Urban Water Treatment Transforms Dissolved Organic Matter, Creating Regional Heterogeneity with Peptide Accumulation in Eastern Shenzhen
Background
Dissolved organic matter (DOM) is critical for drinking water safety and stability, yet its molecular characteristics across urban aquatic systems remain poorly understood. Current water treatment processes significantly alter DOM, but the specific molecular transformations and their regional impacts are often overlooked. This gap hinders effective management of carbon cycling and mitigation of risks like secondary pollution or toxic compound enrichment in urban water supplies, necessitating detailed molecular-level insights into DOM fate.
Study Design
Researchers characterized dissolved organic matter (DOM) in municipal tap water (TW) and source water (SW) from Shenzhen, China. They employed advanced spectroscopic techniques and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) to analyze molecular characteristics. Comparative analyses focused on changes from SW to TW due to treatment and distribution, as well as regional heterogeneity within TW samples across eastern, middle, and western city areas. The study aimed to identify distinct human-associated DOM transformation pathways.
Results
Analysis revealed significant reductions in humic-like fluorescence, molecular weight, aromaticity, unsaturation, and N/S-containing molecules from source water (SW) to tap water (TW), primarily due to treatment processes. While SW samples showed high molecular similarity across regions, TW samples displayed marked regional heterogeneity within the city.
Specifically, TW from the eastern region contained higher concentrations of aliphatic compounds, peptides, and P-containing molecules, indicating a transformation toward carbon source-like compounds. Conversely, TW in the middle and western regions possessed a greater abundance of highly unsaturated compounds, promoting the accumulation of carbon sink-like substances (e.g., highly unsaturated and carboxyl-rich alicyclic molecules). This divergence highlights region-specific
carbon cycling dynamicswithin urban water systems, suggesting a potential trade-off between risks ofsecondary pollutionandtoxic compound enrichmentbased on DOM composition.
Key Findings
- Significant reductions in humic-like fluorescence, molecular weight, aromaticity, unsaturation, and N/S-containing molecules occurred from source water to tap water.
- Tap water exhibited marked regional heterogeneity in dissolved organic matter (DOM) composition within the city.
- Eastern region tap water showed higher concentrations of aliphatic compounds, peptides, and P-containing molecules.
- Middle and western region tap water had a greater abundance of highly unsaturated compounds.
- Two distinct human-associated DOM transformation pathways were identified: carbon source-like (eastern) vs. carbon sink-like (middle/western).
Why It Matters
This study provides crucial molecular-level insights into how urban water treatment and distribution shape dissolved organic matter (DOM), directly impacting drinking water safety. The discovery of region-specific DOM profiles, particularly the accumulation of peptides and lipids in eastern tap water, suggests varying potentials for microbial regrowth or disinfection byproduct formation. Understanding these distinct DOM transformation pathways is essential for developing targeted, region-specific water treatment strategies to mitigate risks of secondary pollution and toxic compound enrichment. This research informs future efforts to ensure reliable and safe drinking water provision by moving beyond a one-size-fits-all approach to water quality management.
dissolved organic matter
dom
drinking water
water treatment
carbon cycling
environmental chemistry