Heavy metals trigger distinct molecular transformations in microplastic-versus natural-derived dissolved organic...

Area of Science:

• Environmental Chemistry
• Aquatic Chemistry
• Environmental Science

Background:

• Dissolved organic matter (DOM) significantly influences heavy metal behavior in aquatic systems.
• Natural DOM (N-DOM) stabilizes metals via complexation, but microplastic-derived DOM (MP-DOM) interactions are poorly understood.
• Increasing plastic pollution raises concerns about MP-DOM's role in heavy metal fate and toxicity.

Purpose of the Study:

• To compare the interactions of heavy metals with N-DOM and MP-DOM.
• To investigate how heavy metals induce molecular transformations in both DOM types.
• To assess the ecological risks posed by MP-DOM degradation in the presence of heavy metals.

Main Methods:

• Comparative analysis of N-DOM and MP-DOM interactions with cadmium, chromium, copper, and lead.
• Utilized fluorescence spectroscopy and molecular analysis techniques.
• Employed mass-difference network analysis and density functional theory calculations.

Main Results:

• N-DOM formed more stable heavy metal complexes than MP-DOM, primarily through oxygen-containing functional groups.
• MP-DOM exhibited less stable complexes and was susceptible to chromium-induced oxidation.
• Both DOM types underwent metal-triggered decarboxylation and dealkylation, but MP-DOM degraded into smaller, hazardous molecules like phenol and benzene.

Conclusions:

• Heavy metals can exacerbate the ecological risks of MP-DOM by triggering its degradation into harmful substances.
• Understanding these interactions is crucial for assessing risks in environments with co-occurring plastic and metal pollution.
• This research provides vital insights for global risk assessment and management strategies.