Nitrogen transport, transformation, and retention in the Three Gorges Reservoir: A mass balance approach

Abstract

Dam construction in river systems affects the biogeochemistry of nitrogen (N), yet most studies on N cycling in reservoirs do not consider the transformations and retention of the different N species. This study addresses the N inputs, transport, transformations, and retention in the Three Gorges Reservoir (TGR) in the Changjiang River, the world largest water storage project, during its filling phase in 2004-2007. The results indicate that dissolved inorganic nitrogen (DIN) was the most abundant N form in the TGR and particulate N was only 2% to the total N flow and retention. About 34% of the dissolved organic nitrogen (DON), 64% of nitrite, and 44% of ammonia were retained by transformation within the TGR in 2007. Time-series data show that about 8% of inflowing total dissolved N was lost by denitrification and sedimentation. Transformations of DON, nitrite and ammonia caused an increase of the nitrate load by 6%; and at the same time the DIN flux increased by 4% while the water moved through the TGR, which is the balance between formation and retention of DIN. The large contribution of biogeochemical transformations to nitrate loading in the TGR indicates the importance of internal processing for the river N species composition.

An Integrated Methodology to Analyze the Total Nitrogen Accumulation in a Drinking Water Reservoir Based on the SWAT Model Driven by CMADS: A Case Study of the Biliuhe Reservoir in Northeast China

“…In the study period, the mean annual TN input flux was 274.41 × 10 4 kg, which was higher than the output flux of 217.14 × 10 4 kg. The average annual accumulation of TN was 57.27 × 10 4 kg, indicating that 19.76% of the TN input was retained by the Biliuhe reservoir, which was higher than the TN retained by the Three Gorges reservoir (China) and Wivenhoe reservoir (Australia) [51,52], but lower than the TN retained by Lake Shelbyville (USA) [53]. The maximum and minimum TN input fluxes were 60.98 × 10 4 kg in 2012 and 78.02 × 10 4 kg in 2014, while the maximum and minimum output fluxes were 582.88 × 10 4 kg in 2012 and 71.75 × 10 4 kg in 2009, indicating that TN accumulation in the study reservoir varied in different hydrological years.…”

Tempo-spatial variations of zooplankton communities in relation to environmental factors and the ecological implications: A case study in the hinterland of the Three Gorges Reservoir area, China

“…Nitrate and ammonia, as substantially existing forms of nitrogen in water body or WLFZ of TGRA, was served as one of the material foundations inducing algae bloom [ 7 , 8 ], relating to exogenous input and endogenous release. The exogenous input mainly included atmospheric deposition, fertilizer use, soil organic carbon leaching, industrial pollution and sewage etc.…”

“…[ 7 , 40 ]. The endogenous release was involved to nitrogen transformation induced by biogeochemical processes, such as nitrification, denitrification, bio-assimilation, sedimentation and sediments release [ 7 , 8 , 41 , 42 ]. Specifically, nitrogenous fertilizer, soil organic nitrogen and sewage were regarded as the dominant nitrogen sources of water body in TGRA [ 6 , 7 , 10 , 43 ]…”

“…forbesi . In winter at HWL, submerged plants and soils in the submerged WLFZ and nitrification in the surface riverine water, together with domestic sewage, led to a moderately high level in water body [ 7 , 8 , 45 , 46 ]. Certain mesozooplanktons and larvae were much more popular under this environment, such as Cyclopoida Copepodid, S .…”

“…The variations of hydrological regime, superimposed on pollutants input originated from urban sewage, industrial wastewater, agricultural fertilizers, leaching of soil organic matters, etc. [ 6 , 7 ], resulted in significant changes in aquatic environment, such as TGR impounding resulted prolonged retention time, materials transport and the associated biochemical processes in urban aquatic ecosystems of the TGR [ 4 , 8 ]. Thus, the relating environment problems, such as soil erosion, heavy metals accumulation, large-scale habitat alterations, degraded water quality, algae bloom, variations of biotic community structure and so on, have been substantially reported [ 4 , 7 , 9 , 10 ].…”