k

)flu

oran

thre

ne

Chy

rsen

e

PA

H C

once

ntra

tion

(g

kg-1

)

0

10

20

30

40

Soil+Biochar

Radish grown in Morris, MN soil (Barnes loam soil)

Radish grown inBiochar amended Morris soil (10% w/w)

0 10 20 30 40 50 60

Ave

rag

e H

eig

ht (c

m)

02468

101214161820

Potting Soil ControlUnground BiocharGround Biochar

0 10 20 30 40 50 60

Ave

rag

e H

eig

ht (c

m)

0

5

10

15

20

25

30

Elapsed Days from Planting

0 10 20 30 40 50 60

Ave

rag

e H

eig

ht (c

m)

0

5

10

15

20

25

30

(A)

(B)

(C)

Cont

rolBC

BC

Biochar Weathering

Research Data• Spectrum of specialty crop PAH uptake:

• Increases• Decreases• No changes

• PAH concentrations are influenced by: • Feedstock moisture levels• Presence of oxygen during pyrolysis, and post-cooling • Post-production handling and storage• Soil organic content• Rate PAH sorbed biochar is applied

Uncertainties• PAH contents of each biochar• Human health impacts

Conclusions• Plant PAH uptake depends on:

• Crop• PAH content of the biochar• PAH content of the original soil• Native soil organic content

• PAH sorbed on biochar may elevate specialty crop PAH levels, especially at higher biochar application rates

AcknowledgementsMinnesota Department of Agriculture

Kurt Spokas

Martin DuSaire

Students: Abby Anderson, Amanda Bidwell, Ed Colosky, Mike Ottman, Tara Phan,Tia Phan, Rena WeissKia Yang, and Vang Yang