基于TASCC的典型农田溪流氨氮滞留及吸收动力学模拟

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

为揭示农田溪流氨氮滞留的动态变化性,选择Na Cl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NNH4-+滞留动态,并以Michaelis-Menten模型(M-M方程)模拟NNH4-+吸收动力学特性.结果表明:背景浓度的NNH4-+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NNH4-+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.NNH4-+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NNH4-+滞留动态和吸收动力学特征的可行性和有效性.

In the present work, instantaneous additions of conservative （NaC1） and non-conservative nutrient （NH4C1） 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 NH4^- N retention dynamics, while the Michaelis-Menten kinetic model was utilized to characterize NH4^＋ - N uptake kinetics. Results showed that the ambient uptake length （Sw-mb） of the study reach ranged from 93.94to 295.54m with an average of 177.41m, the ambient uptake velocity （Vfam） from 0.16to 0.38mrrds averaging 0.26mm/s, and the ambient areal uptake rate （Uamb） from 0.16to 0.38mg/（m^2·s） averaging 0.26mg/（m^2·s）. The Michaelis-Menten kinetic modeling identified the maximum NH：-N uptake （Ur^x） of 0.59~l.38mg/（m^2·s）, and half-saturation constants （Kin） of 1.10-5.03mg/L. Dynamic variations of Sw-add-dyn, Uftot-dyn and Vftot dyn from ambient to saturation demonstrated the feasibility and effectiveness of TASCC approach for characterization of NH：-N retention dynamics and uptake kinetics in an agricultural headwater stream.