الأسبوع 18 · المحور الثالث «حماية كوكبنا»، الوحدة الثالثة «الموارد الموجودة على سطح الأرض»، المفهوم 3.1 (ج) والمفهوم 3.2 «الماء كأهم الموارد الطبيعية على سطح الأرض» (أ): البلاستيك في الماء وتوزيع الماء · 3 دروس
1
Tiny plastic in the water
Discovery Education Science P5: Term 2, Unit 3, pp. 27–29
GoalExplain what microplastics are, how they get into water and food webs, and what people can do about them.
New words
hydrologist · a scientist who studies watermicroplastics · pieces of plastic smaller than 5 mmpollution · harmful things put into water, air or soil
Explanation
A hydrologist is a scientist who studies water. To understand water, a hydrologist must also study how the hydrosphere meets the other spheres: water running over land, water in living things, and water in the air. Rivers carry plastic litter from the land to the sea. In the sun and the waves, big plastic breaks into smaller and smaller pieces. Pieces smaller than 5 mm are called microplastics. Tiny water animals can mistake them for food. When bigger animals eat those animals, the plastic moves up the food web. Scientists have found microplastics in water and soil in almost every habitat. To study a river, they take samples of water and soil and count the pieces. We can help by using less single-use plastic, never dropping litter, and recycling and reusing what we can.
plastic litter on land→the river carries it→sun and waves break it up→tiny animals eat it→it moves up the food web
Worked examples
Piece
Size
Microplastic?
bottle
200 mm
no
fragment
3 mm
yes
bead
2 mm
yes
Only pieces smaller than 5 mm are microplastics. A bottle that is 200 mm long is big plastic. A piece 3 mm wide and a bead 2 mm wide are microplastics.
How plastic reaches bigger animals. A shrimp mistakes a tiny piece of plastic for food. A fish eats the shrimp, and a heron eats the fish. The plastic moves along the food chain.
Place on the river
Pieces in 1 L
before the town
4
at the town
18
near the sea
11
A scientist counts pieces of microplastic in a 1-litre water sample from three places on a river. The town has the most. Between the town and the sea, there are 18 − 11 = 7 fewer pieces.
Class activity
Plastic audit (a grown-up helps, wear gloves for any clean packaging, and never collect litter near canals). For one day, keep the plastic packaging your family throws away. Count the pieces and sort them into single-use and reusable. Choose one single-use item and think of a way to replace it.
Practice
1
What are microplastics?
Pieces of plastic smaller than 5 mm.
2
How do microplastics get into a food web?
Tiny animals mistake them for food, and bigger animals eat those animals, so the plastic moves up the web.
3
Which pieces are microplastics? Say the letters.
Piece
Size
A
12 mm
B
3 mm
C
1 mm
D
8 mm
B and C, because 3 mm and 1 mm are smaller than 5 mm. A (12 mm) and D (8 mm) are bigger.
4
Name two ways people can reduce plastic in rivers and seas.
Any two: use less single-use plastic, never drop litter, recycle, reuse bags and bottles.
