Study On DBP Remediation By Modified Biochar Supported Functional Bacterium Pseudomonas Sp. DNB-S1

Dibutyl phthalate（DBP）is one of the most common phthalate esters（PAEs）,which typically enter the food chain through soil and water environments,posing a threat to human health.Due to the high toxicity and environmental risks of DBP,it poses a threat to human and ecological safety.How to remove DBP from soil in a green,safe,and efficient manner has become a research hotspot in recent years.Based on the above practical problems,this experiment took DBP as the target pollutant,and took nano hydroxyapatite modified biochar loaded DBP efficient degradation bacteria DNB-S1 as the repair material to explore its efficacy in reducing DBP.Nano-hydroxyapatite modified biochar loaded degradation bacteria DNB-S1 was applied to DBP contaminated soil,using Chinese cabbage as the test plant,the effects of modified biochar materials on soil physicochemical properties and physiological and biochemical indicators of Chinese cabbage were studied to elucidate the reduction mechanism of remediation materials on DBP.The main research findings are as follows:（1）The optimal ratio of nano-hydroxyapatite modified biochar was investigated,and its ability to reduce DBP and DNB-S1 loaded with DBP was determined.The basic properties of biochar and modified biochar were studied by Fourier infrared spectroscopy,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）and surface area meter,and the load of modified biochar on degrading bacteria was observed by field emission electron microscopy.Compared with biochar,the carbonyl-C=O kurtosis of 0.5%nano-hydroxyapatite modified biochar was enhanced,and a stronger phosphorus and oxygen group appeared.At the same time,the structure of 0.5%nano-hydroxyapatite modified biochar crystal was complete,the crystal shape was better,the peak strength of O1s was enhanced,and phosphorus and oxygen groups appeared between 532.03 EV-533.62 e V.The results indicate that nano hydroxyapatite has successfully entered biochar.The results of field emission electron microscopy showed that the surface morphology of 0.5%modified biochar was coarser and provided more sites for degrading bacteria.The effect of 0.5%modified biochar loading degrading bacteria DNB-S1 was the best,and the morphology of degrading bacteria was the most complete.The reduction rate of DBP of 100 mg·L^-1 by 0.5%modified biochar supported degradation bacteria reached 86.76%,which was 45.78%higher than that of biochar supported degradation bacteria.（2）Applying 4%modified biochar loaded DNB-S1 to the soil had the best effect on reducing DBP at 20 mg·kg^-1,while Chinese cabbage had the best growth potential.At 49 days,the DBP content in the soil was 2.34 mg·kg^-1,with a reduction rate of 88.30%.At the same time,at 49 days,the DBP content in the aboveground part of Chinese cabbage was only 0.12 mg·kg^-1,and the DBP content in the underground part was 0.37 mg·kg^-1.The plant height of Chinese cabbage reached34.20 cm.Compared with biochar and biochar loaded DNB-S1,modified biochar promotes the production of indoleacetic acid and gibberellin in Chinese cabbage,which has a positive impact on the growth of Chinese cabbage.The application of 4%modified biochar loaded DNB-S1 can regulate soil physical and chemical indicators,and the soil p H,organic carbon,available phosphorus,nitrate nitrogen,ammonium nitrogen,as well as the content of phosphatase and urease are all increased compared to biochar and biochar loaded DNB-S1.According to the correlation analysis between soil physicochemical indicators and DBP reduction rate,it is found that there is a positive correlation between soil p H value,available phosphorus,nitrate nitrogen,organic carbon,phosphatase,urease,and DBP reduction rate.At the same time,modified biochar loaded DNB-S1can also regulate soil p H value and promote DBP reduction in soil.（3）Fluorescence quantitative PCR results showed that DNB-S1 loaded with modified biochar reduced the abundance of soil denitrification functional genes nir S,nor B,nar G,nos Z and nap A,and increased the abundance of carbon cycle functional gene Mcr A.The correlation analysis of soil nitrogen cycle related functional genes,ammonium nitrogen,nitrate nitrogen and soil DBP reduction rate showed that soil DBP reduction rate was significantly negatively correlated with denitrification genes nir S,nor B,nar G,nos Z,nap A,and significantly positively correlated with ammonium nitrogen and nitrate nitrogen.Modified biochar loaded DNB-S1 improved soil nitrogen utilization by promoting nitrification and inhibiting denitrification.