生物炭活化过氧化尿素对农田有机污染土壤的控污增效机制

Biochar has recently received major attention as a very effective environmental sorbent of many organic and inorganic contaminants in soil. However, the absorbed pollutants may be released through desorption. Our previous work revealed that the degradation of organic pollutants can be enhanced by urea hydrogen peroxide (UHP) activated with iron loaded on biochar. However, its mechanisms have yet to be fully elucidated. In this project, the biochars were produced under various pyrolysis temperatures using dairy manure and rice hull as the raw material The mechanisms of controlling organic pollution and improving soil fertility by UHP activated with biochar were investgated. The intermediates were identified based on the National Institute of Standards and Technology database information acquired through headspace GC–MS technologies. Free radical quenching reaction and electronic paramagnetic resonance (EPR) were employed to identify the free radical species. Terminal restriction fragment length polymorphism (T-RFLP) and quantitative polymerase chain reaction (qPCR) were also employed to quantify the change in the number of gene copies of 16S rDNA, PAH-RHDα, and nitrogen cycle genes (nirS) of the bacterial community. Leaching column experiments were used to to evaluate the nutrient transformation and transport in soil.The results obtained from this project has important scientific significance and application value for remediation of organic contaminated soil and increasing soil fertility.

利用生物炭吸附土壤有机污染物是近几年国内外的研究热点。然而，生物炭老化会导致其吸附的有机污染物存在二次释放风险。申请人前期研究发现，生物炭活化新型氮肥过氧化尿素（UHP），具有降解农田有机污染物和增加土壤肥效的双重功能，但是，这种控污增效的机理还不清楚。本项目拟以多环芳烃（PAHs）为目标污染物，以稻壳和牛粪生物炭为研究对象，采用室内模拟和GC-MS等分析技术，研究不同类型生物炭活化UHP对PAHs的催化降解效应，并利用自由基淬灭反应和电子顺磁共振技术对反应体系的主导自由基进行鉴定。在此基础上，采用末端限制性多态分析、荧光定量PCR技术和土柱淋溶实验，研究生物炭活化UHP对PAHs土著微生物降解功能基因和土壤氮利用率的影响，提出生物炭活化UHP对农田有机污染土壤的控污增效机制，研究结果对于推动我国农田污染土壤的原位肥力维持性绿色修复技术发展具有重要的科学意义和应用价值。

项目针对农田污染土壤原位肥力维持性绿色修复技术中迫切需要解决的关键科学问题，以沼渣、稻壳和牛粪生物炭为研究对象, 土壤典型有机污染物多环芳烃BaP和抗生素SMZ为目标污染物，采用生物炭改性、室内模拟和GC-MS分析等技术，开展生物炭制备及其吸附与解吸附动力学研究，明确不同类型生物炭活化UHP和APS的催化降解效应，并利用自由基淬灭反应和电子顺磁共振技术对反应体系的主导自由基进行鉴定。结果表明，生物炭中环境永久自由基（EPFRs）浓度随着生物炭制备温度的升高呈现先升高后降低的趋势,铁改性生物炭FB/UHP处理显著降低全氮淋溶，增加土壤表层的氮素含量，提高氮素的利用效率。改性沼渣生物炭FBC/APS体系, 在宽泛的pH范围内能有效降解多环芳烃BaP。该降解反应受FBC制备温度和反应初始pH值等因素的影响，循环使用试验表明，FBC具有良好的稳定性， 3次循环试验后FBC对BaP的催化降解仍能达到87.36%。FBC/APS体系中BaP降解的可能机制包括自由基和非自由基两种途径。在FBC/APS体系降解BaP的过程中，共鉴定出5个降解中间产物，分别为2,6-二羟基苯乙酮、3-甲基水杨酸、邻苯二甲酸二丁酯、BaP-4,5-二酮和BaP-7,10-二酮。ECOSAR毒性预测评价表明，随着BaP在FBC/APS体系中的降解，这些降解中间产物的分子量越来越小，其毒性也越来越低. FBC/APS体系不仅可以有效降解土壤中的BaP，还可以提高土壤有效钾和有效氮含量，增强土壤肥效。在上述研究基础上，项目还开展了生物炭活化ASP协同植物修复多环芳烃污染土壤研究，结果表明，利用改性沼渣生物炭FBC活化APS联合芳香植物罗勒对多环芳烃污染土壤具有显著协同修复效应，罗勒的生长可以作为一种生物刺激方法来降低高级氧化对土壤微生物群落丰度和多样性的不利影响，协同修复处理可以加速污染土壤细菌和真菌群落组成和功能的恢复，本项目研究成果对于推动我国农田污染土壤的原位肥力维持性绿色修复技术发展具有重要的科学意义和应用价值。