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首页> 外文学位 >Denitrification in riparian zones and other saturated soils of a northeastern agricultural landscape.
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Denitrification in riparian zones and other saturated soils of a northeastern agricultural landscape.

机译：东北农业景观的河岸带和其他饱和土壤中的反硝化作用。

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摘要

Nitrogen (N), particularly nitrate (NO3-), is a critical pollutant in many northeastern US watersheds that is especially detrimental to coastal marine ecosystems. Agricultural land, which receives fertilizers and/or animal manures, is a principal source of N loading to the environment. The most effective NO3- attenuation mechanism is probably microbial denitrification, i.e., the transformation of NO3- into N gases (e.g., NO, N2O, N2). Currently, our estimates of the magnitudes of denitrification rates at landscape scales are "tentative" at best, usually based on large-scale watershed budgets in which denitrification was estimated by difference. One reason that denitrification is hard to quantify is that a large amount of denitrification occurs in disproportionately small parts of the landscape (i.e., hotspots) and over relatively short periods (i.e., hot moments). Denitrification occurs primarily under anaerobic conditions by heterotrophic microbes and is expected to be vigorous in wet soils high in organic carbon. There is good evidence that these conditions correlate strongly with the likelihood of soil saturating, i.e., hydrological sensitivity, thus, by juxtaposing hydrology and biogeochemistry we can elucidate the distribution of denitrification hotspots across the landscape. We used nitrogen isotopes to quantify and characterize spatial patterns of denitrification in riparian zones and other saturated soils (i.e., the shallow saturated zone) of an agricultural landscape. In situ denitrification rates in shallow groundwater were determined monthly using the 15N-NO3- push-pull method. Annual rates of denitrification showed a strong positive relationship with topographic index, a well-known wetness index and indicator of hydrologic similarity. The resulting relationship was used to distribute denitrification rates across the landscape and estimate denitrification N fluxes from the shallow saturated zone. Denitrification in the shallow saturated zone resulted in a N flux that was nearly half of the total denitrification from the landscape---in about a third of the area---as determined from an unusually well-constrained whole-farm N balance constructed from farm records and field measures. Denitrification N flux rates from saturated riparian soils were among the highest in the landscape, however the contribution of riparian areas to total landscape denitrification was less than 10 percent.
机译：氮（N），尤其是硝酸盐（NO 3-）是美国东北许多流域中的关键污染物，对沿海海洋生态系统尤其有害。接收化肥和/或动物粪便的农田是向环境中加载氮的主要来源。最有效的NO3-衰减机理可能是微生物反硝化，即NO3-转化为N气（例如NO，N2O，N2）。当前，我们对景观规模反硝化率幅度的估计充其量只是“初步的”，通常是基于大规模流域预算，其中通过差异估算了反硝化率。反硝化难以量化的一个原因是，大量反硝化发生在景观的不成比例的小部分（即热点）中，并且发生的时间相对较短（即炎热时刻）。反硝化作用主要发生在厌氧条件下，由异养微生物引起，预计在有机碳含量高的潮湿土壤中会很强。有充分的证据表明，这些条件与土壤饱和的可能性（即水文敏感性）密切相关，因此，通过将水文和生物地球化学并置，我们可以阐明反硝化热点在整个景观中的分布。我们使用氮同位素来量化和表征农业景观的河岸带和其他饱和土壤（即浅饱和带）中反硝化的空间格局。使用15N-NO3-推挽法每月测定浅层地下水的原位反硝化率。年反硝化率与地形指数，众所周知的湿度指数和水文相似性指标显示出强烈的正相关关系。由此产生的关系被用来分布整个景观的反硝化率，并估计来自浅饱和区的反硝化氮通量。浅饱和区的反硝化作用产生的氮通量约为景观总反硝化作用的一半（在该区域的三分之一左右），这是由异常约束良好的全农场氮平衡确定的。农场记录和田间措施。来自饱和河岸土壤的反硝化氮通量率在景观中是最高的，但是河岸地区对整个景观反硝化的贡献不足10％。

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  • 作者

    Anderson, Todd Reif.;

  • 作者单位

    Cornell University.;

  • 授予单位 Cornell University.;
  • 学科 Biogeochemistry.;Agriculture Agronomy.;Hydrology.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 173 p.
  • 总页数 173
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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