期刊
GLOBAL BIOGEOCHEMICAL CYCLES
卷 33, 期 11, 页码 1339-1357出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019GB006222
关键词
nitrogen; river damming; nitrogen fixation; denitrification; burial; elimination
资金
- Canada Excellence Research Chair (CERC) program
Damming creates biogeochemical hotspots along rivers that modify the riverine flow of nutrients, including nitrogen (N). Here, we quantify the impact of dams on global riverine N fluxes using a reservoir N mass balance model. In-reservoir processes represented in the model include primary production, mineralization of organic N, denitrification, and sedimentary burial. In addition, we explicitly account for N fixation as a source of N, assuming that the N to phosphorus (P) ratio of the inflow regulates the magnitude of N fixation in reservoirs. The model is scaled up via a Monte Carlo analysis that yields global relationships between N elimination in reservoirs, either by denitrification or burial, and the hydraulic residence time. These relationships are then combined with N loads to the world's dam reservoirs generated by the Global-NEWS model and the estimated N fixation fluxes. According to the results, in year 2000, worldwide N fixation in reservoirs was on the order of 70 Gmol yr(-1), while denitrification and burial in reservoirs eliminated around 270 Gmol yr(-1), equal to 7% of N loading to the global river network. The latter is predicted to double to 14% by 2030, mainly as a result of the current boom in dam building. The results further imply that, largely due to N fixation in reservoirs, damming causes a global upward shift in riverine N:P ratios, thus lessening N limitation in receiving water bodies.
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