Study On The Methane Emiission Flux And Its Influence Factors In Nanning Chao Yang Creek

Methane (CH4) is an important greenhouse gas and it exerts influence on global climate change and atmospheric chemistry. In recent years, as a result of the unbalance of methane sources, CH4 content increased in the atmosphere. Rivers is a natural source of atmospheric Methane (CH4), and urban black-smelly rivers are more serious due to the impact of human activities, domestic sewage and industrial wastewater discharged into the river with the process of industrialization. CH4 released hyperactively, which contributed significantly to the atmospheric CH4. Therefore, the research on the relationship between the urban black-smelly river methane emission flux and the environmental impact factors helps us to understand the methane emission flux from different water, which can provide a reference and date for global methane estimates. Acquired advances are as follows:This article through to investigate the samples of the black smelly-river of Nanning Chao Yang Creek and study them in laboratory, determine the methane emission flux from the upstream, midstream and downstream of the Creek by using static box method. At the same time, this article detect the CODCr, TN, TP and NH4 +-N, pH and sediment organic carbon content in water, the results show that the Chao Yang Creek is an important source of methane emissions, the average methane emission flux is 12.2mg/(m2-h), emission flux change is not significant among upstream, midstream and downstream. Correlation analysis by using partial least squares method, the results show that significantly positive correlations are found between methane flux and temperature, chemical oxygen demand and sediment organic carbon, and negative correlations of dissolved oxygen, but there are less correlation with the total nitrogen, ammonia nitrogen, total phosphorus and pH.Sediment and water methane generation determined by top empty bottles, the results show that methane from water is very small, almost zero, sediment methane-producing rate showed a trend of increased first and then decreased, and sediment methane-producing rate is the largest in the fifth day to 0.0056 mg·g-1, but sediment methane-producing rate is very small after 15 days. According to the experimental data,we can know that under the condition of anaerobic and 25℃, the mathematical relationship between sediment methane initial release quantity of Nanning Chao Yang Creek and incubation time can be expressed as:y= 0.4558× d0.7280.Under different temperature conditions on the influence of sediment methane-producing experiment, we set up three groups of different temperature 15℃,25℃ and 35℃ respectively. Temperature has a significant influence on the sediment methane production, and Methane production rate increased with the increase of temperature.methane-producing rate at 35℃ is 1.9 times more than methane production rate at 15℃. Temperature has significant effect of sediment pollutant release, the higher the temperature, the faster the sediment pollutant release rate, sediment CODCr, TN, TP release rate at 35℃ is 2、4.5 and 3.8 times more than at 15℃ respectively, the degradation rate of sediment organic carbon at 35℃ is 1.7 times more than at 15℃, temperature has an important influence on water to reduce the rate of dissolved oxygen, When the content of organic matter in water is higher, the content of dissolved oxygen in water less influence on sediment methane-producing rate. In the absence of air condition, the mathematical relationship between sediment methane generation and culture time and temperature can be expressed as:CMethane=0.4182·T0.9509·log10(0.091t+1). Significantly positive correlations are found between sediment release of methane generation and sediment CODCr, TP, but there is less correlation with the sediment release TN and consumed water dissolving rate, Sediment by the degradation of organic carbon and sediment methane generation has significant positive correlation.Under the condition of different initial pH of water influence on sediment methane-producing experiment, we set up three groups of different initial water pH of 6、7.5、9 respectively. pH has important influence on sediment methane generation Different pH, methane generation is different. The maximum of methane generation is in pH 9, pH 7.5 followed, and the minimum is in pH 6. When the initial pH of the water is 9, it is beneficial to sediment release TP and CODCr into the sediment-water interface in the water. Methane generation is positively correlated with the CODCr concentration of the sediment-water interface and no correlated with TN, TP concentration of the sediment-water interface. Under different pH conditions, the mathematical relationship between methane generation of sediment and incubation time can be expressed as:CMethane=0.8472·pH1577·log10 (0.036d+1).