兽用抗生素单一和复合污染对农田土壤CH4和N2O排放的影响及其机制

Global warming and organic pollution are important environmental problems today. Antibiotics especially veterinary antibiotics play a big role in the antibacterial treatment, while the abuse of them also has resulted in a great pollution to the ecological environment. The three typical veterinary antibiotics, which exist widely in the domestic environment, will be taken as the research objects in this program. The indoor cultivation experiment under different soil and different moisture conditions and rice-wheat rotation field studies in situ will be conducted. Two rice planting patterns (transplanting + direct-seeding) will be included. Gas chromatography method, isotope dilution method, q-PCR analysis and high-throughput sequencing method will be used to study the effect of single and combined pollution of veterinary antibiotics on soil carbon and nitrogen cycling and CH4 and N2O emissions with or without the application of pig manure, and tries to clarify the impact of veterinary antibiotics on the soil CH4 generation-oxidation, N2O generation- reduction and the response mechanism of soil microorganism related to carbon and nitrogen cycle to the input of antibiotics, to further reveal the greenhouse gas emissions effect of single and combined pollution of antibiotics in rice/wheat farmland. The results will be help to provide a theoretical basis for both evaluating scientifically the ecological environment effect of antibiotic pollution and correctly estimating CH4 and N2O emissions in farmland in the exacerbation of organic pollution.

全球变暖和有机污染加剧是当今极其重要的环境问题。抗生素尤其是兽用抗生素在抗菌治病发挥巨大作用的同时,其大量滥用也对生态环境产生了很大的污染。本研究以国内环境广泛存在的3大典型兽用抗生素为研究对象，通过不同土壤不同水分条件下的室内培养实验和稻麦轮作（其中水稻采用移栽和旱直播两种种植模式）的田间试验，结合气相色谱分析法、同位素稀释法和定量PCR分析及高通量测序技术，研究抗生素单一及复合污染及有无猪粪配施条件下对农田土壤CH4和N2O排放及相关碳氮转化的影响；试图阐明兽用抗生素对农田土壤CH4生成-氧化，N2O生成-还原的影响机理及土壤相关碳氮循环功能微生物对抗生素输入的响应机制，揭示兽用抗生素单一及复合污染对稻麦农田温室气体排放效应的影响，以期为有机污染加剧的情景下科学评估抗生素污染的生态环境效应及正确估算农田温室气体CH4和N2O排放提供理论依据。

畜禽粪便农田施用是温室气体的主要源之一。兽用抗生素滥用导致其在畜禽粪便中高残留，对生态环境产生严重污染的同时，也影响了农田温室气体的产生与排放。本项目结合田间试验和室内模拟实验，系统地研究了磺胺二甲嘧啶（SMZ）及与猪粪或化肥协同作用下对农田土壤CH4、 N2O和NH3排放的影响及其机制。结果表明无论基肥是复合肥还是猪粪，SMZ均未改变稻麦田CH4、N2O排放及NH3挥发的季节性排放规律，但是中高浓度SMZ对N2O排放和NH3挥发均有显著促进作用，且这种促进作用主要表现在稻麦田的追肥期；而对CH4排放不同环境条件表现不一，中、高浓度SMZ对水稻生长季CH4排放有明显的前抑后促特征，尤其与猪粪协同作用下后期促进作用比较明显。SMZ进入农田土壤后母体去除较快，中间降解产物种类复杂，其进一步降解速度缓慢，对土壤环境的中长期效应值得关注。SMZ对CH4和N2O排放的影响有明显的低促高抑浓度效应，具体取决于环境条件的变化。SMZ在淹水条件下与化肥共存对CH4和N2O产生相关的微生物毒理效应要大于与猪粪协同作用，而在旱地条件则相反。SMZ及其中间产物如2-氨基-4,6二甲基嘧啶通过改变产CH4和N2O微生物底物含量（溶解性有机碳、铵氮和硝氮）和相关功能基因（16S rRNA、CH4-16S rRNA、pmoA、mcrA 和AOA amoA、AOB amoA、nirK、nirS、nosZ）丰度，进而对农田CH4和N2O的排放产生直接影响。另外，SMZ还通过提高土壤脲酶活性，改变优势微生物种类及活性，对CH4和N2O的排放产生间接影响。在一定浓度范围内，SMZ、恩诺沙星和四环素三种抗生素均能提高脲酶和β-葡萄糖苷酶的活性，随着苯环数量增加而逐渐增强，促进机理为抗生素与酶结合成复合物，改变了酶活性中心的氨基酸残基微环境，增加酶活位点亲水性，进而增强了酶活性。.本研究结果说明畜禽粪便无论是在旱地还是水田施用，抗生素的存在会进一步加剧活性氮损失，形成恶性循环，其环境影响不可忽略。本研究结果可为全面评估抗生素污染的生态环境效应以及正确评估畜禽粪便源温室气体排放提供科学依据。