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我国的排水管道几乎都存在不同程度的污染物沉积现象,在水流的冲刷下沉积物可能会再次悬浮,部分合流制管道的溢流和分流制雨水管道径流的直接排放[1-2],导致氮、磷进入城市水体[3],加重了水体的富营养化[4]。研究污染物在排水管道沉积物-水系统中的迁移转化规律,对评估管道沉积物带来的污染贡献、优化管道的运行具有重要的现实意义。
氮是管道内重点关注的对象之一,目前对排水管道内氮的转化进行了部分研究。有研究发现,包含氮在内,排水管道沉积物中物质转化主要通过3种途径进行:物理污染物沉积、生物转化吸附、生物转化释放。在污水管道中好氧、厌氧的环境交替,存在各种微生物,通过生物群落的代谢,可以实现氮的去除[5],因此污水管道可以作为反应器来研究氮的转化情况。邢贝米等[6]发现,污水管道中的微生物以有机氮为氮源时,利用蛋白质作为营养物质,代谢产生有机物,以无机氮作为氮源时,利用氨氮和有机物结合产生有机氮。杨柯瑶[7]发现,管道中厌氧环境一定程度上会限制硝化反应,微生物以氨氮为氮源进行细胞合成代谢产生的溶解性代谢产物会释放回水中,导致管道中溶解性有机氮的含量增加。
不同微生物群落对排水管道中氮的转化也产生重要影响。研究表明,变形菌门、厚壁菌门、拟杆菌门的3种菌群在排水管道中的相对丰度较高[8-9],且都属于发酵菌群[10]。同时,管道中较为常见的梭菌纲、β-变形菌纲、拟杆菌纲、互营养菌纲都可以促进有机物的分解[11],而γ-变形菌纲、绿弯菌门、硝化螺旋菌门都属于硝化细菌[12-13],可以分解氨氮,转化为硝态氮、亚硝态氮。艾海男等[14]通过模拟排水管道试验发现C/N较高时,会抑制氨氧化菌的产生,不利于硝化反应的进行。Zhang等[11]发现,总氮含量较高时,互营养菌纲和Caldisericia纲的相对丰度也较高。黄帅辰等[15]调查北京地区的管道沉积物时发现,管道中总氮含量与甲烷微菌纲、互营养菌纲呈正相关,与γ-变形菌纲、δ-变形菌纲呈负相关。
已有研究在排水管道内物质转化过程及微生物作用方面有一些成果。在排水管道沉积物-水系统内不同组分(上覆水、间隙水和沉积物)中,氮生物转化规律及量化计算,以及生物群落的作用少有研究。本研究模拟排水管道内环境,分析管道内生物群落的差异对于氮在沉积物-水系统中迁移转化的影响,初步计算氮在沉积物-水系统间的释放通量。研究有助于预测排水管道中沉积物-水之间氮的交换过程,为掌握管道沉积物中污染物对下游水体的污染负荷量提供理论依据。
排水管道沉积物-水系统中不同微生物群落下氮的迁移转化
The migration and transformation of nitrogen under different microbial communities in sediment-water system of drainage pipe
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摘要: 为探索微生物群落对排水管道沉积物-水系统中氮迁移转化的作用,本文研究了干预组、对照组及初始沉积物中的微生物群落,探索排水管道沉积物-水系统中不同组分氮迁移转化的规律,并进行了量化计算。结果表明, γ-变形菌纲和拟杆菌纲在对照组中相对丰度较高,梭菌纲、互营养菌纲在干预组中更占优势。在浓度差异和生物作用的共同影响下,干预组上覆水氨氮含量增加。γ-变形菌纲发生硝化作用导致对照组上覆水氨氮浓度下降,硝态氮、亚硝态氮含量增加。高、低浓度下,沉积物-水系统中的氨氮均由沉积物向上覆水释放,低浓度下氨氮的释放通量更大,最高值达到了536.76 mg·m−2·d−1。系统中,硝态氮的释放通量很小。Abstract: In order to explore the effect of microbial community on the migration and transformation of nitrogen in the sediment-water system of drainage pipeline, the microbial communities in intervention group、control group and original sediments were studied, the law of nitrogen migration and transformation at different components in the sediment water-system of drainage pipeline was explored and the variation was calculated in this paper. The results showed that the relative abundance of Gammaproteobacteria and Bacteroidia were greater in the control group, Clostridia and Synergistia were more dominant in the intervention group. Under the joint influence of concentration difference and biological effects, the concentration of NH4+-N increased in overlying water in the intervention group. The nitrification of Gammaproteobacteria resulted in the decrease of NH4+-N concentration and the increase of NO3−-N and NO2−-N concentration in the overlying water of the control group. At high or low concentrations of overlying water, NH4+-N was released from sediment to overlying water. At low concentrations, the release flux of NH4+-N was greater, and the highest value was 536.76 mg·m−2·d−1. In the system, the release flux of NO3−-N was very small.
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Key words:
- drain pipe /
- sediment /
- nitrogen /
- microbial community /
- migration /
- release flux
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