Aquatic organic matter: Classification and interaction with organic microcontaminants

Area of Science:

• Environmental Chemistry
• Aquatic Chemistry
• Organic Geochemistry

Background:

• Aquatic organic matter (OM) originates from natural and anthropogenic sources, existing in dissolved, particulate, or colloidal forms.
• OM is classified into non-humic substances (NHS) and humic substances (HS). NHS include carbohydrates, proteins, lipids, and lignin, acting as chemical biomarkers.
• HS properties and functions are crucial for understanding the fate, bioavailability, and toxicity of organic microcontaminants in aquatic environments.

Purpose of the Study:

• To review the main groups constituting NHS and their role as biomarkers.
• To present the characteristics, functions, properties, and mechanisms of HS.
• To discuss the association of HS with the fate, bioavailability, and toxicity of organic microcontaminants in aquatic systems.

Main Methods:

• Literature review focusing on the composition and roles of organic matter fractions in aquatic systems.
• Analysis of existing data on the interactions between humic substances and organic microcontaminants.
• Identification of challenges and limitations in current research methodologies.

Main Results:

• Humic substances (HS) primarily influence the bioavailability and toxicity of organic microcontaminants, often exerting a protective effect by reducing uptake.
• OM can mitigate microcontaminant toxicity through mechanisms like UV radiation absorption and modulation of reactive oxygen species.
• Significant fragmentation exists in research data due to diverse experimental protocols and the non-representative use of commercial humic acid.

Conclusions:

• Organic matter, particularly HS, significantly impacts the environmental behavior and toxicological effects of organic microcontaminants in aquatic ecosystems.
• Standardized experimental approaches are necessary to overcome current research fragmentation and enable robust comparisons.
• Further investigation is required to fully elucidate the complex interactions between diverse OM sources and organic microcontaminants.