养殖塘CH4排放特征及其影响因素

富营养化的养殖塘是重要的甲烷(CH_4)排放源.为明确养殖塘CH_4排放特征及其影响因素,本研究利用倒置漏斗法和体积扩散模型法,分别对安徽全椒两个养殖塘冬、春季CH_4冒泡通量和扩散通量进行了多日连续观测.结果表明,冬季CH_4冒泡通量白天高于夜间,夜间几乎为零;春季夜间高于白天.在季节尺度上,冬季CH_4冒泡通量显著低于春季,分别为3. 92mg·(m~2·d)-1和106. 94 mg·(m~2·d)-1;冬季CH_4扩散通量略高于春季,分别为2. 81 mg·(m~2·d)-1和0. 87 mg·(m~2·d)-1.自然因素(水温和气压)与CH_4冒泡通量和扩散通量显著相关.其中随水温的升高、气压的降低,CH_4冒泡通量分别呈指数递增和线性递增趋势.人工管理措施(冬季排水和春季施粪)会显著提高CH_4冒泡通量,但对扩散通量的影响并不显著.在冬季排水期间,水深与CH_4冒泡通量显著负相关;在春季鸡粪投放点,CH_4冒泡通量可高达1002. 30 mg·(m~2·d)-1.本研究可为评估小型养殖塘对全球碳循环的贡献提供数据支撑.

Methane Emission Characteristics and Its Influencing Factors over Aquaculture Ponds

Eutrophic aquaculture ponds are important methane (CH₄) sources. In order to quantify CH₄ emission characteristics and its influencing factors over aquaculture ponds, we conducted several intensive observations over two ponds located in Quanjiao County, Anhui Province, in 2018. The ebullition and diffusion flux of CH₄ were measured in two seasons (winter and spring) using the inverted-funnel and bulk diffusion model, respectively. In winter, the CH₄ ebullition flux during the daytime was higher than that at night (almost zero), whereas the diurnal pattern was found to be reversed in spring. Seasonally, the CH₄ ebullition flux over the ponds was significantly lower in winter3.92 mg·(m²·d)^-1] than in spring106.94 mg·(m²·d)^-1], while the diffusion flux in winter2.81 mg·(m²·d)^-1] was slightly higher than in spring0.87 mg·(m²·d)^-1]. The CH₄ ebullition and diffusion flux can be significantly controlled by natural factors such as water temperature and air pressure. It was revealed that the CH₄ebullition flux in the studied ponds increased exponentially with increasing water temperature, and increased linearly with decreasing air pressure. Furthermore, we found that artificial management measures (i.e., winter drainage and spring manure treatment) could significantly enhance the CH₄ ebullition flux rather than diffusion flux. For instance, the CH₄ ebullition flux was found to increase with water depth decrease during the winter drainage period, while in the spring, the CH₄ ebullition flux could reach as high as 1002.30 mg·(m²·d)^-1 with chicken manure applicated. This study can provide data support for assessing the contribution of small ponds to the global carbon cycle.