| Biomass is considered to be a resource with great potential for development because of its huge reserves,abundant species and renewability.Nearly 40 million mu of cotton is cultivated in Xinjiang,which may result in a large amount of cotton stalks that cannot be disposed of in time and become solid waste.Hydrothermal carbonization technology is a kind of biomass conversion technology.It has the advantages of mild reaction,no requirement on raw materials and low cost,and is widely used by researchers.However,the liquid phase products of hydrothermal carbonization are seldom used at present.In this study,cotton stalks were used as raw materials for hydrothermal carbonization to prepare hydrothermal carbonization solution for soil improvement.Influences of different reaction conditions and catalysts on hydrothermal carbonization solution were explored,and acids and phenols in the obtained hydrothermal carbonization solution and hydrothermal carbonization solution were prepared into simulated solution and applied to soil.Pot experiments were carried out with cotton seedlings as indicators.To explore the improvement effect of hydrothermal carbonization solution on soil.The main research results are as follows:(1)The physicochemical properties of hydrothermal carbonization solution were most affected by temperature and least affected by solid-liquid ratio;The plant height and plant weight were 16.99% and 14.58%higher than that of the control group when the reaction temperature was 150℃.When the reaction time was1 h,the available phosphorus content was increased by 317.07% compared with CK group.In the 1:14 solidliquid ratio of the experimental group,the alkali-hydrolyzed nitrogen and available potassium increased by13.65% and 5.67%,respectively,compared with the CK group.The most suitable hydrothermal carbonization conditions for soil improvement are as follows: reaction temperature 150℃,reaction time 1 h,solid-liquid ratio 1:14.(2)Hydrothermal carbonization liquid mainly contains acids,phenols,aldehydes,alcohols and other compounds.The contents of acetic acid and propionic acid increased with the increase of the number of cycles.Compared with CK group and SCK group,the plant height,plant weight,leaf area and chlorophyll content of cotton seedlings in C-4 group were increased by 37.76%,32.72%,24.38%,63.67% and 16.28%,23.72%,11.78% and 28.85%,respectively.With the increase of acetic acid concentration,the contents of acetic acid and propionic acid also increased gradually,but the contents of phenol and guaiacol had little change.The growth status of cotton seedlings in group A-5% was not different from that in group C-4.Different catalysts can promote soil enzyme activities and soil nutrients.Overall,the C-4 group had better results.(3)Acids and phenols in hydrothermal carbonization had different effects on plant growth.Acids had obvious effects on plant height,while phenols had obvious effects on plant weight and leaf area.The chlorophyll content of guaiacol group was the highest,which was 52.17% higher than that of water group.The content of MDA in phenol group was the lowest,which was 73.38% lower than that in water group.At30 d,when plants were planted,acids and phenols could improve the activities of urease and catalase,and acetic acid could increase the contents of soil organic matter,alkali-hydrolyzed nitrogen,available phosphorus and available potassium by 1.12,1.17,1.40 and 1.13 times of that in the water group,respectively.When no plants were planted,both acids and phenols could increase the activity of sucrase,and the effect of acetic acid on organic matter content was 1.20 times that of water group.The increasing effect of guaiacol on the content of available phosphorus was 1.81 times that of the clean water group.The acids and phenols in hydrothermal carbonization can change soil enzyme activity,soil nutrient content and soil microbial community structure. |
PDF Full Text Request