Abstract
Biochar can benefit human society as a carbon-negative material and soil amendment. However, negative biochar impacts on plant germination and growth have been observed, and they have not been fully explained. Therefore, protocols to avoid these risks cannot be proposed. We hypothesized that the free radicals generated during charring may inhibit plant germination and growth. Significant electron paramagnetic resonance (EPR) signals were observed in the biochars derived from several types of common biomass (corn stalk, rice, and wheat straws) and the major biopolymer components of biomass (cellulose and lignin), but not in the original materials, suggesting the ubiquitous presence of free radicals in biochars. EPR signal intensity increased with increasing pyrolysis temperature, and it was dominantly contributed by oxygen centered in the mixture of oxygen- and carbon-centered free radicals as the temperature increased. The free radicals in biochars induced strong ·OH radicals in the aqueous phase. Significant germination inhibition, root and shoot growth retardation and plasma membrane damage were observed for biochars with abundant free radicals. Germination inhibition and plasma membrane damage were not obvious for biochars containing low free radicals, but they were apparent at comparable concentrations of conventional contaminants, such as heavy metals and polyaromatic hydrocarbons. The potential risk and harm of relatively persistent free radicals in biochars must be addressed to apply them safely.
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Claims 11
Claim · model-written summary
Biochars from common biomass and biopolymers showed EPR signals absent from original materials.
- Taxon
- Corn, Wheat and Rice Seedlings
Oryza sativa
Triticum aestivum
Zea mays subsp. mayst0 - Outcome
- electron paramagnetic resonance (EPR) signalse0
- Comparator
- original materialse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant electron paramagnetic resonance (EPR) signals were observed in the biochars derived from several types of common biomass (corn stalk, rice, and wheat straws) and the major biopolymer components of biomass (cellulose and lignin), but not in the original materials”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
EPR signal intensity rose with pyrolysis temperature.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- pyrolysis temperaturee0
- Outcome
- EPR signal intensitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“EPR signal intensity increased with increasing pyrolysis temperature”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Oxygen-centered radicals increasingly dominated at higher temperatures.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Outcome
- oxygen centered in the mixture of oxygen- and carbon-centered free radicalse0
- Direction
- as the temperature increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it was dominantly contributed by oxygen centered in the mixture of oxygen- and carbon-centered free radicals as the temperature increased”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Biochar free radicals induced aqueous hydroxyl radicals.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Outcome
- strong ·OH radicals in the aqueous phasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The free radicals in biochars induced strong ·OH radicals in the aqueous phase”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Biochars with abundant free radicals inhibited cereal germination.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- biochars with abundant free radicalse0
- Outcome
- germination inhibitione0
- Direction
- inhibitione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant germination inhibition, root and shoot growth retardation and plasma membrane damage were observed for biochars with abundant free radicals”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Biochars with abundant free radicals retarded root and shoot growth.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- biochars with abundant free radicalse0
- Outcome
- root and shoot growth retardatione0
- Direction
- retardatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant germination inhibition, root and shoot growth retardation and plasma membrane damage were observed for biochars with abundant free radicals”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Biochars with abundant free radicals damaged plasma membranes.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- biochars with abundant free radicalse0
- Outcome
- plasma membrane damagee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant germination inhibition, root and shoot growth retardation and plasma membrane damage were observed for biochars with abundant free radicals”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Low-radical biochars showed no obvious germination inhibition.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- biochars containing low free radicalse0
- Outcome
- Germination inhibitione0
- Direction
- not obviouse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Germination inhibition and plasma membrane damage were not obvious for biochars containing low free radicals”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Low-radical biochars showed no obvious plasma membrane damage.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- biochars containing low free radicalse0
- Outcome
- plasma membrane damagee0
- Direction
- not obviouse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Germination inhibition and plasma membrane damage were not obvious for biochars containing low free radicals”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
Comparable concentrations of conventional contaminants produced apparent inhibition and membrane damage.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Treatment
- conventional contaminantse0
- Outcome
- they were apparente0
- Direction
- apparente0
- Qualifier
- comparable concentrationse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they were apparent at comparable concentrations of conventional contaminants, such as heavy metals and polyaromatic hydrocarbons”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
Claim · model-written summary
The authors recommend addressing persistent biochar radical risks for safe application.
- Taxon
- Corn, Wheat and Rice SeedlingsOryza sativaTriticum aestivumZea mays subsp. mayst0
- Outcome
- must be addressed to apply them safelye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The potential risk and harm of relatively persistent free radicals in biochars must be addressed to apply them safely”
t0“Detecting Free Radicals in Biochars and Determining Their Ability to Inhibit the Germination and Growth of Corn, Wheat and Rice Seedlings”
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See all 85 papers →8 of 9 groups shown: named compounds and organisms first, then groups whose results differ (checked claim by claim), then those with positive and negative results, then the smaller groups.
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.