不同富营养状态下浅水湿地甲烷浓度变化特征研究

Methane Concentration in Shallow Lakes Under Different Eutrophication Levels

以宜昌市12个不同营养状态(轻、中、重富营养)的小面积浅水湿地为研究对象,在2022年3、7、10、12月对水体溶存甲烷(CH_(4))浓度以及水环境因子进行监测,探讨不同营养沉积下浅水湿地溶存CH_(4)浓度和扩散通量的差异性及影响因素.结果表明:不同营养状态下浅水湿地CH_(4)浓度表现出明显的季节变化差异,轻营养状态下溶存CH_(4)浓度季节变化为0.13~2.17μmol·L^(-1),秋季为溶存CH_(4)浓度最高值冬季为最低值;中营养为0.38~2.52μmol·L^(-1),夏季浓度最高春季最低;重营养夏季值最大冬季值最小,变化范围为0.52~5.96μmol·L^(-1);CH_(4)浓度及其扩散通量均随营养状态的增加而增加,总磷浓度是控制轻营养湿地CH_(4)释放的主要因素,随着营养状态的提高CH_(4)浓度主要受水体总氮状态、水深以及温度变化的影响.

Taking 12 small-area shallow-water wetlands with different nutrient levels(light,medium and heavy eutrophication)in Yichang City as the research object,the dissolved methane(CH_(4))concentration and water environmental factors were monitored in March,July,October and December 2022,and the differences and influencing factors of dissolved CH_(4)concentration and diffusion flux in shallow-water wetlands under different nutrient deposition were discussed.The results showed that the seasonal variation of CH_(4)concentration in shallow wetlands under different trophic states was significantly different.The seasonal variation of dissolved CH_(4)concentration in light trophic state was 0.13~2.17μmol·L^(-1)with the highest value of dissolved CH_(4)concentration in autumn and the lowest value in winter.The mesotrophic level was 0.38~2.52μmol·L^(-1),with the highest concentration in summer and the lowest in spring.Similarly,the heavy nutrition level ranges from 0.52 to 5.96μmol·L^(-1),with the maximum value in summer and the minimum value in winter.Both CH_(4)concentration and CH_(4)diffusion flux increased with the increase of nutrient level.Total phosphorus concentration was the main factor controlling the release of CH_(4)in light nutrient wetland.With the increase of nutrient level,CH_(4)concentration was mainly affected by total nitrogen level,water depth and temperature change.