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| Ammonium retention and uptake kinetics process in an agricultural headwater stream based on TASCC approach |
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Abstract In the present work, instantaneous additions of conservative (NaCl) and non-conservative nutrient (NH4Cl) tracers were conducted to characterize ammonium retention dynamics and uptake kinetics in a typical agricultural draining canal, in Nanfeihe River of Chaohu Lake basin. Furthermore, tracer additions for spiraling curve characterization (TASCC) and nutrient spiraling metrics were used to describe retention dynamics, while the Michaelis-Menten kinetic model was utilized to characterize uptake kinetics. Results showed that the ambient uptake length (Sw-amb) of the study reach ranged from 93.94to 295.54m with an average of 177.41m, the ambient uptake velocity (Vf-am) from 0.16to 0.38mm/s averaging 0.26mm/s, and the ambient areal uptake rate (Uamb) from 0.16to 0.38mg/(m2×s) averaging 0.26mg/(m2×s). The Michaelis-Menten kinetic modeling identified the maximum uptake (Umax) of 0.59~1.38mg/(m2×s), and half-saturation constants (Km) of 1.10~5.03mg/L. Dynamic variations of Sw-add-dyn, Utot-dyn and Vf-tot-dyn from ambient to saturation demonstrated the feasibility and effectiveness of TASCC approach for characterization of retention dynamics and uptake kinetics in an agricultural headwater stream.
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Received: 08 October 2014
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