Microplastics Emit Invisible Chemical Clouds, Intensified by Sunlight
Researchers found that microplastics release complex dissolved organic chemicals into water, a process significantly accelerated by sunlight. These unique chemical plumes, differing from natural organic matter, continuously evolve as plastics degrade. Biodegradable plastics show higher leakage. This invisible pollution poses growing environmental risks, potentially disrupting aquatic ecosystems by influencing microbial growth, nutrient cycles, and interactions with other pollutants, underscoring the need to understand their full lifecycle impact.
A new study reveals that microplastics in rivers, lakes, and oceans continuously leak a complex blend of dissolved organic chemicals (MPs DOM) into the water. This chemical release is substantially intensified by exposure to sunlight, providing the most detailed molecular-level understanding of how MPs DOM forms and changes in natural aquatic environments. Researchers analyzed four common plastic types: polyethylene, polyethylene terephthalate (PET), polylactic acid (PLA), and polybutylene adipate co terephthalate (PBAT). Using a combination of kinetic modeling, fluorescence spectroscopy, high-resolution mass spectrometry, and infrared analysis, they demonstrated that each plastic type emits its own distinct chemical mixture. These signatures evolve as sunlight gradually breaks down the plastic surfaces, with plastics labeled as biodegradable (PLA, PBAT) releasing the largest amounts due to their less stable structures. The detailed chemical analyses showed MPs DOM comprises molecules from plastic additives, monomers, oligomers, and fragments formed through photo-oxidized reactions. Over time, an increase in oxygen-containing functional groups like alcohols and carboxylates was observed. Interestingly, MPs DOM closely resembled organic material produced by microbes rather than that from land plants or soils, a significant contrast to natural dissolved organic matter found in rivers. These changing chemical mixtures present growing environmental risks. MPs DOM consists of small, biologically accessible molecules that can stimulate or suppress microbial growth, disrupt nutrient cycles, interact with metals and other pollutants, and produce reactive oxygen species. The study emphasizes the critical need to consider the full life cycle of microplastics, including these invisible dissolved chemicals, as global plastic production continues to rise. Predicting the behavior of these complex and evolving substances will be crucial for assessing their long-term impact on ecosystem health and carbon cycling.
