氧化改性生物炭对设施菜地土壤氮素淋失的阻控作用与机制

Large numbers application, low use efficiency and serious leaching loss of nitrogenous fertilizer, has been serious problems in greenhouse vegetable cultivation. Regulatory roles of biochar on soil nitrogen cycle that has made people realize the potential resistance of control soil nitrogen leaching, but its mechanism is not clear enough.On the basis of previous studies, we think that retention caused by surface physical and chemical properties of biochar and its cooperation with soil microbial may be an important mechanism for biochar control soil nitrogen leaching. Therefore, the essentail issues of studying the effect of biochar on soil nitrogen cycle are how to improve capacity of the retention and show process of the retention.This project intends to treat peanut shell biochar as resrarch materials to improve the retention of biochar through optimization, removing the impurities and oxidation.To design a solid-liquid adsorption system of biochar to nitrogen, to detecte and show the rules of nitrogen accumulation on surface of biochar by scanning electron microscope and spectrum analysis, are to analyze the relationship between physicochemical factors on biochar surface and the sorption of nitrogen. Nitrogen is loaded to biochar by adsorption to make sure that biochar as a nitrogen pool. The function and mechanism of biochar to soil nitrogen cycle can be revealed through setting of indoor soil culture and field plot test, monitoring diversity changes of soil microbial responsible for nitrogen transformation under the condition of application the biochar that with nitrogen, and verifying the effect of biochar control soil nitrogen leaching. Results of the project will provide a new ideas to improve nitrogen fertilizer use efficency in greehoue vegetable cultivation.

氮肥投入量大、利用效率低、淋溶损失严重一直是设施蔬菜生产中致力客服的难题。生物炭对土壤氮素循环的调控作用使人们看到其阻控土壤氮素淋失的潜力，但其作用机制尚未获得共识。基于先前研究，初步认定“生物炭表面特异的理化因子及与微生物互助形成的吸持作用可能是其阻控氮素行为的重要机制”。如何提高这种吸持能力和表征其过程是生物炭影响氮素循环研究的关键问题。本研究拟以花生壳生物炭为材料，对其优选去杂、氧化改性，提高吸持能力。设计生物炭对氮素的固液相吸附体系，借助电镜扫描、光谱分析等技术观察与表征氮素在生物炭表面的累积规律，解析其表面理化因子与氮素吸持的关系。通过吸持作用将氮素锚定于生物炭表面，使其作为氮素贮库。设置土壤培养和田间试验，监测氮转化相关微生物对载氮生物炭输入的响应特征，验证生物炭对氮素土壤淋移的阻控效应，揭示生物炭影响土壤氮素行为的作用与机制。为设施蔬菜生产氮肥高效管理提供新的思路。

本研究在高温（500℃）充N2条件下热解制备花生壳生物炭（PBC），经HCl、H2SO4和H2O2氧化得改性生物炭（HCl-PBC、H2SO4-PBC和H2O2-PBC）。探索氧化剂对生物炭的改性效果，解析氧化改性生物炭吸附铵态氮和硝态氮性能与机制，揭示载氮生物炭对土壤微生物的影响及缓控土壤氮素循环的作用。结果表明：HCl、H2SO4和H2O2处理有效清除生物炭表面灰分，增加可固定碳48.6%-68.8%，增大比表面积10.8%-18.5%，增加C=O、-COO等含氧官能团，降低pHpzc和pH。H2O2处理增大生物炭表面O/C和(O+N)/C值，增强生物炭的亲水性和极性，HCL和H2SO4处理引起过氧化作用，破坏生物炭的大孔。改性效果表现为H2O2＞HCL＞H2SO4。氧化剂处理显著增强生物炭对NH4+-N和NO3--N吸附能力。Langmuir方程均较好地描述等温吸附行为，吸附动态分别符合伪一级、二级方程。以单层物理吸附为主，同时伴随一定的化学吸附，大比表面积提供多吸附位点和丰富的孔隙扩散作用，是其吸附NO3--N和NH4+-N的主要因素，表面-OH通过静电引力、C-O或C=O通过羰胺缩合或亚甲基缩合、-CH3通过共轭效应等生成-C=C=N、-C=N及-C-N键等吸附NH4+-N。表面-OH、C=C或C=O通过形成氢键及π-π共轭方式、离子交换等吸附NO3--N。吸附能力表现为H2O2-PBC＞H2SO4-PBC＞HCL-PBC。适量添加载氮生物炭能够促进土壤真菌、细菌的生长繁殖，而高量施用对其生长代谢产生抑制作用。添加载氮生物炭显著增加土壤中全氮、硝态氮和铵态氮含量。小白菜生物量增加5.4%~8.7%，土壤硝态氮淋失量较等氮量尿素降低75.6%~90.4%，土壤N2O排放量降低3.8%~52.1%，CO2排放增高27.6%-63.1%，CH4排放得到有效抑制。土壤固碳潜力（SOCP）增加16.9%-20.2%，净温室综合效应（GWP）降低1.8%~10.2%，温室气体排放强度（GHGI）降低5.3%~16.2%。载氮生物炭能满足作物对氮素需求，增加土壤固碳潜力，降低温室气体排放，阻控土壤氮素淋溶损失。