Paul Mason 
The Awakening (Factor 4) [EPUB ebook] 

Four friends are exposed to a strange gas that gives them the powers of earth, air, fire and water, and take on new identities as superheroes. Zaf becomes Zephyr, who can fly and direct the wind. Tara becomes Terra, who can make the earth shake and plants grow. Ian becomes Inferno, with the power to create fire. April becomes Aqua, her body turning to water as she creates waves, floods and waterspouts.
When Zaf, Tara, Ian and April find themselves with their new powers, they must work out what they are and how to control them. Can they come to grips with their abilities in time to extinguish a deadly bushfire?