Kill 10 aliens with environmental explosives

While playing you will notice different red objects that explode if you shoot at them, such as barrels, tanks and tubes. There are also some brownish tubes in "The Duke Cave", but that's the only place you'll find those brown ones. Those explosions are what they call "environmental explosives". Sometimes you will see aliens standing next to one of those red objects. Shoot at it and an explosion will go off killing all the aliens around it. But some other times you will just find barrels or tubes somewhere when no aliens are around. To make this trophy/achievement easier you can pick up those red barrels or tubes and throw them at aliens you encounter and the alien will be blown to pieces. But watch out, if an alien starts to shoot at you while carrying one of those, the best thing you can do is to throw it away, or it will most likely be you who gets blown into pieces.