Université Pierre et Maire Curie and CNRS, 75005 Paris, France.
J Environ Qual. 2010 Feb 19;39(2):449-59. doi: 10.2134/jeq2009.0299. Print 2010 Mar-Apr.
To investigate bottom sediment denitrification at the scale of the Seine drainage network, a semi-potential denitrification assay was used in which river sediments (and riparian soils) were incubated for a few hours under anaerobic conditions with non limiting nitrate concentrations. This method allowed the nitrous oxide (N(2)O) concentration in the headspace, as well as the nitrate, nitrite, and ammonium concentrations to be determined during incubation. The rates at which nitrate decreased and N(2)O increased were then used to assess the potential denitrification activity and associated N(2)O production in the Seine River Basin. We observed a longitudinal pattern characterized by a significant increase of the potential rate of denitrification from upstream sectors to large downstream rivers (orders 7-8), from approximately 3.3 to 9.1 microg NO(3)(-)-N g(-1) h(-1), respectively, while the N(2)O production rates was the highest both in headwaters and in large order rivers (0.14 and 0.09 N(2)O-N g(-1) h(-1), respectively) and significantly lower in the intermediate sectors (0.01 and 0.03 N(2)O-N g(-1) h(-1)). Consequently, the ratio N(2)O production:NO(3) reduction was found to reach 5% in headstreams, whereas it averaged 1.2% in the rest of the drainage network, an intermediate percentage being found for the riparian soils. Finally, the ignition loss of sediments, together with other redundant variables (particulate organic carbon content: g C 100 g(-1) dry weight [dw], moisture: g water 100 g(-1) dw, sediment size <50 mum: g material size <50 mum 100 g(-1) dw) were found to control these activities. However, the biodegradability of organic matter must be measured to better understand the factor controlling denitrification and its associated N(2)O production.
为了研究塞纳河流域范围内的底层沉积物脱氮作用，采用半潜力脱氮测定法，即将河底沉积物（和河岸土壤）在几小时的厌氧条件下，用非限制浓度的硝酸盐进行培养。该方法可在培养过程中确定顶空气体中的氧化亚氮（N(2)O）浓度，以及硝酸盐、亚硝酸盐和铵盐浓度。然后，可以利用硝酸盐减少和 N(2)O 增加的速率来评估塞纳河流域的潜在脱氮活性和相关的 N(2)O 生成。我们观察到一个纵向模式，其特征是从上游流域到大型下游河流的潜在脱氮速率显著增加（顺序为 7-8），分别从大约 3.3 到 9.1μgNO(3)(-)-N g(-1) h(-1)，而 N(2)O 生成速率在源头和大型河流中最高（分别为 0.14 和 0.09 N(2)O-N g(-1) h(-1)），在中间流域则显著较低（分别为 0.01 和 0.03 N(2)O-N g(-1) h(-1)）。因此，发现 N(2)O 生成：NO(3)还原比在源头达到 5%，而在排水网络的其余部分平均为 1.2%，在河岸土壤中则发现中间百分比。最后，沉积物的点燃损失以及其他多余变量（颗粒有机碳含量：g C 100 g(-1)干重[dw]，水分：g 水 100 g(-1)dw，<50 μm 的沉积物大小：g 物质大小<50 μm 100 g(-1)dw）被发现可控制这些活性。然而，必须测量有机物质的生物降解性，以更好地理解控制脱氮及其相关 N(2)O 生成的因素。
