Universal molecular structures in natural dissolved organic matter.

Area of Science:

• Environmental chemistry
• Organic geochemistry
• Aquatic chemistry

Background:

• Natural dissolved organic matter (DOM) is a highly complex mixture of organic molecules found in aquatic systems.
• Understanding the composition and origin of DOM is crucial for biogeochemical cycling.
• Previous studies have highlighted the complexity but lacked detailed molecular-level comparisons across diverse environments.

Purpose of the Study:

• To investigate the molecular structural conformity of dissolved organic matter (DOM) across different aquatic environments.
• To identify common molecular features and potential formation pathways of DOM.
• To assess the universality of DOM composition irrespective of its origin.

Main Methods:

• Utilized high-resolution mass spectrometry to determine individual molecular formulae in DOM samples.
• Compared detailed structural fingerprints of molecular formulae from marine and freshwater environments.
• Analyzed the co-occurrence and structural features of isomers representing specific molecular formulae.

Main Results:

• A significant portion of DOM was found to be molecularly indistinguishable across diverse marine and freshwater samples.
• Thousands of identical molecular formulae were identified in DOM from different origins.
• Identical structural features were observed for isomers within common molecular formulae, indicating molecular conformity.

Conclusions:

• A universal background of DOM, characterized by molecular conformity, likely exists in aquatic systems.
• This conformity suggests common degradation processes or synthetic pathways govern DOM formation.
• The findings impact the understanding of long-term DOM turnover, implying universal underlying mechanisms.