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Biochar soil amendment for environmental and agronomic benefits: Selection Criteria Sophie Minori Uchimiya , K. Thomas Klasson, Isabel Lima USDA-ARS Southern Regional Research Center New Orleans, LA 70124. Overview of the sustainable biochar concept Woolf et al. Nature Communications ( 2010). - PowerPoint PPT Presentation
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U n i t e d S t a t e s D e p a r t m e n t o f A g r i c u l t u r e • A g r i c u l t u r a l R e s e a r c h S e r v i c e
Biochar soil amendment for environmental and agronomic benefits: Selection Criteria
Sophie Minori Uchimiya, K. Thomas Klasson, Isabel Lima
USDA-ARS Southern Regional Research CenterNew Orleans, LA 70124
CautionMetals, PAHs, other VM components, air pollution, available biomass, soil type… localized, site-specific, case-by-case biochar utilization for specific purpose
Overview of the sustainable biochar concept Woolf et al. Nature Communications (2010)
photosynthesis
bioenergy
soil fertilizationC sequestrationremediation
Andosol (kuroboku) Volcanic ash+field burning to keep glassland (forest management). Rich in old C (1400 years 14C) as Fe, Al complexes, 3-33% charred carbon Source: Sindo et al. Org. Geochem., 2004; Nishimura et al. Soil Sci. Plant Nutr., 2008.
Charred C globally-Up to 35% of total organic C in US agricultural soils (Skjemstad et al., 2002)-Intentional slash-and-char: oxosol-turned-anthrosol Terra Preta (Lehmann et al., 2003)
Why add biochar?
Charred plant fragments found in the grassland, forest, and field soils, e.g., black chernozem soils
Acknowledgement: National Institute for Agro-Environmental Sciences Tsukuba, Japan
Heavy metal stabilization mechanism
(1) electrostatic interactions between metal cations and –charged biochar surface >PZC
(2) ionic exchange between ionizable protons on biochar surface and metal cations
(3) delocalized electrons of aromatic biochar structure coordinate d-electron especially for softer Lewis acids (Pb<Cu<Cd)
(4) specific binding of metal ions by surface ligands (carboxyl, hydroxyl, phenol, P- and basic N-containing) abundant in VM component of biochar (Polo et al., ES&T, 2002)
(5) ash (e.g., Al2O3)
(6) particulate formation induced by pH, phosphate (e.g., pyromorphite)…
1. Model systems (add Pb, Cu, Ni, Cd to agricultural soils)
• systematically compare different (1) metal contaminants, (2) soil, (3) biochar properties.
Norfolk loamy sand: acidic, eroded, low TOC, low CEC Typic Kandiudult. San Joaquin soil: alkaline, 40-60% clay (montmorillonite) cemented Abruptic Durixeralfs. biochar necessary for Norfolk but not San Joaquin.
• Cu sorption-desorption isotherms for binding reversibility.
• Effects of NOM and carbonized vs. noncarbonized fractions (Cu mobilized by carboxyl)
Degree of stabilization: Pb > Cu > Cd > Ni (common for soil, mineral, chars)
2. Contaminated (shooting range) soils of known pH, CEC, TOC
Co
nce
ntr
atio
n ( M
)
0
20
40
60
80
100
120
140
160
180
200
220
240
CH350CH500
CH650CH800
PS800700BL
soil 020406080
100120140160180200220240260280300320
CH350CH500
CH650CH800
PS800700BL
soil0
20406080
100120140160180200220240260280300320
CH350CH500
CH650CH800
PS800700BL
soil
[Pb
] (
M)
0
20
40
60
80
100
120
140
160
180
200
220
240
CH350CH500
CH650CH800
PS800700BL
soil
[Cu
]+[N
i]+
[Cd
]+[P
b]
(mM
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
CH350CH500
CH650CH800
PS800700BL
soil
pH
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
CH350CH500
CH650CH800
PS800700BL
soil
t0
t48
char
Effects of pyrolysis T on biochar property and heavy metal retention ability
Cu
Pb
CdNi
total pHpHpzc
CH350≈700BL<PS800<CH500≈CH650<<CH800
700BL≈PS800 <CH350≈CH500≈CH650<CH800
CH350<700BL<PS800 <CH500≈CH650<CH800
CH350 << 700BL < PS800 < CH500 ≈ CH650 ≈ CH800
Norfolk soil 10 wt% amendment, 300 M each metal added together
BET surface area fixed C ash content pH
√ volatile matter√ O/C, N/C√ pHpzc
Surface functional groups
phosphoric acidactivated carbon
broiler litterbiochar
0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.30
Co
nce
ntr
atio
n ( M
)
0
20
40
60
80
100
120
140
160
180
200 Cu
0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.300
20406080
100120140160180200220240260280300320
O/C0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.30
020406080
100120140160180200220240260280300320340360
0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.30
[Pb
] (
M)
0
20
40
60
80
100
120
140
160
180
200
220
0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.30
[Cu
]+[N
i]+
[Cd
]+[P
b]
(mM
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
cottonseedhull chars
steam activated carbons
phosphoric acidactivated carbons
Ni Cd
Pb Cu+Ni+Cd+Pb
O/CO/C
Biochar characteristics (O/C) translate into heavy metal sorption ability in soil
steam activated carbons (flax shive, cotton gin)
phosphoric acid activated carbons (pecan shell)
cottonseed hull chars
Heavy metal retention ability O/C
Uchimiya et al., J. Hazard. Mater. 2011, 190, 432–441.
