Seminar

Inland lakes have received growing attentions on their roles in global carbon cycle. Lake Taihu is a large eutrophicated lake located in eastern China. Previous studies have found that the lake was an important source of methane (CH₄) emission, and the variations of the methane flux were believed to be caused by river nutrient discharge, algal biomass, dissolved oxygen concentration, water clarity and bathymetry. Moreover, anoxic aquifers are hotspots for organic matter fermentation, which is an important pathway for methane production. Methane in groundwater may enter the lake by lacustrine groundwater discharge (LGD), and groundwater borne CH₄ has profound impacts on lake methane emission, but these processes has rarely been studied in Taihu. High temporal resolution continuous measurements were conducted at the shorelines of the west lakeshore and inner island of Taihu. Radon-222 (a natural groundwater tracer), CH₄/CO₂ concentrations and fluxes, and carbon isotopes were measured. Results showed that carbon fluxes are likely to be associated with LGD. Ebullition is found to be the predominant process of methane emission in Lake Taihu and this methane is mainly produced by fermentation. Methane emission is intense in west eutrophicated region with the flux of 21.0 mmol m^-2 d^-1 compared to that in mid-east region with the average of 0.71 mmol m^-2 d^-1.

Additional information: Miss SHI Xiaoyan, shixyan@connect.hku.hk