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Loss of optical and molecular indicators of terrigenous dissolved organic matter during long-term photobleaching

机译:长期光漂白过程中陆源溶解有机物的光学和分子指示剂损失

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摘要

Two water samples from the Great Dismal Swamp National Wildlife Refuge with high dissolved organic matter (DOM) concentrations (51 and 121 mg C L~(-1)) were subjected to ultraviolet (UV) light for up to 110 days. During the course of the irradiations, 74-88 % of the original dissolved organic carbon was lost along with 95-99 % of the absorption at 300 nm. Based on changes observed during light exposure, three pools of DOM were identified: photo-labile, photo-refractory, and photo-produced compounds. Solid-state ~(13)C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to determine structural moieties characteristic to each of these pools. These analyses showed aromatic carbons were preferentially removed while carbohydrate-like and amide/peptide-like carbons were preserved during UV exposure. An increase in carbon normalized ~(13)C NMR signal in the 0-50 ppm region suggests that alkyl moieties were produced, while FTIR signal at 1,745 cm~(-1) and two-dimensional ~1H-~(13)C NMR results confirmed the photochemical production of acetate. Several properties typically used to trace terrigenous DOM in ocean margin and marine environments were significantly altered. Optical properties, including absorption spectral slopes and fluorescence indices, as well as carbon-normalized lignin yields shifted from terrestrial values towards those more typical of coastal or open ocean samples. The loss of terrestrial signatures during irradiation highlights the difficulty faced when quantifying the contribution of terrigenous DOM to aquatic carbon pools.
机译:来自大沼泽国家野生动物保护区的两个水样中的高溶解有机物(DOM)浓度(分别为51和121 mg C L〜(-1))经受紫外线(UV)照射长达110天。在照射过程中,最初溶解的有机碳的74-88%损失了,而在300 nm处的吸收损失了95-99%。根据在曝光期间观察到的变化,确定了DOM的三个集合:光不稳定,光难燃的和光产生的化合物。固态〜(13)C核磁共振(NMR)光谱和傅里叶变换红外(FTIR)光谱用于确定每个这些池的特征性结构部分。这些分析表明,在暴露于紫外线期间,芳香族碳被优先去除,而碳水化合物类和酰胺/肽类则被保留。碳归一化〜(13)C NMR信号在0-50 ppm区域的增加表明产生了烷基部分,而FTIR信号在1,745 cm〜(-1)和二维〜1H-〜(13)C NMR结果证实了乙酸的光化学产生。通常用于追踪海洋边缘和海洋环境中的陆源DOM的一些属性已发生了重大变化。光学特性,包括吸收光谱的斜率和荧光指数,以及碳标准化的木质素产量,从地面值向沿海或远洋样品的典型值转移。辐射过程中陆地特征的丧失突出了量化陆源DOM对水生碳库的贡献时面临的困难。

著录项

  • 来源
    《Aquatic Sciences》 |2014年第3期|353-373|共21页
  • 作者单位

    Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Blvd, Norfolk, VA 23529, USA,Department of Chemistry and Biochemistry, University of North Carolina Wilmington, 601 S. College Rd, Wilmington, NC 28403, USA;

    Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Blvd, Norfolk, VA 23529, USA;

    Skidaway Institute of Oceanography, Marine Sciences, University of Georgia, 10 Ocean Science Circle, Savannah, GA 31411, USA;

    Department of Chemistry, Iowa State University, Ames, IA 50011, USA;

    Woods Hole Research Center, Falmouth, MA 02540, USA;

    Department of Land, Air and Water Resources, University of California, One Shields Ave., Davis, CA 95616, USA;

    Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Blvd, Norfolk, VA 23529, USA;

  • 收录信息 美国《科学引文索引》(SCI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    CDOM; Photobleaching; Swamp; UV-vis; NMR; Biomarkers; FTIR;

    机译:CDOM;光漂白;沼泽;紫外线可见;NMR;生物标志物;红外光谱;

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