基于漂浮箱法和扩散模型法测定淡水养殖鱼塘甲烷排放通量的比较

本研究以我国东南部地区淡水养殖鱼塘为研究对象,于2017年9月到2018年8月采用漂浮箱法和扩散模型法同步原位观测其CH_4排放通量,旨在明确运用两种不同方法观测CH_4的排放特征、排放强度及其驱动因子,综合比较两种方法观测结果的差异性,其中扩散模型法能够进一步量化扩散传输对CH_4排放通量的贡献.结果表明,两种方法观测的CH_4排放通量有相似的季节变化特征,即夏秋季排放高,冬春季排放低.通过漂浮箱法观测淡水养殖鱼塘CH_4排放通量的变化范围为0. 14～3. 13 mg·(m~2·h)~(-1),其年平均排放通量为(0. 86±0. 30) mg·(m~2·h)~(-1),而由扩散模型法估算出鱼塘CH_4排放通量变化范围为0. 04～1. 41 mg·(m~2·h)~(-1),其年平均排放通量为(0. 45±0. 08) mg·(m~2·h)~(-1).基于两种方法观测的CH_4排放通量具有相同的环境驱动因子,CH_4排放通量与水温、底泥可溶性有机碳(DOC)和水体化学需氧量(COD)呈现显著的正相关关系,与水体溶解氧(DO)呈现出极显著的负相关关系.综合比较两种方法观测结果,发现由扩散模型法估算出的淡水养殖鱼塘CH_4排放通量约为漂浮箱法测定结果的45%左右(P 0. 01),扩散模型法可能低估淡水养殖系统CH_4排放通量.综上所述,漂浮箱法更适合用于观测我国东南部内陆地区淡水养殖生态系统CH_4排放.

Comparison of Floating Chamber and Diffusion Model Methods for Measuring Methane Emissions from Inland Fish-Aquaculture Ponds

Freshwater aquaculture ponds collectively cover a large area in southeast China. They are an important anthropogenic source of CH₄ emissions, however current knowledge of CH₄ emissions from aquaculture ponds is limited. During September 2017 and August 2018, two independent sampling campaigns of CH₄ flux measurements over annual cycles were carried out in a fish-aquaculture pond in southeast China using a floating chamber and diffusion model methods for comparison. The purpose of this study is to investigate the variation of CH₄ fluxes obtained from the fish-aquaculture pond, analyze the emission mechanisms, and amplify the CH₄ emissions inventory. The diffusion model method can further quantify the contribution of diffusion transmission to CH₄ emissions. The seasonal variations of CH₄ fluxes measured by the two methods were similar, with higher CH₄ fluxes appearing in summer and fall and lower CH₄ fluxes appearing in spring and winter. CH₄ fluxes measured by the floating chamber method and diffusion model method ranged from 0.14-3.13 mg·(m²·h)^-1 and 0.04-1.41 mg·(m²·h)^-1, respectively, and the respective average values were (0.86±0.30) mg·(m²·h)^-1and (0.45±0.08) mg·(m²·h)^-1. The CH₄ fluxes were positively related to water temperature, dissolved organic carbon (DOC) and chemical oxygen demand (COD), but negatively related to the water dissolved oxygen (DO) concentration in the fish-aquaculture pond. CH₄ fluxes calculated by diffusion model methods were 45% lower than those determined by the floating chamber methods over annual cycles. The result suggested that the floating chamber method is more suitable than the diffusion model method for measurements of CH₄ fluxes in freshwater aquaculture ecosystems.