Effect of biochar application at a trace-elements polluted area on soil carbon stability Paloma Campos 1 , Ana Z. Miller 2 , Heike Knicker 1 , Águeda Sánchez-Martín 1 , Elena Fernández-Boy 3 , José María De la Rosa 1 1. Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, 41012, Sevilla, Spain 2. HERCULES Laboratory, University of Évora, Évora, Portugal. 3. Facultad de Química, Universidad de Sevilla. Profesor García González St. 41012, Seville, Spain [email protected] Session SSS5.5 Tuesday, 5 May 2020
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Effect of biochar application at a trace-elements polluted area on soil carbon stability
Paloma Campos1, Ana Z. Miller2, Heike Knicker1, Águeda Sánchez-Martín1,
Elena Fernández-Boy3, José María De la Rosa1
1. Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Av. Reina Mercedes 10, 41012, Sevilla, Spain
2. HERCULES Laboratory, University of Évora, Évora, Portugal.
3. Facultad de Química, Universidad de Sevilla. Profesor García González St. 41012, Seville, Spain
Session SSS5.5Tuesday, 5 May 2020
BIOCHAR
Bio-oilCondenser
Air
Combustion
chamber
Gases(syngas) (CH4)
Pyrolysis
reactor
(O2 < 2%)
Heat
Biochar (BC) is the carbonaceous solid residue produced through the thermochemical conversion (pyrolysis) of
biomass under low O2 atmosphere.
What is biochar?
Soil
Soilremediation
Management of organic
wastes
Biochar applicationsDifferent applications:
Biochar potential to immobilize trace elements
Direct mechanisms
Chemisorption
• Adsorption in oxygenated functional groups (release H+)
• Cationic exchange (Na, Ca, S, K, Mg)
Physisorption
• Electrostatic attraction (π electrons)
Precipitation
• Mineral fraction / biochar ash
Indirect mechanisms
Changes in pH
Organic matter and soluble C
• Priming effect and DOC
Availability of P
Competition with As
Redox
Improvement of soil fertility, plant growth
Reduction of soil nutrient leaching
Mitigation of green house gases
C sequestration
Soil remediation
Biochar properties:
Biochar stability?Stability of biochars under debate
De la Rosa et al. (2018)
Main objetive: Determine the effects of biochar on C stability in trace
element polluted soils.
MRTbiochar>1000 years, when H/Corg<0.4
MRTbiochar>500, when 0.4<H/Corg<0.7
(Lehmann and Joseph, 2015)
Reference Scale of
estimated
MRT
MRT (years)
Masiello and Druffel (1998) Millennial 2400-13900
Cheng et al. (2006) Millennial 1000
Kuzyakov et al. (2009) Millennial 2000
Novak et a. (2010) Millennial 1400-51000
Zimmerman (2010) Centennial to
millennial
100-100000
MRT2 (years)
Pure Cambisol 5.7
Biochars+Cambisol 7.9-43.9
MRT2 (years)
Pure Cambisol 15.7
Biochar+Cambisol 17.4
Pure biochar 87
Dos Anjos Leal et al. (2019)
Respiration experiment – C stability
Respicond apparatus IV
(25°C)
10-20 g soil; 0.5-4 g chars
60% WHC, inoculated
Incubation vessel
KOH
CO2
Multimeter
Respiration experiment – C stability
KOH-solution
Electrodes
Sample
1. CO2 released by the sample is
absorbed in the KOH-solution and
forms carbonate, which decrease the
conductivity.
2. This change is conductivity is
measured by the respirometer.
3. From these values can be calculated:
- Cumulative carbon loss
- Degradation rates
- Mean residence time.
