Effect of organic matter source and salinity on dissolved organic matter isolation via ultrafiltration and solid phase extraction

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Abstract

In this study, samples were taken from three contrasting freshwater sources and amended with salt in order to determine the influence of salinity and dissolved organic matter (DOM) composition on DOM recovery via ultrafiltration and solid phase extraction (SPE) with C18 disks. Salt addition caused variable recovery of DOM when using C18 SPE, and ultraviolet-visible spectroscopic characterization of the extracted material showed spectral responses that varied among sample sources. In contrast, increasing sample salinity from 0 to 30 ppt consistently caused a 15-25% reduction in the amount of high molecular weight DOM isolated by ultrafiltration for both dissolved organic carbon (DOC) and chromophoric DOM (CDOM), regardless of DOM composition. We hypothesize that a change in conformation (such as coiling or disaggregation) of DOM molecules occurs in the presence of salt, allowing them to pass through the ultrafiltration membrane and thereby decreasing the DOM retained by ultrafiltration. These results are important because they demonstrate that changes in salinity can influence DOM recovery in estuaries. Interpretation of DOM characteristics along estuarine gradients needs to account for potential artifacts introduced by sample isolation techniques.

Original languageEnglish (US)
Pages (from-to)405-417
Number of pages13
JournalAquatic Sciences
Volume73
Issue number3
DOIs
StatePublished - Aug 1 2011

Keywords

  • Colored dissolved organic matter
  • Dissolved organic carbon
  • Dissolved organic matter
  • Extraction
  • Salinity
  • Ultrafiltration

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