Effects Of Biochar On Speciation Of Copper In Soil

Biochar is black solid derived from biomass pyrolysis under anaerobic conditions. Copper is an essential micronutrient for plant growth and its bioavailability in soil is closely related to its fractions in soil. In this study, the effects of biochar on the speciation of copper in soil was investigated using pot experiment, considering the lack of effective researches on biochar’s effects on soil copper form transformation and bioavailability. The effects of biochar production factors including raw materials, pyrolysis temperatures and acidification on the effectiveness of biochar were also studied. The main results are as follows:1The speciation of copper in soil was affected by biochar amendment. The contents of different chemical fractions of copper in the copper-added soil with biochar amendment were: Fe-Mn oxides fraction> organic matter fraction> carbonate fraction> exchangeable fraction. The contents of exchangeable, carbonate and Fe-Mn oxidizable fractions of copper in soil decreased with the increasing amount of biochar amended to soil, while the content of organic matter fraction of copper in soil increased with the increasing amount of biochar. The contents of different chemical fractions of copper in natural soils without copper treatment were: carbonate fraction> organic matter fraction> Fe-Mn oxides fraction> exchangeable fraction. In natural loamy soil without copper treatment, the content of exchangeable copper in soil increased with the increasing amount of biochar; the content of carbonate copper in soil decreased with the increasing amount of biochar; the contents of Fe-Mn oxideable fraction and organic matter fraction of copper in soil initially increased and then decreased with the increasing amount of biochar. In natural sandy soil without copper treatment, the contents of exchangeable and carbonate copper in soil increased with the increasing amount of biochar; the content of copper bounded to soil Fe-Mn oxides decreased with the increasing amount of biochar; the content of copper bounded to soil organic matter increased with the increasing amount of biochar.2The effects of biochar on speciation of copper in soil were significantly influenced by soil copper treatment levels. With the increasing levels of copper amended in soil, the contents of the exchangeable, carbonate, Fe-Mn oxideable and organic matter copper in soil were significantly increased with the increasing level of copper amended to soil.3The effects of biochar on speciation of copper in soil were influenced by biochar feedstocks. With the200mg/kg soil copper level and5%(wt.%) application rate of biochar, the content of exchangeable copper in soil amended with biochars produced from different feedstocks was:wheat straw biochar treatment> corn stover biochar treatment> leaf biochar treatment> branch biochar treatment, the wheat straw biochar treatment was significantly different with others; the content of carbonate copper in soil amended with different biochars was:branch biochar treatment> wheat straw biochar treatment> leaf biochar treatment> corn stover biochar treatment, leaf biochar treatment was significantly different with corn stover biochar treatment; the content of Fe-Mn oxideable copper in soil amended with different biochars was:branch biochar treatment> wheat straw biochar treatment> leaf biochar treatment>corn stover biochar treatment, the difference between each treatment was significantly except that between wheat straw biochar treatment and branch biochar treatment; the content of copper bounded to organic matter in soil amended with different biochars was: leaf biochar treatment> branch biochar treatment> wheat straw biochar treatment> corn stover biochar treatment, the differences among the branch biochar treatment,leaf biochar treatment and corn stover biochar treatment were significant.4The effects of biochar on speciation of copper in soil were influenced by biochar pyrolysis temperature. With the200mg/kg soil copper level and5%(wt.%) application rate of biochar, the content of exchangeable copper in soil amended with biochars pyrolysised at different temperatures was:450℃Biochar treatment>600℃Biochar treatment>300℃Biochar treatment; the content of carbonate,Fe-Mn oxideable copper and organic matter fraction of copper in soil amended with different biochars was:300℃Biochar treatment>600℃Biochar treatment>450℃Biochar treatment. In the whole, the contents of various fractions of copper in soil amended with the450℃biochar were significantly different with that of300℃biochar treatment and600℃biochar treatment.5The effects of biochar on speciation of copper in soil were influenced by its acidifying activation. With the200mg/kg soil copper level and5%(wt.%) application rate of wheat straw biochar, the content of exchangeable copper in soil amended with biochar having different pH was:pH9Biochar treatment> pH5Biochar treatment> pH7Biochar treatment,the pH9biochar treatment was significantly different with others; the content of copper bouded to carbonate in soil amended with different biochars was:pH9Biochar treatment> pH7Biochar treatment> pH5Biochar treatment,there were no significant differences amomg those treatments; the content of copper bounded to Fe-Mn oxides in soil amended with different biochars was:pH7Biochar treatment> pH5Biochar treatment> pH9Biochar treatment, there were no significant differences amomg those treatments; the content of copper bounded to organic matter in soil amended with different biochars was:pH7Biochar treatment> pH5Biochar treatment> pH9Biochar treatment, there were significant differences between pH9biochar treatment and others.