| In order to explore the different types of headwater streams of transient storage and nutrient retention capacity, five typical headstreams in four kinds of different land, such as urban, farmland, woodland and suburban were chosen for the object in Hefei area. The solution of nutrient (NH4Cl and KH2PO4) and a conservative tracer (NaCl) were used to conduct field experiments. The OTIS model and the principle of the nutrient spiral were set to quantitative estimation of headwater streams transient storage and nutrient retention capacity, and then to analyze different types of headwater streams transient storage and compare the differences of nutrient retention characteristics. The results of this study were outlined as follows.(1) The hydrological parameters and transient storage of index changing with hydrological conditions show certain differences. Hydraulic diffusivity (D) was 0.010 to 0.223, exchange coefficient was in the order of 10-4 to 10-3, the value of Rh, As/A and Fmed200 in urban channels were 1.405 s-m-1,0.325 and 15.37%, in farmland streams were 4.124 s·m-1,0.433 and 20.21%, in woodland streams were 4.860 s·m-1,0.512 and 30.92%, in suburban drainage ditches were 1.124 s·m-1,0.304 and 20.46%, overall considering the transient storage measures (i.e. Rh?As/A and Fmed200), the size order of transient storage in the four types of headwater streams was presented:woodland streams, farmland streams, urban channels and suburban drainage ditches.(2) The value of nutrient spiraling metrics Vf-NH4 and Vf-SRP was between of the order of 10-5 to 10-3, the value of U-NH4 and U-SRP between the order of 10-3 and 10-1, there are large difference between the uptake lengths of NH4 and SRP. That the nutrient uptakes lengths appear negative value in some headstream imply that the headstream acting as source of N or P, that is to say, the nutrient is in the released state. In most cases, the nutrient uptake length is far more than the length of the stream itself.It means that the N and P play a very small possibility of retention in streams.(3) There was weak correlation among the hydrological parameters (i.e. D?A?As and a) with discharge (Q) and no significant correlations among most of the hydrological parameters with transient storage metrics in regression analysis results. There are several functional relation in pairs among transient storage metrics (i.e. Ts?Ls? Rh and As/A) with discharge (Q). No significant correlations were found among Tc, Fmed200 with discharge (Q). The exchange coefficient (?) and flow rate (v) have positive correlation relationship.(4) The analysis of different mechanisms in OTIS model showed that, without the consideration of the effect of transient storage, the peak value RE1 and the peak time RE1' were 52.33% and-19.99% respectively, If ignoring the effect of lateral inflow, the peak value RE2 and the peak time RE2' were 3.50% and 3.45% respectively. It is showed that for this study, the effects of chloride in the migration of water transportation of transient storage markedly exceeded those of lateral inflow. Analysis results showed that discharge was weaker significantly correlated with the peak value and the peak time, and transient storage was significantly correlated with the peak value and the peak time. |
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