Exploring the correlations between common UV measurements and chemical fractionation for natural waters

Abstract

Chemical fractionation is a powerful tool for unravelling the reasons behind water treatment problems such as the formation of disinfection by-products (DBPs). This technique can however be costly and time-consuming. Hence, exploring quick affordable surrogate measurements to this technique is of great importance for water treatment operators. In this study, the correlations between aquatic carbon fractions and single wavelength and UV ratios of A₂₅₄, A₂₈₀, A₂₅₄/A₂₀₄, A₂₅₀/A₃₆₅ and A₂₅₄/A₄₃₆ were examined for seven water bodies located in South-east Queensland, Australia. It was observed that A₂₅₄/A₂₀₄ has a strong and significant correlation with hydrophobic/hydrophilic ratio (R² = 0.984). A₂₅₀/A₃₆₅ exhibited a weak but significant correlation with the same fraction ratio (R² = 0.687) suggesting that the chemical fractions cannot be assumed of a certain molecular size. A₂₅₄/A₄₃₆ had a weak and insignificant correlation with carbon fractions (R² = 0.0506). The hydrophobic fraction of the seven water bodies showed a strong and significant correlation with A₂₅₄ (R² = 0.968) and A₂₈₀ (R² = 0.958). The diverse carbon source of the tested water bodies confirms the reliability of the observed correlations. The results of this study highlight the potential use of UV absorbance as a real-time technique for monitoring the structural change of aquatic carbon.

Keywords:

• DOC
• Chemical fractionation
• Hydrophobicity
• Hydrophilicity
• Single wavelength UV and UV ratio

Acknowledgement

This work was financially supported by the University of Southern Queensland, Australia. The authors are grateful to Mr John Mills, Principal Scientist, Laboratory Services, Mt Kynoch Water Treatment Plant, Toowoomba, Australia for his help in providing total coliform data. The authors would also like to express their gratitude to Dr Leslie Bowtell for revising the language of the manuscript. The authors appreciate Mr Chris Power's help in creating the map of the sampling sites.