Freeze/Thaw and pH effects on freshwater dissolved organic matter fluorescence and absorbance properties

ARGM Spencer, L Bolton, Andrew Baker

Research output: Contribution to journalArticle

157 Citations (Scopus)


The UV-visible and fluorescence excitation-emission matrix spectrophotometric properties of dissolved organic matter (DOM) were compared for the effects of both pH and freeze/thaw on a wide range of freshwater DOM samples from the United Kingdom. It was observed that the spectrophotometric properties of our freshwater samples were sensitive to pH and that the recorded change varies with fluorescence and absorbance intensity, DOC concentration and the wavelength observed. Large and variable responses to pH were particularly severe at extremes of pH, but within the natural levels typically observed in freshwaters the response to pH was limited. For the same sample set large and variable responses were observed when subjected to freeze/thaw. From our data, knowledge of the original properties cannot be used to determine the amount of change that will occur with freezing and subsequent thawing. It is therefore recommended that in future research, to maintain the natural signal of the DOM, analysis is conducted at natural pH and without freezing to facilitate ease of comparison between studies. Our results also have implications for studies that utilise spectrophotometric techniques to investigate long-term trends in dissolved organic carbon in rivers. Spectrophotometric parameters from upland derived samples show varied responses of samples to pH and there is clear potential to complicate trends in the interpretation of long-term water colour data if pH is changing over time in a system or if samples are treated with different storage protocols with respect to acidification and freezing.
Original languageEnglish
Pages (from-to)2941-2950
Number of pages10
JournalWater Research
Publication statusPublished - 1 Jul 2007


  • freeze-thaw
  • fluorescence
  • dissolved organic matter
  • pH
  • absorbance


Dive into the research topics of 'Freeze/Thaw and pH effects on freshwater dissolved organic matter fluorescence and absorbance properties'. Together they form a unique fingerprint.

Cite this