Integrated Constructed Wetlands (ICW) area technology for the attenuation of contaminants such as organic carbon (C), nitrogen (N), phosphorous (P) and sulphur (S) in water coming from point or diffuse sources. Currently there is a lack of knowledge on the rates of gross N transformations in soils of the ICW bed leading to losses of reactive N to the environment. In addition, the kinetics of these processes need to be studied thoroughly for the sustainable use of ICW for removal of excessive N in the treatment of waste waters. Gross N transformation processes were quantified at two soil depths (0–15 and 30–45 cm) in the bed of a surface flow ICW using a ¹⁵N tracing approach. The ICW, located in Dunhill village at Waterford in Southeastern Ireland, receives 500 person equivalent waste waters containing large quantities of organic pollutants (ca. mean annual C, N, P and S contents of 240, 60, 5 and 73 mg L⁻¹). Soil was removed from these depths in December 2014 and incubated anaerobically in the laboratory, with either ¹⁵N labeled ammonium (NH₄⁺) or nitrate (NO₃⁻), differentially labeled with ¹⁴NH₄¹⁵NO₃ and ¹⁵NH₄¹⁴NO₃ in parallel setups, enriched to 50 atm% ¹⁵N. Results showed that at both soil depths, NO₃⁻ production rates were small, which may have resulted in lower NO₃⁻ reduction by either denitrification or dissimilatory NO₃⁻ reduction to ammonium (DNRA). However, despite being low, the DNRA rates were greater than denitrification rates. Direct transformation of organic N to NO₃⁻, without mineralization to NH₄⁺, was a prevalent pathway of NO₃⁻ production accounting for 28–33% of the total NO₃⁻ production. Relative contribution of this process to the total N mineralization was negligible at depth 1 (0.01%) but dominant at depth 2 (99.7%). Total NO₃⁻production to total immobilization of NH₄⁺ and NO₃⁻ was very small (<0.50%) suggesting that ICW soils are not a source of NO₃⁻. Despite a large potential of N immobilization existed at both the layers, relative N immobilization to the total N conversion was higher at depth 2 (ca. 2.2) than at depth 1 (ca. 1.5). The NH₄⁺ desorption rate at 30–45 cm was high. However, immobilization in the recalcitrant and labile organic N pools was higher. Mineralization and immobilization of NH₄⁺ processes showed that recalcitrant organic N was the predominant source in ICW soils whereas the labile organic N was comparatively small. Source apportionment of N₂O production showed that the majority of the N₂O produced through denitrification (ca. 92.5%) followed by heterotrophic nitrification (ca. 5.5%), co-denitrification (ca. 1.90%) and nitrification (0.20%). These results revealed that application of a detailed ¹⁵N tracing method can provide insights on the underlying processes of ecosystem based abundances of reactive N. A key finding of this study was that both investigated ICW layers were characterised by large N immobilization which restricts production of NO₃⁻ and further gaseous N losses.

综合人工湿地（ICW）区域技术，用于衰减来自点源或扩散源的水中污染物，例如有机碳（C），氮（N），磷（P）和硫（S）。目前，缺乏关于ICW床土壤中总N转化率的知识，这导致反应性N损失到环境中。此外，需要对这些过程的动力学进行彻底研究，以可持续利用ICW去除废水中的过量N。在表面流ICW的两个土壤深度（0–15和30–45 cm）处，使用^15的N对总氮转化过程进行了定量。N追踪方法。ICW位于爱尔兰东南部沃特福德的登喜路村，接收500人当量的废水，其中包含大量的有机污染物（每年平均C，N，P和S含量为240、60、5和73 mg L ^-1）。从这些深度中除去土壤在2014年12月和在实验室中厌氧培养，与任一¹⁵ Ñ标记铵（NH ₄ ⁺）或硝酸盐（NO ₃ ^{- ），}其中差异标记¹⁴ NH ₄ ¹⁵ NO ₃和¹⁵ NH ₄ ¹⁴ NO ₃平行设置，浓缩至50 atm％¹⁵N.结果表明，在两个土层，NO ₃ ^-生产速率太小，这可能导致较低的NO ₃ ^-还原由任一脱硝或异化NO ₃ ^-还原为铵（DNRA）。但是，尽管较低，但DNRA率大于反硝化率。的有机氮为NO直接转化₃ ^- ，而不矿化到NH ₄ ⁺，NO被一个普遍的路径₃ ^-生产占总NO的28-33％₃ ^-生产。该过程对总氮矿化的相对贡献在深度1（0.01％）可以忽略不计，但在深度2（99.7％）则占主导地位。总NO ₃ ^-生产到NH的总固定₄ ⁺和NO ₃ ^-是非常小的（<0.50％），这表明ICW土壤不是NO的来源₃ ^- 。尽管两层都有很大的固氮潜力，但在深度2（约2.2）处相对于总N转化的相对氮固定比深度1（约1.5）高。30–45 cm处的NH ₄ ⁺解吸速率很高。然而，顽固和不稳定的有机氮库中的固定化更高。NH的矿化和固定化₄ ⁺过程表明，顽固性有机氮是ICW土壤中的主要来源，而不稳定的有机氮相对较小。N ₂ O产生的来源分摊显示，大部分N ₂ O通过反硝化（约占92.5％），随后的异养硝化（约5.5％），共脱氮（约1.90％）和硝化作用（约0.20％）产生。 ）。这些结果表明，采用详细的¹⁵ N示踪方法可以提供基于生态系统反应性N丰度的潜在过程的见解。这项研究的关键发现是，两个被调查的ICW层均具有大面积的N固定化特征，这限制了NO的产生₃ ^- 以及更多的气态氮损失。