Characteristics Of Nitrogen And Phosphorus Retentio And Influencing Factors In A Headwater Agricultural Stream With Distinct Geomorphic Setting

To reveal the transient storage and retention of nitrogen and phosphorus nutrients in different topography channels,a conservative tracer?NaBr?and nutrient supplement?NH₄Cl,KNO₃ and KH₂PO₄?had been carried out tracer experiments in an agricultural headstream of Ershibu River,Lake Chaohu basin.Based on the concentration of conservative tracer,using the OTIS model to simulate the hydrological parameter whose sensitivity was analyzed.Combined with the physical parameters and the transient storage index,the transient storage capacity was quantitatively evaluated.On the basis of the nutrient spiraling parameters,the nutrient retention capacity was analyzed and the factors of influencing nutrient retention capacity was recognized.In addition,the TASCC approach was applied for the simulation of uptake dynamics and absorption kinetics of nitrate nitrogen.The main results were summed up as follows:?1?Average values of hydrological parameters D,A,A_s and?which were simulated by OTIS model were 0.087 m²·s^-1,0.547 m²,0.247 m² and 2.61×10^-3s^-1,respectively.Parameter sensitivity analysis results were that the order of modeled parameters was A>A_s>?>D.?2?For the transient storage indexF_me²⁰ _d⁰,the in-stream pool and the semi-circular channel were 29.05%and 31.43%which implied large transient storage potential.It was consistent with regularity of the reach-scale geomorphic complexity?3?As far as the nutrient spiraling parameter was concerned,It can directly reflect the retention of nutrients.In general,the in-stream pool was benefit to the retention of SRP and the nitrate nitrogen and the semi-circular channel had a certain effect on the ammonia nitrogen.At the same time,the influence of the transient storage index,hydrological parameter and topography metrics on nitrate retention were still important.?4?The average of S_w-amb,U_maxax and K_m in the creek fully mixed were 199.06m,631.13?g/?m²·s?and 1.46 mg/L,respectively.The dynamic nutrient spiraling parameter showed some correlation with the landscape features of the creek.Clearly,the influence of geomorphic complexity parameters on nitrate retention was still important.