Study On Influence Factors On Methane Emission Flux And Methane Production Capacity In Poyang Lake Wetland

With global warming situation developing more and more severe,methane(CH4), the second largest greenhouse gas, gradually attracted people’s attention which has great warming potential. Wetland was the largest natural sources for CH4 and contributed significantly for methane emission. The largest fresh water wetland in China – Poyang Lake wetland was selected as study area in this paper.Considering the key problem of different factors’ interaction in soil, the influences of Humic acid, Fe(III), Mn(IV), substrates, temperatures and pH value on methane production were discussed combing with soil elements distribution in Jiangxi province. The mechanism of changing environments’ impact on methane production capacity was revealed and the effect of wetland function of carbon sources and carbon sinks on ecosystem was explored. It is of guiding significance for understanding the spatial and temporal methane emission distribution and the impacts of different factors on methane production in Poyang Lake wetland. The result was as follows:(1)Methane fluxes of Poyang Lake wetland were respectively 0.094, 0.250,0.082, 1.64 × 10-3mg · m- 2h– 1in spring, summer, autumn and winter seasons,which exhibited a sequence: summer > spring > autumn > winter. Diurnal methane fluxes showed that the fluxes were high in daytime and low in night with temperatures changing. In addition, methane fluxes in Poyang lake wetland, air temperature, water temperature and water levels were positively correlated and methane fluxes increase with temperatures as exponential growth with certain temperature range. However the influence of water level on methane emissions was relatively complex and it doesn’t exhibit a specific math functions.(2)Trimethylamine(TMA) is the main substrate for methane production in Poyang Lake sediment, the maximum of methane production capacity without amendment was 0.0131 μgCH4 g(soil d.w.)-1 d-1. Methane production capacity maximum varies from 0.0444 to 0.0832 μgCH4 g(soil d.w.)-1 d-1 after acetate adding, however, it becomes 0.2703- 0.5924 μgCH4 g(soil d.w.)-1d-1after TMA addition, which was relatedto the pH value of regional sediment.(3)The optimum temperature for Poyang Lake sediment slurries producing methane was 35 ℃ and both low temperature(15 ℃) and high temperature(55 ℃)inhibited methane production even substrate was adequate. Methane production capacity from Poyang Lake sediment slurries was larger under alkaline condition.Compared with temperature pH value could be excluded as a key factor for methane production.(4)The inhibition sequence for different electron acceptors was that FeCl3 >MnO2 > DOM > Fe2O3. FeCl3 of 20 mmol·l-1 not only decrease methane production but also delayed methane production but other electron acceptors just decrease methane production. The concentrations of FeCl3, MnO2 and Fe2O3 were higher, the inhibitions were stronger, which were contrary to DOM. Although the inhibition of DOM to methane production capacity is not so obvious, as a natural electron acceptor,it is very significant inhibition of methane emission.