In the water cycle, which process leaves salt behind as water rises into the air?
AnswerEvaporation
When seawater evaporates, the salt stays behind, so rain falls as fresh water.
Nature · Facts & stats
Clearwater facts & stats
7 fact-checked facts about clear water, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which of these animals cleans water by filtering out tiny particles as it feeds?
AnswerOysters
Oysters are filter feeders that strain plankton and particles from the water they pump.
Going deeper
Why does very clear, deep water look blue?
AnswerWater absorbs red light more strongly than blue
Water molecules absorb red wavelengths, so the light that travels back to our eyes is bluish.
What does a sand filter do in water treatment?
AnswerTraps small particles as water trickles through
Layers of sand and gravel catch particles as water slowly passes through them.
What is an algal bloom?
AnswerA rapid increase of algae that can cloud water
Blooms happen when algae multiply quickly, turning water green and murky.
Expert level
How does ultraviolet (UV) light help treat drinking water?
AnswerIt damages the DNA of microorganisms
UV light disrupts the genetic material of bacteria and viruses so they cannot reproduce.
Which unit is commonly used to report turbidity?
AnswerNTU (Nephelometric Turbidity Units)
NTU readings come from measuring how much light is scattered by particles in a sample.
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