Loss of nitrogen from the soil-plant system has raised environmental concern. This study assessed the fluxes of nitrous oxide (N2O) in the subsurface flow constructed wetlands (CWs). To better understand the mechanism of N2O emission, spatial distribution of ammonia-oxidizing bacteria (AOB) in four kinds of wetlands soil were compared. N2O emission data showed large temporal and spatial variation ranging from -5.5 to 32.7 mg N2O m(-2) d(-1). The highest N2O emission occurred in the cell planted with Phragmites australis and Zizania latifolia. Whereas, the lower emission rate were obtained in the cell planted with P. australis and Typha latifolia. These revealed that Z. latifolia stimulated the N2O emission. Transportation of more organic matter and oxygen for AOB growth may be the reason. The study of AOB also supported this result, indicating that the root structure of Z. latifolia was favored by AOB for N2O formation. 相似文献
Environmental Science and Pollution Research - Critical periods (CPs) and critical source areas (CSAs) refer to the high-risk periods and areas of nonpoint source (NPS) pollution in a watershed,... 相似文献
In this study, we investigated the combined effects of temperatures fluencies and mercury (Hg) on glutathione-dependent antioxidant system in fish, by measuring the oxidative stress indicator (LPO, lipid peroxidation) and the parameters involved in the glutathione-related antioxidant defense system (GPx, glutathione peroxidase; GR, glutathione reductase; GST, glutathione S-transferase; GSH, reduced glutathione), as well as the expression of related genes in grass carp, Ctenopharyngodon idella. Fish (45.37?±?3.58 g) were exposed to 10 test groups, e.g., 15 °C with/without Hg, 20 °C with/without Hg, 25 °C with/without Hg, 30 °C with/without Hg, 35 °C with/without Hg for 4 weeks. Three-way ANOVA was used to analyze the correlation between the measured parameters and experimental conditions (water temperature, Hg exposure, exposure time, and their interactions.). Our results show that there is no interaction between mercury and low temperature, but the combined effect at high temperature has been confirmed, which indicated the glutathione-dependent enzyme system in grass carp has a complex regulatory mechanism with temperature fluctuations. In the actual field monitoring, it is necessary to consider the impact of extreme temperature on the toxicity of pollutants in the aquatic ecosystem.