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农田中的氮磷难以被农作物完全吸收,并容易随农田排水进入自然环境之中,这会导致了区域水体的富营养化从而对生态系统产生严重威胁[1-2]。根据2015年中国农业部的相关数据,我国农业化肥的使用量高达6022万吨,但利用率仅为35.2%,这导致自然水体中的氮磷主要来自于农业中的化肥施用,其贡献率高达57.2 %和67.4 %[3]。与此同时,抗菌药物已经广泛应用于农业生产中,但它们在动物体内的降解效率较低从而大量残留于畜禽粪便中,而畜禽粪便的土地利用导致了耐药基因在自然环境中的富集与传播,其所引发的抗生素抗性问题已经成为了当今世界最大的公共健康问题之一[4-7]。农田土壤作为地球上微生物多样化程度最高的栖息地之一,是耐药基因的巨大储存库,其中部分耐药基因能够随着农田排水进入自然环境之中,而上述耐药基因能够以环境微生物为宿主从而进一步地传播与扩散[8-9]。已有研究表明农业灌溉系统中含有丰富的耐药基因,而农田排水向自然水体的释放可能会成为耐药基因在水体环境中积累与传播的主要途径之一[10]。综上所述,农田排水中的耐药基因能够以微生物为宿主在环境中富集与传播,而其中的氮磷则会导致自然水体富营养化,这对自然环境和公共健康产生极大的潜在威胁。
农田排水沟渠系统作为农田与自然水体的过渡带,已经成为了控制农田中氮磷与耐药基因向自然环境中传播与扩散的关键。传统的农田排水沟渠系统采用混凝土构筑,无法有效拦截农田排水中的氮磷,同时它们较差的水土保持能力容易引起水土流失[11-13]。生态沟渠是对传统农田排水沟渠系统的升级与改造,它通过土壤-微生物-植物形成生态链平衡系统,并利用其新陈代谢协同降解农田排水中的有机物、氮、磷等污染物,同时辅助脱氮除磷装置,拦截转化池,底泥污染捕获系统等功能性设备,进一步提高农田排水中污染物的拦截效果[14-15]。然而,生态沟渠对于农田排水中耐药基因的拦截效果尚未被研究,同时能够有效提高农田排水水质并降低其中氮磷浓度及耐药基因丰度的生态沟渠建设模式仍需探索。
开展生态沟渠系统建设是农业水环境治理的迫切需要,也是促进农业绿色发展、建设美丽田园的重要举措。因此,浙江省积极开展生态沟渠系统的建设工作,并在宁波市、湖州市、嘉兴市、绍兴市和台州市建设了20条高标准建设模式的生态沟渠。然而,生态沟渠的运行效果容易受多种因素影响,包括农田排水水力负荷、沟渠内部的水深、沟渠内部植物的种类以及水力停留时间等[1]。因此,本文全面评价20条高标准建设模式的生态沟渠对农田排水中氮磷的拦截效果,从而明确生态沟渠的建设模式对农田排水中氮磷拦截的影响。同时,生态沟渠系统中的水生植物和生态拦截功能设备能够有效控制来自于农田排水中的微生物,而耐药基因往往是被微生物所携带的[6-7, 16]。因此,生态沟渠系统具有降低农田排水中耐药基因的丰度,从而限制抗生素抗性的传播的应用潜质,但生态沟渠对农田排水中菌群和耐药基因的影响却鲜有研究。综上所述,本文评价浙江省生态沟渠对农田排水中氮磷的拦截效果,并进一步探究其对农田排水中耐药基因和细菌群落的影响,从而为生态沟渠的优化运行及推广建设、构建农业面源污染防控生态工程提供理论依据。
生态沟渠对农田排水中菌群组分、耐药基因谱及氮磷浓度的影响
Effects of the ecological ditches on bacterial community composition, antibiotic resistance gene profiles, nitrogen and phosphorus concentrations in farmland drainage
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摘要: 农田排水中的耐药基因能够以微生物为宿主在环境中富集与传播,而其中的氮磷则会导致自然水体富营养化。生态沟渠作为农田排水的末端处理系统,是控制农田中氮磷向自然环境中转移的关键,但其对农田排水中菌群和耐药基因的影响却鲜有研究。本研究对浙江省内20条生态沟渠的氮磷拦截效果进行了评价,然后利用宏基因组测序技术对其中效果较好的生态沟渠进行了菌群组分和耐药基因谱的分析。研究结果表明,浙江省内生态沟渠有效的拦截了农田排水中的氮磷,其中湖州市生态沟渠-1对农田排水中总氮和总磷拦截率均接近50%,相较于其他生态沟渠具有更好的氮磷拦截效果。同时,湖州市生态沟渠-1有效降低了农田排水中耐药基因的种类,并将主要耐药基因子类(mfd、dfrE和tetT)的丰度降低了12.0%—41.4%。此外,湖州市生态沟渠-1有效降低了农田排水中Proteobacteria门和Verrucomicrobia门的微生物丰度,并提高了其中Actinobacteria门的微生物丰度。综上可知,浙江省生态沟渠不仅能够拦截农田排水中的氮磷和耐药基因还能够影响其中细菌群落组分,但相关机制仍需进一步研究。Abstract:
The antibiotic resistance genes (ARGs) in farmland drainage promote the increase and spread of antibiotic resistance among environmental microbe and the anthropogenic nutrient (nitrogen and phosphorus) accelerates the eutrophication of lakes and streams. The ecological ditches, as the end treatment system of farmland drainage, are vital to mitigate the transfer of nitrogen and phosphorus from farmland drainage into natural environment, but few studies focused on the influences of the ecological ditches on ARGs and bacterial community in farmland drainage. This study comprehensively evaluated the effects of 20 ecological ditches in Zhejiang province on nutrients removal, then further applied the technology of metagenomic sequencing to analyze ARG profiles and bacterial community composition in the ecological ditch with effective nutrients removal. The related results indicated that the ecological ditches are effective in nutrients removal from farmland drainage, and the average interception efficiency of total nitrogen and total phosphorus were both closed to 50% in the Huzhou ecological ditch-1, which is more efficient comparing with that of other ecological ditches. Meantime, the Huzhou ecological ditch-1 effectively reduced the diversity of ARG subtypes in farmland drainage, and reduced the abundances of main ARGs (mfd、dfrE and tetT)by 12.0%—41.4%. In addition, the abundance of bacteria belonging to the phylum of Proteobacteri and Verrucomicrobia has been reduced, while the abundance of bacteria belonging to the phylum of Actinobacteria has been increased after the treatment of Huzhou ecological ditch-1. In summary, the ecological ditches not only contribute to the removal of nitrogen, phosphorus and ARGs in farmland drainage but also influencing its bacterial community, but the related mechanism needs to be further investigated. -
Key words:
- Antibiotic resistance genes /
- Ecological ditch /
- Farmland drainage /
- Bacterial community
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表 1 湖州市生态沟渠-1不同阶段水体样品DNA性质
Table 1. The properties of DNA extracted from different water samples in the Huzhou ecological ditch-1
水体样品
Water SampleDNA浓度/(μg·L−1)
DNA ConcentrationDNA纯度
DNA Purity(OD260/280)DNA总量
Total DNA生态沟渠上游阶段 31.0 1.81 总量满足宏基因组一次标准建库要求 生态沟渠中游阶段 6.10 2.31 总量满足宏基因组一次标准建库要求 生态沟渠下游阶段 9.70 2.01 总量满足宏基因组一次标准建库要求 -
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