The Balance Of Nitrogen And Phosphorus During The Trandportion In Da-Liao River

The nutrients transportation in river mainly involves retention and nutrients exchange between sediment-water interface (internal loads). The nutrients balance of those processes determines the nutrients budget that export to sea.Therefore, it’s necessary to study the cycling process of nutrients during river transportion, which would show important role in water manogement..nitrogen and phosphorus attracted more and more scholars’ attention with increased nutrients loads in terrestrial ecosystem.This article studied the deposition, aquatic biological absorption, denitrification and exchange rate across sediment and water interface of nitrogen and phosphorus in Da-Liao River through the in-situ measured, simulation research and empirical model. The conclusion of our research includes:(1Concentrations of total nitrogen(TN), total phosphorus(TP) range from4.80to7.59,0.17to0.47mg/L in Da-Liao River, and the dissolved total nitrogen (DTN) is the main form of total nitrogen(TN) with proportion of86%;particulate phosphorus (PP) is the main form of total phosphorus (TP) with percentage of69%. Statistical analysis showed that concentrations of nitrogen and phosphorus in Da-Liao River showed significant temporal variation. The seasonality character of TN and TP concentration was spring<summer<antumn (P<0.05). However, TN and TP showed no significantly spatial difference. In addition, concentration of TN but TP show apparent vertical distribution pattern:surface water(0.5m)<middle water(4m)<overlying waterfer(7m).(2) The up take rate of TN anf TP by aquatic plants estimated based on water level and flow data is about-0.1%. This result indicates that aquatic plants up take nitrogen and phosphorus from sediments, and finaly nitrogen and phosphorus in plants relase to water body with the death of plant. Overall, aquatic plants has no significant effect on the nitrogen and phosphorus balance during transportation in Da-Liao River.(3)3%of nitrogen and19%of phosphorus was deposited during transportion, respectively. The average denitrification rates of sediments in Daliao River was164.5mg/m·d, thus we can estimated that the lost of nitrogen via denitrification process is about7%of the nitrogen loads.(4) During the study period, the average exchange fluxes of NO2--N,NO3--N,NH4+-N and DIN(NO2--N+NH4+-N+NO3--N) in sediment-water inferface wererange from-9.43to2.10(average:-124.7±23.74),317.79to38.5(average:-127.7±23.74),14.66to824.55(average:220.97±57.29) and-155.51to599.10(average:93.92±60.25) μmol/m2·d, respectively. PO43--P exchange fluxes were ranged-0.36to0.57μmol/m2·d, the mean value was (0.00±0.05) μmol/m·d. Therefore, sediment acts as sinks of NO2-N and NO3--N, and source of NH+-N and DIN. And the PO43--P exchange flus was basic balance. Taking the river bed area (30km2) into account, it is estimated the less than1%of nitrogen and phosphorus loads was consumed. Thus, exchange flux of nitrogen and phosphorus during the transportion has no sifnificant influence in nutrients budget in Da-Liao River.Integrating retention process as well as sediment-water interface exchange of nitrogen and phosphorus, it is estimated that about10%of the nitrogen and19%of the phosphorus loads in the Da-liao River would be retented in the river. Therefore, it was necessary to consider the impact of retention rate of nitrogen and phosphorus into consideration in the future management of coastal water.