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.