Separating physical and biological nutrient retention and quantifying uptake kinetics from ambient to saturation in successive mountain stream reaches
Separating physical and biological nutrient retention and quantifying uptake kinetics from ambient to saturation in successive mountain stream reaches
复制标题
分离物理和生物养分保留并量化连续山溪河段从环境到饱和的吸收动力学
DOI：
10.1029/2009jg001263
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发表时间：
2010
影响因子：
--
通讯作者：
M. Baker
中科院分区：
文献类型：
--
作者：
T. Covino;B. McGlynn;M. Baker
[1]河流河段的水文和生态地球化学过程影响着营养盐的向下游输送。一个流到达的输出成为下一个流到达的输入，从而导致沿着流网络进行串行处理。每个河段的吸收-浓度曲线的形状表示营养物的流内生物吸收。结合由于水文周转的物理保留，生物和物理保留将控制下游的营养输出。我们进行了一个保守的瞬时加法，（氯化物，Cl）和非保守性养分（硝酸盐氮，NO3-N）示踪剂，以确定在锯齿山沿沿着3744米河流网络的四个相邻河段的物理和生物保留的相对作用，物理保留占总保留的主导地位，范围从15%到58%，在各个河段，在整个流长度总计81%。在每个到达，生物吸收强烈控制营养浓度。我们对每个河段的连续米氏动力学曲线进行了定量，并确定了环境吸收量（Uamb）范围为19至58 μg m−2 min−1，最大吸收量（Umax）范围为65至240 μg m−2 min−1，半饱和常数（Km）范围为4.2至14.4 μg l−1 NO3-N。由Umax表示的生物保留容量沿下游方向下降。虽然生物截留能力下降移动下游，它并没有减少那么多的物理保留，这导致生物保留包括在下游河段的总保留的更大部分。我们建议，准确评估总保留跨流到达和流网络需要量化的物理保留和浓度依赖性的生物吸收。
[1] Hydrological and biogeochemical processes in stream reaches impact the downstream transport of nutrients. The output from one stream reach becomes the input for the next, leading to serial processing along stream networks. The shape of the uptake-concentration curve for each reach indicates in-stream biological uptake of nutrient. Combined with physical retention due to hydrologic turnover, both biological and physical retention will control nutrient export downstream. We performed an instantaneous addition of conservative (chloride, Cl) and nonconservative nutrient (nitrate-nitrogen, NO3-N) tracers to ascertain the relative roles of physical and biological retention across four adjacent reaches along a 3744 m stream network in the Sawtooth Mountains, ID. Physical retention dominated total retention ranging from 15% to 58% across individual reaches and totaling 81% across the entire stream length. Within each reach, biological uptake was strongly controlled by nutrient concentration. We quantified continuous Michaelis-Menten (M-M) kinetic curves for each reach and determined that ambient uptake (Uamb) ranged from 19 to 58 μg m−2 min−1, maximum uptake (Umax) from 65 to 240 μg m−2 min−1, and half-saturation constants (Km) from 4.2 to 14.4 μg l−1 NO3-N. Biological retention capacity indicated by Umax decreased in a downstream direction. Although biological retention capacity decreased moving downstream, it did not decrease as much as physical retention, which led to biological retention comprising a larger portion of total retention at downstream reaches. We suggest that accurate assessment of total retention across stream reaches and stream networks requires quantification of physical retention and the concentration-dependent nature of biological uptake.