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首页> 外文会议>Second International Conference on Wetlands amp; Remediation, Sep 5-6, 2001, Burlington, Vermont >N-15 SIGNALS OF NITROGEN SOURCE AND FATE IN A SEMIARID WETLAND
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N-15 SIGNALS OF NITROGEN SOURCE AND FATE IN A SEMIARID WETLAND

机译：半干旱湿地中氮源和命运的N-15信号

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摘要

Nitrogen isotope measurements of plants and waters are being used to identify nitrogen fluxes and transformations occurring in a natural cattail marsh in Sandia Canyon at Los Alamos National Laboratory (LANL). The marsh receives inputs of treated sewage wastewater, containing nitrate enriched in ~(15)N (δ~(15)N of 32.4 per thousand, concentrations up to 30 mg/L). Cattails growing near the head of the primary wetland have δ~(15)N values up to 37.8 per thousand, suggesting that sewage nitrate is their main source of nitrogen with in-situ denitrification leading to further enrichment of the wetland nitrate pool. These cattails also have lower molar C/N ratios, relative to other cattails in the system, with values around 16. These results suggest that nitrogen is both lost from the system via denitrification and stored in plant material. Cattails growing near the distal end of the wetland, in more strongly reducing sediments that potentially have higher denitrification rates, were enriched in ~(13)C. This is due to decreased isotopic fractionation during uptake and assimilation of CO_2, resulting from partial closure of stomata under physiological redox stress. These cattails were enriched in ~(15)N, relative to cattails growing in central portions of the wetland. Natural abundance level isotopic measurements of wetland plants and waters could provide an effective technique to identify spatial gradients in nitrogen inputs, outputs, and transformation, in both natural and constructed wetlands.
机译：植物和水体的氮同位素测量被用于识别洛斯阿拉莫斯国家实验室（LANL）桑迪亚峡谷天然香蒲沼泽中发生的氮通量和转化。沼泽收到经过处理的污水的输入，其中包含的硝酸盐富含〜（15）N（δ〜（15）N为千分之32.4，浓度最高为30 mg / L）。生长在主要湿地顶部附近的香蒲的δ〜（15）N值高达37.8 /千，表明硝酸盐是其主要的氮源，并进行原位反硝化作用，从而进一步丰富了湿地硝酸盐库。相对于系统中的其他香蒲，这些香蒲的C / N摩尔比也较低，约为16。这些结果表明，氮通过反硝化作用从系统中损失掉并存储在植物材料中。香蒲生长在湿地远端附近，以更强烈地减少可能具有更高反硝化速率的沉积物，富含〜（13）C。这是由于在生理氧化还原胁迫下气孔的部分关闭导致了CO_2的吸收和同化过程中同位素分数的降低。相对于在湿地中部生长的香蒲，这些香蒲富含〜（15）N。湿地植物和水域的自然丰度水平同位素测量可以提供一种有效的技术，以识别天然和人工湿地中氮素输入，输出和转化的空间梯度。

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