湟水河西宁段水体和沉积物中氮素转化关键过程与影响因素分析

于丰水期(2018年7月)和枯水期(2019年4月)分别在湟水河西宁段典型断面采集水体和沉积物样品共58个,枯水期同时采集污水处理厂出水样6个。利用实时荧光定量PCR方法,对12种氮转化功能基因进行定量分析。结果表明,湟水河平均总氮浓度为3.06±1.23 (1.308～6.51) mg/L。水体和沉积物中相对丰度较高的氮转化功能基因是narG,nirS和nosZ。氮转化功能基因的丰度和组成在沉积物中存在明显的季节差异,在水体中无明显季节差异。关键氮素转化过程是反硝化,对水体和沉积物氮素的去除贡献率分别为88%和98%。水体氮素转化主要受pH值、总氮及NO₃^--N调控,其中,氨氧化与NO₃^--N浓度负相关,反硝化与pH负相关。沉积物氮素转化与水体氮素浓度、沉积物pH值、总氮、总磷和有机碳等相关,其中,氨氧化与水体氮素浓度负相关,而反硝化主要受沉积物性质影响。进一步的分析结果表明,污水处理厂排放会显著降低水体中AOA-amoA, CMX-amo A, nir S, nxr B, napA, nar G...

Microbial Nitrogen Transformation Key Processes and Its InfluencingFactors in Water and Sediment of Xining Section of the Huangshui River

A total of 58 water and sediment samples were collected in the typical sampling section of the Xining section of the Huangshui River during the wet season (July 2018) and the dry season (April 2019), respectively, and 6 wastewater samples were directly taken from the effluents of wastewater treatment plants (WWTPs) in the dry season. A total of 12 nitrogen functional genes were quantitatively analyzed by real-time fluorescence quanti-tative PCR technology (qPCR). The results showed that the average of total nitrogen (TN) concentration in Huangshui River was 3.06±1.23 (1.308–6.51) mg/L. The nitrogen functional genes with high relative abundance in water and sediments were narG, nirS and nosZ. There were significant seasonal differences in the abundance and composition of nitrogen functional genes in sediments rather than those in water. The key nitrogen transformation process was denitrification, and its average contribution to nitrogen removal in water and sediment were 88% and 98%, respectively. The nitrogen transformation process in water was mainly impacted by pH, TN and NO₃^--N, the ammonia oxidation process was negatively correlated with the NO₃^--N concentration, and the denitrification process was negatively correlated with the pH. The nitrogen transformation process in sediment was mainly related to the water nitrogen concentration, sediment pH, TN, total phosphorus and organic carbon concentration, etc., the ammonia oxidation process was negatively related to the water nitrogen concentration, and the denitrification process was related to the sediment properties. Further analysis showed that the wastewater treatment plant effluents significantly reduced the abundance of genes such as AOA-amoA, CMX-amoA, nirS, nxrB, napA, narG, hzsA in the received water, which might lead to the limitation of the denitrification, anammox, nitrification and comammox processes, but at the same time elevated the abundance of nrfA genes and increased the contribution rate of dissimilatory nitrate reduction to ammonium (DNRA) to nitrogen removal in water. The relative abundances, such as AOA-amoA, nxrB and CMX-amoA, were significantly reduced in the sediments in the affected river segments, and nitrification and comammox processes in sediments were suppressed. This study can provide a scientific basis for nitrogen pollution control in the Xining section of Huangshui River.