flax shive steam (O/C = 0.04)
30% HNO3 (O/C = 0.18)
chemical oxidation to increase O/C
various oxidants available (H2O2, KMnO4, ozone, air)
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
[Cu
] (
M)
0
2
4
6
8
10
12
14
16
020406080
100120140160180200220240260280300320
(e) Ni(d) Cd
(b) Pb (soil-only = 212 ± 4 M)
PL350
PL700
TL350
TL700
FL350
FL700
MD35
0
MD70
0
SW35
0
SW70
0[N
i] ( M
)
[Pb
] (
M)
PL350
PL700
TL350
TL700
FL350
FL700
MD35
0
MD70
0
SW35
0
SW70
0so
il
PL350
PL700
TL350
TL700
FL350
FL700
MD35
0
MD70
0
SW35
0
SW70
0so
il
PL350
PL700
TL350
TL700
FL350
FL700
MD35
0
MD70
0
SW35
0
SW70
0
(c) Cu (soil-only = 226 ± 14 M)
soil
PL350
PL700
TL350
TL700
FL350
FL700
MD35
0
MD70
0
SW35
0
SW70
0so
il5.1
5.4
5.7
6.0
6.3
6.6
6.9
7.2
7.5
7.8
8.1
(a) pH (after 48h equilibration)
pH
[Cd
] (
M)
Uchimiya et al., J. Environ. Qual., 2012, 41, 1138-1149.
poultry
turkey
feedlot
dairy
swine
Comparison of 5 Manure Varieties (350, 700 oC)
*work conducted in collaborationwith ARS Florence, SC
“best” Pb, Cu, Ni, Cd stabilizer: 700oC poultry, turkey, feedlot
pH Pb
Cu NiCd
poor stabilizers contained very high (swine) or low (dairy) ash, P biochar properties help predict function in soil
300 M eachmetal at t0
Biochar for Shooting Range Remediation
Typical Firing Range
Highest Pb Concentrations
Collaboration with Dr. Desmond Bannon (Aberdeen Proving Ground)Bannon et al. Environ. Sci. Technol. 2009, 43, 9071-9076.Uchimiya et al. J. Agr. Food Chem., 2012, 60, 1798–1809.Uchimiya et al. J. Agr. Food Chem., 2012, 60, 5035−5044.
close up
portable x-ray fluorescence for in situ screening of soil metal concentrations
Images provided by Dr. Bannon (US Army)
heavy metal contaminated training range soils (Bannon et al., ES&T 2010)
Biochar for Pb, Cu Stabilization in Arms Range Soils
Heavy metal-contaminated shooting range, mine, and industrially impacted soils
• >3,000 DoD ranges: chemical stabilization (e.g., phosphate rock for Pb) as an alternative to costly soil excavation and disposal (Cao et al., Environ. Pollut. 2010). • Mixed results for biochar: Cd, Zn, PAHs; As, Cu (Beesley et al., Environ. Pollut. 2010).How do biochars retain heavy metals in Pb, Cu contaminated arms range soils?
Surface ligand complexation: biochar with and without oxidation (conc. HNO3/H2SO4,70 oC, 6h) same stability (H/C, fixed C), higher O/C and carboxyl content.
Stable phosphorus phases: manure biochars (350, 650 oC).
pH: equilibration in acetate buffer (5 mg L-1 Pb TCLP regulatory limit).
Soil property, equilibration condition, and additional elements (Sb, P, K…)
Biochar-induced changes in soil property: pH, CEC, TOC, DOC, inorganic elements
Impact of extraction fluid/cycle on equilibrium soluble concentrations of heavy metals and additional elements of biochar/soil origin: Sb, Zn, Al, P, K, Na, Ca “best” biochar depends on purpose, remediation vs. agricultural use,risk of oxoanions (As, Sb)…
O/C0.00 0.06 0.12 0.18 0.24 0.30 0.36 0.42 0.48 0.54 0.60 0.66 0.72
H/C
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
cottonseed hulls
grass (Keiluweit)
wood (Keilweit)
pine needle (Chen)
broiler litter
dehydration
base treatment
stea
m a
ctiv
atio
n
steam
pyrolysis temperature (oC)
100 200 300 350 400 600 650500250 700 80025
Biochar oxidation to increase surface functional groups (O/C) while maintaining stability (H/C)
Uchimiya et al. J. Agr. Food Chem. 2011, 59, 2501–2510.
