Catchment topography and the distribution of electron donors for denitrification control the nitrate concentration in headwater streams of the Lake Hachiro watershed
Catchment topography and the distribution of electron donors for denitrification control the nitrate concentration in headwater streams of the Lake Hachiro watershed
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DOI：
10.1080/00380768.2020.1827292
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发表时间：
2020-10
影响因子：
2
通讯作者：
A. Hayakawa;Y. Funaki;T. Sudo;Ryoki Asano;H. Murano;Shintaro Watanabe;T. Ishida;Y. Ishikawa;S. Hidaka
中科院分区：
文献类型：
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作者：
A. Hayakawa;Y. Funaki;T. Sudo;Ryoki Asano;H. Murano;Shintaro Watanabe;T. Ishida;Y. Ishikawa;S. Hidaka
摘要我们研究了地形和电子供体之间的联系，反硝化作用在流NO3-浓度在八代湖流域的河源集水区海洋沉积岩，日本。在35个河源集水区（0.07-16.9平方公里），我们采样溪流水每个季节在2年。分析了水样中NO3 -、溶解的一氧化二氮（dN 2 O）和SO 4 2 -的浓度。河流沉积物取样一次，用于测量反硝化潜力（DP）。测定了沉积物中水溶态有机碳（WESOC）和易氧化硫化物（EOS）的含量，它们被认为是反硝化作用的主要潜在电子供体。每个流域的地形特征计算使用数字高程模型与10米网格单元。流域内NO3 -浓度的空间变异范围为0.06 ~ 0.52 mg N L-1，与地形湿度指数（TWI）呈显著负相关（P < 0.01），与流域坡度呈正相关（P <0.01），表明流域内NO3 -浓度在较湿润和缓坡流域内呈下降趋势。沉积物DP和沉积物中WESOC含量与TWI呈显著正相关。这些结果表明，反硝化作用可能发生在较高的TWI集水区。广义线性模型表明，TWI，坡度，泥沙DP显着影响在流NO3 -浓度和WESOC是一个显着的解释变量泥沙DP。没有选择河床沉积物中的EOS含量作为流中NO3 −浓度或沉积物DP的重要解释变量。但在河流沉积物中EOS含量较高的流域河岸底土中检测到较高的土壤DP和较高的EOS，这表明河流沉积物中的EOS可以包含硫化物驱动的反硝化热点的特定信息。我们的结论是，流域地形和河床沉积物中的电子供体的分布可以解释在流NO3 -浓度和沉积物DP的空间变化的重要因素。
ABSTRACT We examined the linkages between topography and electron donors for denitrification on in-stream NO3 − concentration in headwater catchments in the Lake Hachiro watershed having marine sedimentary rock, Japan. In 35 headwater catchments (0.07–16.9 km2), we sampled stream water every season in 2 years. The water samples were analyzed for NO3 –, dissolved nitrous oxide (dN2O), and SO4 2 – concentrations. Stream sediment was sampled once for the measurement of denitrification potential (DP). Water-extractable soil organic carbon (WESOC) and easily oxidizable sulfide (EOS) in the sediment, which can be considered the principal potential electron donors for denitrification, were measured. The topographical features of each catchment were calculated using a digital elevation model with 10-m grid cells. Stream NO3 – concentrations displayed large spatial variation among catchments, ranging from 0.06 to 0.52 mg N L–1, and were negatively correlated with topographic wetness index (TWI) (P < 0.01) and were positively correlated with catchment slope (P < 0.01), indicating that NO3 – concentrations decreased in wetter and gentle slope catchments. Sediment DP and the WESOC content in sediments were positively correlated with TWI, significantly. These results suggested denitrification was likely to occur in higher TWI catchments. Generalized linear model showed that TWI, slope aspect, and sediment DP significantly affected in-stream NO3 – concentration and WESOC was a significant explanatory variable for sediment DP. EOS content in riverbed sediments was not selected as a significant explanatory variable for either in-stream NO3 − concentrations or sediment DP. But higher soil DP with higher EOS was detected in the stream bank subsoil at the catchment where the higher EOS content in the riverbed sediment was observed, which suggested EOS in riverbed sediments can contain site-specific information about denitrification hotspot driven by sulfides. We conclude that catchment topography and the distribution of electron donors in riverbed sediment can be important factors to explain the spatial variation in in-stream NO3 – concentration and sediment DP.