New Insights into the Seasonal Variation of DOM Quality of a Humic-Rich Drinking-Water Reservoir—Coupling 2D-Fluorescence and FTICR MS Measurements

Christin Wilske,Wolf Von Tümpling,Norbert Kamjunke,Jürgen W Einax,Oliver J Lechtenfeld,Peter Herzsprung

doi:10.3390/w13121703

Christin Wilske, Wolf Von Tümpling + Show 4 more

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https://doi.org/10.3390/w13121703

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Abstract

Long-term changes in dissolved organic matter (DOM) quality, especially in humic-rich raw waters, may lead to intensive adaptions in drinking-water processing. However, seasonal DOM quality changes in standing waters are poorly understood. To fill this gap, the DOM quality of a German drinking water reservoir was investigated on a monthly basis by Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS) measurements and 2D fluorescence for 18 months. FTICR MS results showed seasonal changes of molecular formula (MF) intensities, indicating photochemical transformation of DOM as a significant process for DOM quality variation. For an assessment of the two humic-like components, identified by parallel factor analysis (PARAFAC) of excitation–emission matrices (EEM), their loadings were Spearman’s rank-correlated with the intensities of the FTICR MS-derived MF. One of the two PARAFAC components correlated to oxygen-rich and relatively unsaturated MF identified as easily photo-degradable, also known as coagulants in flocculation processes. The other PARAFAC component showed opposite seasonal fluctuations and correlated with more saturated MF identified as photo-products with some of them being potential precursors of disinfection byproducts. Our study indicated the importance of elucidating both the chemical background and seasonal behavior of DOM if raw water-quality control is implemented by bulk optical parameters.

Highlights

Our study indicated the importance of elucidating both the chemical background and seasonal behavior of dissolved organic matter (DOM) if raw water-quality control is implemented by bulk optical parameters
Several studies have documented this part of the dissolved organic carbon (DOC), which is mainly subjected to coagulation, and some studies have noted the chemical composition of this dissolved organic matter part, the molecules of which potentially act as precursors for halogenated disinfection byproducts [4,11,12,13,14,15]
The seasonal change of DOM quality was detected in a reservoir dominated by terrestrial material, which could be explained mainly by photochemical transformations

Summary

Introduction

Until now only minor information has been available regarding how and whether DOM quality undergoes seasonal changes in drinking-water reservoirs. This appears to be an important subject for research, as a part of the DOC is usually removed from raw waters [8,9,10]. Changes in DOM quality in raw waters can lead to substantial consequences for the drinking-water treatment procedure. These results provide essential information regarding the estimation of the level of technical expense with respect to drinking-water processing.

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