In the marine environment, plastics primarily break down into smaller pieces through physical and chemical processes driven by natural forces, eventually forming microscopic particles.
The Breakdown Process
Plastics don't biodegrade quickly like organic materials. Instead, they undergo a process of fragmentation. This breakdown is significantly influenced by environmental factors.
- Fragmentation: Due to factors like solar radiation, wind, currents, and other natural forces, larger plastic items break down into increasingly smaller particles. This process is often referred to as photodegradation (due to sunlight) and mechanical abrasion (due to waves, wind, etc.).
The result of this fragmentation is the formation of tiny plastic particles:
- Microplastics: These are plastic particles smaller than 5 mm.
- Nanoplastics: These are even smaller, with particles measuring less than 100 nm (nanometers).
These particles persist in the environment for very long periods, potentially accumulating in the water column, sediments, and marine organisms.
Sources of Microplastic
While fragmentation of larger debris is a major source of microplastics, some are introduced directly into the marine environment as primary microplastics.
- Primary Microplastics: These particles are shed from products during their use. Examples include:
- Particles shed from synthetic textiles (like polyester or nylon) during washing cycles.
- Wear particles from tyres on roads, which can be washed into waterways and eventually the ocean.
Here's a simplified view of the breakdown process:
| Factor | Mechanism | Resulting Particle Size |
|---|---|---|
| Solar Radiation | Photodegradation | Microplastic, Nanoplastic |
| Wind & Currents | Mechanical Abrasion | Microplastic, Nanoplastic |
| Other Factors | Physical Stress | Microplastic, Nanoplastic |
| Product Use | Abrasion (e.g., tires, textiles) | Primary Microplastic |
Understanding this breakdown is crucial because these microscopic particles pose significant risks to marine life and ecosystems. They can be ingested by animals of all sizes, entering the food web and potentially carrying harmful chemicals. Efforts to mitigate plastic pollution therefore focus on reducing plastic use, improving waste management, and preventing plastic from entering the ocean in the first place.
