基于TASCC的典型农田溪流氨氮滞留及吸收动力学模拟

为揭示农田溪流氨氮滞留的动态变化性,选择NaCl为保守示踪剂、NH4Cl为添加营养盐开展野外瞬时投加示踪实验.在此基础上,采用TASCC方法和养分螺旋指标定量刻画 滞留动态,并以Michaelis-Menten模型(M-M方程)模拟 吸收动力学特性.结果表明:背景浓度的 吸收长度Sw-amb变化范围为93.94~295.54m,平均值为177.41m;质量传输系数Vf-amb变化范围为0.16~0.38mm/s,平均值为0.26mm/s;吸收速率Uamb变化范围为0.16~0.38mg/(m2×s),平均值为0.26mg/(m2×s).由M-M方程模拟得到的 最大吸收速率Umax为0.59~1.38mg/(m2×s),半饱和常数Km为1.10~5.03mg/L. 在从背景浓度到饱和浓度区间范围内展现出的Sw-add-dyn、Utot-dyn和Vf-tot-dyn动态变化性,验证了TASCC解析 滞留动态和吸收动力学特征的可行性和有效性.

Ammonium retention and uptake kinetics process in an agricultural headwater stream based on TASCC approach

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.