Study On Methane And Nitrous Oxide Emissions From Polluted Water In Nanjing

Greenhouse gas emissioned from sewage treatment sector is the second largest source in waste disposal sector, and is considered as one of the important sources of greenhouse gas emission. The situation of greenhouse gas emission from sewage treatment is grim because of China’s huge population and sewage treatment facilities in rapid urbanization and the vast rural area is imperfect. Based on static chamber&gas chromatographic techniques, the characteristics of emission fluxes about CH4and N2O over three types of contaminated water named Tuanjie River, Jinchuan River and Zhangdong Pond in Nanjing were examined. And we also conducted their seasonal variations including summer, autumn and winter. In addition, the relationship between emission fluxes of CH4and N2O and water temperature, air temperature, COD were established. Finally, the total emissions of CH4and N2O from domestic sewage without centrally treated in2009of Nanjing were estimated according to the method recommended by2006IPCC Guide for National Greenhouse Gas Inventories. The goals of this study were to gain an insight into the current state of greenhouse gas emissions from uncentrally treated domestic sewage and make some contribution to greenhouse gas emission inventory for sewage treatment sector. Specific results were showed as follows:(1)The seasonal variations of CH4and N2O emission fluxes from Tuanjie River and Jinchuan River are obvious, that for Zhangdongcun Pond is non-significant. CH4emission fluxes from two rivers are significant higher in summer than in autumn and in winter. N2O emission fluxes from two rivers are significant higher in winter than in summer and autumn, and there is no significant difference between summer and autumn. There is not clear regulation of diurnal variations of CH4and N2O emission flux during daytime observations in summer, autumn and winter.(2) It clearly shows that CH4emission fluxes of Tuanjie River is higher than Jinchuan River and Zhangdongcun Pond in summer and autumn with no significant differences among three water bodies in winter. And we also find that N2O emission fluxes over Tuanjie River and Zhangdongcun Pond are significantly higher than Jinchuan River in summer and autumn with an opposite trend in winter.(3) There are positive relationships between CH4emission fluxes over three water bodies and air and water temperature in summer, autumn and winter. It also clearly shows that N2O emission fluxes from Tuanjie River and Jinchuan River are increased with air temperature and water temperature reduced, but not significantly for Zhangdongcun Pond.(4) The average CH4and N2O emission fluxes of three water bodies are34.85±37.38mg-m-2·h-1and20.53±19.78μ g·m-2-h-1. Compared to other typical researches, the CH4and N2O emission fluxes from typical polluted water in Nanjing are all at higher level, which suggests that polluted water in urbanized areas is an important potential source of CH4and N2O.The total CH4emissions and N2O emissions from sewage polluted water in Nanjing in2009are9.49kt and99.78t followed with2006IPCC guide, and it is3.71kt±3.83kt and2.16t±2.04t estimated by measured value. It shows that total emissions estimated followed IPCC guide is higher than followed by measured value.