| With the gradual expansion of hydropower development on a global scale,the environmental effects of river basins caused by dam interception have received increasing attention.Due to the slowing of the flow rate,the increase of the transparency of the water body and the change of biological effects directly lead to the“river reservoirization”,which makes the water body of the water storage river different from the natural river water body in physical,chemical and biological aspects.The circulation of nutrients under this influence is bound to undergo a series of complex changes.In this study,four reservoirs of different types in the Wujiang River Basin were selected as research objects.After high-density sampling in the first six months of 2017,the nutrients of water(TDP?PO43-?TDN?NH4+?NO3-?NO2-?DSi)and the temporal and spatial variation characteristics of the nitrogen and oxygen isotopes(?15N-NO3-and?18O-NO3-)of nitrate were analyzed.The research results showed that:?1?The Hongfeng Reservoir and the Silin Reservoir in spring and summer have obvious nutrient salt retention effects.Among them,the retention effect of DSi is the most obvious,and TDP and TDN have similar changes,but the changes in the waters of Hongfeng Lake with dense human activities are more complicated.?2?Nitrate isotope results of water in the profile water show that the assimilation and absorption of nitrogen in the surface water is the main process of nitrogen conversion.In the middle water body,nitrification is the main reaction process;in the deep to the bottom water,the denitrification process in the reducing environment is the main process of the nitrogen cycle.?3?Based on the SIAR model,the nitrate nitrogen and oxygen isotope traceability results show that organic fertilizer and sewage are the main contributions?percentage?of nitrate in Wujiang River Basin,especially in Hongfeng Lake waters,indicating that anthropogenic emissions are the most important cause of nitrate pollution. |
PDF Full Text Request