Sunlight Accelerates Microplastic Chemical Release into Water
Microplastics release complex dissolved organic chemicals into aquatic environments, a process significantly accelerated by sunlight, particularly UV light. Research shows different plastic types, including biodegradable ones, constantly leach chemicals, impacting microbial food webs, metal interactions, and water quality. These invisible chemical clouds pose risks for ecosystems and drinking water, underscoring the need for comprehensive risk assessment of microplastic pollution's full life cycle and its widespread environmental effects.
New research published in New Contaminants details how microplastics release invisible chemical clouds, known as dissolved organic matter (DOM), into rivers, lakes, and oceans, a process significantly intensified by sunlight. This continuous leaching affects water quality far beyond the plastic particles themselves. The study found that sunlight, especially ultraviolet light, breaks chemical bonds on plastic surfaces, causing small molecules—including additives, polymer building blocks, and degradation fragments—to escape into the water. Biodegradable plastics, due to their weaker polymer backbones, released more dissolved carbon than petroleum-based plastics.The release speed exhibited zero-order behavior, meaning it remained constant, controlled by physical limits on the plastic surface rather than chemical concentration in the water. Unlike natural organic matter, which shows little response to UV light, plastic-derived DOM reacts strongly, becoming chemically flexible and changing rapidly over time. These complex chemical mixtures, including newly formed oxygen-rich compounds like alcohols and acids, pose significant environmental concerns. They can enter microbial food webs, altering metabolism and affecting carbon cycling and oxygen balance. Furthermore, plastic-derived DOM interacts with heavy metals like copper, cadmium, and lead, modifying their mobility and toxicity. It also influences mineral reactions and nutrient transport.The sunlight-driven reactions also produce reactive oxygen species, impacting pollutant breakdown, plastic aging, and potentially forming unwanted byproducts in drinking water treatment. Scientists emphasize the critical need to consider the full life cycle of microplastics, including these invisible dissolved chemicals. They suggest leveraging machine learning to predict the chemical behavior of microplastic-derived DOM, which would improve risk assessment for ecosystems, water treatment, and carbon cycling, especially as plastic production continues to rise globally.