Respiration experiment – C stability
Re
ma
inin
gC
r(%
ofC
tota
l)
Incubation time (h)
94
95
96
97
98
99
100
101
0 500 1000 1500 2000 2500
Degradation rate constant
Fast pool Slow pool
Cr (%) =Cf*e(-kf*t)+ CS*e(-ks*t)
R2 =0.998
HPS - Highly Polluted SoilMPS - Moderately Polluted Soil
Green Corridor of Guadiamar (25 km north Seville)
2 soil (Typic Xerofluvent):
MPS: Moderately Polluted Soil
HPS: High Polluted Soil
WHC (%) Bulk density (g/ml) pH (CaCl2) EC (S/cm) % C
HPS 32.73 1.1 3.62 3610 0.8
MPS 51.45 1.2 6.47 1809 1.7
Materials: soilsThe Aznalcóllar Mine Accident
Location:
-Iberian Pyrite Belt (SW Spain-Portugal)
-Aznalcóllar (30 km from Seville)
25th April 1998 (3:30 am)
• 4 millions m3 acidic water
• 2 millions m3 toxic mud
The Aznalcóllar Mine [email protected]
Pyrolysis conditions• Temperature 500 ºC
• Time 2 h
• N2 atmosphere
• Heating rate 20 °C min-1
Batch reactor
N2
NaOH-water-oil
Reactor
Materials: biocharsFeedstock Biochar production
Rice Husk(RH)
Olive Pit(OP)
AlmondShell (AS)
Certified biochar (B1)• Material: Mixed wood sieving from
wood chip
• Pyrolysis: 20 min, 620 ºC
• Swiss Biochar, Laussane, Switzerland
One-exponential model
Underestimation of biochar stability?
Leng et al. (2019), Sci. Total Environ. 664, 11-23
Biochars – C stability
99.65
99.7
99.75
99.8
99.85
99.9
99.95
100
100.05
0 1000 2000 3000 4000
Rem
ain
ing
C (
% o
f in
itia
l C
)
Incubation time (h)
RHB500_2
OPB500_2
ASB500_2
B1
RHB
B1
ASB
OPB
No fast pool
𝐴 = 𝐴2 · ⅇ−𝑘2𝑡
Results [email protected]
Greater stability
of biochars
Effects of biochar in MPS – C stability
90
92
94
96
98
100
102
0 1000 2000 3000 4000
Rem
ain
ing
C (
% o
f in
itia
l C
)
Incubation time (h)
C_MPS
10%RHB500_2_MPS
10%OPB500_2_MPS
10%ASB500_2_MPS
10%B1_MPS
Control
RHBB1ASBOPB
𝐴 t = 𝐴1 · ⅇ−𝑘1𝑡 +𝐴2 · ⅇ
−𝑘2𝑡
Results [email protected]
Greater stability of biochar
amended soilThe curves were fitted by the following equation:
The curves were fitted by the following equation:
Except C_HPS and 10%OPB500_2_HPS that
were fitted by one-exponential model:
Effects of biochar in HPS – C stability
96.5
97.0
97.5
98.0
98.5
99.0
99.5
100.0
100.5
0 1000 2000 3000 4000
Rem
ain
ing
C (
% o
f in
itia
l C
)
Incubation time (h)
C_HPS
10%RHB500_2_HPS
10%OPB500_2_HPS
10%ASB500_2_HPS
10%B1_HPS
RHB
B1
ASBOPB
Control
Results [email protected]
𝐴 t = 𝐴1 · ⅇ−𝑘1𝑡 +𝐴2 · ⅇ
−𝑘2𝑡
Greater stability of biochar
amended soil
Experiment long enough?
Underestimation of C stability?
Leng et al. (2019), Sci. Total Environ. 664, 11-23
𝐴 = 𝐴2 · ⅇ−𝑘2𝑡
Conclusions
All biochars showed MRT > 100 years, being greater for OPB and ASB than RHB and the certified B1.
In moderately polluted soil, biochars:
• Did not modified the labile C fraction of soil.
• Increased MRT2 in 2-10 times in comparison to the control soil.
In highly polluted soil, biochars :
• Enhanced the degradation of a small fraction of labile C.
• Increased in 2.8-13.1 times the MRT2 of the more recalcitrant C fraction of soil.
Longer experiments would be recommended in order to distinguish if the C fraction found in control HPS was the labile fraction or all C in this soil has this degradability.
Acknowledgements:Grupo MOSS (IRNAS-CSIC)
MINEICO: CGL2016-76498-R and CGL2015-64811-P projects
Fundación Tatiana Pérez de Guzmán el Bueno
Thank you for your attention
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