N2O fluxes from the littoral zone of a Chinese reservoir

[摘要] There have been few studies of greenhouse gas emissions from reservoirs,despite the remarkable growth in the number of reservoirs in developingcountries. We report a case study that focuses on the littoral zone of amajor Chinese reservoir, where we established measurements of N₂O fluxesusing the static chamber technique at five different water levels (deepwater, shallow water, seasonally flooded, control for seasonally flooded, andnon-flooded). The "control for seasonal flooded" had similar vegetation tothe "seasonally flooded" but was not actually flooded as it was on a higherpiece of land. Seasonal, diurnal and spatial variations of N₂O flux andenvironmental factors were monitored throughout the growing season whichincluded a flood event during summer rains. The N₂O flux ranged from−136.6 to 381.8 μg m⁻² h⁻¹ averaging6.8 μg m⁻² h⁻¹. Seasonal and spatial variation wassignificant but diurnal variation was not. Non-flooded dry land emitted moreN₂O than flooded land, no matter whether it was permanently orseasonally flooded. Piecewise correlation was found between N₂O flux,air temperature and soil nitrate concentration. Positive correlation wasshown between N₂O flux and dissolved oxygen in water. There weresignificantly higher emissions from farmland. We compared these results withour recently published study of CH₄ emissions, carried outsimultaneously at the same site as those in the present study. Completelydifferent patterns between the two gases are demonstrated. We conclude thatthe littoral zone is a hotspot for N₂O emissions in the summer,especially when the shores of the lake are used for the farming of maize. Butin terms of the overall greenhouse gas budget, the fluxes of N₂O are notas important as those of CH₄.

[学科分类] 地球化学与岩石