The spatial distribution and emission of nitrous oxide (N₂O) in a large eutrophic lake in eastern China: Anthropogenic effects

The emission of N₂O from China is globally significant, but relatively few direct observations have been made in many of the fresh water environments most likely to be important sites of N₂O production. In this paper, N₂O saturations were examined in the ecologically heterogeneous, eutrophied, Lake Taihu, as well as in surrounding rivers in eastern China. The emissions of N₂O were estimated and compared with those from other landscapes within the Lake Taihu drainage basin. We found that anthropogenically-enhanced inorganic N inputs act as a limited primary control on the spatial distribution of N₂O saturations in heavily eutrophied parts of the lake only and that overall, lake N₂O production and emission are not raised as significantly as expected due to high N inputs. In comparison, the heavily eutrophied river network is an important fraction of the local N₂O budget, and when considered together with emissions of N₂O from the lake, constitute a major (10-50% depending on season) fraction of total N₂O emissions from the Lake Taihu drainage basin.