Plastic pollution enters the ocean mostly from land, where everyday items like bottles, bags, wrappers, and packaging are dropped, blown, or washed into waterways. Rain moves litter along streets and sidewalks into gutters, storm drains, and streams. Because many storm drains lead directly to rivers without treatment, plastic can travel far from the place where it was first thrown away.
This matters because ocean plastic harms wildlife, damages habitats, and breaks into tiny pieces that are difficult to remove.
Key Facts
- About 80% of ocean plastic pollution is carried from land by rivers and runoff.
- Storm drains often flow directly to streams, rivers, or the ocean without filtering trash.
- Large rivers such as the Yangtze, Ganges, and Niger can transport major amounts of plastic waste to the sea.
- Runoff amount can be estimated by Q = C i A, where Q is runoff flow, C is runoff coefficient, i is rainfall intensity, and A is area.
- Plastic can fragment into microplastics, which are pieces smaller than 5 mm.
- Floating plastic can collect in ocean gyres, forming garbage patches where currents concentrate debris.
Vocabulary
- Runoff
- Runoff is water from rain or melting snow that flows over land instead of soaking into the ground.
- Storm drain
- A storm drain is a street or gutter opening that carries rainwater and debris into drainage pipes.
- Watershed
- A watershed is the land area where all water drains toward the same river, lake, or ocean.
- Microplastic
- A microplastic is a plastic piece smaller than 5 millimeters that forms from small products or broken larger plastics.
- Ocean gyre
- An ocean gyre is a large rotating system of currents that can trap floating debris in one region.
Common Mistakes to Avoid
- Thinking ocean plastic only comes from beaches is wrong because most plastic starts on land and travels through drains, streams, and rivers.
- Assuming storm drains clean water is wrong because many storm drains send water and trash directly to natural waterways without treatment.
- Believing plastic disappears when it breaks apart is wrong because it usually fragments into smaller pieces called microplastics that can remain for a very long time.
- Ignoring small litter like wrappers and bottle caps is wrong because small items are easily carried by wind and runoff into drains and rivers.
Practice Questions
- 1 A city estimates that 2,000 kg of plastic litter reaches nearby waterways in one month. If 80% is carried by rivers to the ocean, how many kilograms may reach the ocean?
- 2 During a cleanup, students collect 360 plastic bottles from streets near storm drains. If each bottle has a mass of 20 g, what is the total mass in kilograms of bottles removed before they could enter the drainage system?
- 3 Explain why reducing single-use plastic in a city far from the coast can still help reduce plastic pollution in the ocean.