| China is one of the most important agricultural countries in the world. There would be a mass of crop straw every year. Crop straw is the natural resource that is abundant, cheap and easy to obtain. It has become a challenge faced to modern agriculture how to use this natural resource environmentally friendly,. Continuous application of straws is a measure which could improve the soil fertility effectively. So it has been widely recognized. However, it also can significantly increase the emissions of greenhouse gases. Therefore, it is meaningful to find appropriate measures to reduce emissions after continuous application of straws.This study researches the difference of the rate of straws decomposition and methane and carbon dioxide emissions by using different straw stalk agents and celluloses to define the impact of using straw stalk agent and cellulose on methane and carbon dioxide emissions. Results are as follows.(1) The impacts on the rate of straws decomposition by using different straw stalk agents are significant different. In this study, the "Result" straw stalk agent (RL) makes the highest contribution to the decomposition rate of straws. And the total methane emission significantly increased with the increasing weight loss of straws after 60 days (R=0.491, p<0.05). In addition, the total carbon dioxide emission had no significant correlation with the weight loss of straws after 60 days (p>0.05). In greenhouse condition, all the straw stalk agents make no significant contribution to the decomposition rate of straws. Combining straw stalk agent and cellulose not only have no significant contribution, but also increase methane and carbon dioxide emissions significantly (p<0.05).(2) In different temperatures, compared with control group, the microorganism of "Jinkuizi" straw stalk agent (JKh) is more suited to 40℃, and can significantly raise the weight loss of straws at this temperature (p<0.05). In this condition, "Jinkuizi" straw stalk agent (JKh) makes significant contribution to the decomposition rate of straws, and can reduce methane and carbon dioxide emissions significantly (p<0.05).Besides, this study constructs microbial fuel cells (MFCs) that using different external resistances or adding different quantity of straws, and measure the methane and carbon dioxide emissions for microbiological electrogenesis. Moreover, the abundance of methanogenic archaea and methanotrophic bacteria and soil physicochemical properties have been analyzed to define how microbiological electrogenesis affect emissions of methane and carbon dioxide. Meanwhile, reveal the microbiological effect mechanisms of this. Results are as follows.(1) The peak of methane emission flux and total methane emission increased with the increasing of external resistances. The total methane emission in 30 days significantly increased with the increasing external resistances (R=0.817, p<0.01). But the MFCs using different external resistances have no significant difference on the peak of carbon dioxide emission flux and total carbon dioxide emission. External resistances had no significant effect on the total carbon dioxide emission of 30 days (p>0.05).(2) The total methane emission significantly increased with the increasing of quantity of straws (Open Circuit groups, OC for short):R=0.941, p<0.01; Close Circuit groups (CC for short):R=0.946, p<0.01). The total carbon dioxide emission also significantly increased with the increasing quantity of straws (OC:R=0.941, p<0.01; CC:R=0.946, p<0.01). Furthermore, compared with the CC group, the MFCs within 0.5% straws reduce total methane emission 47.43% significantly (p<0.05). The significant difference disappeared when adding no straw. However, The MFCs within 1% and 2% rice straw increase methane emission 52.05% and 131.07% respectively (p<0.05). In addition, running MFCs had no significant effect on carbon dioxide emission.(3) The abundance of methanogenic archaea between OC groups and CC groups with equal quantity of straws have no significant difference (p>0.05). The abundance of methanotrophic bacteria between OC and CC group with 0.5% straw also have no significant difference (p>0.05). However, the abundance of methanotrophic bacteria of OC group (OC4) within 2% straws is significantly higher than that of CC (CC4). Thus, when adding 0.5% straws the effect to reduce methane emission is predominant. When adding 2% straws the effect to reduce methane oxidation is predominant yet.At the same time, this study also constructs microbial fuel cells (MFCs) that adding different quantity of straws and planting rice in greenhouse as well. Then we measure the methane and carbon dioxide emissions and analyse soil physicochemical properties to define how MFCs affect emissions of methane and carbon dioxide in greenhouse condition, and can planting rice affect emissions of methane and carbon dioxide. Results show that the result in greenhouse condition is similar with that without planting rice. Moreover, running MFCs has no significantly effect on rice growth.This study defines the impact of using straw stalk agent and cellulose on methane and carbon dioxide emissions, and defines how microbiological electrogenesis affect emissions of methane and carbon dioxide. These may provide a new train of thought and method to... |
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