H/C aromaticity
O/C polarity
O/C without changing H/C bychemical oxidation (30% HNO3) of flax shive (steam activated)
800900100011001200130014001500160017001800
C=OC=C C-Ocarboxyl
C=O flax-conc.nitric/sulfuricflax-30%nitric
flax
Wavenumber (cm-1)800900100011001200130014001500160017001800
C=OC=C C-Ocarboxyl
C=O CH800-conc.nitric/sulfuricCH800-30%nitric
CH800
3:1 = sulfuric:nitric(both conc.)highly exothermic
5g char/400mL acid 6 hr at 70 oC
Method sourceCho et al. (Langmuir 2010) carboxyl the most for MWCNTs
O/C total acidity fixed C
wt% mequiv g-1 wt%
flax 0.04 0 89
flax-oxidized 0.39 3.3 N/A
CH800 0.06 0 77
CH800-oxidized 0.31 2.7 N/A
Conc. nitric/sulfuric acid oxidation:
carboxyl, hydroxyl, carbonyl
×5-10 O/C
0 2 4 6 8 10 12 14 16 18 200.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 2 4 6 8 10 12 14 16 18 200.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 2 4 6 8 10 12 14 16 18 20
[Cu
] (m
g L
-1)
0.0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8 10 12 14 16 18 20
[Pb
] (m
g L
-1)
0
2
4
6
8
10
12
14
16
18
20flax
biochar amendment rate (wt%)
MD1 soil-onlyflax-oxidized
flax-oxidized
flax
MD1 soil-only
MD2 soil-only
BL650
BL350
biochar amendment rate (wt%)
MD2 soil-only
BL350
BL650
Equilibration#1 (no buffer, 1wk) *some biochars (CH350 for MD2) increased Pb and Cu.
Broiler litter (BL) biochars:No clear temperature effects on Pb or Cu
Oxidation enhanced Pb, Cu retention
O/C = 0.04
O/C = 0.39
0 2 4 6 8 10 12 14 16 18 20
pH
0
1
2
3
4
5
6
0 2 4 6 8 10 12 14 16 18 206.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
biochar amendment rate (wt%) biochar amendment rate (wt%)
MD2 soil-only
MD1 soil-only flax
flax-oxidized
BL350
BL650
√ pH is not the sole factor use buffer (pH 4.9 acetate) to further investigate.
Are biochars still effective for Pb, Cu retention under acidic pH?
Equilibration#1 (no buffer, 1wk)
pH change vs. Pb, Cu retention as a function of biochar amendment rate
pH Pb Cu
flax-oxidized
flax ≈ ≈
BL650
BL350 Uchimiya et al. (J. Agr. Food Chem. 2012)
0 2 4 6 8 10 12 14 16 18 200
30
60
90
120
150
180
210
240
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
16
0 2 4 6 8 10 12 14 16 18 20
[Cu
] (m
g L
-1)
0
2
4
6
8
10
12
0 2 4 6 8 10 12 14 16 18 20
[Pb
] (m
g L
-1)
0
30
60
90
120
150
180
210 MD1 soil-only
(c) flax (Cu)
biochar amendment rate (wt%)
flax
flax-oxidized
MD1 soil-only
flax-oxidized
flax
MD2 soil-only
BL650
BL350
biochar amendment rate (wt%)
BL650
BL350
Equilibration#2 (pH4.9 acetate) >10-fold Pb, Cu without biochar compared to Eq#1 for both soils
All biochars effective for Pb, Cu despite acidic pH√ Oxygen-containing surface functional groups√ Complex formation and solid phase formation with phosphate (especially Pb)
Oxidation enhanced Pb, Cu retention
Broiler litter (BL) biocharsBL350 more effective for Pb
Element leaching summary
Ash content: Greater acid dissolution of Ca, P, Mg for manure biochar (>35 wt% ash)than plant biochar (10 wt% ash)
Alkali metals (Na, K): nearly100% dissolution at initial equilibration period
Alkaline earth metals (Ca, Mg): stabilized as carbonate and phosphate phases at high pH; significant acid dissolution
Phosphorus: amendment rate-dependent release behaviors with and without buffer for manure biochars (up to 6wt% P)
Oxoanion (SbV(OH)6–)
Plant biochars rich in COO– desorption by repulsive interactionsManure biochars rich in PO4
3– no desorptionSb stabilized by Al2O3, MgO, and other ash components?
Total (microwave digestion) elemental composition does not predict the release behaviors
Biochar selection for Pb stabilization
low Sb, As risk, excess P undesirable (e.g., disused shooting range) COO– rich biochars
oxoanion is a risk, P desirable as plant nutrient manure biochars
Which biochar to use?
Uchimiya et al. (J. Agr. Food Chem. 2012)
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