Paul Mason 
Tiger, Tiger (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.
The superhero team take a break from being eco-warriors to visit Bangladesh, but find themselves in the middle of a tiger-poaching ring. The second exciting adventure of Factor 4.