Ash can be harmful to an environment. It mostly depends on how much ash there is though. If a volcano erupted such as Mt. St. Helen's then yes that can harm an environment. Ash can cover the sky and block out the sun for days before disappearing and that will affect the life of plants
Hmmm i think its the third one because men only have 1 x chromosome therefore without the other one if the x chromosome on a men carries a disorder it will show because there is no other chromosome to balance it out and in women the disorder has to show on both X chronosome (and its rarer) for a disorder to appear therefore women having a second X chromosome is effectively a protection
Should be decontamination because you are removing the pollution that has been dispersed.
Increases plant growth, more transpiration