Salt Solution
In places with cold winters, snow and ice can cause traffic accidents.
To prevent them, salt is often spread on roads in winter.
This is done because salt allows ice to melt at temperatures lower than 0°C.
For example, a 10 percent saltwater mixture lowers the melting temperature of ice
from 0°C to minus 6°C.
A 20 percent mixture lowers this temperature further to minus 16°C.
However, using salt in this way ( 24 ).
Cars, roads, and even the natural environment can be damaged by salt.
Research has shown that when salt is used on roads, it ( 25 ). Instead,
it is carried into the ground by the melted ice.
Much of the salt ends up in lakes and rivers
where it can harm underwater plants, fish, and other creatures.
High levels of salt can, for example, reduce the size of baby fish by up to onethird.
Moreover, salt can lead to an increase in bacteria
which not only harm underwater species but also affect the water that people drink.
To avoid these problems, natural alternatives to salt are being tested.
One idea has been to use juice from vegetables called beets to melt ice.
However, although beet juice is natural,
it reduces the amount of oxygen in lakes and rivers,
which makes it hard for plants and fish to survive.
This is not an easy problem to solve,
but researchers are continuing to try different ways to melt ice.
( 26 ), they will be able to find a substance that can help prevent traffic accidents
but does not damage the environment. |
英語検定 ２級(2021年第3回No.3)