Here are a few websites t get you started.
Please feel free to find your own!
Global Climate Change
http://www.epa.gov/climatechange/
http://environment.nationalgeographic.com/environment/global-warming/
Ozone Layer Depletion
http://www.epa.gov/sunwise/kids/kids_ozone.html
http://www.research.noaa.gov/climate/t_ozonelayer.html
http://www.un.org/en/events/ozoneday/science.shtml
Acid Rain
http://www.epa.gov/acidrain/
http://environment.nationalgeographic.com/environment/global-warming/acid-rain-overview/
Deforestation
http://greenliving.nationalgeographic.com/deforestation-effects-global-scale-2214.html
http://www.wri.org/publication/content/8368
Potable (safe to drink) Water
http://www.who.int/water_sanitation_health/mdg1/en/index.html
http://blueplanetnetwork.org/water/
http://globalwater.org/whywater.htm
Landfills
http://greenliving.lovetoknow.com/Environmental_Problems:_Landfills
http://www.bbc.co.uk/learningzone/clips/environmental-problems-associated-with-landfill/1576.html
http://people.hws.edu/halfman/Data/PublicInterestArticles/Landfills.pdf
General/Human Population
http://redpath-museum.mcgill.ca/Qbp/3.Conservation/impacts.htm