Influence Factors of Potential Nitrification Rates and Functional Genes Abundance in the Jinshui River and the Qihe River of the Hanjiang River Basin

Abstract

In the context of increasing nitrogen loading in river systems worldwide, it is critically important to understand nitrification to maintain river ecosystem health. This comparative study was conducted to explore the relationships among the intensity of human disturbance, environmental factors, potential nitrification rate, and functional gene abundance in the Jinshui River (slightly disturbed basin) and the Qihe River (intensely disturbed basin). The results showed that AOA-amoA gene abundance was higher than that of AOB-amoA. The potential nitrification rate in the Qihe River was higher than that in the Jinshui River. There was no significant difference in AOA-amoA gene abundance between the two rivers; however, the AOB-amoA gene abundance in the Qihe River was significantly higher than that in the Jinshui River in the low flow season. The abundance of nitrification functional genes was significantly correlated with water temperature, pH, NO3-, NH4+, and organic carbon. The potential nitrification rate was positively correlated with water temperature, pH, and NO3-, and negatively correlated with AOB-amoA gene abundance. These results showed that the intensely disturbed sites had higher potential nitrification rates and nitrification functional genes abundances, and potential nitrification rates and abundances of nitrification function genes were significantly related to physical and chemical water and sediment factors. This study will be important for nitrogen pollution control in the river systems.