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Identification of dissolved organic matter size components in freshwater and marine environments
Limnology and Oceanography ( IF 4.5 ) Pub Date : 2021-01-26 , DOI: 10.1002/lno.11692
Eero Asmala 1 , Philippe Massicotte 2 , Jacob Carstensen 3
Affiliation  

Dissolved organic matter (DOM) in the transition zone from freshwater to marine systems was analyzed with a new approach for parameterizing the size distribution of organic compounds. We used size‐exclusion chromatography for molecular size analysis and quantified colored DOM (CDOM) on samples from two coastal environments in the Baltic Sea (Roskilde Fjord, Denmark and Gulf of Gdansk, Poland). We applied a Gaussian decomposition method to identify peaks from the chromatograms, providing information beyond bulk size properties. This approach complements methods where DOM is separated into size classes with pre‐defined filtering cutoffs, or methods where chromatograms are used only to infer average molecular weight. With this decomposition method, we extracted between three and five peaks from each chromatogram and clustered these into three size groups. To test the applicability of our method, we linked our decomposed peaks with salinity, a major environmental driver in the freshwater‐marine continuum. Our results show that when moving from freshwater to low‐salinity coastal waters, the observed steep decrease of apparent molecular weight is mostly due to loss of the high‐molecular‐weight fraction (HMW; >2 kDa) of CDOM. Furthermore, most of the CDOM absorbance in freshwater originates from HMW DOM, whereas the absorbing moieties are more equally distributed along the smaller size range (< 2 kDa) in marine samples.

中文翻译:

识别淡水和海洋环境中溶解的有机物尺寸成分

用一种新的方法来分析从淡水到海洋系统的过渡带中的溶解有机物(DOM),以参数化有机化合物的大小分布。我们使用尺寸排阻色谱进行分子大小分析,并对波罗的海两个沿海环境(丹麦的罗斯基勒峡湾和波兰的格但斯克湾)的样品进行了定量的有色DOM(CDOM)定量分析。我们应用了高斯分解方法来从色谱图中识别峰,从而提供了体积大小特性以外的信息。这种方法是对将DOM划分为具有预定义的过滤截止值的尺寸类别的方法或色谱图仅用于推断平均分子量的方法的补充。通过这种分解方法,我们从每个色谱图中提取了三到五个峰,并将它们聚集成三个大小组。为了测试我们方法的适用性,我们将分解峰与盐度联系在一起,盐度是淡水-海洋连续体中的主要环境驱动因素。我们的结果表明,当从淡水转向低盐度沿海水域时,观察到的表观分子量的急剧下降主要是由于CDOM的高分子量部分(HMW;> 2 kDa)的损失。此外,淡水中大多数CDOM吸收来自HMW DOM,而在海洋样本中,吸收部分在较小的尺寸范围(<2 kDa)中更均等地分布。我们的结果表明,当从淡水转向低盐度沿海水域时,观察到的表观分子量的急剧下降主要是由于CDOM的高分子量部分(HMW;> 2 kDa)的损失。此外,淡水中大多数CDOM吸收来自HMW DOM,而在海洋样本中,吸收部分在较小的尺寸范围(<2 kDa)中更均等地分布。我们的结果表明,当从淡水转向低盐度沿海水域时,观察到的表观分子量的急剧下降主要是由于CDOM的高分子量部分(HMW;> 2 kDa)的损失。此外,淡水中大多数CDOM吸收来自HMW DOM,而在海洋样本中,吸收部分在较小的尺寸范围(<2 kDa)中更均等地分布。
更新日期:2021-01-26
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