Effects Of Biochar On Exogenous Cadmium Forms And Cadmium Uptake By Cotton

[Object]:In recent years,inorganic pollutants have become more and more harmful to agricultural soils in China.Among them,heavy metal Cd is one of the major inorganic elements that contaminate farmland soil.As a potential environmental remediation mater ial,biochar has rich surface functional groups,high pH,and good adsorption properties.It has good effects on removing heavy metals in soil,and biochar itself is rich in ash and mineral elements for crops.Growth and development have positive functional effects and are therefore widely used in eliminating soil environmental pollution.[Method]:In this study,exogenous heavy metal Cd was applied to cotton soil in Xinjiang as the research object.Biochar was used to relieve soil Cd pollution and relieve Cd accumulation in cotton as a starting point.A two-year pot experiment was used to investigate the application of different biochar C1?1.5%?and Soil pH,Cd content,Cd at C2?3%?levels of 1 mg·kg^-1?H1?,2 mg·kg^-1?H2?,and 4mg·kg^-1?H3?at different levels of Cd pollution Morphological transformation and the effect of biochar on the accumulation of Cd in cotton aboveground organs further discussed the relationship between cotton aboveground and soil Cd.[Results]:Both the C1 and C2 biochar application s ignif icantly increased the soil p H value,and the increase range increased with the increase of the application amount.There was no signif icant difference in the effect of biochar application amount between C1 and C2 on soil pH value.The amount of heavy metal Cd had no significant effect on the pH of the soil.With the continuation of the culture time,the pH decreased.Different biochar application rates could significantly reduced the available Cd content in soil,The greatest reduction was C2H3 treatment,which was 41.03%;and the larger the decline with the increase of biochar,and the full-scale and effective Cd of biochar on the time scale.Reduce trends are similar.The application of biochar was shown to promote the conversion of exchangeable and carbonate-bound Cd to organic-bound Cd in the soil at 30,60 and 90 days of culture,and soil exchangeable and carbonic acid at 120 and 150 days.The conversion of salt-bonded state to iron-manganese oxidation state Cd,that is,biochar can increase the soil pH to reach the effect of adsorbing soil Cd,and promote the conversion of exchangeable state and carbonate-bound Cd to iron-manganese oxidation state and organic matter binding state.This in turn reduces the bioavailability of Cd.Under the application of biochar treatment,the content of Cd in cotton leaves and stems showed a trend of gradual change with the increase of the first growth period,and the application of biochar can relieve the enrichment of heavy metal Cd in cotton leaves,stems,and flower buds.The greater the application amount of biochar,the better the alleviation effect.Among them,the effect of biochar on the reduction of Cd in the aboveground parts of cotton was leaf>stem>leaf bell;the content of Cd in cott on leaf and stem was the same with cotton.The period of childbear ing is manifested as a trend of decreasing first and then tending to be gentle.The enrichment of heavy metal Cd in the aboveground parts of cotton showed as leaf>stem>breast ring;the application of biochar had no significant effect on the partition coefficient of Cd in cotton aboveground parts,that is,biochar made the cotton from the bottom up Hysteresis occurs in Cd transport.The application of biochar increased the dry weight of the cotton aboveground,and the C1 biochar treatment showed a significantly higher trend than the control when cultured for 30 and 60 days.However,at 120 and 150 days,the C1 biochar treatment showed no signif icant difference compared with the control,but it was comparable.The control value is still on the rise,C2 biochar treatment is significantly higher than the control,The application of biochar increased the boll number and boll weight,which had a significant effect on cotton yield?P<0.05?,that is,biochar can alleviate the enrichment of heavy metal Cd in cotton,and has a positive impact on the growth and development of cotton.The correlation results showed that the correlation between soil p H value and available,exchangeable and carbonate bound Cd in soil reached a signif icant level?P<0.01?.There was a highly signif icant positive correlation between Cd content in cotton leaves and stems,soil Cd content,soil exchangeable and available Cd content?P<0.01?,and there was a signif icant negative corr elation between Cd content and organic matter bound Cd.?P<0.01?.?Conclusion?The long-term continuous cropping of cotton fields in Xinjiang and the large investment in chemical fertilizers,pesticides,and agricultural films have led to an increase in soil heavy metal pollution in cotton fields.Biochar can reduce the soil available Cd by increasing soil p H and promote the exchangeable and carbonate bound states Cd.The conversion of organic matter binding state and iron-manganese oxidation state Cd,thereby slowing down the bioavailability of Cd,played a certain role in promoting the growth and development of cotton,and achieved the purpose of improving the heavy metal pollution in cotton field soil.