[Greenhouse Gas Fluxes at Water-Air Interface in Small Pond Using Flux-Gradient Method Based on Spectrum Analyzer].

As an important part of inland waters,small pond is a neglected source of greenhouse gas.The main objective of the study was to quantify greenhouse gas fluxes (CO2 and CH4) from small pond in the Yangtze Delta using flux-gradient method.The results showed that:① zero-gradient test indicated that the flux measurement precision for water vapor,CO2,and CH4 was 7.525 W·m-2,0.022 mg·(m2·s)-1,and 0.054 µg·(m2·s)-1,respectively.During the test period,84%,80%,and 94% of half-hourly flux data for H2O,CO2,and CH4 were higher than the zero-gradient measurement precision.② Based on the measurement,the small pond was the source of CO2 and CH4 for the atmosphere in summer,the mean emission flux of CO2 and CH4 was 0.038 mg·(m2·s)-1 and 0.889 µg·(m2·s)-1,respectively.The CH4 emission fluxes from the small pond were more higher than the median value of emission for global lakes.The results indicated that greenhouse gas emission from small pond was an important part for estimating inland water greenhouse gas emissions,especially for CH4 emission.These results can provide scientific reference for making emission inventory of regional greenhouse gas.

[Temporal Dynamics of Stable Isotopic Composition in Lake Taihu and Controlling Factors].

The composition of hydrogen and oxygen stable isotopes in lake water is important to the researches in hydrology, meteorology and paleoclimatology. In this study, long-term and continuous measurement on the compositions of HDO and H218O in lake water (δDL and δ18OL) was conducted over Lake Taihu, the deuterium excess (dL) was calculated, and the temporal variability and controlling factors were analyzed. The results indicated that ① the variation of isotopic enrichment in lake water was significant, ranging from -59.8‰ to -24.2‰ for δDL, from -8.6‰ to -2.6‰ for δ18OL, and from -7.9‰ to 12.9‰ for dL, respectively. In comparison to cold season, δDL and δ18OL were higher and dL was lower during warm season. ② On monthly time-scale, lake evaporation and the ratio of total water inputs lost by evaporation controlled the isotopic enrichment in lake water. When lake evaporation or the ratio increased, δDL and δ18OL increased, but dL decreased. ③ Over Lake Taihu, the isotopic composition in precipitation and water temperature did not control the isotopic enrichment. The results provide scientific reference for isotope hydrology and the researches related to the isotopic enrichment in lake water in meteorology and paleoclimate.